System.Data.SQLite
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/********************************************************
 * ADO.NET 2.0 Data Provider for SQLite Version 3.X
 * Written by Joe Mistachkin (joe@mistachkin.com)
 *
 * Released to the public domain, use at your own risk!
 ********************************************************/

using System.Collections.Generic;
using System.Globalization;

#if !PLATFORM_COMPACTFRAMEWORK
using System.Runtime.CompilerServices;
#endif

using System.Runtime.InteropServices;
using System.Text;

namespace System.Data.SQLite
{
    #region SQLiteContext Helper Class
    /// <summary>
    /// This class represents a context from the SQLite core library that can
    /// be passed to the sqlite3_result_*() and associated functions.
    /// </summary>
    public sealed class SQLiteContext : ISQLiteNativeHandle
    {
        #region Private Data
        /// <summary>
        /// The native context handle.
        /// </summary>
        private IntPtr pContext;
        #endregion

        ///////////////////////////////////////////////////////////////////////

        #region Private Constructors
        /// <summary>
        /// Constructs an instance of this class using the specified native
        /// context handle.
        /// </summary>
        /// <param name="pContext">
        /// The native context handle to use.
        /// </param>
        internal SQLiteContext(IntPtr pContext)
        {
            this.pContext = pContext;
        }
        #endregion

        ///////////////////////////////////////////////////////////////////////

        #region ISQLiteNativeHandle Members
        /// <summary>
        /// Returns the underlying SQLite native handle associated with this
        /// object instance.
        /// </summary>
        public IntPtr NativeHandle
        {
            get { return pContext; }
        }
        #endregion

        ///////////////////////////////////////////////////////////////////////

        #region Public Methods
        /// <summary>
        /// Sets the context result to NULL.
        /// </summary>
        public void SetNull()
        {
            if (pContext == IntPtr.Zero)
                throw new InvalidOperationException();

            UnsafeNativeMethods.sqlite3_result_null(pContext);
        }

        ///////////////////////////////////////////////////////////////////////

        /// <summary>
        /// Sets the context result to the specified <see cref="Double" />
        /// value.
        /// </summary>
        /// <param name="value">
        /// The <see cref="Double" /> value to use.
        /// </param>
        public void SetDouble(double value)
        {
            if (pContext == IntPtr.Zero)
                throw new InvalidOperationException();

#if !PLATFORM_COMPACTFRAMEWORK
            UnsafeNativeMethods.sqlite3_result_double(pContext, value);
#elif !SQLITE_STANDARD
            UnsafeNativeMethods.sqlite3_result_double_interop(pContext, ref value);
#else
            throw new NotImplementedException();
#endif
        }

        ///////////////////////////////////////////////////////////////////////

        /// <summary>
        /// Sets the context result to the specified <see cref="Int32" />
        /// value.
        /// </summary>
        /// <param name="value">
        /// The <see cref="Int32" /> value to use.
        /// </param>
        public void SetInt(int value)
        {
            if (pContext == IntPtr.Zero)
                throw new InvalidOperationException();

            UnsafeNativeMethods.sqlite3_result_int(pContext, value);
        }

        ///////////////////////////////////////////////////////////////////////

        /// <summary>
        /// Sets the context result to the specified <see cref="Int64" />
        /// value.
        /// </summary>
        /// <param name="value">
        /// The <see cref="Int64" /> value to use.
        /// </param>
        public void SetInt64(long value)
        {
            if (pContext == IntPtr.Zero)
                throw new InvalidOperationException();

#if !PLATFORM_COMPACTFRAMEWORK
            UnsafeNativeMethods.sqlite3_result_int64(pContext, value);
#elif !SQLITE_STANDARD
            UnsafeNativeMethods.sqlite3_result_int64_interop(pContext, ref value);
#else
            throw new NotImplementedException();
#endif
        }

        ///////////////////////////////////////////////////////////////////////

        /// <summary>
        /// Sets the context result to the specified <see cref="String" />
        /// value.
        /// </summary>
        /// <param name="value">
        /// The <see cref="String" /> value to use.  This value will be
        /// converted to the UTF-8 encoding prior to being used.
        /// </param>
        public void SetString(string value)
        {
            if (pContext == IntPtr.Zero)
                throw new InvalidOperationException();

            byte[] bytes = SQLiteString.GetUtf8BytesFromString(value);

            if (bytes == null)
                throw new ArgumentNullException("value");

            UnsafeNativeMethods.sqlite3_result_text(
                pContext, bytes, bytes.Length, (IntPtr)(-1));
        }

        ///////////////////////////////////////////////////////////////////////

        /// <summary>
        /// Sets the context result to the specified <see cref="String" />
        /// value containing an error message.
        /// </summary>
        /// <param name="value">
        /// The <see cref="String" /> value containing the error message text.
        /// This value will be converted to the UTF-8 encoding prior to being
        /// used.
        /// </param>
        public void SetError(string value)
        {
            if (pContext == IntPtr.Zero)
                throw new InvalidOperationException();

            byte[] bytes = SQLiteString.GetUtf8BytesFromString(value);

            if (bytes == null)
                throw new ArgumentNullException("value");

            UnsafeNativeMethods.sqlite3_result_error(
                pContext, bytes, bytes.Length);
        }

        ///////////////////////////////////////////////////////////////////////

        /// <summary>
        /// Sets the context result to the specified <see cref="SQLiteErrorCode" />
        /// value.
        /// </summary>
        /// <param name="value">
        /// The <see cref="SQLiteErrorCode" /> value to use.
        /// </param>
        public void SetErrorCode(SQLiteErrorCode value)
        {
            if (pContext == IntPtr.Zero)
                throw new InvalidOperationException();

            UnsafeNativeMethods.sqlite3_result_error_code(pContext, value);
        }

        ///////////////////////////////////////////////////////////////////////

        /// <summary>
        /// Sets the context result to contain the error code SQLITE_TOOBIG.
        /// </summary>
        public void SetErrorTooBig()
        {
            if (pContext == IntPtr.Zero)
                throw new InvalidOperationException();

            UnsafeNativeMethods.sqlite3_result_error_toobig(pContext);
        }

        ///////////////////////////////////////////////////////////////////////

        /// <summary>
        /// Sets the context result to contain the error code SQLITE_NOMEM.
        /// </summary>
        public void SetErrorNoMemory()
        {
            if (pContext == IntPtr.Zero)
                throw new InvalidOperationException();

            UnsafeNativeMethods.sqlite3_result_error_nomem(pContext);
        }

        ///////////////////////////////////////////////////////////////////////

        /// <summary>
        /// Sets the context result to the specified <see cref="Byte" /> array
        /// value.
        /// </summary>
        /// <param name="value">
        /// The <see cref="Byte" /> array value to use.
        /// </param>
        public void SetBlob(byte[] value)
        {
            if (pContext == IntPtr.Zero)
                throw new InvalidOperationException();

            if (value == null)
                throw new ArgumentNullException("value");

            UnsafeNativeMethods.sqlite3_result_blob(
                pContext, value, value.Length, (IntPtr)(-1));
        }

        ///////////////////////////////////////////////////////////////////////

        /// <summary>
        /// Sets the context result to a BLOB of zeros of the specified size.
        /// </summary>
        /// <param name="value">
        /// The number of zero bytes to use for the BLOB context result.
        /// </param>
        public void SetZeroBlob(int value)
        {
            if (pContext == IntPtr.Zero)
                throw new InvalidOperationException();

            UnsafeNativeMethods.sqlite3_result_zeroblob(pContext, value);
        }

        ///////////////////////////////////////////////////////////////////////

        /// <summary>
        /// Sets the context result to the specified <see cref="SQLiteValue" />.
        /// </summary>
        /// <param name="value">
        /// The <see cref="SQLiteValue" /> to use.
        /// </param>
        public void SetValue(SQLiteValue value)
        {
            if (pContext == IntPtr.Zero)
                throw new InvalidOperationException();

            if (value == null)
                throw new ArgumentNullException("value");

            UnsafeNativeMethods.sqlite3_result_value(
                pContext, value.NativeHandle);
        }
        #endregion
    }
    #endregion

    ///////////////////////////////////////////////////////////////////////////

    #region SQLiteValue Helper Class
    /// <summary>
    /// This class represents a value from the SQLite core library that can be
    /// passed to the sqlite3_value_*() and associated functions.
    /// </summary>
    public sealed class SQLiteValue : ISQLiteNativeHandle
    {
        #region Private Data
        /// <summary>
        /// The native value handle.
        /// </summary>
        private IntPtr pValue;
        #endregion

        ///////////////////////////////////////////////////////////////////////

        #region Private Constructors
        /// <summary>
        /// Constructs an instance of this class using the specified native
        /// value handle.
        /// </summary>
        /// <param name="pValue">
        /// The native value handle to use.
        /// </param>
        private SQLiteValue(IntPtr pValue)
        {
            this.pValue = pValue;
        }
        #endregion

        ///////////////////////////////////////////////////////////////////////

        #region Private Methods
        /// <summary>
        /// Invalidates the native value handle, thereby preventing further
        /// access to it from this object instance.
        /// </summary>
        private void PreventNativeAccess()
        {
            pValue = IntPtr.Zero;
        }
        #endregion

        ///////////////////////////////////////////////////////////////////////

        #region Internal Marshal Helper Methods
        /// <summary>
        /// Converts a native pointer to a native sqlite3_value structure into
        /// a managed <see cref="SQLiteValue" /> object instance.
        /// </summary>
        /// <param name="pValue">
        /// The native pointer to a native sqlite3_value structure to convert.
        /// </param>
        /// <returns>
        /// The managed <see cref="SQLiteValue" /> object instance or null upon
        /// failure.
        /// </returns>
        internal static SQLiteValue FromIntPtr(
            IntPtr pValue
            )
        {
            if (pValue == IntPtr.Zero) return null;
            return new SQLiteValue(pValue);
        }

        ///////////////////////////////////////////////////////////////////////

        /// <summary>
        /// Converts a logical array of native pointers to native sqlite3_value
        /// structures into a managed array of <see cref="SQLiteValue" />
        /// object instances.
        /// </summary>
        /// <param name="argc">
        /// The number of elements in the logical array of native sqlite3_value
        /// structures.
        /// </param>
        /// <param name="argv">
        /// The native pointer to the logical array of native sqlite3_value
        /// structures to convert.
        /// </param>
        /// <returns>
        /// The managed array of <see cref="SQLiteValue" /> object instances or
        /// null upon failure.
        /// </returns>
        internal static SQLiteValue[] ArrayFromSizeAndIntPtr(
            int argc,
            IntPtr argv
            )
        {
            if (argc < 0)
                return null;

            if (argv == IntPtr.Zero)
                return null;

            SQLiteValue[] result = new SQLiteValue[argc];

            for (int index = 0, offset = 0;
                    index < result.Length;
                    index++, offset += IntPtr.Size)
            {
                IntPtr pArg = SQLiteMarshal.ReadIntPtr(argv, offset);

                result[index] = (pArg != IntPtr.Zero) ?
                    new SQLiteValue(pArg) : null;
            }

            return result;
        }
        #endregion

        ///////////////////////////////////////////////////////////////////////

        #region ISQLiteNativeHandle Members
        /// <summary>
        /// Returns the underlying SQLite native handle associated with this
        /// object instance.
        /// </summary>
        public IntPtr NativeHandle
        {
            get { return pValue; }
        }
        #endregion

        ///////////////////////////////////////////////////////////////////////

        #region Public Properties
        private bool persisted;
        /// <summary>
        /// Returns non-zero if the native SQLite value has been successfully
        /// persisted as a managed value within this object instance (i.e. the
        /// <see cref="Value" /> property may then be read successfully).
        /// </summary>
        public bool Persisted
        {
            get { return persisted; }
        }

        ///////////////////////////////////////////////////////////////////////

        private object value;
        /// <summary>
        /// If the managed value for this object instance is available (i.e. it
        /// has been previously persisted via the <see cref="Persist" />) method,
        /// that value is returned; otherwise, an exception is thrown.  The
        /// returned value may be null.
        /// </summary>
        public object Value
        {
            get
            {
                if (!persisted)
                {
                    throw new InvalidOperationException(
                        "value was not persisted");
                }

                return value;
            }
        }
        #endregion

        ///////////////////////////////////////////////////////////////////////

        #region Public Methods
        /// <summary>
        /// Gets and returns the type affinity associated with this value.
        /// </summary>
        /// <returns>
        /// The type affinity associated with this value.
        /// </returns>
        public TypeAffinity GetTypeAffinity()
        {
            if (pValue == IntPtr.Zero) return TypeAffinity.None;
            return UnsafeNativeMethods.sqlite3_value_type(pValue);
        }

        ///////////////////////////////////////////////////////////////////////

        /// <summary>
        /// Gets and returns the number of bytes associated with this value, if
        /// it refers to a UTF-8 encoded string.
        /// </summary>
        /// <returns>
        /// The number of bytes associated with this value.  The returned value
        /// may be zero.
        /// </returns>
        public int GetBytes()
        {
            if (pValue == IntPtr.Zero) return 0;
            return UnsafeNativeMethods.sqlite3_value_bytes(pValue);
        }

        ///////////////////////////////////////////////////////////////////////

        /// <summary>
        /// Gets and returns the <see cref="Int32" /> associated with this
        /// value.
        /// </summary>
        /// <returns>
        /// The <see cref="Int32" /> associated with this value.
        /// </returns>
        public int GetInt()
        {
            if (pValue == IntPtr.Zero) return default(int);
            return UnsafeNativeMethods.sqlite3_value_int(pValue);
        }

        ///////////////////////////////////////////////////////////////////////

        /// <summary>
        /// Gets and returns the <see cref="Int64" /> associated with
        /// this value.
        /// </summary>
        /// <returns>
        /// The <see cref="Int64" /> associated with this value.
        /// </returns>
        public long GetInt64()
        {
            if (pValue == IntPtr.Zero) return default(long);

#if !PLATFORM_COMPACTFRAMEWORK
            return UnsafeNativeMethods.sqlite3_value_int64(pValue);
#elif !SQLITE_STANDARD
            long value = 0;
            UnsafeNativeMethods.sqlite3_value_int64_interop(pValue, ref value);
            return value;
#else
            throw new NotImplementedException();
#endif
        }

        ///////////////////////////////////////////////////////////////////////

        /// <summary>
        /// Gets and returns the <see cref="Double" /> associated with this
        /// value.
        /// </summary>
        /// <returns>
        /// The <see cref="Double" /> associated with this value.
        /// </returns>
        public double GetDouble()
        {
            if (pValue == IntPtr.Zero) return default(double);

#if !PLATFORM_COMPACTFRAMEWORK
            return UnsafeNativeMethods.sqlite3_value_double(pValue);
#elif !SQLITE_STANDARD
            double value = 0.0;
            UnsafeNativeMethods.sqlite3_value_double_interop(pValue, ref value);
            return value;
#else
            throw new NotImplementedException();
#endif
        }

        ///////////////////////////////////////////////////////////////////////

        /// <summary>
        /// Gets and returns the <see cref="String" /> associated with this
        /// value.
        /// </summary>
        /// <returns>
        /// The <see cref="String" /> associated with this value.  The value is
        /// converted from the UTF-8 encoding prior to being returned.
        /// </returns>
        public string GetString()
        {
            if (pValue == IntPtr.Zero) return null;

            int length;
            IntPtr pString;

#if SQLITE_STANDARD
            length = UnsafeNativeMethods.sqlite3_value_bytes(pValue);
            pString = UnsafeNativeMethods.sqlite3_value_text(pValue);
#else
            length = 0;

            pString = UnsafeNativeMethods.sqlite3_value_text_interop(
                pValue, ref length);
#endif

            return SQLiteString.StringFromUtf8IntPtr(pString, length);
        }

        ///////////////////////////////////////////////////////////////////////

        /// <summary>
        /// Gets and returns the <see cref="Byte" /> array associated with this
        /// value.
        /// </summary>
        /// <returns>
        /// The <see cref="Byte" /> array associated with this value.
        /// </returns>
        public byte[] GetBlob()
        {
            if (pValue == IntPtr.Zero) return null;

            return SQLiteBytes.FromIntPtr(
                UnsafeNativeMethods.sqlite3_value_blob(pValue), GetBytes());
        }

        ///////////////////////////////////////////////////////////////////////

        /// <summary>
        /// Gets and returns an <see cref="Object" /> instance associated with
        /// this value.
        /// </summary>
        /// <returns>
        /// The <see cref="Object" /> associated with this value.  If the type
        /// affinity of the object is unknown or cannot be determined, a null
        /// value will be returned.
        /// </returns>
        public object GetObject()
        {
            switch (GetTypeAffinity())
            {
                case TypeAffinity.Uninitialized:
                    {
                        return null;
                    }
                case TypeAffinity.Int64:
                    {
                        return GetInt64();
                    }
                case TypeAffinity.Double:
                    {
                        return GetDouble();
                    }
                case TypeAffinity.Text:
                    {
                        return GetString();
                    }
                case TypeAffinity.Blob:
                    {
                        return GetBytes();
                    }
                case TypeAffinity.Null:
                    {
                        return DBNull.Value;
                    }
                default:
                    {
                        return null;
                    }
            }
        }

        ///////////////////////////////////////////////////////////////////////

        /// <summary>
        /// Uses the native value handle to obtain and store the managed value
        /// for this object instance, thus saving it for later use.  The type
        /// of the managed value is determined by the type affinity of the
        /// native value.  If the type affinity is not recognized by this
        /// method, no work is done and false is returned.
        /// </summary>
        /// <returns>
        /// Non-zero if the native value was persisted successfully.
        /// </returns>
        public bool Persist()
        {
            switch (GetTypeAffinity())
            {
                case TypeAffinity.Uninitialized:
                    {
                        value = null;
                        PreventNativeAccess();
                        return (persisted = true);
                    }
                case TypeAffinity.Int64:
                    {
                        value = GetInt64();
                        PreventNativeAccess();
                        return (persisted = true);
                    }
                case TypeAffinity.Double:
                    {
                        value = GetDouble();
                        PreventNativeAccess();
                        return (persisted = true);
                    }
                case TypeAffinity.Text:
                    {
                        value = GetString();
                        PreventNativeAccess();
                        return (persisted = true);
                    }
                case TypeAffinity.Blob:
                    {
                        value = GetBytes();
                        PreventNativeAccess();
                        return (persisted = true);
                    }
                case TypeAffinity.Null:
                    {
                        value = DBNull.Value;
                        PreventNativeAccess();
                        return (persisted = true);
                    }
                default:
                    {
                        return false;
                    }
            }
        }
        #endregion
    }
    #endregion

    ///////////////////////////////////////////////////////////////////////////

    #region SQLiteIndexConstraintOp Enumeration
    /// <summary>
    /// These are the allowed values for the operators that are part of a
    /// constraint term in the WHERE clause of a query that uses a virtual
    /// table.
    /// </summary>
    public enum SQLiteIndexConstraintOp : byte
    {
        /// <summary>
        /// This value represents the equality operator.
        /// </summary>
        EqualTo = 2,

        /// <summary>
        /// This value represents the greater than operator.
        /// </summary>
        GreaterThan = 4,

        /// <summary>
        /// This value represents the less than or equal to operator.
        /// </summary>
        LessThanOrEqualTo = 8,

        /// <summary>
        /// This value represents the less than operator.
        /// </summary>
        LessThan = 16,

        /// <summary>
        /// This value represents the greater than or equal to operator.
        /// </summary>
        GreaterThanOrEqualTo = 32,

        /// <summary>
        /// This value represents the MATCH operator.
        /// </summary>
        Match = 64,

        /// <summary>
        /// This value represents the LIKE operator.
        /// </summary>
        Like = 65,

        /// <summary>
        /// This value represents the GLOB operator.
        /// </summary>
        Glob = 66,

        /// <summary>
        /// This value represents the REGEXP operator.
        /// </summary>
        Regexp = 67,

        /// <summary>
        /// This value represents the inequality operator.
        /// </summary>
        NotEqualTo = 68,

        /// <summary>
        /// This value represents the IS NOT operator.
        /// </summary>
        IsNot = 69,

        /// <summary>
        /// This value represents the IS NOT NULL operator.
        /// </summary>
        IsNotNull = 70,

        /// <summary>
        /// This value represents the IS NULL operator.
        /// </summary>
        IsNull = 71,

        /// <summary>
        /// This value represents the IS operator.
        /// </summary>
        Is = 72
    }
    #endregion

    ///////////////////////////////////////////////////////////////////////////

    #region SQLiteIndexFlags Enumeration
    /// <summary>
    /// These are the allowed values for the index flags from the
    /// <see cref="ISQLiteManagedModule.BestIndex" /> method.
    /// </summary>
    [Flags()]
    public enum SQLiteIndexFlags
    {
        /// <summary>
        /// No special handling.  This is the default.
        /// </summary>
        None = 0x0,

        /// <summary>
        /// This value indicates that the scan of the index will visit at
        /// most one row.
        /// </summary>
        ScanUnique = 0x1
    }
    #endregion

    ///////////////////////////////////////////////////////////////////////////

    #region SQLiteIndexConstraint Helper Class
    /// <summary>
    /// This class represents the native sqlite3_index_constraint structure
    /// from the SQLite core library.
    /// </summary>
    public sealed class SQLiteIndexConstraint
    {
        #region Internal Constructors
        /// <summary>
        /// Constructs an instance of this class using the specified native
        /// sqlite3_index_constraint structure.
        /// </summary>
        /// <param name="constraint">
        /// The native sqlite3_index_constraint structure to use.
        /// </param>
        internal SQLiteIndexConstraint(
            UnsafeNativeMethods.sqlite3_index_constraint constraint
            )
            : this(constraint.iColumn, constraint.op, constraint.usable,
                   constraint.iTermOffset)
        {
            // do nothing.
        }
        #endregion

        //////////////////////////////////////////////////////////////////////

        #region Private Constructors
        /// <summary>
        /// Constructs an instance of this class using the specified field
        /// values.
        /// </summary>
        /// <param name="iColumn">
        /// Column on left-hand side of constraint.
        /// </param>
        /// <param name="op">
        /// Constraint operator (<see cref="SQLiteIndexConstraintOp" />).
        /// </param>
        /// <param name="usable">
        /// True if this constraint is usable.
        /// </param>
        /// <param name="iTermOffset">
        /// Used internally - <see cref="ISQLiteManagedModule.BestIndex" />
        /// should ignore.
        /// </param>
        private SQLiteIndexConstraint(
            int iColumn,
            SQLiteIndexConstraintOp op,
            byte usable,
            int iTermOffset
            )
        {
            this.iColumn = iColumn;
            this.op = op;
            this.usable = usable;
            this.iTermOffset = iTermOffset;
        }
        #endregion

        //////////////////////////////////////////////////////////////////////

        #region Public Fields
        /// <summary>
        /// Column on left-hand side of constraint.
        /// </summary>
        public int iColumn;

        //////////////////////////////////////////////////////////////////////

        /// <summary>
        /// Constraint operator (<see cref="SQLiteIndexConstraintOp" />).
        /// </summary>
        public SQLiteIndexConstraintOp op;

        //////////////////////////////////////////////////////////////////////

        /// <summary>
        /// True if this constraint is usable.
        /// </summary>
        public byte usable;

        //////////////////////////////////////////////////////////////////////

        /// <summary>
        /// Used internally - <see cref="ISQLiteManagedModule.BestIndex" />
        /// should ignore.
        /// </summary>
        public int iTermOffset;
        #endregion
    }
    #endregion

    ///////////////////////////////////////////////////////////////////////////

    #region SQLiteIndexOrderBy Helper Class
    /// <summary>
    /// This class represents the native sqlite3_index_orderby structure from
    /// the SQLite core library.
    /// </summary>
    public sealed class SQLiteIndexOrderBy
    {
        #region Internal Constructors
        /// <summary>
        /// Constructs an instance of this class using the specified native
        /// sqlite3_index_orderby structure.
        /// </summary>
        /// <param name="orderBy">
        /// The native sqlite3_index_orderby structure to use.
        /// </param>
        internal SQLiteIndexOrderBy(
            UnsafeNativeMethods.sqlite3_index_orderby orderBy
            )
            : this(orderBy.iColumn, orderBy.desc)
        {
            // do nothing.
        }
        #endregion

        //////////////////////////////////////////////////////////////////////

        #region Private Constructors
        /// <summary>
        /// Constructs an instance of this class using the specified field
        /// values.
        /// </summary>
        /// <param name="iColumn">
        /// Column number.
        /// </param>
        /// <param name="desc">
        /// True for DESC.  False for ASC.
        /// </param>
        private SQLiteIndexOrderBy(
            int iColumn,
            byte desc
            )
        {
            this.iColumn = iColumn;
            this.desc = desc;
        }
        #endregion

        //////////////////////////////////////////////////////////////////////

        #region Public Fields
        /// <summary>
        /// Column number.
        /// </summary>
        public int iColumn;

        //////////////////////////////////////////////////////////////////////

        /// <summary>
        /// True for DESC.  False for ASC.
        /// </summary>
        public byte desc;
        #endregion
    }
    #endregion

    ///////////////////////////////////////////////////////////////////////////

    #region SQLiteIndexConstraintUsage Helper Class
    /// <summary>
    /// This class represents the native sqlite3_index_constraint_usage
    /// structure from the SQLite core library.
    /// </summary>
    public sealed class SQLiteIndexConstraintUsage
    {
        #region Internal Constructors
        /// <summary>
        /// Constructs a default instance of this class.
        /// </summary>
        internal SQLiteIndexConstraintUsage()
        {
            // do nothing.
        }

        //////////////////////////////////////////////////////////////////////

        /// <summary>
        /// Constructs an instance of this class using the specified native
        /// sqlite3_index_constraint_usage structure.
        /// </summary>
        /// <param name="constraintUsage">
        /// The native sqlite3_index_constraint_usage structure to use.
        /// </param>
        internal SQLiteIndexConstraintUsage(
            UnsafeNativeMethods.sqlite3_index_constraint_usage constraintUsage
            )
            : this(constraintUsage.argvIndex, constraintUsage.omit)
        {
            // do nothing.
        }
        #endregion

        //////////////////////////////////////////////////////////////////////

        #region Private Constructors
        /// <summary>
        /// Constructs an instance of this class using the specified field
        /// values.
        /// </summary>
        /// <param name="argvIndex">
        /// If greater than 0, constraint is part of argv to xFilter.
        /// </param>
        /// <param name="omit">
        /// Do not code a test for this constraint.
        /// </param>
        private SQLiteIndexConstraintUsage(
            int argvIndex,
            byte omit
            )
        {
            this.argvIndex = argvIndex;
            this.omit = omit;
        }
        #endregion

        ///////////////////////////////////////////////////////////////////////

        #region Public Fields
        /// <summary>
        /// If greater than 0, constraint is part of argv to xFilter.
        /// </summary>
        public int argvIndex;

        ///////////////////////////////////////////////////////////////////////

        /// <summary>
        /// Do not code a test for this constraint.
        /// </summary>
        public byte omit;
        #endregion
    }
    #endregion

    ///////////////////////////////////////////////////////////////////////////

    #region SQLiteIndexInputs Helper Class
    /// <summary>
    /// This class represents the various inputs provided by the SQLite core
    /// library to the <see cref="ISQLiteManagedModule.BestIndex" /> method.
    /// </summary>
    public sealed class SQLiteIndexInputs
    {
        #region Internal Constructors
        /// <summary>
        /// Constructs an instance of this class.
        /// </summary>
        /// <param name="nConstraint">
        /// The number of <see cref="SQLiteIndexConstraint" /> instances to
        /// pre-allocate space for.
        /// </param>
        /// <param name="nOrderBy">
        /// The number of <see cref="SQLiteIndexOrderBy" /> instances to
        /// pre-allocate space for.
        /// </param>
        internal SQLiteIndexInputs(int nConstraint, int nOrderBy)
        {
            constraints = new SQLiteIndexConstraint[nConstraint];
            orderBys = new SQLiteIndexOrderBy[nOrderBy];
        }
        #endregion

        ///////////////////////////////////////////////////////////////////////

        #region Public Properties
        private SQLiteIndexConstraint[] constraints;
        /// <summary>
        /// An array of <see cref="SQLiteIndexConstraint" /> object instances,
        /// each containing information supplied by the SQLite core library.
        /// </summary>
        public SQLiteIndexConstraint[] Constraints
        {
            get { return constraints; }
        }

        ///////////////////////////////////////////////////////////////////////

        private SQLiteIndexOrderBy[] orderBys;
        /// <summary>
        /// An array of <see cref="SQLiteIndexOrderBy" /> object instances,
        /// each containing information supplied by the SQLite core library.
        /// </summary>
        public SQLiteIndexOrderBy[] OrderBys
        {
            get { return orderBys; }
        }
        #endregion
    }
    #endregion

    ///////////////////////////////////////////////////////////////////////////

    #region SQLiteIndexOutputs Helper Class
    /// <summary>
    /// This class represents the various outputs provided to the SQLite core
    /// library by the <see cref="ISQLiteManagedModule.BestIndex" /> method.
    /// </summary>
    public sealed class SQLiteIndexOutputs
    {
        #region Internal Constructors
        /// <summary>
        /// Constructs an instance of this class.
        /// </summary>
        /// <param name="nConstraint">
        /// The number of <see cref="SQLiteIndexConstraintUsage" /> instances
        /// to pre-allocate space for.
        /// </param>
        internal SQLiteIndexOutputs(int nConstraint)
        {
            constraintUsages = new SQLiteIndexConstraintUsage[nConstraint];

            //
            // BUGFIX: Create the [empty] constraint usages now so they can be
            //         used by the xBestIndex callback.
            //
            for (int iConstraint = 0; iConstraint < nConstraint; iConstraint++)
                constraintUsages[iConstraint] = new SQLiteIndexConstraintUsage();
        }
        #endregion

        ///////////////////////////////////////////////////////////////////////

        /// <summary>
        /// Determines if the native estimatedRows field can be used, based on
        /// the available version of the SQLite core library.
        /// </summary>
        /// <returns>
        /// Non-zero if the <see cref="EstimatedRows" /> property is supported
        /// by the SQLite core library.
        /// </returns>
        public bool CanUseEstimatedRows()
        {
            if (UnsafeNativeMethods.sqlite3_libversion_number() >= 3008002)
                return true;

            return false;
        }

        ///////////////////////////////////////////////////////////////////////

        /// <summary>
        /// Determines if the native flags field can be used, based on the
        /// available version of the SQLite core library.
        /// </summary>
        /// <returns>
        /// Non-zero if the <see cref="IndexFlags" /> property is supported by
        /// the SQLite core library.
        /// </returns>
        public bool CanUseIndexFlags()
        {
            if (UnsafeNativeMethods.sqlite3_libversion_number() >= 3009000)
                return true;

            return false;
        }

        ///////////////////////////////////////////////////////////////////////

        /// <summary>
        /// Determines if the native flags field can be used, based on the
        /// available version of the SQLite core library.
        /// </summary>
        /// <returns>
        /// Non-zero if the <see cref="ColumnsUsed" /> property is supported by
        /// the SQLite core library.
        /// </returns>
        public bool CanUseColumnsUsed()
        {
            if (UnsafeNativeMethods.sqlite3_libversion_number() >= 3010000)
                return true;

            return false;
        }

        ///////////////////////////////////////////////////////////////////////

        #region Public Properties
        private SQLiteIndexConstraintUsage[] constraintUsages;
        /// <summary>
        /// An array of <see cref="SQLiteIndexConstraintUsage" /> object
        /// instances, each containing information to be supplied to the SQLite
        /// core library.
        /// </summary>
        public SQLiteIndexConstraintUsage[] ConstraintUsages
        {
            get { return constraintUsages; }
        }

        ///////////////////////////////////////////////////////////////////////

        private int indexNumber;
        /// <summary>
        /// Number used to help identify the selected index.  This value will
        /// later be provided to the <see cref="ISQLiteManagedModule.Filter" />
        /// method.
        /// </summary>
        public int IndexNumber
        {
            get { return indexNumber; }
            set { indexNumber = value; }
        }

        ///////////////////////////////////////////////////////////////////////

        private string indexString;
        /// <summary>
        /// String used to help identify the selected index.  This value will
        /// later be provided to the <see cref="ISQLiteManagedModule.Filter" />
        /// method.
        /// </summary>
        public string IndexString
        {
            get { return indexString; }
            set { indexString = value; }
        }

        ///////////////////////////////////////////////////////////////////////

        private int needToFreeIndexString;
        /// <summary>
        /// Non-zero if the index string must be freed by the SQLite core
        /// library.
        /// </summary>
        public int NeedToFreeIndexString
        {
            get { return needToFreeIndexString; }
            set { needToFreeIndexString = value; }
        }

        ///////////////////////////////////////////////////////////////////////

        private int orderByConsumed;
        /// <summary>
        /// True if output is already ordered.
        /// </summary>
        public int OrderByConsumed
        {
            get { return orderByConsumed; }
            set { orderByConsumed = value; }
        }

        ///////////////////////////////////////////////////////////////////////

        private double? estimatedCost;
        /// <summary>
        /// Estimated cost of using this index.  Using a null value here
        /// indicates that a default estimated cost value should be used.
        /// </summary>
        public double? EstimatedCost
        {
            get { return estimatedCost; }
            set { estimatedCost = value; }
        }

        ///////////////////////////////////////////////////////////////////////

        private long? estimatedRows;
        /// <summary>
        /// Estimated number of rows returned.  Using a null value here
        /// indicates that a default estimated rows value should be used.
        /// This property has no effect if the SQLite core library is not at
        /// least version 3.8.2.
        /// </summary>
        public long? EstimatedRows
        {
            get { return estimatedRows; }
            set { estimatedRows = value; }
        }

        ///////////////////////////////////////////////////////////////////////

        private SQLiteIndexFlags? indexFlags;
        /// <summary>
        /// The flags that should be used with this index.  Using a null value
        /// here indicates that a default flags value should be used.  This
        /// property has no effect if the SQLite core library is not at least
        /// version 3.9.0.
        /// </summary>
        public SQLiteIndexFlags? IndexFlags
        {
            get { return indexFlags; }
            set { indexFlags = value; }
        }

        ///////////////////////////////////////////////////////////////////////

        private long? columnsUsed;
        /// <summary>
        /// <para>
        /// Indicates which columns of the virtual table may be required by the
        /// current scan.  Virtual table columns are numbered from zero in the
        /// order in which they appear within the CREATE TABLE statement passed
        /// to sqlite3_declare_vtab().  For the first 63 columns (columns 0-62),
        /// the corresponding bit is set within the bit mask if the column may
        /// be required by SQLite.  If the table has at least 64 columns and
        /// any column to the right of the first 63 is required, then bit 63 of
        /// colUsed is also set.  In other words, column iCol may be required
        /// if the expression
        /// </para>
        /// <para><code>
        /// (colUsed &amp; ((sqlite3_uint64)1 &lt;&lt; (iCol&gt;=63 ? 63 : iCol)))
        /// </code></para>
        /// <para>
        /// evaluates to non-zero.  Using a null value here indicates that a
        /// default flags value should be used.  This property has no effect if
        /// the SQLite core library is not at least version 3.10.0.
        /// </para>
        /// </summary>
        public long? ColumnsUsed
        {
            get { return columnsUsed; }
            set { columnsUsed = value; }
        }
        #endregion
    }
    #endregion

    ///////////////////////////////////////////////////////////////////////////

    #region SQLiteIndex Helper Class
    /// <summary>
    /// This class represents the various inputs and outputs used with the
    /// <see cref="ISQLiteManagedModule.BestIndex" /> method.
    /// </summary>
    public sealed class SQLiteIndex
    {
        #region Internal Constructors
        /// <summary>
        /// Constructs an instance of this class.
        /// </summary>
        /// <param name="nConstraint">
        /// The number of <see cref="SQLiteIndexConstraint" /> (and
        /// <see cref="SQLiteIndexConstraintUsage" />) instances to
        /// pre-allocate space for.
        /// </param>
        /// <param name="nOrderBy">
        /// The number of <see cref="SQLiteIndexOrderBy" /> instances to
        /// pre-allocate space for.
        /// </param>
        internal SQLiteIndex(
            int nConstraint,
            int nOrderBy
            )
        {
            inputs = new SQLiteIndexInputs(nConstraint, nOrderBy);
            outputs = new SQLiteIndexOutputs(nConstraint);
        }
        #endregion

        ///////////////////////////////////////////////////////////////////////

        #region Private Marshal Helper Methods (For Test Use Only)
        /// <summary>
        /// Attempts to determine the structure sizes needed to create and
        /// populate a native
        /// <see cref="UnsafeNativeMethods.sqlite3_index_info" />
        /// structure.
        /// </summary>
        /// <param name="sizeOfInfoType">
        /// The size of the native
        /// <see cref="UnsafeNativeMethods.sqlite3_index_info" />
        /// structure is stored here.
        /// </param>
        /// <param name="sizeOfConstraintType">
        /// The size of the native
        /// <see cref="UnsafeNativeMethods.sqlite3_index_constraint" />
        /// structure is stored here.
        /// </param>
        /// <param name="sizeOfOrderByType">
        /// The size of the native
        /// <see cref="UnsafeNativeMethods.sqlite3_index_orderby" />
        /// structure is stored here.
        /// </param>
        /// <param name="sizeOfConstraintUsageType">
        /// The size of the native
        /// <see cref="UnsafeNativeMethods.sqlite3_index_constraint_usage" />
        /// structure is stored here.
        /// </param>
        private static void SizeOfNative(
            out int sizeOfInfoType,
            out int sizeOfConstraintType,
            out int sizeOfOrderByType,
            out int sizeOfConstraintUsageType
            )
        {
            sizeOfInfoType = Marshal.SizeOf(typeof(
                UnsafeNativeMethods.sqlite3_index_info));

            sizeOfConstraintType = Marshal.SizeOf(typeof(
                UnsafeNativeMethods.sqlite3_index_constraint));

            sizeOfOrderByType = Marshal.SizeOf(typeof(
                UnsafeNativeMethods.sqlite3_index_orderby));

            sizeOfConstraintUsageType = Marshal.SizeOf(typeof(
                UnsafeNativeMethods.sqlite3_index_constraint_usage));
        }

        ///////////////////////////////////////////////////////////////////////

        /// <summary>
        /// Attempts to allocate and initialize a native
        /// <see cref="UnsafeNativeMethods.sqlite3_index_info" />
        /// structure.
        /// </summary>
        /// <param name="nConstraint">
        /// The number of <see cref="SQLiteIndexConstraint" /> instances to
        /// pre-allocate space for.
        /// </param>
        /// <param name="nOrderBy">
        /// The number of <see cref="SQLiteIndexOrderBy" /> instances to
        /// pre-allocate space for.
        /// </param>
        /// <returns>
        /// The newly allocated native
        /// <see cref="UnsafeNativeMethods.sqlite3_index_info" /> structure
        /// -OR- <see cref="IntPtr.Zero" /> if it could not be fully allocated.
        /// </returns>
        private static IntPtr AllocateAndInitializeNative(
            int nConstraint,
            int nOrderBy
            )
        {
            IntPtr pIndex = IntPtr.Zero;
            IntPtr pInfo = IntPtr.Zero;
            IntPtr pConstraint = IntPtr.Zero;
            IntPtr pOrderBy = IntPtr.Zero;
            IntPtr pConstraintUsage = IntPtr.Zero;

            try
            {
                int sizeOfInfoType;
                int sizeOfOrderByType;
                int sizeOfConstraintType;
                int sizeOfConstraintUsageType;

                SizeOfNative(out sizeOfInfoType, out sizeOfConstraintType,
                    out sizeOfOrderByType, out sizeOfConstraintUsageType);

                if ((sizeOfInfoType > 0) &&
                    (sizeOfConstraintType > 0) &&
                    (sizeOfOrderByType > 0) &&
                    (sizeOfConstraintUsageType > 0))
                {
                    pInfo = SQLiteMemory.Allocate(sizeOfInfoType);

                    pConstraint = SQLiteMemory.Allocate(
                        sizeOfConstraintType * nConstraint);

                    pOrderBy = SQLiteMemory.Allocate(
                        sizeOfOrderByType * nOrderBy);

                    pConstraintUsage = SQLiteMemory.Allocate(
                        sizeOfConstraintUsageType * nConstraint);

                    if ((pInfo != IntPtr.Zero) &&
                        (pConstraint != IntPtr.Zero) &&
                        (pOrderBy != IntPtr.Zero) &&
                        (pConstraintUsage != IntPtr.Zero))
                    {
                        int offset = 0;

                        SQLiteMarshal.WriteInt32(
                            pInfo, offset, nConstraint);

                        offset = SQLiteMarshal.NextOffsetOf(
                            offset, sizeof(int), IntPtr.Size);

                        SQLiteMarshal.WriteIntPtr(
                            pInfo, offset, pConstraint);

                        offset = SQLiteMarshal.NextOffsetOf(
                            offset, IntPtr.Size, sizeof(int));

                        SQLiteMarshal.WriteInt32(
                            pInfo, offset, nOrderBy);

                        offset = SQLiteMarshal.NextOffsetOf(
                            offset, sizeof(int), IntPtr.Size);

                        SQLiteMarshal.WriteIntPtr(
                            pInfo, offset, pOrderBy);

                        offset = SQLiteMarshal.NextOffsetOf(
                            offset, IntPtr.Size, IntPtr.Size);

                        SQLiteMarshal.WriteIntPtr(
                            pInfo, offset, pConstraintUsage);

                        pIndex = pInfo; /* NOTE: Success. */
                    }
                }
            }
            finally
            {
                if (pIndex == IntPtr.Zero) /* NOTE: Failure? */
                {
                    if (pConstraintUsage != IntPtr.Zero)
                    {
                        SQLiteMemory.Free(pConstraintUsage);
                        pConstraintUsage = IntPtr.Zero;
                    }

                    if (pOrderBy != IntPtr.Zero)
                    {
                        SQLiteMemory.Free(pOrderBy);
                        pOrderBy = IntPtr.Zero;
                    }

                    if (pConstraint != IntPtr.Zero)
                    {
                        SQLiteMemory.Free(pConstraint);
                        pConstraint = IntPtr.Zero;
                    }

                    if (pInfo != IntPtr.Zero)
                    {
                        SQLiteMemory.Free(pInfo);
                        pInfo = IntPtr.Zero;
                    }
                }
            }

            return pIndex;
        }

        ///////////////////////////////////////////////////////////////////////

        /// <summary>
        /// Frees all the memory associated with a native
        /// <see cref="UnsafeNativeMethods.sqlite3_index_info" />
        /// structure.
        /// </summary>
        /// <param name="pIndex">
        /// The native pointer to the native sqlite3_index_info structure to
        /// free.
        /// </param>
        private static void FreeNative(
            IntPtr pIndex
            )
        {
            if (pIndex == IntPtr.Zero)
                return;

            int offset = 0;

            offset = SQLiteMarshal.NextOffsetOf(
                offset, sizeof(int), IntPtr.Size);

            IntPtr pConstraint = SQLiteMarshal.ReadIntPtr(
                pIndex, offset);

            int constraintOffset = offset;

            offset = SQLiteMarshal.NextOffsetOf(
                offset, IntPtr.Size, sizeof(int));

            offset = SQLiteMarshal.NextOffsetOf(
                offset, sizeof(int), IntPtr.Size);

            IntPtr pOrderBy = SQLiteMarshal.ReadIntPtr(
                pIndex, offset);

            int orderByOffset = offset;

            offset = SQLiteMarshal.NextOffsetOf(
                offset, IntPtr.Size, IntPtr.Size);

            IntPtr pConstraintUsage = SQLiteMarshal.ReadIntPtr(
                pIndex, offset);

            int constraintUsageOffset = offset;

            if (pConstraintUsage != IntPtr.Zero)
            {
                SQLiteMemory.Free(pConstraintUsage);
                pConstraintUsage = IntPtr.Zero;

                SQLiteMarshal.WriteIntPtr(
                    pIndex, constraintUsageOffset, pConstraintUsage);
            }

            if (pOrderBy != IntPtr.Zero)
            {
                SQLiteMemory.Free(pOrderBy);
                pOrderBy = IntPtr.Zero;

                SQLiteMarshal.WriteIntPtr(
                    pIndex, orderByOffset, pOrderBy);
            }

            if (pConstraint != IntPtr.Zero)
            {
                SQLiteMemory.Free(pConstraint);
                pConstraint = IntPtr.Zero;

                SQLiteMarshal.WriteIntPtr(
                    pIndex, constraintOffset, pConstraint);
            }

            if (pIndex != IntPtr.Zero)
            {
                SQLiteMemory.Free(pIndex);
                pIndex = IntPtr.Zero;
            }
        }
        #endregion

        ///////////////////////////////////////////////////////////////////////

        #region Internal Marshal Helper Methods
        /// <summary>
        /// Converts a native pointer to a native sqlite3_index_info structure
        /// into a new <see cref="SQLiteIndex" /> object instance.
        /// </summary>
        /// <param name="pIndex">
        /// The native pointer to the native sqlite3_index_info structure to
        /// convert.
        /// </param>
        /// <param name="includeOutput">
        /// Non-zero to include fields from the outputs portion of the native
        /// structure; otherwise, the "output" fields will not be read.
        /// </param>
        /// <param name="index">
        /// Upon success, this parameter will be modified to contain the newly
        /// created <see cref="SQLiteIndex" /> object instance.
        /// </param>
        internal static void FromIntPtr(
            IntPtr pIndex,
            bool includeOutput,
            ref SQLiteIndex index
            )
        {
            if (pIndex == IntPtr.Zero)
                return;

            int offset = 0;

            int nConstraint = SQLiteMarshal.ReadInt32(
                pIndex, offset);

            offset = SQLiteMarshal.NextOffsetOf(
                offset, sizeof(int), IntPtr.Size);

            IntPtr pConstraint = SQLiteMarshal.ReadIntPtr(
                pIndex, offset);

            offset = SQLiteMarshal.NextOffsetOf(
                offset, IntPtr.Size, sizeof(int));

            int nOrderBy = SQLiteMarshal.ReadInt32(
                pIndex, offset);

            offset = SQLiteMarshal.NextOffsetOf(
                offset, sizeof(int), IntPtr.Size);

            IntPtr pOrderBy = SQLiteMarshal.ReadIntPtr(
                pIndex, offset);

            IntPtr pConstraintUsage = IntPtr.Zero;

            if (includeOutput)
            {
                offset = SQLiteMarshal.NextOffsetOf(
                    offset, IntPtr.Size, IntPtr.Size);

                pConstraintUsage = SQLiteMarshal.ReadIntPtr(
                    pIndex, offset);
            }

            index = new SQLiteIndex(nConstraint, nOrderBy);
            SQLiteIndexInputs inputs = index.Inputs;

            if (inputs == null)
                return;

            SQLiteIndexConstraint[] constraints = inputs.Constraints;

            if (constraints == null)
                return;

            SQLiteIndexOrderBy[] orderBys = inputs.OrderBys;

            if (orderBys == null)
                return;

            Type constraintType = typeof(
                UnsafeNativeMethods.sqlite3_index_constraint);

            int sizeOfConstraintType = Marshal.SizeOf(
                constraintType);

            for (int iConstraint = 0; iConstraint < nConstraint; iConstraint++)
            {
                IntPtr pOffset = SQLiteMarshal.IntPtrForOffset(
                    pConstraint, iConstraint * sizeOfConstraintType);

                UnsafeNativeMethods.sqlite3_index_constraint constraint =
                    (UnsafeNativeMethods.sqlite3_index_constraint)
                        Marshal.PtrToStructure(pOffset, constraintType);

                constraints[iConstraint] = new SQLiteIndexConstraint(
                    constraint);
            }

            Type orderByType = typeof(
                UnsafeNativeMethods.sqlite3_index_orderby);

            int sizeOfOrderByType = Marshal.SizeOf(orderByType);

            for (int iOrderBy = 0; iOrderBy < nOrderBy; iOrderBy++)
            {
                IntPtr pOffset = SQLiteMarshal.IntPtrForOffset(
                    pOrderBy, iOrderBy * sizeOfOrderByType);

                UnsafeNativeMethods.sqlite3_index_orderby orderBy =
                    (UnsafeNativeMethods.sqlite3_index_orderby)
                        Marshal.PtrToStructure(pOffset, orderByType);

                orderBys[iOrderBy] = new SQLiteIndexOrderBy(orderBy);
            }

            if (includeOutput)
            {
                SQLiteIndexOutputs outputs = index.Outputs;

                if (outputs == null)
                    return;

                SQLiteIndexConstraintUsage[] constraintUsages =
                    outputs.ConstraintUsages;

                if (constraintUsages == null)
                    return;

                Type constraintUsageType = typeof(
                    UnsafeNativeMethods.sqlite3_index_constraint_usage);

                int sizeOfConstraintUsageType = Marshal.SizeOf(
                    constraintUsageType);

                for (int iConstraint = 0; iConstraint < nConstraint; iConstraint++)
                {
                    IntPtr pOffset = SQLiteMarshal.IntPtrForOffset(
                        pConstraintUsage, iConstraint * sizeOfConstraintUsageType);

                    UnsafeNativeMethods.sqlite3_index_constraint_usage constraintUsage =
                        (UnsafeNativeMethods.sqlite3_index_constraint_usage)
                            Marshal.PtrToStructure(pOffset, constraintUsageType);

                    constraintUsages[iConstraint] = new SQLiteIndexConstraintUsage(
                        constraintUsage);
                }

                offset = SQLiteMarshal.NextOffsetOf(
                    offset, IntPtr.Size, sizeof(int));

                outputs.IndexNumber = SQLiteMarshal.ReadInt32(
                    pIndex, offset);

                offset = SQLiteMarshal.NextOffsetOf(
                    offset, sizeof(int), IntPtr.Size);

                outputs.IndexString = SQLiteString.StringFromUtf8IntPtr(
                    SQLiteMarshal.ReadIntPtr(pIndex, offset));

                offset = SQLiteMarshal.NextOffsetOf(
                    offset, IntPtr.Size, sizeof(int));

                outputs.NeedToFreeIndexString = SQLiteMarshal.ReadInt32(
                    pIndex, offset);

                offset = SQLiteMarshal.NextOffsetOf(
                    offset, sizeof(int), sizeof(int));

                outputs.OrderByConsumed = SQLiteMarshal.ReadInt32(
                    pIndex, offset);

                offset = SQLiteMarshal.NextOffsetOf(
                    offset, sizeof(int), sizeof(double));

                outputs.EstimatedCost = SQLiteMarshal.ReadDouble(
                    pIndex, offset);

                offset = SQLiteMarshal.NextOffsetOf(
                    offset, sizeof(double), sizeof(long));

                if (outputs.CanUseEstimatedRows())
                {
                    outputs.EstimatedRows = SQLiteMarshal.ReadInt64(
                        pIndex, offset);
                }

                offset = SQLiteMarshal.NextOffsetOf(
                    offset, sizeof(long), sizeof(int));

                if (outputs.CanUseIndexFlags())
                {
                    outputs.IndexFlags = (SQLiteIndexFlags)
                        SQLiteMarshal.ReadInt32(pIndex, offset);
                }

                offset = SQLiteMarshal.NextOffsetOf(
                    offset, sizeof(int), sizeof(long));

                if (outputs.CanUseColumnsUsed())
                {
                    outputs.ColumnsUsed = SQLiteMarshal.ReadInt64(
                        pIndex, offset);
                }
            }
        }

        ///////////////////////////////////////////////////////////////////////

        /// <summary>
        /// Populates the outputs of a pre-allocated native sqlite3_index_info
        /// structure using an existing <see cref="SQLiteIndex" /> object
        /// instance.
        /// </summary>
        /// <param name="index">
        /// The existing <see cref="SQLiteIndex" /> object instance containing
        /// the output data to use.
        /// </param>
        /// <param name="pIndex">
        /// The native pointer to the pre-allocated native sqlite3_index_info
        /// structure.
        /// </param>
        /// <param name="includeInput">
        /// Non-zero to include fields from the inputs portion of the native
        /// structure; otherwise, the "input" fields will not be written.
        /// </param>
        internal static void ToIntPtr(
            SQLiteIndex index,
            IntPtr pIndex,
            bool includeInput
            )
        {
            if (index == null)
                return;

            SQLiteIndexOutputs outputs = index.Outputs;

            if (outputs == null)
                return;

            SQLiteIndexConstraintUsage[] constraintUsages =
                outputs.ConstraintUsages;

            if (constraintUsages == null)
                return;

            SQLiteIndexInputs inputs = null;
            SQLiteIndexConstraint[] constraints = null;
            SQLiteIndexOrderBy[] orderBys = null;

            if (includeInput)
            {
                inputs = index.Inputs;

                if (inputs == null)
                    return;

                constraints = inputs.Constraints;

                if (constraints == null)
                    return;

                orderBys = inputs.OrderBys;

                if (orderBys == null)
                    return;
            }

            if (pIndex == IntPtr.Zero)
                return;

            int offset = 0;

            int nConstraint = SQLiteMarshal.ReadInt32(pIndex, offset);

            if (includeInput && (nConstraint != constraints.Length))
                return;

            if (nConstraint != constraintUsages.Length)
                return;

            offset = SQLiteMarshal.NextOffsetOf(
                offset, sizeof(int), IntPtr.Size);

            if (includeInput)
            {
                IntPtr pConstraint = SQLiteMarshal.ReadIntPtr(
                    pIndex, offset);

                int sizeOfConstraintType = Marshal.SizeOf(typeof(
                    UnsafeNativeMethods.sqlite3_index_constraint));

                for (int iConstraint = 0; iConstraint < nConstraint; iConstraint++)
                {
                    UnsafeNativeMethods.sqlite3_index_constraint constraint =
                        new UnsafeNativeMethods.sqlite3_index_constraint(
                            constraints[iConstraint]);

                    Marshal.StructureToPtr(
                        constraint, SQLiteMarshal.IntPtrForOffset(
                        pConstraint, iConstraint * sizeOfConstraintType),
                        false);
                }
            }

            offset = SQLiteMarshal.NextOffsetOf(
                offset, IntPtr.Size, sizeof(int));

            int nOrderBy = includeInput ?
                SQLiteMarshal.ReadInt32(pIndex, offset) : 0;

            if (includeInput && (nOrderBy != orderBys.Length))
                return;

            offset = SQLiteMarshal.NextOffsetOf(
                offset, sizeof(int), IntPtr.Size);

            if (includeInput)
            {
                IntPtr pOrderBy = SQLiteMarshal.ReadIntPtr(pIndex, offset);

                int sizeOfOrderByType = Marshal.SizeOf(typeof(
                    UnsafeNativeMethods.sqlite3_index_orderby));

                for (int iOrderBy = 0; iOrderBy < nOrderBy; iOrderBy++)
                {
                    UnsafeNativeMethods.sqlite3_index_orderby orderBy =
                        new UnsafeNativeMethods.sqlite3_index_orderby(
                            orderBys[iOrderBy]);

                    Marshal.StructureToPtr(
                        orderBy, SQLiteMarshal.IntPtrForOffset(
                        pOrderBy, iOrderBy * sizeOfOrderByType),
                        false);
                }
            }

            offset = SQLiteMarshal.NextOffsetOf(
                offset, IntPtr.Size, IntPtr.Size);

            IntPtr pConstraintUsage = SQLiteMarshal.ReadIntPtr(
                pIndex, offset);

            int sizeOfConstraintUsageType = Marshal.SizeOf(typeof(
                UnsafeNativeMethods.sqlite3_index_constraint_usage));

            for (int iConstraint = 0; iConstraint < nConstraint; iConstraint++)
            {
                UnsafeNativeMethods.sqlite3_index_constraint_usage constraintUsage =
                    new UnsafeNativeMethods.sqlite3_index_constraint_usage(
                        constraintUsages[iConstraint]);

                Marshal.StructureToPtr(
                    constraintUsage, SQLiteMarshal.IntPtrForOffset(
                    pConstraintUsage, iConstraint * sizeOfConstraintUsageType),
                    false);
            }

            offset = SQLiteMarshal.NextOffsetOf(
                offset, IntPtr.Size, sizeof(int));

            SQLiteMarshal.WriteInt32(pIndex, offset,
                outputs.IndexNumber);

            offset = SQLiteMarshal.NextOffsetOf(
                offset, sizeof(int), IntPtr.Size);

            SQLiteMarshal.WriteIntPtr(pIndex, offset,
                SQLiteString.Utf8IntPtrFromString(outputs.IndexString));

            offset = SQLiteMarshal.NextOffsetOf(
                offset, IntPtr.Size, sizeof(int));

            //
            // NOTE: We just allocated the IndexString field; therefore, we
            //       need to set make sure the NeedToFreeIndexString field
            //       is non-zero; however, we are not picky about the exact
            //       value.
            //
            int needToFreeIndexString = outputs.NeedToFreeIndexString != 0 ?
                outputs.NeedToFreeIndexString : 1;

            SQLiteMarshal.WriteInt32(pIndex, offset,
                needToFreeIndexString);

            offset = SQLiteMarshal.NextOffsetOf(
                offset, sizeof(int), sizeof(int));

            SQLiteMarshal.WriteInt32(pIndex, offset,
                outputs.OrderByConsumed);

            offset = SQLiteMarshal.NextOffsetOf(
                offset, sizeof(int), sizeof(double));

            if (outputs.EstimatedCost.HasValue)
            {
                SQLiteMarshal.WriteDouble(pIndex, offset,
                    outputs.EstimatedCost.GetValueOrDefault());
            }

            offset = SQLiteMarshal.NextOffsetOf(
                offset, sizeof(double), sizeof(long));

            if (outputs.CanUseEstimatedRows() &&
                outputs.EstimatedRows.HasValue)
            {
                SQLiteMarshal.WriteInt64(pIndex, offset,
                    outputs.EstimatedRows.GetValueOrDefault());
            }

            offset = SQLiteMarshal.NextOffsetOf(
                offset, sizeof(long), sizeof(int));

            if (outputs.CanUseIndexFlags() &&
                outputs.IndexFlags.HasValue)
            {
                SQLiteMarshal.WriteInt32(pIndex, offset,
                   (int)outputs.IndexFlags.GetValueOrDefault());
            }

            offset = SQLiteMarshal.NextOffsetOf(
                offset, sizeof(int), sizeof(long));

            if (outputs.CanUseColumnsUsed() &&
                outputs.ColumnsUsed.HasValue)
            {
                SQLiteMarshal.WriteInt64(pIndex, offset,
                    outputs.ColumnsUsed.GetValueOrDefault());
            }
        }
        #endregion

        ///////////////////////////////////////////////////////////////////////

        #region Public Properties
        private SQLiteIndexInputs inputs;
        /// <summary>
        /// The <see cref="SQLiteIndexInputs" /> object instance containing
        /// the inputs to the <see cref="ISQLiteManagedModule.BestIndex" />
        /// method.
        /// </summary>
        public SQLiteIndexInputs Inputs
        {
            get { return inputs; }
        }

        ///////////////////////////////////////////////////////////////////////

        private SQLiteIndexOutputs outputs;
        /// <summary>
        /// The <see cref="SQLiteIndexOutputs" /> object instance containing
        /// the outputs from the <see cref="ISQLiteManagedModule.BestIndex" />
        /// method.
        /// </summary>
        public SQLiteIndexOutputs Outputs
        {
            get { return outputs; }
        }
        #endregion
    }
    #endregion

    ///////////////////////////////////////////////////////////////////////////

    #region SQLiteVirtualTable Base Class
    /// <summary>
    /// This class represents a managed virtual table implementation.  It is
    /// not sealed and should be used as the base class for any user-defined
    /// virtual table classes implemented in managed code.
    /// </summary>
    public class SQLiteVirtualTable :
            ISQLiteNativeHandle, IDisposable /* NOT SEALED */
    {
        #region Private Constants
        /// <summary>
        /// The index within the array of strings provided to the
        /// <see cref="ISQLiteManagedModule.Create" /> and
        /// <see cref="ISQLiteManagedModule.Connect" /> methods containing the
        /// name of the module implementing this virtual table.
        /// </summary>
        private const int ModuleNameIndex = 0;

        ///////////////////////////////////////////////////////////////////////

        /// <summary>
        /// The index within the array of strings provided to the
        /// <see cref="ISQLiteManagedModule.Create" /> and
        /// <see cref="ISQLiteManagedModule.Connect" /> methods containing the
        /// name of the database containing this virtual table.
        /// </summary>
        private const int DatabaseNameIndex = 1;

        ///////////////////////////////////////////////////////////////////////

        /// <summary>
        /// The index within the array of strings provided to the
        /// <see cref="ISQLiteManagedModule.Create" /> and
        /// <see cref="ISQLiteManagedModule.Connect" /> methods containing the
        /// name of the virtual table.
        /// </summary>
        private const int TableNameIndex = 2;
        #endregion

        ///////////////////////////////////////////////////////////////////////

        #region Public Constructors
        /// <summary>
        /// Constructs an instance of this class.
        /// </summary>
        /// <param name="arguments">
        /// The original array of strings provided to the
        /// <see cref="ISQLiteManagedModule.Create" /> and
        /// <see cref="ISQLiteManagedModule.Connect" /> methods.
        /// </param>
        public SQLiteVirtualTable(
            string[] arguments
            )
        {
            this.arguments = arguments;
        }
        #endregion

        ///////////////////////////////////////////////////////////////////////

        #region Public Properties
        private string[] arguments;
        /// <summary>
        /// The original array of strings provided to the
        /// <see cref="ISQLiteManagedModule.Create" /> and
        /// <see cref="ISQLiteManagedModule.Connect" /> methods.
        /// </summary>
        public virtual string[] Arguments
        {
            get { CheckDisposed(); return arguments; }
        }

        ///////////////////////////////////////////////////////////////////////

        /// <summary>
        /// The name of the module implementing this virtual table.
        /// </summary>
        public virtual string ModuleName
        {
            get
            {
                CheckDisposed();

                string[] arguments = Arguments;

                if ((arguments != null) &&
                    (arguments.Length > ModuleNameIndex))
                {
                    return arguments[ModuleNameIndex];
                }
                else
                {
                    return null;
                }
            }
        }

        ///////////////////////////////////////////////////////////////////////

        /// <summary>
        /// The name of the database containing this virtual table.
        /// </summary>
        public virtual string DatabaseName
        {
            get
            {
                CheckDisposed();

                string[] arguments = Arguments;

                if ((arguments != null) &&
                    (arguments.Length > DatabaseNameIndex))
                {
                    return arguments[DatabaseNameIndex];
                }
                else
                {
                    return null;
                }
            }
        }

        ///////////////////////////////////////////////////////////////////////

        /// <summary>
        /// The name of the virtual table.
        /// </summary>
        public virtual string TableName
        {
            get
            {
                CheckDisposed();

                string[] arguments = Arguments;

                if ((arguments != null) &&
                    (arguments.Length > TableNameIndex))
                {
                    return arguments[TableNameIndex];
                }
                else
                {
                    return null;
                }
            }
        }

        ///////////////////////////////////////////////////////////////////////

        private SQLiteIndex index;
        /// <summary>
        /// The <see cref="SQLiteIndex" /> object instance containing all the
        /// data for the inputs and outputs relating to the most recent index
        /// selection.
        /// </summary>
        public virtual SQLiteIndex Index
        {
            get { CheckDisposed(); return index; }
        }
        #endregion

        ///////////////////////////////////////////////////////////////////////

        #region Public Methods
        /// <summary>
        /// This method should normally be used by the
        /// <see cref="ISQLiteManagedModule.BestIndex" /> method in order to
        /// perform index selection based on the constraints provided by the
        /// SQLite core library.
        /// </summary>
        /// <param name="index">
        /// The <see cref="SQLiteIndex" /> object instance containing all the
        /// data for the inputs and outputs relating to index selection.
        /// </param>
        /// <returns>
        /// Non-zero upon success.
        /// </returns>
        public virtual bool BestIndex(
            SQLiteIndex index
            )
        {
            CheckDisposed();

            this.index = index;

            return true;
        }

        ///////////////////////////////////////////////////////////////////////

        /// <summary>
        /// Attempts to record the renaming of the virtual table associated
        /// with this object instance.
        /// </summary>
        /// <param name="name">
        /// The new name for the virtual table.
        /// </param>
        /// <returns>
        /// Non-zero upon success.
        /// </returns>
        public virtual bool Rename(
            string name
            )
        {
            CheckDisposed();

            if ((arguments != null) &&
                (arguments.Length > TableNameIndex))
            {
                arguments[TableNameIndex] = name;
                return true;
            }

            return false;
        }
        #endregion

        ///////////////////////////////////////////////////////////////////////

        #region ISQLiteNativeHandle Members
        private IntPtr nativeHandle;
        /// <summary>
        /// Returns the underlying SQLite native handle associated with this
        /// object instance.
        /// </summary>
        public virtual IntPtr NativeHandle
        {
            get { CheckDisposed(); return nativeHandle; }
            internal set { nativeHandle = value; }
        }
        #endregion

        ///////////////////////////////////////////////////////////////////////

        #region IDisposable Members
        /// <summary>
        /// Disposes of this object instance.
        /// </summary>
        public void Dispose()
        {
            Dispose(true);
            GC.SuppressFinalize(this);
        }
        #endregion

        ///////////////////////////////////////////////////////////////////////

        #region IDisposable "Pattern" Members
        private bool disposed;
        /// <summary>
        /// Throws an <see cref="ObjectDisposedException" /> if this object
        /// instance has been disposed.
        /// </summary>
        private void CheckDisposed() /* throw */
        {
#if THROW_ON_DISPOSED
            if (disposed)
            {
                throw new ObjectDisposedException(
                    typeof(SQLiteVirtualTable).Name);
            }
#endif
        }

        ///////////////////////////////////////////////////////////////////////

        /// <summary>
        /// Disposes of this object instance.
        /// </summary>
        /// <param name="disposing">
        /// Non-zero if this method is being called from the
        /// <see cref="Dispose()" /> method.  Zero if this method is being called
        /// from the finalizer.
        /// </param>
        protected virtual void Dispose(bool disposing)
        {
            if (!disposed)
            {
                //if (disposing)
                //{
                //    ////////////////////////////////////
                //    // dispose managed resources here...
                //    ////////////////////////////////////
                //}

                //////////////////////////////////////
                // release unmanaged resources here...
                //////////////////////////////////////

                disposed = true;
            }
        }
        #endregion

        ///////////////////////////////////////////////////////////////////////

        #region Destructor
        /// <summary>
        /// Finalizes this object instance.
        /// </summary>
        ~SQLiteVirtualTable()
        {
            Dispose(false);
        }
        #endregion
    }
    #endregion

    ///////////////////////////////////////////////////////////////////////////

    #region SQLiteVirtualTableCursor Base Class
    /// <summary>
    /// This class represents a managed virtual table cursor implementation.
    /// It is not sealed and should be used as the base class for any
    /// user-defined virtual table cursor classes implemented in managed code.
    /// </summary>
    public class SQLiteVirtualTableCursor :
            ISQLiteNativeHandle, IDisposable /* NOT SEALED */
    {
        #region Protected Constants
        /// <summary>
        /// This value represents an invalid integer row sequence number.
        /// </summary>
        protected static readonly int InvalidRowIndex = 0;
        #endregion

        ///////////////////////////////////////////////////////////////////////

        #region Private Data
        /// <summary>
        /// The field holds the integer row sequence number for the current row
        /// pointed to by this cursor object instance.
        /// </summary>
        private int rowIndex;
        #endregion

        ///////////////////////////////////////////////////////////////////////

        #region Public Constructors
        /// <summary>
        /// Constructs an instance of this class.
        /// </summary>
        /// <param name="table">
        /// The <see cref="SQLiteVirtualTable" /> object instance associated
        /// with this object instance.
        /// </param>
        public SQLiteVirtualTableCursor(
            SQLiteVirtualTable table
            )
            : this()
        {
            this.table = table;
        }
        #endregion

        ///////////////////////////////////////////////////////////////////////

        #region Private Constructors
        /// <summary>
        /// Constructs an instance of this class.
        /// </summary>
        private SQLiteVirtualTableCursor()
        {
            rowIndex = InvalidRowIndex;
        }
        #endregion

        ///////////////////////////////////////////////////////////////////////

        #region Public Properties
        private SQLiteVirtualTable table;
        /// <summary>
        /// The <see cref="SQLiteVirtualTable" /> object instance associated
        /// with this object instance.
        /// </summary>
        public virtual SQLiteVirtualTable Table
        {
            get { CheckDisposed(); return table; }
        }

        ///////////////////////////////////////////////////////////////////////

        private int indexNumber;
        /// <summary>
        /// Number used to help identify the selected index.  This value will
        /// be set via the <see cref="Filter" /> method.
        /// </summary>
        public virtual int IndexNumber
        {
            get { CheckDisposed(); return indexNumber; }
        }

        ///////////////////////////////////////////////////////////////////////

        private string indexString;
        /// <summary>
        /// String used to help identify the selected index.  This value will
        /// be set via the <see cref="Filter" /> method.
        /// </summary>
        public virtual string IndexString
        {
            get { CheckDisposed(); return indexString; }
        }

        ///////////////////////////////////////////////////////////////////////

        private SQLiteValue[] values;
        /// <summary>
        /// The values used to filter the rows returned via this cursor object
        /// instance.  This value will be set via the <see cref="Filter" />
        /// method.
        /// </summary>
        public virtual SQLiteValue[] Values
        {
            get { CheckDisposed(); return values; }
        }
        #endregion

        ///////////////////////////////////////////////////////////////////////

        #region Protected Methods
        /// <summary>
        /// Attempts to persist the specified <see cref="SQLiteValue" /> object
        /// instances in order to make them available after the
        /// <see cref="ISQLiteManagedModule.Filter" /> method returns.
        /// </summary>
        /// <param name="values">
        /// The array of <see cref="SQLiteValue" /> object instances to be
        /// persisted.
        /// </param>
        /// <returns>
        /// The number of <see cref="SQLiteValue" /> object instances that were
        /// successfully persisted.
        /// </returns>
        protected virtual int TryPersistValues(
            SQLiteValue[] values
            )
        {
            int result = 0;

            if (values != null)
            {
                foreach (SQLiteValue value in values)
                {
                    if (value == null)
                        continue;

                    if (value.Persist())
                        result++;
                }
            }

            return result;
        }
        #endregion

        ///////////////////////////////////////////////////////////////////////

        #region Public Methods
        /// <summary>
        /// This method should normally be used by the
        /// <see cref="ISQLiteManagedModule.Filter" /> method in order to
        /// perform filtering of the result rows and/or to record the filtering
        /// criteria provided by the SQLite core library.
        /// </summary>
        /// <param name="indexNumber">
        /// Number used to help identify the selected index.
        /// </param>
        /// <param name="indexString">
        /// String used to help identify the selected index.
        /// </param>
        /// <param name="values">
        /// The values corresponding to each column in the selected index.
        /// </param>
        public virtual void Filter(
            int indexNumber,
            string indexString,
            SQLiteValue[] values
            )
        {
            CheckDisposed();

            if ((values != null) &&
                (TryPersistValues(values) != values.Length))
            {
                throw new SQLiteException(
                    "failed to persist one or more values");
            }

            this.indexNumber = indexNumber;
            this.indexString = indexString;
            this.values = values;
        }

        ///////////////////////////////////////////////////////////////////////

        /// <summary>
        /// Determines the integer row sequence number for the current row.
        /// </summary>
        /// <returns>
        /// The integer row sequence number for the current row -OR- zero if
        /// it cannot be determined.
        /// </returns>
        public virtual int GetRowIndex()
        {
            return rowIndex;
        }

        ///////////////////////////////////////////////////////////////////////

        /// <summary>
        /// Adjusts the integer row sequence number so that it refers to the
        /// next row.
        /// </summary>
        public virtual void NextRowIndex()
        {
            rowIndex++;
        }
        #endregion

        ///////////////////////////////////////////////////////////////////////

        #region ISQLiteNativeHandle Members
        private IntPtr nativeHandle;
        /// <summary>
        /// Returns the underlying SQLite native handle associated with this
        /// object instance.
        /// </summary>
        public virtual IntPtr NativeHandle
        {
            get { CheckDisposed(); return nativeHandle; }
            internal set { nativeHandle = value; }
        }
        #endregion

        ///////////////////////////////////////////////////////////////////////

        #region IDisposable Members
        /// <summary>
        /// Disposes of this object instance.
        /// </summary>
        public void Dispose()
        {
            Dispose(true);
            GC.SuppressFinalize(this);
        }
        #endregion

        ///////////////////////////////////////////////////////////////////////

        #region IDisposable "Pattern" Members
        private bool disposed;
        /// <summary>
        /// Throws an <see cref="ObjectDisposedException" /> if this object
        /// instance has been disposed.
        /// </summary>
        private void CheckDisposed() /* throw */
        {
#if THROW_ON_DISPOSED
            if (disposed)
            {
                throw new ObjectDisposedException(
                    typeof(SQLiteVirtualTableCursor).Name);
            }
#endif
        }

        ///////////////////////////////////////////////////////////////////////

        /// <summary>
        /// Disposes of this object instance.
        /// </summary>
        /// <param name="disposing">
        /// Non-zero if this method is being called from the
        /// <see cref="Dispose()" /> method.  Zero if this method is being called
        /// from the finalizer.
        /// </param>
        protected virtual void Dispose(bool disposing)
        {
            if (!disposed)
            {
                //if (disposing)
                //{
                //    ////////////////////////////////////
                //    // dispose managed resources here...
                //    ////////////////////////////////////
                //}

                //////////////////////////////////////
                // release unmanaged resources here...
                //////////////////////////////////////

                disposed = true;
            }
        }
        #endregion

        ///////////////////////////////////////////////////////////////////////

        #region Destructor
        /// <summary>
        /// Finalizes this object instance.
        /// </summary>
        ~SQLiteVirtualTableCursor()
        {
            Dispose(false);
        }
        #endregion
    }
    #endregion

    ///////////////////////////////////////////////////////////////////////////

    #region ISQLiteNativeHandle Interface
    /// <summary>
    /// This interface represents a native handle provided by the SQLite core
    /// library.
    /// </summary>
    public interface ISQLiteNativeHandle
    {
        /// <summary>
        /// The native handle value.
        /// </summary>
        IntPtr NativeHandle { get; }
    }
    #endregion

    ///////////////////////////////////////////////////////////////////////////

    #region ISQLiteManagedModule Interface
    /// <summary>
    /// This interface represents a virtual table implementation written in
    /// managed code.
    /// </summary>
    public interface ISQLiteManagedModule
    {
        /// <summary>
        /// Returns non-zero if the schema for the virtual table has been
        /// declared.
        /// </summary>
        bool Declared { get; }

        ///////////////////////////////////////////////////////////////////////

        /// <summary>
        /// Returns the name of the module as it was registered with the SQLite
        /// core library.
        /// </summary>
        string Name { get; }

        ///////////////////////////////////////////////////////////////////////

        /// <summary>
        /// This method is called in response to the
        /// <see cref="ISQLiteNativeModule.xCreate" /> method.
        /// </summary>
        /// <param name="connection">
        /// The <see cref="SQLiteConnection" /> object instance associated with
        /// the virtual table.
        /// </param>
        /// <param name="pClientData">
        /// The native user-data pointer associated with this module, as it was
        /// provided to the SQLite core library when the native module instance
        /// was created.
        /// </param>
        /// <param name="arguments">
        /// The module name, database name, virtual table name, and all other
        /// arguments passed to the CREATE VIRTUAL TABLE statement.
        /// </param>
        /// <param name="table">
        /// Upon success, this parameter must be modified to contain the
        /// <see cref="SQLiteVirtualTable" /> object instance associated with
        /// the virtual table.
        /// </param>
        /// <param name="error">
        /// Upon failure, this parameter must be modified to contain an error
        /// message.
        /// </param>
        /// <returns>
        /// A standard SQLite return code.
        /// </returns>
        SQLiteErrorCode Create(
            SQLiteConnection connection,  /* in */
            IntPtr pClientData,           /* in */
            string[] arguments,           /* in */
            ref SQLiteVirtualTable table, /* out */
            ref string error              /* out */
            );

        ///////////////////////////////////////////////////////////////////////

        /// <summary>
        /// This method is called in response to the
        /// <see cref="ISQLiteNativeModule.xConnect" /> method.
        /// </summary>
        /// <param name="connection">
        /// The <see cref="SQLiteConnection" /> object instance associated with
        /// the virtual table.
        /// </param>
        /// <param name="pClientData">
        /// The native user-data pointer associated with this module, as it was
        /// provided to the SQLite core library when the native module instance
        /// was created.
        /// </param>
        /// <param name="arguments">
        /// The module name, database name, virtual table name, and all other
        /// arguments passed to the CREATE VIRTUAL TABLE statement.
        /// </param>
        /// <param name="table">
        /// Upon success, this parameter must be modified to contain the
        /// <see cref="SQLiteVirtualTable" /> object instance associated with
        /// the virtual table.
        /// </param>
        /// <param name="error">
        /// Upon failure, this parameter must be modified to contain an error
        /// message.
        /// </param>
        /// <returns>
        /// A standard SQLite return code.
        /// </returns>
        SQLiteErrorCode Connect(
            SQLiteConnection connection,  /* in */
            IntPtr pClientData,           /* in */
            string[] arguments,           /* in */
            ref SQLiteVirtualTable table, /* out */
            ref string error              /* out */
            );

        ///////////////////////////////////////////////////////////////////////

        /// <summary>
        /// This method is called in response to the
        /// <see cref="ISQLiteNativeModule.xBestIndex" /> method.
        /// </summary>
        /// <param name="table">
        /// The <see cref="SQLiteVirtualTable" /> object instance associated
        /// with this virtual table.
        /// </param>
        /// <param name="index">
        /// The <see cref="SQLiteIndex" /> object instance containing all the
        /// data for the inputs and outputs relating to index selection.
        /// </param>
        /// <returns>
        /// A standard SQLite return code.
        /// </returns>
        SQLiteErrorCode BestIndex(
            SQLiteVirtualTable table, /* in */
            SQLiteIndex index         /* in, out */
            );

        ///////////////////////////////////////////////////////////////////////

        /// <summary>
        /// This method is called in response to the
        /// <see cref="ISQLiteNativeModule.xDisconnect" /> method.
        /// </summary>
        /// <param name="table">
        /// The <see cref="SQLiteVirtualTable" /> object instance associated
        /// with this virtual table.
        /// </param>
        /// <returns>
        /// A standard SQLite return code.
        /// </returns>
        SQLiteErrorCode Disconnect(
            SQLiteVirtualTable table /* in */
            );

        ///////////////////////////////////////////////////////////////////////

        /// <summary>
        /// This method is called in response to the
        /// <see cref="ISQLiteNativeModule.xDestroy" /> method.
        /// </summary>
        /// <param name="table">
        /// The <see cref="SQLiteVirtualTable" /> object instance associated
        /// with this virtual table.
        /// </param>
        /// <returns>
        /// A standard SQLite return code.
        /// </returns>
        SQLiteErrorCode Destroy(
            SQLiteVirtualTable table /* in */
            );

        ///////////////////////////////////////////////////////////////////////

        /// <summary>
        /// This method is called in response to the
        /// <see cref="ISQLiteNativeModule.xOpen" /> method.
        /// </summary>
        /// <param name="table">
        /// The <see cref="SQLiteVirtualTable" /> object instance associated
        /// with this virtual table.
        /// </param>
        /// <param name="cursor">
        /// Upon success, this parameter must be modified to contain the
        /// <see cref="SQLiteVirtualTableCursor" /> object instance associated
        /// with the newly opened virtual table cursor.
        /// </param>
        /// <returns>
        /// A standard SQLite return code.
        /// </returns>
        SQLiteErrorCode Open(
            SQLiteVirtualTable table,           /* in */
            ref SQLiteVirtualTableCursor cursor /* out */
            );

        ///////////////////////////////////////////////////////////////////////

        /// <summary>
        /// This method is called in response to the
        /// <see cref="ISQLiteNativeModule.xClose" /> method.
        /// </summary>
        /// <param name="cursor">
        /// The <see cref="SQLiteVirtualTableCursor" /> object instance
        /// associated with the previously opened virtual table cursor to be
        /// used.
        /// </param>
        /// <returns>
        /// A standard SQLite return code.
        /// </returns>
        SQLiteErrorCode Close(
            SQLiteVirtualTableCursor cursor /* in */
            );

        ///////////////////////////////////////////////////////////////////////

        /// <summary>
        /// This method is called in response to the
        /// <see cref="ISQLiteNativeModule.xFilter" /> method.
        /// </summary>
        /// <param name="cursor">
        /// The <see cref="SQLiteVirtualTableCursor" /> object instance
        /// associated with the previously opened virtual table cursor to be
        /// used.
        /// </param>
        /// <param name="indexNumber">
        /// Number used to help identify the selected index.
        /// </param>
        /// <param name="indexString">
        /// String used to help identify the selected index.
        /// </param>
        /// <param name="values">
        /// The values corresponding to each column in the selected index.
        /// </param>
        /// <returns>
        /// A standard SQLite return code.
        /// </returns>
        SQLiteErrorCode Filter(
            SQLiteVirtualTableCursor cursor, /* in */
            int indexNumber,                 /* in */
            string indexString,              /* in */
            SQLiteValue[] values             /* in */
            );

        ///////////////////////////////////////////////////////////////////////

        /// <summary>
        /// This method is called in response to the
        /// <see cref="ISQLiteNativeModule.xNext" /> method.
        /// </summary>
        /// <param name="cursor">
        /// The <see cref="SQLiteVirtualTableCursor" /> object instance
        /// associated with the previously opened virtual table cursor to be
        /// used.
        /// </param>
        /// <returns>
        /// A standard SQLite return code.
        /// </returns>
        SQLiteErrorCode Next(
            SQLiteVirtualTableCursor cursor /* in */
            );

        ///////////////////////////////////////////////////////////////////////

        /// <summary>
        /// This method is called in response to the
        /// <see cref="ISQLiteNativeModule.xEof" /> method.
        /// </summary>
        /// <param name="cursor">
        /// The <see cref="SQLiteVirtualTableCursor" /> object instance
        /// associated with the previously opened virtual table cursor to be
        /// used.
        /// </param>
        /// <returns>
        /// Non-zero if no more rows are available; zero otherwise.
        /// </returns>
        bool Eof(
            SQLiteVirtualTableCursor cursor /* in */
            );

        ///////////////////////////////////////////////////////////////////////

        /// <summary>
        /// This method is called in response to the
        /// <see cref="ISQLiteNativeModule.xColumn" /> method.
        /// </summary>
        /// <param name="cursor">
        /// The <see cref="SQLiteVirtualTableCursor" /> object instance
        /// associated with the previously opened virtual table cursor to be
        /// used.
        /// </param>
        /// <param name="context">
        /// The <see cref="SQLiteContext" /> object instance to be used for
        /// returning the specified column value to the SQLite core library.
        /// </param>
        /// <param name="index">
        /// The zero-based index corresponding to the column containing the
        /// value to be returned.
        /// </param>
        /// <returns>
        /// A standard SQLite return code.
        /// </returns>
        SQLiteErrorCode Column(
            SQLiteVirtualTableCursor cursor, /* in */
            SQLiteContext context,           /* in */
            int index                        /* in */
            );

        ///////////////////////////////////////////////////////////////////////

        /// <summary>
        /// This method is called in response to the
        /// <see cref="ISQLiteNativeModule.xRowId" /> method.
        /// </summary>
        /// <param name="cursor">
        /// The <see cref="SQLiteVirtualTableCursor" /> object instance
        /// associated with the previously opened virtual table cursor to be
        /// used.
        /// </param>
        /// <param name="rowId">
        /// Upon success, this parameter must be modified to contain the unique
        /// integer row identifier for the current row for the specified cursor.
        /// </param>
        /// <returns>
        /// A standard SQLite return code.
        /// </returns>
        SQLiteErrorCode RowId(
            SQLiteVirtualTableCursor cursor, /* in */
            ref long rowId                   /* out */
            );

        ///////////////////////////////////////////////////////////////////////

        /// <summary>
        /// This method is called in response to the
        /// <see cref="ISQLiteNativeModule.xUpdate" /> method.
        /// </summary>
        /// <param name="table">
        /// The <see cref="SQLiteVirtualTable" /> object instance associated
        /// with this virtual table.
        /// </param>
        /// <param name="values">
        /// The array of <see cref="SQLiteValue" /> object instances containing
        /// the new or modified column values, if any.
        /// </param>
        /// <param name="rowId">
        /// Upon success, this parameter must be modified to contain the unique
        /// integer row identifier for the row that was inserted, if any.
        /// </param>
        /// <returns>
        /// A standard SQLite return code.
        /// </returns>
        SQLiteErrorCode Update(
            SQLiteVirtualTable table, /* in */
            SQLiteValue[] values,     /* in */
            ref long rowId            /* out */
            );

        ///////////////////////////////////////////////////////////////////////

        /// <summary>
        /// This method is called in response to the
        /// <see cref="ISQLiteNativeModule.xBegin" /> method.
        /// </summary>
        /// <param name="table">
        /// The <see cref="SQLiteVirtualTable" /> object instance associated
        /// with this virtual table.
        /// </param>
        /// <returns>
        /// A standard SQLite return code.
        /// </returns>
        SQLiteErrorCode Begin(
            SQLiteVirtualTable table /* in */
            );

        ///////////////////////////////////////////////////////////////////////

        /// <summary>
        /// This method is called in response to the
        /// <see cref="ISQLiteNativeModule.xSync" /> method.
        /// </summary>
        /// <param name="table">
        /// The <see cref="SQLiteVirtualTable" /> object instance associated
        /// with this virtual table.
        /// </param>
        /// <returns>
        /// A standard SQLite return code.
        /// </returns>
        SQLiteErrorCode Sync(
            SQLiteVirtualTable table /* in */
            );

        ///////////////////////////////////////////////////////////////////////

        /// <summary>
        /// This method is called in response to the
        /// <see cref="ISQLiteNativeModule.xCommit" /> method.
        /// </summary>
        /// <param name="table">
        /// The <see cref="SQLiteVirtualTable" /> object instance associated
        /// with this virtual table.
        /// </param>
        /// <returns>
        /// A standard SQLite return code.
        /// </returns>
        SQLiteErrorCode Commit(
            SQLiteVirtualTable table /* in */
            );

        ///////////////////////////////////////////////////////////////////////

        /// <summary>
        /// This method is called in response to the
        /// <see cref="ISQLiteNativeModule.xRollback" /> method.
        /// </summary>
        /// <param name="table">
        /// The <see cref="SQLiteVirtualTable" /> object instance associated
        /// with this virtual table.
        /// </param>
        /// <returns>
        /// A standard SQLite return code.
        /// </returns>
        SQLiteErrorCode Rollback(
            SQLiteVirtualTable table /* in */
            );

        ///////////////////////////////////////////////////////////////////////

        /// <summary>
        /// This method is called in response to the
        /// <see cref="ISQLiteNativeModule.xFindFunction" /> method.
        /// </summary>
        /// <param name="table">
        /// The <see cref="SQLiteVirtualTable" /> object instance associated
        /// with this virtual table.
        /// </param>
        /// <param name="argumentCount">
        /// The number of arguments to the function being sought.
        /// </param>
        /// <param name="name">
        /// The name of the function being sought.
        /// </param>
        /// <param name="function">
        /// Upon success, this parameter must be modified to contain the
        /// <see cref="SQLiteFunction" /> object instance responsible for
        /// implementing the specified function.
        /// </param>
        /// <param name="pClientData">
        /// Upon success, this parameter must be modified to contain the
        /// native user-data pointer associated with
        /// <paramref name="function" />.
        /// </param>
        /// <returns>
        /// Non-zero if the specified function was found; zero otherwise.
        /// </returns>
        bool FindFunction(
            SQLiteVirtualTable table,    /* in */
            int argumentCount,           /* in */
            string name,                 /* in */
            ref SQLiteFunction function, /* out */
            ref IntPtr pClientData       /* out */
            );

        ///////////////////////////////////////////////////////////////////////

        /// <summary>
        /// This method is called in response to the
        /// <see cref="ISQLiteNativeModule.xRename" /> method.
        /// </summary>
        /// <param name="table">
        /// The <see cref="SQLiteVirtualTable" /> object instance associated
        /// with this virtual table.
        /// </param>
        /// <param name="newName">
        /// The new name for the virtual table.
        /// </param>
        /// <returns>
        /// A standard SQLite return code.
        /// </returns>
        SQLiteErrorCode Rename(
            SQLiteVirtualTable table, /* in */
            string newName            /* in */
            );

        ///////////////////////////////////////////////////////////////////////

        /// <summary>
        /// This method is called in response to the
        /// <see cref="ISQLiteNativeModule.xSavepoint" /> method.
        /// </summary>
        /// <param name="table">
        /// The <see cref="SQLiteVirtualTable" /> object instance associated
        /// with this virtual table.
        /// </param>
        /// <param name="savepoint">
        /// This is an integer identifier under which the the current state of
        /// the virtual table should be saved.
        /// </param>
        /// <returns>
        /// A standard SQLite return code.
        /// </returns>
        SQLiteErrorCode Savepoint(
            SQLiteVirtualTable table, /* in */
            int savepoint             /* in */
            );

        ///////////////////////////////////////////////////////////////////////

        /// <summary>
        /// This method is called in response to the
        /// <see cref="ISQLiteNativeModule.xRelease" /> method.
        /// </summary>
        /// <param name="table">
        /// The <see cref="SQLiteVirtualTable" /> object instance associated
        /// with this virtual table.
        /// </param>
        /// <param name="savepoint">
        /// This is an integer used to indicate that any saved states with an
        /// identifier greater than or equal to this should be deleted by the
        /// virtual table.
        /// </param>
        /// <returns>
        /// A standard SQLite return code.
        /// </returns>
        SQLiteErrorCode Release(
            SQLiteVirtualTable table, /* in */
            int savepoint             /* in */
            );

        ///////////////////////////////////////////////////////////////////////

        /// <summary>
        /// This method is called in response to the
        /// <see cref="ISQLiteNativeModule.xRollbackTo" /> method.
        /// </summary>
        /// <param name="table">
        /// The <see cref="SQLiteVirtualTable" /> object instance associated
        /// with this virtual table.
        /// </param>
        /// <param name="savepoint">
        /// This is an integer identifier used to specify a specific saved
        /// state for the virtual table for it to restore itself back to, which
        /// should also have the effect of deleting all saved states with an
        /// integer identifier greater than this one.
        /// </param>
        /// <returns>
        /// A standard SQLite return code.
        /// </returns>
        SQLiteErrorCode RollbackTo(
            SQLiteVirtualTable table, /* in */
            int savepoint             /* in */
            );
    }
    #endregion

    ///////////////////////////////////////////////////////////////////////////

    #region SQLiteMemory Static Class
    /// <summary>
    /// This class contains static methods that are used to allocate,
    /// manipulate, and free native memory provided by the SQLite core library.
    /// </summary>
    internal static class SQLiteMemory
    {
        #region Private Data
#if TRACK_MEMORY_BYTES
        /// <summary>
        /// This object instance is used to synchronize access to the other
        /// static fields of this class.
        /// </summary>
        private static object syncRoot = new object();

        ///////////////////////////////////////////////////////////////////////

        /// <summary>
        /// The total number of outstanding memory bytes allocated by this
        /// class using the SQLite core library.
        /// </summary>
        private static int bytesAllocated;

        ///////////////////////////////////////////////////////////////////////

        /// <summary>
        /// The maximum number of outstanding memory bytes ever allocated by
        /// this class using the SQLite core library.
        /// </summary>
        private static int maximumBytesAllocated;
#endif
        #endregion

        ///////////////////////////////////////////////////////////////////////

        #region Memory Allocation Helper Methods
        /// <summary>
        /// Allocates at least the specified number of bytes of native memory
        /// via the SQLite core library sqlite3_malloc() function and returns
        /// the resulting native pointer.
        /// </summary>
        /// <param name="size">
        /// The number of bytes to allocate.
        /// </param>
        /// <returns>
        /// The native pointer that points to a block of memory of at least the
        /// specified size -OR- <see cref="IntPtr.Zero" /> if the memory could
        /// not be allocated.
        /// </returns>
        public static IntPtr Allocate(int size)
        {
            IntPtr pMemory = UnsafeNativeMethods.sqlite3_malloc(size);

#if TRACK_MEMORY_BYTES
            if (pMemory != IntPtr.Zero)
            {
                int blockSize = Size(pMemory);

                if (blockSize > 0)
                {
                    lock (syncRoot)
                    {
                        bytesAllocated += blockSize;

                        if (bytesAllocated > maximumBytesAllocated)
                            maximumBytesAllocated = bytesAllocated;
                    }
                }
            }
#endif

            return pMemory;
        }

        ///////////////////////////////////////////////////////////////////////

        /// <summary>
        /// Gets and returns the actual size of the specified memory block that
        /// was previously obtained from the <see cref="Allocate" /> method.
        /// </summary>
        /// <param name="pMemory">
        /// The native pointer to the memory block previously obtained from the
        /// <see cref="Allocate" /> method.
        /// </param>
        /// <returns>
        /// The actual size, in bytes, of the memory block specified via the
        /// native pointer.
        /// </returns>
        public static int Size(IntPtr pMemory)
        {
#if !SQLITE_STANDARD
            return UnsafeNativeMethods.sqlite3_malloc_size_interop(pMemory);
#elif TRACK_MEMORY_BYTES
            //
            // HACK: Ok, we cannot determine the size of the memory block;
            //       therefore, just track number of allocations instead.
            //
            return (pMemory != IntPtr.Zero) ? 1 : 0;
#else
            return 0;
#endif
        }

        ///////////////////////////////////////////////////////////////////////

        /// <summary>
        /// Frees a memory block previously obtained from the
        /// <see cref="Allocate" /> method.
        /// </summary>
        /// <param name="pMemory">
        /// The native pointer to the memory block previously obtained from the
        /// <see cref="Allocate" /> method.
        /// </param>
        public static void Free(IntPtr pMemory)
        {
#if TRACK_MEMORY_BYTES
            if (pMemory != IntPtr.Zero)
            {
                int blockSize = Size(pMemory);

                if (blockSize > 0)
                {
                    lock (syncRoot)
                    {
                        bytesAllocated -= blockSize;
                    }
                }
            }
#endif

            UnsafeNativeMethods.sqlite3_free(pMemory);
        }
        #endregion
    }
    #endregion

    ///////////////////////////////////////////////////////////////////////////

    #region SQLiteString Static Class
    /// <summary>
    /// This class contains static methods that are used to deal with native
    /// UTF-8 string pointers to be used with the SQLite core library.
    /// </summary>
    internal static class SQLiteString
    {
        #region Private Constants
        /// <summary>
        /// This is the maximum possible length for the native UTF-8 encoded
        /// strings used with the SQLite core library.
        /// </summary>
        private static int ThirtyBits = 0x3fffffff;

        ///////////////////////////////////////////////////////////////////////

        /// <summary>
        /// This is the <see cref="Encoding" /> object instance used to handle
        /// conversions from/to UTF-8.
        /// </summary>
        private static readonly Encoding Utf8Encoding = Encoding.UTF8;
        #endregion

        ///////////////////////////////////////////////////////////////////////

        #region UTF-8 Encoding Helper Methods
        /// <summary>
        /// Converts the specified managed string into the UTF-8 encoding and
        /// returns the array of bytes containing its representation in that
        /// encoding.
        /// </summary>
        /// <param name="value">
        /// The managed string to convert.
        /// </param>
        /// <returns>
        /// The array of bytes containing the representation of the managed
        /// string in the UTF-8 encoding or null upon failure.
        /// </returns>
        public static byte[] GetUtf8BytesFromString(
            string value
            )
        {
            if (value == null)
                return null;

            return Utf8Encoding.GetBytes(value);
        }

        ///////////////////////////////////////////////////////////////////////

        /// <summary>
        /// Converts the specified array of bytes representing a string in the
        /// UTF-8 encoding and returns a managed string.
        /// </summary>
        /// <param name="bytes">
        /// The array of bytes to convert.
        /// </param>
        /// <returns>
        /// The managed string or null upon failure.
        /// </returns>
        public static string GetStringFromUtf8Bytes(
            byte[] bytes
            )
        {
            if (bytes == null)
                return null;

#if !PLATFORM_COMPACTFRAMEWORK
            return Utf8Encoding.GetString(bytes);
#else
            return Utf8Encoding.GetString(bytes, 0, bytes.Length);
#endif
        }
        #endregion

        ///////////////////////////////////////////////////////////////////////

        #region UTF-8 String Helper Methods
        /// <summary>
        /// Probes a native pointer to a string in the UTF-8 encoding for its
        /// terminating NUL character, within the specified length limit.
        /// </summary>
        /// <param name="pValue">
        /// The native NUL-terminated string pointer.
        /// </param>
        /// <param name="limit">
        /// The maximum length of the native string, in bytes.
        /// </param>
        /// <returns>
        /// The length of the native string, in bytes -OR- zero if the length
        /// could not be determined.
        /// </returns>
        public static int ProbeForUtf8ByteLength(
            IntPtr pValue,
            int limit
            )
        {
            int length = 0;

            if ((pValue != IntPtr.Zero) && (limit > 0))
            {
                do
                {
                    if (Marshal.ReadByte(pValue, length) == 0)
                        break;

                    if (length >= limit)
                        break;

                    length++;
                } while (true);
            }

            return length;
        }

        ///////////////////////////////////////////////////////////////////////

        /// <summary>
        /// Converts the specified native NUL-terminated UTF-8 string pointer
        /// into a managed string.
        /// </summary>
        /// <param name="pValue">
        /// The native NUL-terminated UTF-8 string pointer.
        /// </param>
        /// <returns>
        /// The managed string or null upon failure.
        /// </returns>
        public static string StringFromUtf8IntPtr(
            IntPtr pValue
            )
        {
            return StringFromUtf8IntPtr(pValue,
                ProbeForUtf8ByteLength(pValue, ThirtyBits));
        }

        ///////////////////////////////////////////////////////////////////////

        /// <summary>
        /// Converts the specified native UTF-8 string pointer of the specified
        /// length into a managed string.
        /// </summary>
        /// <param name="pValue">
        /// The native UTF-8 string pointer.
        /// </param>
        /// <param name="length">
        /// The length of the native string, in bytes.
        /// </param>
        /// <returns>
        /// The managed string or null upon failure.
        /// </returns>
        public static string StringFromUtf8IntPtr(
            IntPtr pValue,
            int length
            )
        {
            if (pValue == IntPtr.Zero)
                return null;

            if (length > 0)
            {
                byte[] bytes = new byte[length];

                Marshal.Copy(pValue, bytes, 0, length);

                return GetStringFromUtf8Bytes(bytes);
            }

            return String.Empty;
        }

        ///////////////////////////////////////////////////////////////////////

        /// <summary>
        /// Converts the specified managed string into a native NUL-terminated
        /// UTF-8 string pointer using memory obtained from the SQLite core
        /// library.
        /// </summary>
        /// <param name="value">
        /// The managed string to convert.
        /// </param>
        /// <returns>
        /// The native NUL-terminated UTF-8 string pointer or
        /// <see cref="IntPtr.Zero" /> upon failure.
        /// </returns>
        public static IntPtr Utf8IntPtrFromString(
            string value
            )
        {
            int length = 0;

            return Utf8IntPtrFromString(value, ref length);
        }

        ///////////////////////////////////////////////////////////////////////

        /// <summary>
        /// Converts the specified managed string into a native NUL-terminated
        /// UTF-8 string pointer using memory obtained from the SQLite core
        /// library.
        /// </summary>
        /// <param name="value">
        /// The managed string to convert.
        /// </param>
        /// <param name="length">
        /// The length of the native string, in bytes.
        /// </param>
        /// <returns>
        /// The native NUL-terminated UTF-8 string pointer or
        /// <see cref="IntPtr.Zero" /> upon failure.
        /// </returns>
        public static IntPtr Utf8IntPtrFromString(
            string value,
            ref int length
            )
        {
            if (value == null)
                return IntPtr.Zero;

            IntPtr result = IntPtr.Zero;
            byte[] bytes = GetUtf8BytesFromString(value);

            if (bytes == null)
                return IntPtr.Zero;

            length = bytes.Length;

            result = SQLiteMemory.Allocate(length + 1);

            if (result == IntPtr.Zero)
                return IntPtr.Zero;

            Marshal.Copy(bytes, 0, result, length);
            Marshal.WriteByte(result, length, 0);

            return result;
        }
        #endregion

        ///////////////////////////////////////////////////////////////////////

        #region UTF-8 String Array Helper Methods
        /// <summary>
        /// Converts a logical array of native NUL-terminated UTF-8 string
        /// pointers into an array of managed strings.
        /// </summary>
        /// <param name="argc">
        /// The number of elements in the logical array of native
        /// NUL-terminated UTF-8 string pointers.
        /// </param>
        /// <param name="argv">
        /// The native pointer to the logical array of native NUL-terminated
        /// UTF-8 string pointers to convert.
        /// </param>
        /// <returns>
        /// The array of managed strings or null upon failure.
        /// </returns>
        public static string[] StringArrayFromUtf8SizeAndIntPtr(
            int argc,
            IntPtr argv
            )
        {
            if (argc < 0)
                return null;

            if (argv == IntPtr.Zero)
                return null;

            string[] result = new string[argc];

            for (int index = 0, offset = 0;
                    index < result.Length;
                    index++, offset += IntPtr.Size)
            {
                IntPtr pArg = SQLiteMarshal.ReadIntPtr(argv, offset);

                result[index] = (pArg != IntPtr.Zero) ?
                    StringFromUtf8IntPtr(pArg) : null;
            }

            return result;
        }

        ///////////////////////////////////////////////////////////////////////

        /// <summary>
        /// Converts an array of managed strings into an array of native
        /// NUL-terminated UTF-8 string pointers.
        /// </summary>
        /// <param name="values">
        /// The array of managed strings to convert.
        /// </param>
        /// <returns>
        /// The array of native NUL-terminated UTF-8 string pointers or null
        /// upon failure.
        /// </returns>
        public static IntPtr[] Utf8IntPtrArrayFromStringArray(
            string[] values
            )
        {
            if (values == null)
                return null;

            IntPtr[] result = new IntPtr[values.Length];

            for (int index = 0; index < result.Length; index++)
                result[index] = Utf8IntPtrFromString(values[index]);

            return result;
        }
        #endregion
    }
    #endregion

    ///////////////////////////////////////////////////////////////////////////

    #region SQLiteBytes Static Class
    /// <summary>
    /// This class contains static methods that are used to deal with native
    /// pointers to memory blocks that logically contain arrays of bytes to be
    /// used with the SQLite core library.
    /// </summary>
    internal static class SQLiteBytes
    {
        #region Byte Array Helper Methods
        /// <summary>
        /// Converts a native pointer to a logical array of bytes of the
        /// specified length into a managed byte array.
        /// </summary>
        /// <param name="pValue">
        /// The native pointer to the logical array of bytes to convert.
        /// </param>
        /// <param name="length">
        /// The length, in bytes, of the logical array of bytes to convert.
        /// </param>
        /// <returns>
        /// The managed byte array or null upon failure.
        /// </returns>
        public static byte[] FromIntPtr(
            IntPtr pValue,
            int length
            )
        {
            if (pValue == IntPtr.Zero)
                return null;

            if (length == 0)
                return new byte[0];

            byte[] result = new byte[length];

            Marshal.Copy(pValue, result, 0, length);

            return result;
        }

        ///////////////////////////////////////////////////////////////////////

        /// <summary>
        /// Converts a managed byte array into a native pointer to a logical
        /// array of bytes.
        /// </summary>
        /// <param name="value">
        /// The managed byte array to convert.
        /// </param>
        /// <returns>
        /// The native pointer to a logical byte array or null upon failure.
        /// </returns>
        public static IntPtr ToIntPtr(
            byte[] value
            )
        {
            int length = 0;

            return ToIntPtr(value, ref length);
        }

        ///////////////////////////////////////////////////////////////////////

        /// <summary>
        /// Converts a managed byte array into a native pointer to a logical
        /// array of bytes.
        /// </summary>
        /// <param name="value">
        /// The managed byte array to convert.
        /// </param>
        /// <param name="length">
        /// The length, in bytes, of the converted logical array of bytes.
        /// </param>
        /// <returns>
        /// The native pointer to a logical byte array or null upon failure.
        /// </returns>
        public static IntPtr ToIntPtr(
            byte[] value,
            ref int length
            )
        {
            if (value == null)
                return IntPtr.Zero;

            length = value.Length;

            if (length == 0)
                return IntPtr.Zero;

            IntPtr result = SQLiteMemory.Allocate(length);

            if (result == IntPtr.Zero)
                return IntPtr.Zero;

            Marshal.Copy(value, 0, result, length);

            return result;
        }
        #endregion
    }
    #endregion

    ///////////////////////////////////////////////////////////////////////////

    #region SQLiteMarshal Static Class
    /// <summary>
    /// This class contains static methods that are used to perform several
    /// low-level data marshalling tasks between native and managed code.
    /// </summary>
    internal static class SQLiteMarshal
    {
        #region IntPtr Helper Methods
        /// <summary>
        /// Returns a new <see cref="IntPtr" /> object instance based on the
        /// specified <see cref="IntPtr" /> object instance and an integer
        /// offset.
        /// </summary>
        /// <param name="pointer">
        /// The <see cref="IntPtr" /> object instance representing the base
        /// memory location.
        /// </param>
        /// <param name="offset">
        /// The integer offset from the base memory location that the new
        /// <see cref="IntPtr" /> object instance should point to.
        /// </param>
        /// <returns>
        /// The new <see cref="IntPtr" /> object instance.
        /// </returns>
        public static IntPtr IntPtrForOffset(
            IntPtr pointer,
            int offset
            )
        {
            return new IntPtr(pointer.ToInt64() + offset);
        }

        ///////////////////////////////////////////////////////////////////////

        /// <summary>
        /// Rounds up an integer size to the next multiple of the alignment.
        /// </summary>
        /// <param name="size">
        /// The size, in bytes, to be rounded up.
        /// </param>
        /// <param name="alignment">
        /// The required alignment for the return value.
        /// </param>
        /// <returns>
        /// The size, in bytes, rounded up to the next multiple of the
        /// alignment.  This value may end up being the same as the original
        /// size.
        /// </returns>
        public static int RoundUp(
            int size,
            int alignment
            )
        {
            int alignmentMinusOne = alignment - 1;
            return ((size + alignmentMinusOne) & ~alignmentMinusOne);
        }

        ///////////////////////////////////////////////////////////////////////

        /// <summary>
        /// Determines the offset, in bytes, of the next structure member.
        /// </summary>
        /// <param name="offset">
        /// The offset, in bytes, of the current structure member.
        /// </param>
        /// <param name="size">
        /// The size, in bytes, of the current structure member.
        /// </param>
        /// <param name="alignment">
        /// The alignment, in bytes, of the next structure member.
        /// </param>
        /// <returns>
        /// The offset, in bytes, of the next structure member.
        /// </returns>
        public static int NextOffsetOf(
            int offset,
            int size,
            int alignment
            )
        {
            return RoundUp(offset + size, alignment);
        }
        #endregion

        ///////////////////////////////////////////////////////////////////////

        #region Marshal Read Helper Methods
        /// <summary>
        /// Reads a <see cref="Int32" /> value from the specified memory
        /// location.
        /// </summary>
        /// <param name="pointer">
        /// The <see cref="IntPtr" /> object instance representing the base
        /// memory location.
        /// </param>
        /// <param name="offset">
        /// The integer offset from the base memory location where the
        /// <see cref="Int32" /> value to be read is located.
        /// </param>
        /// <returns>
        /// The <see cref="Int32" /> value at the specified memory location.
        /// </returns>
        public static int ReadInt32(
            IntPtr pointer,
            int offset
            )
        {
#if !PLATFORM_COMPACTFRAMEWORK
            return Marshal.ReadInt32(pointer, offset);
#else
            return Marshal.ReadInt32(IntPtrForOffset(pointer, offset));
#endif
        }

        ///////////////////////////////////////////////////////////////////////

        /// <summary>
        /// Reads a <see cref="Int64" /> value from the specified memory
        /// location.
        /// </summary>
        /// <param name="pointer">
        /// The <see cref="IntPtr" /> object instance representing the base
        /// memory location.
        /// </param>
        /// <param name="offset">
        /// The integer offset from the base memory location where the
        /// <see cref="Int64" /> value to be read is located.
        /// </param>
        /// <returns>
        /// The <see cref="Int64" /> value at the specified memory location.
        /// </returns>
        public static long ReadInt64(
            IntPtr pointer,
            int offset
            )
        {
#if !PLATFORM_COMPACTFRAMEWORK
            return Marshal.ReadInt64(pointer, offset);
#else
            return Marshal.ReadInt64(IntPtrForOffset(pointer, offset));
#endif
        }

        ///////////////////////////////////////////////////////////////////////

        /// <summary>
        /// Reads a <see cref="Double" /> value from the specified memory
        /// location.
        /// </summary>
        /// <param name="pointer">
        /// The <see cref="IntPtr" /> object instance representing the base
        /// memory location.
        /// </param>
        /// <param name="offset">
        /// The integer offset from the base memory location where the
        /// <see cref="Double" /> to be read is located.
        /// </param>
        /// <returns>
        /// The <see cref="Double" /> value at the specified memory location.
        /// </returns>
        public static double ReadDouble(
            IntPtr pointer,
            int offset
            )
        {
#if !PLATFORM_COMPACTFRAMEWORK
            return BitConverter.Int64BitsToDouble(Marshal.ReadInt64(
                pointer, offset));
#else
            return BitConverter.ToDouble(BitConverter.GetBytes(
                Marshal.ReadInt64(IntPtrForOffset(pointer, offset))), 0);
#endif
        }

        ///////////////////////////////////////////////////////////////////////

        /// <summary>
        /// Reads an <see cref="IntPtr" /> value from the specified memory
        /// location.
        /// </summary>
        /// <param name="pointer">
        /// The <see cref="IntPtr" /> object instance representing the base
        /// memory location.
        /// </param>
        /// <param name="offset">
        /// The integer offset from the base memory location where the
        /// <see cref="IntPtr" /> value to be read is located.
        /// </param>
        /// <returns>
        /// The <see cref="IntPtr" /> value at the specified memory location.
        /// </returns>
        public static IntPtr ReadIntPtr(
            IntPtr pointer,
            int offset
            )
        {
#if !PLATFORM_COMPACTFRAMEWORK
            return Marshal.ReadIntPtr(pointer, offset);
#else
            return Marshal.ReadIntPtr(IntPtrForOffset(pointer, offset));
#endif
        }
        #endregion

        ///////////////////////////////////////////////////////////////////////

        #region Marshal Write Helper Methods
        /// <summary>
        /// Writes an <see cref="Int32" /> value to the specified memory
        /// location.
        /// </summary>
        /// <param name="pointer">
        /// The <see cref="IntPtr" /> object instance representing the base
        /// memory location.
        /// </param>
        /// <param name="offset">
        /// The integer offset from the base memory location where the
        /// <see cref="Int32" /> value to be written is located.
        /// </param>
        /// <param name="value">
        /// The <see cref="Int32" /> value to write.
        /// </param>
        public static void WriteInt32(
            IntPtr pointer,
            int offset,
            int value
            )
        {
#if !PLATFORM_COMPACTFRAMEWORK
            Marshal.WriteInt32(pointer, offset, value);
#else
            Marshal.WriteInt32(IntPtrForOffset(pointer, offset), value);
#endif
        }

        ///////////////////////////////////////////////////////////////////////

        /// <summary>
        /// Writes an <see cref="Int64" /> value to the specified memory
        /// location.
        /// </summary>
        /// <param name="pointer">
        /// The <see cref="IntPtr" /> object instance representing the base
        /// memory location.
        /// </param>
        /// <param name="offset">
        /// The integer offset from the base memory location where the
        /// <see cref="Int64" /> value to be written is located.
        /// </param>
        /// <param name="value">
        /// The <see cref="Int64" /> value to write.
        /// </param>
        public static void WriteInt64(
            IntPtr pointer,
            int offset,
            long value
            )
        {
#if !PLATFORM_COMPACTFRAMEWORK
            Marshal.WriteInt64(pointer, offset, value);
#else
            Marshal.WriteInt64(IntPtrForOffset(pointer, offset), value);
#endif
        }

        ///////////////////////////////////////////////////////////////////////

        /// <summary>
        /// Writes a <see cref="Double" /> value to the specified memory
        /// location.
        /// </summary>
        /// <param name="pointer">
        /// The <see cref="IntPtr" /> object instance representing the base
        /// memory location.
        /// </param>
        /// <param name="offset">
        /// The integer offset from the base memory location where the
        /// <see cref="Double" /> value to be written is located.
        /// </param>
        /// <param name="value">
        /// The <see cref="Double" /> value to write.
        /// </param>
        public static void WriteDouble(
            IntPtr pointer,
            int offset,
            double value
            )
        {
#if !PLATFORM_COMPACTFRAMEWORK
            Marshal.WriteInt64(pointer, offset,
                BitConverter.DoubleToInt64Bits(value));
#else
            Marshal.WriteInt64(IntPtrForOffset(pointer, offset),
                BitConverter.ToInt64(BitConverter.GetBytes(value), 0));
#endif
        }

        ///////////////////////////////////////////////////////////////////////

        /// <summary>
        /// Writes a <see cref="IntPtr" /> value to the specified memory
        /// location.
        /// </summary>
        /// <param name="pointer">
        /// The <see cref="IntPtr" /> object instance representing the base
        /// memory location.
        /// </param>
        /// <param name="offset">
        /// The integer offset from the base memory location where the
        /// <see cref="IntPtr" /> value to be written is located.
        /// </param>
        /// <param name="value">
        /// The <see cref="IntPtr" /> value to write.
        /// </param>
        public static void WriteIntPtr(
            IntPtr pointer,
            int offset,
            IntPtr value
            )
        {
#if !PLATFORM_COMPACTFRAMEWORK
            Marshal.WriteIntPtr(pointer, offset, value);
#else
            Marshal.WriteIntPtr(IntPtrForOffset(pointer, offset), value);
#endif
        }
        #endregion

        ///////////////////////////////////////////////////////////////////////

        #region Object Helper Methods
        /// <summary>
        /// Generates a hash code value for the object.
        /// </summary>
        /// <param name="value">
        /// The object instance used to calculate the hash code.
        /// </param>
        /// <param name="identity">
        /// Non-zero if different object instances with the same value should
        /// generate different hash codes, where applicable.  This parameter
        /// has no effect on the .NET Compact Framework.
        /// </param>
        /// <returns>
        /// The hash code value -OR- zero if the object is null.
        /// </returns>
        public static int GetHashCode(
            object value,
            bool identity
            )
        {
#if !PLATFORM_COMPACTFRAMEWORK
            if (identity)
                return RuntimeHelpers.GetHashCode(value);
#endif

            if (value == null) return 0;
            return value.GetHashCode();
        }
        #endregion
    }
    #endregion

    ///////////////////////////////////////////////////////////////////////////

    #region SQLiteModule Base Class
    /// <summary>
    /// This class represents a managed virtual table module implementation.
    /// It is not sealed and must be used as the base class for any
    /// user-defined virtual table module classes implemented in managed code.
    /// </summary>
    public abstract class SQLiteModule :
            ISQLiteManagedModule, /*ISQLiteNativeModule,*/
            IDisposable /* NOT SEALED */
    {
        #region SQLiteNativeModule Private Class
        /// <summary>
        /// This class implements the <see cref="ISQLiteNativeModule" />
        /// interface by forwarding those method calls to the
        /// <see cref="SQLiteModule" /> object instance it contains.  If the
        /// contained <see cref="SQLiteModule" /> object instance is null, all
        /// the <see cref="ISQLiteNativeModule" /> methods simply generate an
        /// error.
        /// </summary>
        private sealed class SQLiteNativeModule :
                ISQLiteNativeModule, IDisposable
        {
            #region Private Constants
            /// <summary>
            /// This is the value that is always used for the "logErrors"
            /// parameter to the various static error handling methods provided
            /// by the <see cref="SQLiteModule" /> class.
            /// </summary>
            private const bool DefaultLogErrors = true;

            ///////////////////////////////////////////////////////////////////

            /// <summary>
            /// This is the value that is always used for the "logExceptions"
            /// parameter to the various static error handling methods provided
            /// by the <see cref="SQLiteModule" /> class.
            /// </summary>
            private const bool DefaultLogExceptions = true;

            ///////////////////////////////////////////////////////////////////

            /// <summary>
            /// This is the error message text used when the contained
            /// <see cref="SQLiteModule" /> object instance is not available
            /// for any reason.
            /// </summary>
            private const string ModuleNotAvailableErrorMessage =
                "native module implementation not available";
            #endregion

            ///////////////////////////////////////////////////////////////////

            #region Private Data
            /// <summary>
            /// The <see cref="SQLiteModule" /> object instance used to provide
            /// an implementation of the <see cref="ISQLiteNativeModule" />
            /// interface.
            /// </summary>
            private SQLiteModule module;
            #endregion

            ///////////////////////////////////////////////////////////////////

            #region Public Constructors
            /// <summary>
            /// Constructs an instance of this class.
            /// </summary>
            /// <param name="module">
            /// The <see cref="SQLiteModule" /> object instance used to provide
            /// an implementation of the <see cref="ISQLiteNativeModule" />
            /// interface.
            /// </param>
            public SQLiteNativeModule(
                SQLiteModule module
                )
            {
                this.module = module;
            }
            #endregion

            ///////////////////////////////////////////////////////////////////

            #region Private Static Methods
            /// <summary>
            /// Sets the table error message to one that indicates the native
            /// module implementation is not available.
            /// </summary>
            /// <param name="pVtab">
            /// The native pointer to the sqlite3_vtab derived structure.
            /// </param>
            /// <returns>
            /// The value of <see cref="SQLiteErrorCode.Error" />.
            /// </returns>
            private static SQLiteErrorCode ModuleNotAvailableTableError(
                IntPtr pVtab
                )
            {
                SetTableError(null, pVtab, DefaultLogErrors,
                    DefaultLogExceptions, ModuleNotAvailableErrorMessage);

                return SQLiteErrorCode.Error;
            }

            ///////////////////////////////////////////////////////////////////

            /// <summary>
            /// Sets the table error message to one that indicates the native
            /// module implementation is not available.
            /// </summary>
            /// <param name="pCursor">
            /// The native pointer to the sqlite3_vtab_cursor derived
            /// structure.
            /// </param>
            /// <returns>
            /// The value of <see cref="SQLiteErrorCode.Error" />.
            /// </returns>
            private static SQLiteErrorCode ModuleNotAvailableCursorError(
                IntPtr pCursor
                )
            {
                SetCursorError(null, pCursor, DefaultLogErrors,
                    DefaultLogExceptions, ModuleNotAvailableErrorMessage);

                return SQLiteErrorCode.Error;
            }
            #endregion

            ///////////////////////////////////////////////////////////////////

            #region ISQLiteNativeModule Members
            /// <summary>
            /// See the <see cref="ISQLiteNativeModule.xCreate" /> method.
            /// </summary>
            /// <param name="pDb">
            /// See the <see cref="ISQLiteNativeModule.xCreate" /> method.
            /// </param>
            /// <param name="pAux">
            /// See the <see cref="ISQLiteNativeModule.xCreate" /> method.
            /// </param>
            /// <param name="argc">
            /// See the <see cref="ISQLiteNativeModule.xCreate" /> method.
            /// </param>
            /// <param name="argv">
            /// See the <see cref="ISQLiteNativeModule.xCreate" /> method.
            /// </param>
            /// <param name="pVtab">
            /// See the <see cref="ISQLiteNativeModule.xCreate" /> method.
            /// </param>
            /// <param name="pError">
            /// See the <see cref="ISQLiteNativeModule.xCreate" /> method.
            /// </param>
            /// <returns>
            /// See the <see cref="ISQLiteNativeModule.xCreate" /> method.
            /// </returns>
            public SQLiteErrorCode xCreate(
                IntPtr pDb,
                IntPtr pAux,
                int argc,
                IntPtr argv,
                ref IntPtr pVtab,
                ref IntPtr pError
                )
            {
                //
                // NOTE: Called by native code.
                //
                // CheckDisposed(); /* EXEMPT */

                if (module == null)
                {
                    pError = SQLiteString.Utf8IntPtrFromString(
                        ModuleNotAvailableErrorMessage);

                    return SQLiteErrorCode.Error;
                }

                return module.xCreate(
                    pDb, pAux, argc, argv, ref pVtab, ref pError);
            }

            ///////////////////////////////////////////////////////////////////

            /// <summary>
            /// See the <see cref="ISQLiteNativeModule.xConnect" /> method.
            /// </summary>
            /// <param name="pDb">
            /// See the <see cref="ISQLiteNativeModule.xConnect" /> method.
            /// </param>
            /// <param name="pAux">
            /// See the <see cref="ISQLiteNativeModule.xConnect" /> method.
            /// </param>
            /// <param name="argc">
            /// See the <see cref="ISQLiteNativeModule.xConnect" /> method.
            /// </param>
            /// <param name="argv">
            /// See the <see cref="ISQLiteNativeModule.xConnect" /> method.
            /// </param>
            /// <param name="pVtab">
            /// See the <see cref="ISQLiteNativeModule.xConnect" /> method.
            /// </param>
            /// <param name="pError">
            /// See the <see cref="ISQLiteNativeModule.xConnect" /> method.
            /// </param>
            /// <returns>
            /// See the <see cref="ISQLiteNativeModule.xConnect" /> method.
            /// </returns>
            public SQLiteErrorCode xConnect(
                IntPtr pDb,
                IntPtr pAux,
                int argc,
                IntPtr argv,
                ref IntPtr pVtab,
                ref IntPtr pError
                )
            {
                //
                // NOTE: Called by native code.
                //
                // CheckDisposed(); /* EXEMPT */

                if (module == null)
                {
                    pError = SQLiteString.Utf8IntPtrFromString(
                        ModuleNotAvailableErrorMessage);

                    return SQLiteErrorCode.Error;
                }

                return module.xConnect(
                    pDb, pAux, argc, argv, ref pVtab, ref pError);
            }

            ///////////////////////////////////////////////////////////////////

            /// <summary>
            /// See the <see cref="ISQLiteNativeModule.xBestIndex" /> method.
            /// </summary>
            /// <param name="pVtab">
            /// See the <see cref="ISQLiteNativeModule.xBestIndex" /> method.
            /// </param>
            /// <param name="pIndex">
            /// See the <see cref="ISQLiteNativeModule.xBestIndex" /> method.
            /// </param>
            /// <returns>
            /// See the <see cref="ISQLiteNativeModule.xBestIndex" /> method.
            /// </returns>
            public SQLiteErrorCode xBestIndex(
                IntPtr pVtab,
                IntPtr pIndex
                )
            {
                //
                // NOTE: Called by native code.
                //
                // CheckDisposed(); /* EXEMPT */

                if (module == null)
                    return ModuleNotAvailableTableError(pVtab);

                return module.xBestIndex(pVtab, pIndex);
            }

            ///////////////////////////////////////////////////////////////////

            /// <summary>
            /// See the <see cref="ISQLiteNativeModule.xDisconnect" /> method.
            /// </summary>
            /// <param name="pVtab">
            /// See the <see cref="ISQLiteNativeModule.xDisconnect" /> method.
            /// </param>
            /// <returns>
            /// See the <see cref="ISQLiteNativeModule.xDisconnect" /> method.
            /// </returns>
            public SQLiteErrorCode xDisconnect(
                IntPtr pVtab
                )
            {
                //
                // NOTE: Called by native code.
                //
                // CheckDisposed(); /* EXEMPT */

                if (module == null)
                    return ModuleNotAvailableTableError(pVtab);

                return module.xDisconnect(pVtab);
            }

            ///////////////////////////////////////////////////////////////////

            /// <summary>
            /// See the <see cref="ISQLiteNativeModule.xDestroy" /> method.
            /// </summary>
            /// <param name="pVtab">
            /// See the <see cref="ISQLiteNativeModule.xDestroy" /> method.
            /// </param>
            /// <returns>
            /// See the <see cref="ISQLiteNativeModule.xDestroy" /> method.
            /// </returns>
            public SQLiteErrorCode xDestroy(
                IntPtr pVtab
                )
            {
                //
                // NOTE: Called by native code.
                //
                // CheckDisposed(); /* EXEMPT */

                if (module == null)
                    return ModuleNotAvailableTableError(pVtab);

                return module.xDestroy(pVtab);
            }

            ///////////////////////////////////////////////////////////////////

            /// <summary>
            /// See the <see cref="ISQLiteNativeModule.xOpen" /> method.
            /// </summary>
            /// <param name="pVtab">
            /// See the <see cref="ISQLiteNativeModule.xOpen" /> method.
            /// </param>
            /// <param name="pCursor">
            /// See the <see cref="ISQLiteNativeModule.xOpen" /> method.
            /// </param>
            /// <returns>
            /// See the <see cref="ISQLiteNativeModule.xOpen" /> method.
            /// </returns>
            public SQLiteErrorCode xOpen(
                IntPtr pVtab,
                ref IntPtr pCursor
                )
            {
                //
                // NOTE: Called by native code.
                //
                // CheckDisposed(); /* EXEMPT */

                if (module == null)
                    return ModuleNotAvailableTableError(pVtab);

                return module.xOpen(pVtab, ref pCursor);
            }

            ///////////////////////////////////////////////////////////////////

            /// <summary>
            /// See the <see cref="ISQLiteNativeModule.xClose" /> method.
            /// </summary>
            /// <param name="pCursor">
            /// See the <see cref="ISQLiteNativeModule.xClose" /> method.
            /// </param>
            /// <returns>
            /// See the <see cref="ISQLiteNativeModule.xClose" /> method.
            /// </returns>
            public SQLiteErrorCode xClose(
                IntPtr pCursor
                )
            {
                //
                // NOTE: Called by native code.
                //
                // CheckDisposed(); /* EXEMPT */

                if (module == null)
                    return ModuleNotAvailableCursorError(pCursor);

                return module.xClose(pCursor);
            }

            ///////////////////////////////////////////////////////////////////

            /// <summary>
            /// See the <see cref="ISQLiteNativeModule.xFilter" /> method.
            /// </summary>
            /// <param name="pCursor">
            /// See the <see cref="ISQLiteNativeModule.xFilter" /> method.
            /// </param>
            /// <param name="idxNum">
            /// See the <see cref="ISQLiteNativeModule.xFilter" /> method.
            /// </param>
            /// <param name="idxStr">
            /// See the <see cref="ISQLiteNativeModule.xFilter" /> method.
            /// </param>
            /// <param name="argc">
            /// See the <see cref="ISQLiteNativeModule.xFilter" /> method.
            /// </param>
            /// <param name="argv">
            /// See the <see cref="ISQLiteNativeModule.xFilter" /> method.
            /// </param>
            /// <returns>
            /// See the <see cref="ISQLiteNativeModule.xFilter" /> method.
            /// </returns>
            public SQLiteErrorCode xFilter(
                IntPtr pCursor,
                int idxNum,
                IntPtr idxStr,
                int argc,
                IntPtr argv
                )
            {
                //
                // NOTE: Called by native code.
                //
                // CheckDisposed(); /* EXEMPT */

                if (module == null)
                    return ModuleNotAvailableCursorError(pCursor);

                return module.xFilter(pCursor, idxNum, idxStr, argc, argv);
            }

            ///////////////////////////////////////////////////////////////////

            /// <summary>
            /// See the <see cref="ISQLiteNativeModule.xNext" /> method.
            /// </summary>
            /// <param name="pCursor">
            /// See the <see cref="ISQLiteNativeModule.xNext" /> method.
            /// </param>
            /// <returns>
            /// See the <see cref="ISQLiteNativeModule.xNext" /> method.
            /// </returns>
            public SQLiteErrorCode xNext(
                IntPtr pCursor
                )
            {
                //
                // NOTE: Called by native code.
                //
                // CheckDisposed(); /* EXEMPT */

                if (module == null)
                    return ModuleNotAvailableCursorError(pCursor);

                return module.xNext(pCursor);
            }

            ///////////////////////////////////////////////////////////////////

            /// <summary>
            /// See the <see cref="ISQLiteNativeModule.xEof" /> method.
            /// </summary>
            /// <param name="pCursor">
            /// See the <see cref="ISQLiteNativeModule.xEof" /> method.
            /// </param>
            /// <returns>
            /// See the <see cref="ISQLiteNativeModule.xEof" /> method.
            /// </returns>
            public int xEof(
                IntPtr pCursor
                )
            {
                //
                // NOTE: Called by native code.
                //
                // CheckDisposed(); /* EXEMPT */

                if (module == null)
                {
                    ModuleNotAvailableCursorError(pCursor);
                    return 1;
                }

                return module.xEof(pCursor);
            }

            ///////////////////////////////////////////////////////////////////

            /// <summary>
            /// See the <see cref="ISQLiteNativeModule.xColumn" /> method.
            /// </summary>
            /// <param name="pCursor">
            /// See the <see cref="ISQLiteNativeModule.xColumn" /> method.
            /// </param>
            /// <param name="pContext">
            /// See the <see cref="ISQLiteNativeModule.xColumn" /> method.
            /// </param>
            /// <param name="index">
            /// See the <see cref="ISQLiteNativeModule.xColumn" /> method.
            /// </param>
            /// <returns>
            /// See the <see cref="ISQLiteNativeModule.xColumn" /> method.
            /// </returns>
            public SQLiteErrorCode xColumn(
                IntPtr pCursor,
                IntPtr pContext,
                int index
                )
            {
                //
                // NOTE: Called by native code.
                //
                // CheckDisposed(); /* EXEMPT */

                if (module == null)
                    return ModuleNotAvailableCursorError(pCursor);

                return module.xColumn(pCursor, pContext, index);
            }

            ///////////////////////////////////////////////////////////////////

            /// <summary>
            /// See the <see cref="ISQLiteNativeModule.xRowId" /> method.
            /// </summary>
            /// <param name="pCursor">
            /// See the <see cref="ISQLiteNativeModule.xRowId" /> method.
            /// </param>
            /// <param name="rowId">
            /// See the <see cref="ISQLiteNativeModule.xRowId" /> method.
            /// </param>
            /// <returns>
            /// See the <see cref="ISQLiteNativeModule.xRowId" /> method.
            /// </returns>
            public SQLiteErrorCode xRowId(
                IntPtr pCursor,
                ref long rowId
                )
            {
                //
                // NOTE: Called by native code.
                //
                // CheckDisposed(); /* EXEMPT */

                if (module == null)
                    return ModuleNotAvailableCursorError(pCursor);

                return module.xRowId(pCursor, ref rowId);
            }

            ///////////////////////////////////////////////////////////////////

            /// <summary>
            /// See the <see cref="ISQLiteNativeModule.xUpdate" /> method.
            /// </summary>
            /// <param name="pVtab">
            /// See the <see cref="ISQLiteNativeModule.xUpdate" /> method.
            /// </param>
            /// <param name="argc">
            /// See the <see cref="ISQLiteNativeModule.xUpdate" /> method.
            /// </param>
            /// <param name="argv">
            /// See the <see cref="ISQLiteNativeModule.xUpdate" /> method.
            /// </param>
            /// <param name="rowId">
            /// See the <see cref="ISQLiteNativeModule.xUpdate" /> method.
            /// </param>
            /// <returns>
            /// See the <see cref="ISQLiteNativeModule.xUpdate" /> method.
            /// </returns>
            public SQLiteErrorCode xUpdate(
                IntPtr pVtab,
                int argc,
                IntPtr argv,
                ref long rowId
                )
            {
                //
                // NOTE: Called by native code.
                //
                // CheckDisposed(); /* EXEMPT */

                if (module == null)
                    return ModuleNotAvailableTableError(pVtab);

                return module.xUpdate(pVtab, argc, argv, ref rowId);
            }

            ///////////////////////////////////////////////////////////////////

            /// <summary>
            /// See the <see cref="ISQLiteNativeModule.xBegin" /> method.
            /// </summary>
            /// <param name="pVtab">
            /// See the <see cref="ISQLiteNativeModule.xBegin" /> method.
            /// </param>
            /// <returns>
            /// See the <see cref="ISQLiteNativeModule.xBegin" /> method.
            /// </returns>
            public SQLiteErrorCode xBegin(
                IntPtr pVtab
                )
            {
                //
                // NOTE: Called by native code.
                //
                // CheckDisposed(); /* EXEMPT */

                if (module == null)
                    return ModuleNotAvailableTableError(pVtab);

                return module.xBegin(pVtab);
            }

            ///////////////////////////////////////////////////////////////////

            /// <summary>
            /// See the <see cref="ISQLiteNativeModule.xSync" /> method.
            /// </summary>
            /// <param name="pVtab">
            /// See the <see cref="ISQLiteNativeModule.xSync" /> method.
            /// </param>
            /// <returns>
            /// See the <see cref="ISQLiteNativeModule.xSync" /> method.
            /// </returns>
            public SQLiteErrorCode xSync(
                IntPtr pVtab
                )
            {
                //
                // NOTE: Called by native code.
                //
                // CheckDisposed(); /* EXEMPT */

                if (module == null)
                    return ModuleNotAvailableTableError(pVtab);

                return module.xSync(pVtab);
            }

            ///////////////////////////////////////////////////////////////////

            /// <summary>
            /// See the <see cref="ISQLiteNativeModule.xCommit" /> method.
            /// </summary>
            /// <param name="pVtab">
            /// See the <see cref="ISQLiteNativeModule.xCommit" /> method.
            /// </param>
            /// <returns>
            /// See the <see cref="ISQLiteNativeModule.xCommit" /> method.
            /// </returns>
            public SQLiteErrorCode xCommit(
                IntPtr pVtab
                )
            {
                //
                // NOTE: Called by native code.
                //
                // CheckDisposed(); /* EXEMPT */

                if (module == null)
                    return ModuleNotAvailableTableError(pVtab);

                return module.xCommit(pVtab);
            }

            ///////////////////////////////////////////////////////////////////

            /// <summary>
            /// See the <see cref="ISQLiteNativeModule.xRollback" /> method.
            /// </summary>
            /// <param name="pVtab">
            /// See the <see cref="ISQLiteNativeModule.xRollback" /> method.
            /// </param>
            /// <returns>
            /// See the <see cref="ISQLiteNativeModule.xRollback" /> method.
            /// </returns>
            public SQLiteErrorCode xRollback(
                IntPtr pVtab
                )
            {
                //
                // NOTE: Called by native code.
                //
                // CheckDisposed(); /* EXEMPT */

                if (module == null)
                    return ModuleNotAvailableTableError(pVtab);

                return module.xRollback(pVtab);
            }

            ///////////////////////////////////////////////////////////////////

            /// <summary>
            /// See the <see cref="ISQLiteNativeModule.xFindFunction" /> method.
            /// </summary>
            /// <param name="pVtab">
            /// See the <see cref="ISQLiteNativeModule.xFindFunction" /> method.
            /// </param>
            /// <param name="nArg">
            /// See the <see cref="ISQLiteNativeModule.xFindFunction" /> method.
            /// </param>
            /// <param name="zName">
            /// See the <see cref="ISQLiteNativeModule.xFindFunction" /> method.
            /// </param>
            /// <param name="callback">
            /// See the <see cref="ISQLiteNativeModule.xFindFunction" /> method.
            /// </param>
            /// <param name="pClientData">
            /// See the <see cref="ISQLiteNativeModule.xFindFunction" /> method.
            /// </param>
            /// <returns>
            /// See the <see cref="ISQLiteNativeModule.xFindFunction" /> method.
            /// </returns>
            public int xFindFunction(
                IntPtr pVtab,
                int nArg,
                IntPtr zName,
                ref SQLiteCallback callback,
                ref IntPtr pClientData
                )
            {
                //
                // NOTE: Called by native code.
                //
                // CheckDisposed(); /* EXEMPT */

                if (module == null)
                {
                    ModuleNotAvailableTableError(pVtab);
                    return 0;
                }

                return module.xFindFunction(
                    pVtab, nArg, zName, ref callback, ref pClientData);
            }

            ///////////////////////////////////////////////////////////////////

            /// <summary>
            /// See the <see cref="ISQLiteNativeModule.xRename" /> method.
            /// </summary>
            /// <param name="pVtab">
            /// See the <see cref="ISQLiteNativeModule.xRename" /> method.
            /// </param>
            /// <param name="zNew">
            /// See the <see cref="ISQLiteNativeModule.xRename" /> method.
            /// </param>
            /// <returns>
            /// See the <see cref="ISQLiteNativeModule.xRename" /> method.
            /// </returns>
            public SQLiteErrorCode xRename(
                IntPtr pVtab,
                IntPtr zNew
                )
            {
                //
                // NOTE: Called by native code.
                //
                // CheckDisposed(); /* EXEMPT */

                if (module == null)
                    return ModuleNotAvailableTableError(pVtab);

                return module.xRename(pVtab, zNew);
            }

            ///////////////////////////////////////////////////////////////////

            /// <summary>
            /// See the <see cref="ISQLiteNativeModule.xSavepoint" /> method.
            /// </summary>
            /// <param name="pVtab">
            /// See the <see cref="ISQLiteNativeModule.xSavepoint" /> method.
            /// </param>
            /// <param name="iSavepoint">
            /// See the <see cref="ISQLiteNativeModule.xSavepoint" /> method.
            /// </param>
            /// <returns>
            /// See the <see cref="ISQLiteNativeModule.xSavepoint" /> method.
            /// </returns>
            public SQLiteErrorCode xSavepoint(
                IntPtr pVtab,
                int iSavepoint
                )
            {
                //
                // NOTE: Called by native code.
                //
                // CheckDisposed(); /* EXEMPT */

                if (module == null)
                    return ModuleNotAvailableTableError(pVtab);

                return module.xSavepoint(pVtab, iSavepoint);
            }

            ///////////////////////////////////////////////////////////////////

            /// <summary>
            /// See the <see cref="ISQLiteNativeModule.xRelease" /> method.
            /// </summary>
            /// <param name="pVtab">
            /// See the <see cref="ISQLiteNativeModule.xRelease" /> method.
            /// </param>
            /// <param name="iSavepoint">
            /// See the <see cref="ISQLiteNativeModule.xRelease" /> method.
            /// </param>
            /// <returns>
            /// See the <see cref="ISQLiteNativeModule.xRelease" /> method.
            /// </returns>
            public SQLiteErrorCode xRelease(
                IntPtr pVtab,
                int iSavepoint
                )
            {
                //
                // NOTE: Called by native code.
                //
                // CheckDisposed(); /* EXEMPT */

                if (module == null)
                    return ModuleNotAvailableTableError(pVtab);

                return module.xRelease(pVtab, iSavepoint);
            }

            ///////////////////////////////////////////////////////////////////

            /// <summary>
            /// See the <see cref="ISQLiteNativeModule.xRollbackTo" /> method.
            /// </summary>
            /// <param name="pVtab">
            /// See the <see cref="ISQLiteNativeModule.xRollbackTo" /> method.
            /// </param>
            /// <param name="iSavepoint">
            /// See the <see cref="ISQLiteNativeModule.xRollbackTo" /> method.
            /// </param>
            /// <returns>
            /// See the <see cref="ISQLiteNativeModule.xRollbackTo" /> method.
            /// </returns>
            public SQLiteErrorCode xRollbackTo(
                IntPtr pVtab,
                int iSavepoint
                )
            {
                //
                // NOTE: Called by native code.
                //
                // CheckDisposed(); /* EXEMPT */

                if (module == null)
                    return ModuleNotAvailableTableError(pVtab);

                return module.xRollbackTo(pVtab, iSavepoint);
            }
            #endregion

            ///////////////////////////////////////////////////////////////////

            #region IDisposable Members
            /// <summary>
            /// Disposes of this object instance.
            /// </summary>
            public void Dispose()
            {
                Dispose(true);
                GC.SuppressFinalize(this);
            }
            #endregion

            ///////////////////////////////////////////////////////////////////

            #region IDisposable "Pattern" Members
            private bool disposed;
            /// <summary>
            /// Throws an <see cref="ObjectDisposedException" /> if this object
            /// instance has been disposed.
            /// </summary>
            private void CheckDisposed() /* throw */
            {
#if THROW_ON_DISPOSED
                if (disposed)
                {
                    throw new ObjectDisposedException(
                        typeof(SQLiteNativeModule).Name);
                }
#endif
            }

            ///////////////////////////////////////////////////////////////////

            /// <summary>
            /// Disposes of this object instance.
            /// </summary>
            /// <param name="disposing">
            /// Non-zero if this method is being called from the
            /// <see cref="Dispose()" /> method.  Zero if this method is being
            /// called from the finalizer.
            /// </param>
            private /* protected virtual */ void Dispose(bool disposing)
            {
                if (!disposed)
                {
                    //if (disposing)
                    //{
                    //    ////////////////////////////////////
                    //    // dispose managed resources here...
                    //    ////////////////////////////////////
                    //}

                    //////////////////////////////////////
                    // release unmanaged resources here...
                    //////////////////////////////////////

                    //
                    // NOTE: The module is not owned by us; therefore, do not
                    //       dispose it.
                    //
                    if (module != null)
                        module = null;

                    disposed = true;
                }
            }
            #endregion

            ///////////////////////////////////////////////////////////////////

            #region Destructor
            /// <summary>
            /// Finalizes this object instance.
            /// </summary>
            ~SQLiteNativeModule()
            {
                Dispose(false);
            }
            #endregion
        }
        #endregion

        ///////////////////////////////////////////////////////////////////////

        #region Private Constants
        /// <summary>
        /// The default version of the native sqlite3_module structure in use.
        /// </summary>
        private static readonly int DefaultModuleVersion = 2;
        #endregion

        ///////////////////////////////////////////////////////////////////////

        #region Private Data
        /// <summary>
        /// This field is used to store the native sqlite3_module structure
        /// associated with this object instance.
        /// </summary>
        private UnsafeNativeMethods.sqlite3_module nativeModule;

        ///////////////////////////////////////////////////////////////////////

        /// <summary>
        /// This field is used to store the destructor delegate to be passed to
        /// the SQLite core library via the sqlite3_create_disposable_module()
        /// function.
        /// </summary>
        private UnsafeNativeMethods.xDestroyModule destroyModule;

        ///////////////////////////////////////////////////////////////////////

        /// <summary>
        /// This field is used to store a pointer to the native sqlite3_module
        /// structure returned by the sqlite3_create_disposable_module
        /// function.
        /// </summary>
        private IntPtr disposableModule;

        ///////////////////////////////////////////////////////////////////////

#if PLATFORM_COMPACTFRAMEWORK
        /// <summary>
        /// This field is used to hold the block of native memory that contains
        /// the native sqlite3_module structure associated with this object
        /// instance when running on the .NET Compact Framework.
        /// </summary>
        private IntPtr pNativeModule;
#endif

        ///////////////////////////////////////////////////////////////////////

        /// <summary>
        /// This field is used to store the virtual table instances associated
        /// with this module.  The native pointer to the sqlite3_vtab derived
        /// structure is used to key into this collection.
        /// </summary>
        private Dictionary<IntPtr, SQLiteVirtualTable> tables;

        ///////////////////////////////////////////////////////////////////////

        /// <summary>
        /// This field is used to store the virtual table cursor instances
        /// associated with this module.  The native pointer to the
        /// sqlite3_vtab_cursor derived structure is used to key into this
        /// collection.
        /// </summary>
        private Dictionary<IntPtr, SQLiteVirtualTableCursor> cursors;

        ///////////////////////////////////////////////////////////////////////

        /// <summary>
        /// This field is used to store the virtual table function instances
        /// associated with this module.  The case-insensitive function name
        /// and the number of arguments (with -1 meaning "any") are used to
        /// construct the string that is used to key into this collection.
        /// </summary>
        private Dictionary<string, SQLiteFunction> functions;
        #endregion

        ///////////////////////////////////////////////////////////////////////

        #region Public Constructors
        /// <summary>
        /// Constructs an instance of this class.
        /// </summary>
        /// <param name="name">
        /// The name of the module.  This parameter cannot be null.
        /// </param>
        public SQLiteModule(string name)
        {
            if (name == null)
                throw new ArgumentNullException("name");

            this.name = name;
            this.tables = new Dictionary<IntPtr, SQLiteVirtualTable>();
            this.cursors = new Dictionary<IntPtr, SQLiteVirtualTableCursor>();
            this.functions = new Dictionary<string, SQLiteFunction>();
        }
        #endregion

        ///////////////////////////////////////////////////////////////////////

        #region Internal Methods
        /// <summary>
        /// Calls the native SQLite core library in order to create a new
        /// disposable module containing the implementation of a virtual table.
        /// </summary>
        /// <param name="pDb">
        /// The native database connection pointer to use.
        /// </param>
        /// <returns>
        /// Non-zero upon success.
        /// </returns>
        internal bool CreateDisposableModule(
            IntPtr pDb
            )
        {
            if (disposableModule != IntPtr.Zero)
                return true;

            IntPtr pName = IntPtr.Zero;

            try
            {
                pName = SQLiteString.Utf8IntPtrFromString(name);

                UnsafeNativeMethods.sqlite3_module nativeModule =
                    AllocateNativeModule();

                destroyModule = new UnsafeNativeMethods.xDestroyModule(
                    xDestroyModule);

#if !PLATFORM_COMPACTFRAMEWORK
                disposableModule =
                    UnsafeNativeMethods.sqlite3_create_disposable_module(
                        pDb, pName, ref nativeModule, IntPtr.Zero, destroyModule);

                return (disposableModule != IntPtr.Zero);
#elif !SQLITE_STANDARD
                disposableModule =
                    UnsafeNativeMethods.sqlite3_create_disposable_module_interop(
                       pDb, pName, AllocateNativeModuleInterop(),
                       nativeModule.iVersion, nativeModule.xCreate,
                       nativeModule.xConnect, nativeModule.xBestIndex,
                       nativeModule.xDisconnect, nativeModule.xDestroy,
                       nativeModule.xOpen, nativeModule.xClose,
                       nativeModule.xFilter, nativeModule.xNext,
                       nativeModule.xEof, nativeModule.xColumn,
                       nativeModule.xRowId, nativeModule.xUpdate,
                       nativeModule.xBegin, nativeModule.xSync,
                       nativeModule.xCommit, nativeModule.xRollback,
                       nativeModule.xFindFunction, nativeModule.xRename,
                       nativeModule.xSavepoint, nativeModule.xRelease,
                       nativeModule.xRollbackTo, IntPtr.Zero, destroyModule);

                return (disposableModule != IntPtr.Zero);
#else
                throw new NotImplementedException();
#endif
            }
            finally
            {
                if (pName != IntPtr.Zero)
                {
                    SQLiteMemory.Free(pName);
                    pName = IntPtr.Zero;
                }
            }
        }
        #endregion

        ///////////////////////////////////////////////////////////////////////

        #region Private Methods
        /// <summary>
        /// This method is called by the SQLite core library when the native
        /// module associated with this object instance is being destroyed due
        /// to its parent connection being closed.  It may also be called by
        /// the "vtshim" module if/when the sqlite3_dispose_module() function
        /// is called.
        /// </summary>
        /// <param name="pClientData">
        /// The native user-data pointer associated with this module, as it was
        /// provided to the SQLite core library when the native module instance
        /// was created.
        /// </param>
        private void xDestroyModule(
            IntPtr pClientData /* NOT USED */
            )
        {
            //
            // NOTE: At this point, just make sure that this native module
            //       handle is not reused, nor passed into the native
            //       sqlite3_dispose_module() function later (i.e. if/when
            //       the Dispose() method of this object instance is called).
            //
            disposableModule = IntPtr.Zero;
        }

        ///////////////////////////////////////////////////////////////////////

        /// <summary>
        /// Creates and returns the native sqlite_module structure using the
        /// configured (or default) <see cref="ISQLiteNativeModule" />
        /// interface implementation.
        /// </summary>
        /// <returns>
        /// The native sqlite_module structure using the configured (or
        /// default) <see cref="ISQLiteNativeModule" /> interface
        /// implementation.
        /// </returns>
        private UnsafeNativeMethods.sqlite3_module AllocateNativeModule()
        {
            return AllocateNativeModule(GetNativeModuleImpl());
        }

        ///////////////////////////////////////////////////////////////////////

#if PLATFORM_COMPACTFRAMEWORK
        /// <summary>
        /// Creates and returns a memory block obtained from the SQLite core
        /// library used to store the native sqlite3_module structure for this
        /// object instance when running on the .NET Compact Framework.
        /// </summary>
        /// <returns>
        /// The native pointer to the native sqlite3_module structure.
        /// </returns>
        private IntPtr AllocateNativeModuleInterop()
        {
            if (pNativeModule == IntPtr.Zero)
            {
                //
                // HACK: No easy way to determine the size of the native
                //       sqlite_module structure when running on the .NET
                //       Compact Framework; therefore, just base the size
                //       on what we know:
                //
                //       There is one integer member.
                //       There are 22 function pointer members.
                //
                pNativeModule = SQLiteMemory.Allocate(23 * IntPtr.Size);

                if (pNativeModule == IntPtr.Zero)
                    throw new OutOfMemoryException("sqlite3_module");
            }

            return pNativeModule;
        }
#endif

        ///////////////////////////////////////////////////////////////////////

        /// <summary>
        /// Creates and returns the native sqlite_module structure using the
        /// specified <see cref="ISQLiteNativeModule" /> interface
        /// implementation.
        /// </summary>
        /// <param name="module">
        /// The <see cref="ISQLiteNativeModule" /> interface implementation to
        /// use.
        /// </param>
        /// <returns>
        /// The native sqlite_module structure using the specified
        /// <see cref="ISQLiteNativeModule" /> interface implementation.
        /// </returns>
        private UnsafeNativeMethods.sqlite3_module AllocateNativeModule(
            ISQLiteNativeModule module
            )
        {
            nativeModule = new UnsafeNativeMethods.sqlite3_module();
            nativeModule.iVersion = DefaultModuleVersion;

            if (module != null)
            {
                nativeModule.xCreate = new UnsafeNativeMethods.xCreate(
                   module.xCreate);

                nativeModule.xConnect = new UnsafeNativeMethods.xConnect(
                    module.xConnect);

                nativeModule.xBestIndex = new UnsafeNativeMethods.xBestIndex(
                    module.xBestIndex);

                nativeModule.xDisconnect = new UnsafeNativeMethods.xDisconnect(
                    module.xDisconnect);

                nativeModule.xDestroy = new UnsafeNativeMethods.xDestroy(
                    module.xDestroy);

                nativeModule.xOpen = new UnsafeNativeMethods.xOpen(
                    module.xOpen);

                nativeModule.xClose = new UnsafeNativeMethods.xClose(
                    module.xClose);

                nativeModule.xFilter = new UnsafeNativeMethods.xFilter(
                    module.xFilter);

                nativeModule.xNext = new UnsafeNativeMethods.xNext(
                    module.xNext);

                nativeModule.xEof = new UnsafeNativeMethods.xEof(module.xEof);

                nativeModule.xColumn = new UnsafeNativeMethods.xColumn(
                    module.xColumn);

                nativeModule.xRowId = new UnsafeNativeMethods.xRowId(
                    module.xRowId);

                nativeModule.xUpdate = new UnsafeNativeMethods.xUpdate(
                    module.xUpdate);

                nativeModule.xBegin = new UnsafeNativeMethods.xBegin(
                    module.xBegin);

                nativeModule.xSync = new UnsafeNativeMethods.xSync(
                    module.xSync);

                nativeModule.xCommit = new UnsafeNativeMethods.xCommit(
                    module.xCommit);

                nativeModule.xRollback = new UnsafeNativeMethods.xRollback(
                    module.xRollback);

                nativeModule.xFindFunction = new UnsafeNativeMethods.xFindFunction(
                    module.xFindFunction);

                nativeModule.xRename = new UnsafeNativeMethods.xRename(
                    module.xRename);

                nativeModule.xSavepoint = new UnsafeNativeMethods.xSavepoint(
                    module.xSavepoint);

                nativeModule.xRelease = new UnsafeNativeMethods.xRelease(
                    module.xRelease);

                nativeModule.xRollbackTo = new UnsafeNativeMethods.xRollbackTo(
                    module.xRollbackTo);
            }
            else
            {
                nativeModule.xCreate = new UnsafeNativeMethods.xCreate(
                    xCreate);

                nativeModule.xConnect = new UnsafeNativeMethods.xConnect(
                    xConnect);

                nativeModule.xBestIndex = new UnsafeNativeMethods.xBestIndex(
                    xBestIndex);

                nativeModule.xDisconnect = new UnsafeNativeMethods.xDisconnect(
                    xDisconnect);

                nativeModule.xDestroy = new UnsafeNativeMethods.xDestroy(
                    xDestroy);

                nativeModule.xOpen = new UnsafeNativeMethods.xOpen(xOpen);
                nativeModule.xClose = new UnsafeNativeMethods.xClose(xClose);

                nativeModule.xFilter = new UnsafeNativeMethods.xFilter(
                    xFilter);

                nativeModule.xNext = new UnsafeNativeMethods.xNext(xNext);
                nativeModule.xEof = new UnsafeNativeMethods.xEof(xEof);

                nativeModule.xColumn = new UnsafeNativeMethods.xColumn(
                    xColumn);

                nativeModule.xRowId = new UnsafeNativeMethods.xRowId(xRowId);

                nativeModule.xUpdate = new UnsafeNativeMethods.xUpdate(
                    xUpdate);

                nativeModule.xBegin = new UnsafeNativeMethods.xBegin(xBegin);
                nativeModule.xSync = new UnsafeNativeMethods.xSync(xSync);

                nativeModule.xCommit = new UnsafeNativeMethods.xCommit(
                    xCommit);

                nativeModule.xRollback = new UnsafeNativeMethods.xRollback(
                    xRollback);

                nativeModule.xFindFunction = new UnsafeNativeMethods.xFindFunction(
                    xFindFunction);

                nativeModule.xRename = new UnsafeNativeMethods.xRename(
                    xRename);

                nativeModule.xSavepoint = new UnsafeNativeMethods.xSavepoint(
                    xSavepoint);

                nativeModule.xRelease = new UnsafeNativeMethods.xRelease(
                    xRelease);

                nativeModule.xRollbackTo = new UnsafeNativeMethods.xRollbackTo(
                    xRollbackTo);
            }

            return nativeModule;
        }

        ///////////////////////////////////////////////////////////////////////

        /// <summary>
        /// Creates a copy of the specified
        /// <see cref="UnsafeNativeMethods.sqlite3_module" /> object instance,
        /// using default implementations for the contained delegates when
        /// necessary.
        /// </summary>
        /// <param name="module">
        /// The <see cref="UnsafeNativeMethods.sqlite3_module" /> object
        /// instance to copy.
        /// </param>
        /// <returns>
        /// The new <see cref="UnsafeNativeMethods.sqlite3_module" /> object
        /// instance.
        /// </returns>
        private UnsafeNativeMethods.sqlite3_module CopyNativeModule(
            UnsafeNativeMethods.sqlite3_module module
            )
        {
            UnsafeNativeMethods.sqlite3_module newModule =
                new UnsafeNativeMethods.sqlite3_module();

            newModule.iVersion = module.iVersion;

            newModule.xCreate = new UnsafeNativeMethods.xCreate(
                (module.xCreate != null) ? module.xCreate : xCreate);

            newModule.xConnect = new UnsafeNativeMethods.xConnect(
                (module.xConnect != null) ? module.xConnect : xConnect);

            newModule.xBestIndex = new UnsafeNativeMethods.xBestIndex(
                (module.xBestIndex != null) ? module.xBestIndex : xBestIndex);

            newModule.xDisconnect = new UnsafeNativeMethods.xDisconnect(
                (module.xDisconnect != null) ? module.xDisconnect :
                xDisconnect);

            newModule.xDestroy = new UnsafeNativeMethods.xDestroy(
                (module.xDestroy != null) ? module.xDestroy : xDestroy);

            newModule.xOpen = new UnsafeNativeMethods.xOpen(
                (module.xOpen != null) ? module.xOpen : xOpen);

            newModule.xClose = new UnsafeNativeMethods.xClose(
                (module.xClose != null) ? module.xClose : xClose);

            newModule.xFilter = new UnsafeNativeMethods.xFilter(
                (module.xFilter != null) ? module.xFilter : xFilter);

            newModule.xNext = new UnsafeNativeMethods.xNext(
                (module.xNext != null) ? module.xNext : xNext);

            newModule.xEof = new UnsafeNativeMethods.xEof(
                (module.xEof != null) ? module.xEof : xEof);

            newModule.xColumn = new UnsafeNativeMethods.xColumn(
                (module.xColumn != null) ? module.xColumn : xColumn);

            newModule.xRowId = new UnsafeNativeMethods.xRowId(
                (module.xRowId != null) ? module.xRowId : xRowId);

            newModule.xUpdate = new UnsafeNativeMethods.xUpdate(
                (module.xUpdate != null) ? module.xUpdate : xUpdate);

            newModule.xBegin = new UnsafeNativeMethods.xBegin(
                (module.xBegin != null) ? module.xBegin : xBegin);

            newModule.xSync = new UnsafeNativeMethods.xSync(
                (module.xSync != null) ? module.xSync : xSync);

            newModule.xCommit = new UnsafeNativeMethods.xCommit(
                (module.xCommit != null) ? module.xCommit : xCommit);

            newModule.xRollback = new UnsafeNativeMethods.xRollback(
                (module.xRollback != null) ? module.xRollback : xRollback);

            newModule.xFindFunction = new UnsafeNativeMethods.xFindFunction(
                (module.xFindFunction != null) ? module.xFindFunction :
                xFindFunction);

            newModule.xRename = new UnsafeNativeMethods.xRename(
                (module.xRename != null) ? module.xRename : xRename);

            newModule.xSavepoint = new UnsafeNativeMethods.xSavepoint(
                (module.xSavepoint != null) ? module.xSavepoint : xSavepoint);

            newModule.xRelease = new UnsafeNativeMethods.xRelease(
                (module.xRelease != null) ? module.xRelease : xRelease);

            newModule.xRollbackTo = new UnsafeNativeMethods.xRollbackTo(
                (module.xRollbackTo != null) ? module.xRollbackTo :
                xRollbackTo);

            return newModule;
        }

        ///////////////////////////////////////////////////////////////////////

        /// <summary>
        /// Calls one of the virtual table initialization methods.
        /// </summary>
        /// <param name="create">
        /// Non-zero to call the <see cref="ISQLiteManagedModule.Create" />
        /// method; otherwise, the <see cref="ISQLiteManagedModule.Connect" />
        /// method will be called.
        /// </param>
        /// <param name="pDb">
        /// The native database connection handle.
        /// </param>
        /// <param name="pAux">
        /// The original native pointer value that was provided to the
        /// sqlite3_create_module(), sqlite3_create_module_v2() or
        /// sqlite3_create_disposable_module() functions.
        /// </param>
        /// <param name="argc">
        /// The number of arguments from the CREATE VIRTUAL TABLE statement.
        /// </param>
        /// <param name="argv">
        /// The array of string arguments from the CREATE VIRTUAL TABLE
        /// statement.
        /// </param>
        /// <param name="pVtab">
        /// Upon success, this parameter must be modified to point to the newly
        /// created native sqlite3_vtab derived structure.
        /// </param>
        /// <param name="pError">
        /// Upon failure, this parameter must be modified to point to the error
        /// message, with the underlying memory having been obtained from the
        /// sqlite3_malloc() function.
        /// </param>
        /// <returns>
        /// A standard SQLite return code.
        /// </returns>
        private SQLiteErrorCode CreateOrConnect(
            bool create,
            IntPtr pDb,
            IntPtr pAux,
            int argc,
            IntPtr argv,
            ref IntPtr pVtab,
            ref IntPtr pError
            )
        {
            try
            {
                string fileName = SQLiteString.StringFromUtf8IntPtr(
                    UnsafeNativeMethods.sqlite3_db_filename(pDb, IntPtr.Zero));

                using (SQLiteConnection connection = new SQLiteConnection(
                        pDb, fileName, false))
                {
                    SQLiteVirtualTable table = null;
                    string error = null;

                    if ((create && Create(connection, pAux,
                            SQLiteString.StringArrayFromUtf8SizeAndIntPtr(argc,
                            argv), ref table, ref error) == SQLiteErrorCode.Ok) ||
                        (!create && Connect(connection, pAux,
                            SQLiteString.StringArrayFromUtf8SizeAndIntPtr(argc,
                            argv), ref table, ref error) == SQLiteErrorCode.Ok))
                    {
                        if (table != null)
                        {
                            pVtab = TableToIntPtr(table);
                            return SQLiteErrorCode.Ok;
                        }
                        else
                        {
                            pError = SQLiteString.Utf8IntPtrFromString(
                                "no table was created");
                        }
                    }
                    else
                    {
                        pError = SQLiteString.Utf8IntPtrFromString(error);
                    }
                }
            }
            catch (Exception e) /* NOTE: Must catch ALL. */
            {
                pError = SQLiteString.Utf8IntPtrFromString(e.ToString());
            }

            return SQLiteErrorCode.Error;
        }

        ///////////////////////////////////////////////////////////////////////

        /// <summary>
        /// Calls one of the virtual table finalization methods.
        /// </summary>
        /// <param name="destroy">
        /// Non-zero to call the <see cref="ISQLiteManagedModule.Destroy" />
        /// method; otherwise, the
        /// <see cref="ISQLiteManagedModule.Disconnect" /> method will be
        /// called.
        /// </param>
        /// <param name="pVtab">
        /// The native pointer to the sqlite3_vtab derived structure.
        /// </param>
        /// <returns>
        /// A standard SQLite return code.
        /// </returns>
        private SQLiteErrorCode DestroyOrDisconnect(
            bool destroy,
            IntPtr pVtab
            )
        {
            try
            {
                SQLiteVirtualTable table = TableFromIntPtr(pVtab);

                if (table != null)
                {
                    if ((destroy && (Destroy(table) == SQLiteErrorCode.Ok)) ||
                        (!destroy && (Disconnect(table) == SQLiteErrorCode.Ok)))
                    {
                        if (tables != null)
                            tables.Remove(pVtab);

                        return SQLiteErrorCode.Ok;
                    }
                }
            }
            catch (Exception e) /* NOTE: Must catch ALL. */
            {
                //
                // NOTE: At this point, there is no way to report the error
                //       condition back to the caller; therefore, use the
                //       logging facility instead.
                //
                try
                {
                    if (LogExceptionsNoThrow)
                    {
                        /* throw */
                        SQLiteLog.LogMessage(SQLiteBase.COR_E_EXCEPTION,
                            HelperMethods.StringFormat(
                            CultureInfo.CurrentCulture,
                            UnsafeNativeMethods.ExceptionMessageFormat,
                            destroy ? "xDestroy" : "xDisconnect", e));
                    }
                }
                catch
                {
                    // do nothing.
                }
            }
            finally
            {
                FreeTable(pVtab);
            }

            return SQLiteErrorCode.Error;
        }

        ///////////////////////////////////////////////////////////////////////

        #region Static Error Handling Helper Methods
        /// <summary>
        /// Arranges for the specified error message to be placed into the
        /// zErrMsg field of a sqlite3_vtab derived structure, freeing the
        /// existing error message, if any.
        /// </summary>
        /// <param name="module">
        /// The <see cref="SQLiteModule" /> object instance to be used.
        /// </param>
        /// <param name="pVtab">
        /// The native pointer to the sqlite3_vtab derived structure.
        /// </param>
        /// <param name="logErrors">
        /// Non-zero if this error message should also be logged using the
        /// <see cref="SQLiteLog" /> class.
        /// </param>
        /// <param name="logExceptions">
        /// Non-zero if caught exceptions should be logged using the
        /// <see cref="SQLiteLog" /> class.
        /// </param>
        /// <param name="error">
        /// The error message.
        /// </param>
        /// <returns>
        /// Non-zero upon success.
        /// </returns>
        private static bool SetTableError(
            SQLiteModule module,
            IntPtr pVtab,
            bool logErrors,
            bool logExceptions,
            string error
            )
        {
            try
            {
                if (logErrors)
                {
                    SQLiteLog.LogMessage(SQLiteErrorCode.Error,
                        HelperMethods.StringFormat(
                        CultureInfo.CurrentCulture,
                        "Virtual table error: {0}", error)); /* throw */
                }
            }
            catch
            {
                // do nothing.
            }

            bool success = false;
            IntPtr pNewError = IntPtr.Zero;

            try
            {
                if (pVtab == IntPtr.Zero)
                    return false;

                int offset = 0;

                offset = SQLiteMarshal.NextOffsetOf(
                    offset, IntPtr.Size, sizeof(int));

                offset = SQLiteMarshal.NextOffsetOf(
                    offset, sizeof(int), IntPtr.Size);

                IntPtr pOldError = SQLiteMarshal.ReadIntPtr(pVtab, offset);

                if (pOldError != IntPtr.Zero)
                {
                    SQLiteMemory.Free(pOldError); pOldError = IntPtr.Zero;
                    SQLiteMarshal.WriteIntPtr(pVtab, offset, pOldError);
                }

                if (error == null)
                    return true;

                pNewError = SQLiteString.Utf8IntPtrFromString(error);
                SQLiteMarshal.WriteIntPtr(pVtab, offset, pNewError);
                success = true;
            }
            catch (Exception e) /* NOTE: Must catch ALL. */
            {
                try
                {
                    if (logExceptions)
                    {
                        SQLiteLog.LogMessage(SQLiteBase.COR_E_EXCEPTION,
                            HelperMethods.StringFormat(
                            CultureInfo.CurrentCulture,
                            UnsafeNativeMethods.ExceptionMessageFormat,
                            "SetTableError", e)); /* throw */
                    }
                }
                catch
                {
                    // do nothing.
                }
            }
            finally
            {
                if (!success && (pNewError != IntPtr.Zero))
                {
                    SQLiteMemory.Free(pNewError);
                    pNewError = IntPtr.Zero;
                }
            }

            return success;
        }

        ///////////////////////////////////////////////////////////////////////

        /// <summary>
        /// Arranges for the specified error message to be placed into the
        /// zErrMsg field of a sqlite3_vtab derived structure, freeing the
        /// existing error message, if any.
        /// </summary>
        /// <param name="module">
        /// The <see cref="SQLiteModule" /> object instance to be used.
        /// </param>
        /// <param name="table">
        /// The <see cref="SQLiteVirtualTable" /> object instance used to
        /// lookup the native pointer to the sqlite3_vtab derived structure.
        /// </param>
        /// <param name="logErrors">
        /// Non-zero if this error message should also be logged using the
        /// <see cref="SQLiteLog" /> class.
        /// </param>
        /// <param name="logExceptions">
        /// Non-zero if caught exceptions should be logged using the
        /// <see cref="SQLiteLog" /> class.
        /// </param>
        /// <param name="error">
        /// The error message.
        /// </param>
        /// <returns>
        /// Non-zero upon success.
        /// </returns>
        private static bool SetTableError(
            SQLiteModule module,
            SQLiteVirtualTable table,
            bool logErrors,
            bool logExceptions,
            string error
            )
        {
            if (table == null)
                return false;

            IntPtr pVtab = table.NativeHandle;

            if (pVtab == IntPtr.Zero)
                return false;

            return SetTableError(
                module, pVtab, logErrors, logExceptions, error);
        }

        ///////////////////////////////////////////////////////////////////////

        /// <summary>
        /// Arranges for the specified error message to be placed into the
        /// zErrMsg field of a sqlite3_vtab derived structure, freeing the
        /// existing error message, if any.
        /// </summary>
        /// <param name="module">
        /// The <see cref="SQLiteModule" /> object instance to be used.
        /// </param>
        /// <param name="pCursor">
        /// The native pointer to the sqlite3_vtab_cursor derived structure
        /// used to get the native pointer to the sqlite3_vtab derived
        /// structure.
        /// </param>
        /// <param name="logErrors">
        /// Non-zero if this error message should also be logged using the
        /// <see cref="SQLiteLog" /> class.
        /// </param>
        /// <param name="logExceptions">
        /// Non-zero if caught exceptions should be logged using the
        /// <see cref="SQLiteLog" /> class.
        /// </param>
        /// <param name="error">
        /// The error message.
        /// </param>
        /// <returns>
        /// Non-zero upon success.
        /// </returns>
        private static bool SetCursorError(
            SQLiteModule module,
            IntPtr pCursor,
            bool logErrors,
            bool logExceptions,
            string error
            )
        {
            if (pCursor == IntPtr.Zero)
                return false;

            IntPtr pVtab = TableFromCursor(module, pCursor);

            if (pVtab == IntPtr.Zero)
                return false;

            return SetTableError(
                module, pVtab, logErrors, logExceptions, error);
        }

        ///////////////////////////////////////////////////////////////////////

        /// <summary>
        /// Arranges for the specified error message to be placed into the
        /// zErrMsg field of a sqlite3_vtab derived structure, freeing the
        /// existing error message, if any.
        /// </summary>
        /// <param name="module">
        /// The <see cref="SQLiteModule" /> object instance to be used.
        /// </param>
        /// <param name="cursor">
        /// The <see cref="SQLiteVirtualTableCursor" /> object instance used to
        /// lookup the native pointer to the sqlite3_vtab derived structure.
        /// </param>
        /// <param name="logErrors">
        /// Non-zero if this error message should also be logged using the
        /// <see cref="SQLiteLog" /> class.
        /// </param>
        /// <param name="logExceptions">
        /// Non-zero if caught exceptions should be logged using the
        /// <see cref="SQLiteLog" /> class.
        /// </param>
        /// <param name="error">
        /// The error message.
        /// </param>
        /// <returns>
        /// Non-zero upon success.
        /// </returns>
        private static bool SetCursorError(
            SQLiteModule module,
            SQLiteVirtualTableCursor cursor,
            bool logErrors,
            bool logExceptions,
            string error
            )
        {
            if (cursor == null)
                return false;

            IntPtr pCursor = cursor.NativeHandle;

            if (pCursor == IntPtr.Zero)
                return false;

            return SetCursorError(
                module, pCursor, logErrors, logExceptions, error);
        }
        #endregion
        #endregion

        ///////////////////////////////////////////////////////////////////////

        #region Protected Members
        #region Module Helper Methods
        /// <summary>
        /// Gets and returns the <see cref="ISQLiteNativeModule" /> interface
        /// implementation to be used when creating the native sqlite3_module
        /// structure.  Derived classes may override this method to supply an
        /// alternate implementation for the <see cref="ISQLiteNativeModule" />
        /// interface.
        /// </summary>
        /// <returns>
        /// The <see cref="ISQLiteNativeModule" /> interface implementation to
        /// be used when populating the native sqlite3_module structure.  If
        /// the returned value is null, the private methods provided by the
        /// <see cref="SQLiteModule" /> class and relating to the
        /// <see cref="ISQLiteNativeModule" /> interface  will be used to
        /// create the necessary delegates.
        /// </returns>
        protected virtual ISQLiteNativeModule GetNativeModuleImpl()
        {
            return null; /* NOTE: Use the built-in default delegates. */
        }

        ///////////////////////////////////////////////////////////////////////

        /// <summary>
        /// Creates and returns the <see cref="ISQLiteNativeModule" />
        /// interface implementation corresponding to the current
        /// <see cref="SQLiteModule" /> object instance.
        /// </summary>
        /// <returns>
        /// The <see cref="ISQLiteNativeModule" /> interface implementation
        /// corresponding to the current <see cref="SQLiteModule" /> object
        /// instance.
        /// </returns>
        protected virtual ISQLiteNativeModule CreateNativeModuleImpl()
        {
            return new SQLiteNativeModule(this);
        }
        #endregion

        ///////////////////////////////////////////////////////////////////////

        #region Native Table Helper Methods
        /// <summary>
        /// Allocates a native sqlite3_vtab derived structure and returns a
        /// native pointer to it.
        /// </summary>
        /// <returns>
        /// A native pointer to a native sqlite3_vtab derived structure.
        /// </returns>
        protected virtual IntPtr AllocateTable()
        {
            int size = Marshal.SizeOf(typeof(
                UnsafeNativeMethods.sqlite3_vtab));

            return SQLiteMemory.Allocate(size);
        }

        ///////////////////////////////////////////////////////////////////////

        /// <summary>
        /// Zeros out the fields of a native sqlite3_vtab derived structure.
        /// </summary>
        /// <param name="pVtab">
        /// The native pointer to the native sqlite3_vtab derived structure to
        /// zero.
        /// </param>
        protected virtual void ZeroTable(
            IntPtr pVtab
            )
        {
            if (pVtab == IntPtr.Zero)
                return;

            int offset = 0;

            SQLiteMarshal.WriteIntPtr(pVtab, offset, IntPtr.Zero);

            offset = SQLiteMarshal.NextOffsetOf(
                offset, IntPtr.Size, sizeof(int));

            SQLiteMarshal.WriteInt32(pVtab, offset, 0);

            offset = SQLiteMarshal.NextOffsetOf(
                offset, sizeof(int), IntPtr.Size);

            SQLiteMarshal.WriteIntPtr(pVtab, offset, IntPtr.Zero);
        }

        ///////////////////////////////////////////////////////////////////////

        /// <summary>
        /// Frees a native sqlite3_vtab structure using the provided native
        /// pointer to it.
        /// </summary>
        /// <param name="pVtab">
        /// A native pointer to a native sqlite3_vtab derived structure.
        /// </param>
        protected virtual void FreeTable(
            IntPtr pVtab
            )
        {
            SetTableError(pVtab, null);
            SQLiteMemory.Free(pVtab);
        }
        #endregion

        ///////////////////////////////////////////////////////////////////////

        #region Native Cursor Helper Methods
        /// <summary>
        /// Allocates a native sqlite3_vtab_cursor derived structure and
        /// returns a native pointer to it.
        /// </summary>
        /// <returns>
        /// A native pointer to a native sqlite3_vtab_cursor derived structure.
        /// </returns>
        protected virtual IntPtr AllocateCursor()
        {
            int size = Marshal.SizeOf(typeof(
                UnsafeNativeMethods.sqlite3_vtab_cursor));

            return SQLiteMemory.Allocate(size);
        }

        ///////////////////////////////////////////////////////////////////////

        /// <summary>
        /// Frees a native sqlite3_vtab_cursor structure using the provided
        /// native pointer to it.
        /// </summary>
        /// <param name="pCursor">
        /// A native pointer to a native sqlite3_vtab_cursor derived structure.
        /// </param>
        protected virtual void FreeCursor(
            IntPtr pCursor
            )
        {
            SQLiteMemory.Free(pCursor);
        }
        #endregion

        ///////////////////////////////////////////////////////////////////////

        #region Static Table Lookup Methods
        /// <summary>
        /// Reads and returns the native pointer to the sqlite3_vtab derived
        /// structure based on the native pointer to the sqlite3_vtab_cursor
        /// derived structure.
        /// </summary>
        /// <param name="module">
        /// The <see cref="SQLiteModule" /> object instance to be used.
        /// </param>
        /// <param name="pCursor">
        /// The native pointer to the sqlite3_vtab_cursor derived structure
        /// from which to read the native pointer to the sqlite3_vtab derived
        /// structure.
        /// </param>
        /// <returns>
        /// The native pointer to the sqlite3_vtab derived structure -OR-
        /// <see cref="IntPtr.Zero" /> if it cannot be determined.
        /// </returns>
        private static IntPtr TableFromCursor(
            SQLiteModule module,
            IntPtr pCursor
            )
        {
            if (pCursor == IntPtr.Zero)
                return IntPtr.Zero;

            return Marshal.ReadIntPtr(pCursor);
        }
        #endregion

        ///////////////////////////////////////////////////////////////////////

        #region Table Lookup Methods
        /// <summary>
        /// Reads and returns the native pointer to the sqlite3_vtab derived
        /// structure based on the native pointer to the sqlite3_vtab_cursor
        /// derived structure.
        /// </summary>
        /// <param name="pCursor">
        /// The native pointer to the sqlite3_vtab_cursor derived structure
        /// from which to read the native pointer to the sqlite3_vtab derived
        /// structure.
        /// </param>
        /// <returns>
        /// The native pointer to the sqlite3_vtab derived structure -OR-
        /// <see cref="IntPtr.Zero" /> if it cannot be determined.
        /// </returns>
        protected virtual IntPtr TableFromCursor(
            IntPtr pCursor
            )
        {
            return TableFromCursor(this, pCursor);
        }

        ///////////////////////////////////////////////////////////////////////

        /// <summary>
        /// Looks up and returns the <see cref="SQLiteVirtualTable" /> object
        /// instance based on the native pointer to the sqlite3_vtab derived
        /// structure.
        /// </summary>
        /// <param name="pVtab">
        /// The native pointer to the sqlite3_vtab derived structure.
        /// </param>
        /// <returns>
        /// The <see cref="SQLiteVirtualTable" /> object instance or null if
        /// the corresponding one cannot be found.
        /// </returns>
        protected virtual SQLiteVirtualTable TableFromIntPtr(
            IntPtr pVtab
            )
        {
            if (pVtab == IntPtr.Zero)
            {
                SetTableError(pVtab, "invalid native table");
                return null;
            }

            SQLiteVirtualTable table;

            if ((tables != null) &&
                tables.TryGetValue(pVtab, out table))
            {
                return table;
            }

            SetTableError(pVtab, HelperMethods.StringFormat(
                CultureInfo.CurrentCulture,
                "managed table for {0} not found", pVtab));

            return null;
        }

        ///////////////////////////////////////////////////////////////////////

        /// <summary>
        /// Allocates and returns a native pointer to a sqlite3_vtab derived
        /// structure and creates an association between it and the specified
        /// <see cref="SQLiteVirtualTable" /> object instance.
        /// </summary>
        /// <param name="table">
        /// The <see cref="SQLiteVirtualTable" /> object instance to be used
        /// when creating the association.
        /// </param>
        /// <returns>
        /// The native pointer to a sqlite3_vtab derived structure or
        /// <see cref="IntPtr.Zero" /> if the method fails for any reason.
        /// </returns>
        protected virtual IntPtr TableToIntPtr(
            SQLiteVirtualTable table
            )
        {
            if ((table == null) || (tables == null))
                return IntPtr.Zero;

            IntPtr pVtab = IntPtr.Zero;
            bool success = false;

            try
            {
                pVtab = AllocateTable();

                if (pVtab != IntPtr.Zero)
                {
                    ZeroTable(pVtab);
                    table.NativeHandle = pVtab;
                    tables.Add(pVtab, table);
                    success = true;
                }
            }
            finally
            {
                if (!success && (pVtab != IntPtr.Zero))
                {
                    FreeTable(pVtab);
                    pVtab = IntPtr.Zero;
                }
            }

            return pVtab;
        }
        #endregion

        ///////////////////////////////////////////////////////////////////////

        #region Cursor Lookup Methods
        /// <summary>
        /// Looks up and returns the <see cref="SQLiteVirtualTableCursor" />
        /// object instance based on the native pointer to the
        /// sqlite3_vtab_cursor derived structure.
        /// </summary>
        /// <param name="pVtab">
        /// The native pointer to the sqlite3_vtab derived structure.
        /// </param>
        /// <param name="pCursor">
        /// The native pointer to the sqlite3_vtab_cursor derived structure.
        /// </param>
        /// <returns>
        /// The <see cref="SQLiteVirtualTableCursor" /> object instance or null
        /// if the corresponding one cannot be found.
        /// </returns>
        protected virtual SQLiteVirtualTableCursor CursorFromIntPtr(
            IntPtr pVtab,
            IntPtr pCursor
            )
        {
            if (pCursor == IntPtr.Zero)
            {
                SetTableError(pVtab, "invalid native cursor");
                return null;
            }

            SQLiteVirtualTableCursor cursor;

            if ((cursors != null) &&
                cursors.TryGetValue(pCursor, out cursor))
            {
                return cursor;
            }

            SetTableError(pVtab, HelperMethods.StringFormat(
                CultureInfo.CurrentCulture,
                "managed cursor for {0} not found", pCursor));

            return null;
        }

        ///////////////////////////////////////////////////////////////////////

        /// <summary>
        /// Allocates and returns a native pointer to a sqlite3_vtab_cursor
        /// derived structure and creates an association between it and the
        /// specified <see cref="SQLiteVirtualTableCursor" /> object instance.
        /// </summary>
        /// <param name="cursor">
        /// The <see cref="SQLiteVirtualTableCursor" /> object instance to be
        /// used when creating the association.
        /// </param>
        /// <returns>
        /// The native pointer to a sqlite3_vtab_cursor derived structure or
        /// <see cref="IntPtr.Zero" /> if the method fails for any reason.
        /// </returns>
        protected virtual IntPtr CursorToIntPtr(
            SQLiteVirtualTableCursor cursor
            )
        {
            if ((cursor == null) || (cursors == null))
                return IntPtr.Zero;

            IntPtr pCursor = IntPtr.Zero;
            bool success = false;

            try
            {
                pCursor = AllocateCursor();

                if (pCursor != IntPtr.Zero)
                {
                    cursor.NativeHandle = pCursor;
                    cursors.Add(pCursor, cursor);
                    success = true;
                }
            }
            finally
            {
                if (!success && (pCursor != IntPtr.Zero))
                {
                    FreeCursor(pCursor);
                    pCursor = IntPtr.Zero;
                }
            }

            return pCursor;
        }
        #endregion

        ///////////////////////////////////////////////////////////////////////

        #region Function Lookup Methods
        /// <summary>
        /// Deterimines the key that should be used to identify and store the
        /// <see cref="SQLiteFunction" /> object instance for the virtual table
        /// (i.e. to be returned via the
        /// <see cref="ISQLiteNativeModule.xFindFunction" /> method).
        /// </summary>
        /// <param name="argumentCount">
        /// The number of arguments to the virtual table function.
        /// </param>
        /// <param name="name">
        /// The name of the virtual table function.
        /// </param>
        /// <param name="function">
        /// The <see cref="SQLiteFunction" /> object instance associated with
        /// this virtual table function.
        /// </param>
        /// <returns>
        /// The string that should be used to identify and store the virtual
        /// table function instance.  This method cannot return null.  If null
        /// is returned from this method, the behavior is undefined.
        /// </returns>
        protected virtual string GetFunctionKey(
            int argumentCount,
            string name,
            SQLiteFunction function
            )
        {
            return HelperMethods.StringFormat(
                CultureInfo.InvariantCulture,
                "{0}:{1}", argumentCount, name);
        }
        #endregion

        ///////////////////////////////////////////////////////////////////////

        #region Table Declaration Helper Methods
        /// <summary>
        /// Attempts to declare the schema for the virtual table using the
        /// specified database connection.
        /// </summary>
        /// <param name="connection">
        /// The <see cref="SQLiteConnection" /> object instance to use when
        /// declaring the schema of the virtual table.  This parameter may not
        /// be null.
        /// </param>
        /// <param name="sql">
        /// The string containing the CREATE TABLE statement that completely
        /// describes the schema for the virtual table.  This parameter may not
        /// be null.
        /// </param>
        /// <param name="error">
        /// Upon failure, this parameter must be modified to contain an error
        /// message.
        /// </param>
        /// <returns>
        /// A standard SQLite return code.
        /// </returns>
        protected virtual SQLiteErrorCode DeclareTable(
            SQLiteConnection connection,
            string sql,
            ref string error
            )
        {
            if (connection == null)
            {
                error = "invalid connection";
                return SQLiteErrorCode.Error;
            }

            SQLiteBase sqliteBase = connection._sql;

            if (sqliteBase == null)
            {
                error = "connection has invalid handle";
                return SQLiteErrorCode.Error;
            }

            if (sql == null)
            {
                error = "invalid SQL statement";
                return SQLiteErrorCode.Error;
            }

            return sqliteBase.DeclareVirtualTable(this, sql, ref error);
        }
        #endregion

        ///////////////////////////////////////////////////////////////////////

        #region Function Declaration Helper Methods
        /// <summary>
        /// Calls the native SQLite core library in order to declare a virtual
        /// table function in response to a call into the
        /// <see cref="ISQLiteNativeModule.xCreate" />
        /// or <see cref="ISQLiteNativeModule.xConnect" /> virtual table
        /// methods.
        /// </summary>
        /// <param name="connection">
        /// The <see cref="SQLiteConnection" /> object instance to use when
        /// declaring the schema of the virtual table.
        /// </param>
        /// <param name="argumentCount">
        /// The number of arguments to the function being declared.
        /// </param>
        /// <param name="name">
        /// The name of the function being declared.
        /// </param>
        /// <param name="error">
        /// Upon success, the contents of this parameter are undefined.  Upon
        /// failure, it should contain an appropriate error message.
        /// </param>
        /// <returns>
        /// A standard SQLite return code.
        /// </returns>
        protected virtual SQLiteErrorCode DeclareFunction(
            SQLiteConnection connection,
            int argumentCount,
            string name,
            ref string error
            )
        {
            if (connection == null)
            {
                error = "invalid connection";
                return SQLiteErrorCode.Error;
            }

            SQLiteBase sqliteBase = connection._sql;

            if (sqliteBase == null)
            {
                error = "connection has invalid handle";
                return SQLiteErrorCode.Error;
            }

            return sqliteBase.DeclareVirtualFunction(
                this, argumentCount, name, ref error);
        }
        #endregion

        ///////////////////////////////////////////////////////////////////////

        #region Error Handling Properties
        private bool logErrors;
        /// <summary>
        /// Returns or sets a boolean value indicating whether virtual table
        /// errors should be logged using the <see cref="SQLiteLog" /> class.
        /// </summary>
        protected virtual bool LogErrorsNoThrow
        {
            get { return logErrors; }
            set { logErrors = value; }
        }

        ///////////////////////////////////////////////////////////////////////

        private bool logExceptions;
        /// <summary>
        /// Returns or sets a boolean value indicating whether exceptions
        /// caught in the
        /// <see cref="ISQLiteNativeModule.xDisconnect" /> method,
        /// the <see cref="ISQLiteNativeModule.xDestroy" /> method,
        /// the <see cref="SetTableError(IntPtr,string)" /> method,
        /// the <see cref="SetTableError(SQLiteVirtualTable,string)" /> method,
        /// and the <see cref="Dispose()" /> method should be logged using the
        /// <see cref="SQLiteLog" /> class.
        /// </summary>
        protected virtual bool LogExceptionsNoThrow
        {
            get { return logExceptions; }
            set { logExceptions = value; }
        }
        #endregion

        ///////////////////////////////////////////////////////////////////////

        #region Error Handling Helper Methods
        /// <summary>
        /// Arranges for the specified error message to be placed into the
        /// zErrMsg field of a sqlite3_vtab derived structure, freeing the
        /// existing error message, if any.
        /// </summary>
        /// <param name="pVtab">
        /// The native pointer to the sqlite3_vtab derived structure.
        /// </param>
        /// <param name="error">
        /// The error message.
        /// </param>
        /// <returns>
        /// Non-zero upon success.
        /// </returns>
        protected virtual bool SetTableError(
            IntPtr pVtab,
            string error
            )
        {
            return SetTableError(
                this, pVtab, LogErrorsNoThrow, LogExceptionsNoThrow, error);
        }

        ///////////////////////////////////////////////////////////////////////

        /// <summary>
        /// Arranges for the specified error message to be placed into the
        /// zErrMsg field of a sqlite3_vtab derived structure, freeing the
        /// existing error message, if any.
        /// </summary>
        /// <param name="table">
        /// The <see cref="SQLiteVirtualTable" /> object instance used to
        /// lookup the native pointer to the sqlite3_vtab derived structure.
        /// </param>
        /// <param name="error">
        /// The error message.
        /// </param>
        /// <returns>
        /// Non-zero upon success.
        /// </returns>
        protected virtual bool SetTableError(
            SQLiteVirtualTable table,
            string error
            )
        {
            return SetTableError(
                this, table, LogErrorsNoThrow, LogExceptionsNoThrow, error);
        }

        ///////////////////////////////////////////////////////////////////////

        /// <summary>
        /// Arranges for the specified error message to be placed into the
        /// zErrMsg field of a sqlite3_vtab derived structure, freeing the
        /// existing error message, if any.
        /// </summary>
        /// <param name="cursor">
        /// The <see cref="SQLiteVirtualTableCursor" /> object instance used to
        /// lookup the native pointer to the sqlite3_vtab derived structure.
        /// </param>
        /// <param name="error">
        /// The error message.
        /// </param>
        /// <returns>
        /// Non-zero upon success.
        /// </returns>
        protected virtual bool SetCursorError(
            SQLiteVirtualTableCursor cursor,
            string error
            )
        {
            return SetCursorError(
                this, cursor, LogErrorsNoThrow, LogExceptionsNoThrow, error);
        }
        #endregion

        ///////////////////////////////////////////////////////////////////////

        #region Index Handling Helper Methods
        /// <summary>
        /// Modifies the specified <see cref="SQLiteIndex" /> object instance
        /// to contain the specified estimated cost.
        /// </summary>
        /// <param name="index">
        /// The <see cref="SQLiteIndex" /> object instance to modify.
        /// </param>
        /// <param name="estimatedCost">
        /// The estimated cost value to use.  Using a null value means that the
        /// default value provided by the SQLite core library should be used.
        /// </param>
        /// <returns>
        /// Non-zero upon success.
        /// </returns>
        protected virtual bool SetEstimatedCost(
            SQLiteIndex index,
            double? estimatedCost
            )
        {
            if ((index == null) || (index.Outputs == null))
                return false;

            index.Outputs.EstimatedCost = estimatedCost;
            return true;
        }

        ///////////////////////////////////////////////////////////////////////

        /// <summary>
        /// Modifies the specified <see cref="SQLiteIndex" /> object instance
        /// to contain the default estimated cost.
        /// </summary>
        /// <param name="index">
        /// The <see cref="SQLiteIndex" /> object instance to modify.
        /// </param>
        /// <returns>
        /// Non-zero upon success.
        /// </returns>
        protected virtual bool SetEstimatedCost(
            SQLiteIndex index
            )
        {
            return SetEstimatedCost(index, null);
        }

        ///////////////////////////////////////////////////////////////////////

        /// <summary>
        /// Modifies the specified <see cref="SQLiteIndex" /> object instance
        /// to contain the specified estimated rows.
        /// </summary>
        /// <param name="index">
        /// The <see cref="SQLiteIndex" /> object instance to modify.
        /// </param>
        /// <param name="estimatedRows">
        /// The estimated rows value to use.  Using a null value means that the
        /// default value provided by the SQLite core library should be used.
        /// </param>
        /// <returns>
        /// Non-zero upon success.
        /// </returns>
        protected virtual bool SetEstimatedRows(
            SQLiteIndex index,
            long? estimatedRows
            )
        {
            if ((index == null) || (index.Outputs == null))
                return false;

            index.Outputs.EstimatedRows = estimatedRows;
            return true;
        }

        ///////////////////////////////////////////////////////////////////////

        /// <summary>
        /// Modifies the specified <see cref="SQLiteIndex" /> object instance
        /// to contain the default estimated rows.
        /// </summary>
        /// <param name="index">
        /// The <see cref="SQLiteIndex" /> object instance to modify.
        /// </param>
        /// <returns>
        /// Non-zero upon success.
        /// </returns>
        protected virtual bool SetEstimatedRows(
            SQLiteIndex index
            )
        {
            return SetEstimatedRows(index, null);
        }

        ///////////////////////////////////////////////////////////////////////

        /// <summary>
        /// Modifies the specified <see cref="SQLiteIndex" /> object instance
        /// to contain the specified flags.
        /// </summary>
        /// <param name="index">
        /// The <see cref="SQLiteIndex" /> object instance to modify.
        /// </param>
        /// <param name="indexFlags">
        /// The index flags value to use.  Using a null value means that the
        /// default value provided by the SQLite core library should be used.
        /// </param>
        /// <returns>
        /// Non-zero upon success.
        /// </returns>
        protected virtual bool SetIndexFlags(
            SQLiteIndex index,
            SQLiteIndexFlags? indexFlags
            )
        {
            if ((index == null) || (index.Outputs == null))
                return false;

            index.Outputs.IndexFlags = indexFlags;
            return true;
        }

        ///////////////////////////////////////////////////////////////////////

        /// <summary>
        /// Modifies the specified <see cref="SQLiteIndex" /> object instance
        /// to contain the default index flags.
        /// </summary>
        /// <param name="index">
        /// The <see cref="SQLiteIndex" /> object instance to modify.
        /// </param>
        /// <returns>
        /// Non-zero upon success.
        /// </returns>
        protected virtual bool SetIndexFlags(
            SQLiteIndex index
            )
        {
            return SetIndexFlags(index, null);
        }
        #endregion
        #endregion

        ///////////////////////////////////////////////////////////////////////

        #region Public Properties
        /// <summary>
        /// Returns or sets a boolean value indicating whether virtual table
        /// errors should be logged using the <see cref="SQLiteLog" /> class.
        /// </summary>
        public virtual bool LogErrors
        {
            get { CheckDisposed(); return LogErrorsNoThrow; }
            set { CheckDisposed(); LogErrorsNoThrow = value; }
        }

        ///////////////////////////////////////////////////////////////////////

        /// <summary>
        /// Returns or sets a boolean value indicating whether exceptions
        /// caught in the
        /// <see cref="ISQLiteNativeModule.xDisconnect" /> method,
        /// <see cref="ISQLiteNativeModule.xDestroy" /> method, and the
        /// <see cref="Dispose()" /> method should be logged using the
        /// <see cref="SQLiteLog" /> class.
        /// </summary>
        public virtual bool LogExceptions
        {
            get { CheckDisposed(); return LogExceptionsNoThrow; }
            set { CheckDisposed(); LogExceptionsNoThrow = value; }
        }
        #endregion

        ///////////////////////////////////////////////////////////////////////

        #region ISQLiteNativeModule Members
        /// <summary>
        /// See the <see cref="ISQLiteNativeModule.xCreate" /> method.
        /// </summary>
        /// <param name="pDb">
        /// See the <see cref="ISQLiteNativeModule.xCreate" /> method.
        /// </param>
        /// <param name="pAux">
        /// See the <see cref="ISQLiteNativeModule.xCreate" /> method.
        /// </param>
        /// <param name="argc">
        /// See the <see cref="ISQLiteNativeModule.xCreate" /> method.
        /// </param>
        /// <param name="argv">
        /// See the <see cref="ISQLiteNativeModule.xCreate" /> method.
        /// </param>
        /// <param name="pVtab">
        /// See the <see cref="ISQLiteNativeModule.xCreate" /> method.
        /// </param>
        /// <param name="pError">
        /// See the <see cref="ISQLiteNativeModule.xCreate" /> method.
        /// </param>
        /// <returns>
        /// See the <see cref="ISQLiteNativeModule.xCreate" /> method.
        /// </returns>
        private SQLiteErrorCode xCreate(
            IntPtr pDb,
            IntPtr pAux,
            int argc,
            IntPtr argv,
            ref IntPtr pVtab,
            ref IntPtr pError
            )
        {
            return CreateOrConnect(
                true, pDb, pAux, argc, argv, ref pVtab, ref pError);
        }

        ///////////////////////////////////////////////////////////////////////

        /// <summary>
        /// See the <see cref="ISQLiteNativeModule.xConnect" /> method.
        /// </summary>
        /// <param name="pDb">
        /// See the <see cref="ISQLiteNativeModule.xConnect" /> method.
        /// </param>
        /// <param name="pAux">
        /// See the <see cref="ISQLiteNativeModule.xConnect" /> method.
        /// </param>
        /// <param name="argc">
        /// See the <see cref="ISQLiteNativeModule.xConnect" /> method.
        /// </param>
        /// <param name="argv">
        /// See the <see cref="ISQLiteNativeModule.xConnect" /> method.
        /// </param>
        /// <param name="pVtab">
        /// See the <see cref="ISQLiteNativeModule.xConnect" /> method.
        /// </param>
        /// <param name="pError">
        /// See the <see cref="ISQLiteNativeModule.xConnect" /> method.
        /// </param>
        /// <returns>
        /// See the <see cref="ISQLiteNativeModule.xConnect" /> method.
        /// </returns>
        private SQLiteErrorCode xConnect(
            IntPtr pDb,
            IntPtr pAux,
            int argc,
            IntPtr argv,
            ref IntPtr pVtab,
            ref IntPtr pError
            )
        {
            return CreateOrConnect(
                false, pDb, pAux, argc, argv, ref pVtab, ref pError);
        }

        ///////////////////////////////////////////////////////////////////////

        /// <summary>
        /// See the <see cref="ISQLiteNativeModule.xBestIndex" /> method.
        /// </summary>
        /// <param name="pVtab">
        /// See the <see cref="ISQLiteNativeModule.xBestIndex" /> method.
        /// </param>
        /// <param name="pIndex">
        /// See the <see cref="ISQLiteNativeModule.xBestIndex" /> method.
        /// </param>
        /// <returns>
        /// See the <see cref="ISQLiteNativeModule.xBestIndex" /> method.
        /// </returns>
        private SQLiteErrorCode xBestIndex(
            IntPtr pVtab,
            IntPtr pIndex
            )
        {
            try
            {
                SQLiteVirtualTable table = TableFromIntPtr(pVtab);

                if (table != null)
                {
                    SQLiteIndex index = null;

                    SQLiteIndex.FromIntPtr(pIndex, true, ref index);

                    if (BestIndex(table, index) == SQLiteErrorCode.Ok)
                    {
                        SQLiteIndex.ToIntPtr(index, pIndex, true);
                        return SQLiteErrorCode.Ok;
                    }
                }
            }
            catch (Exception e) /* NOTE: Must catch ALL. */
            {
                SetTableError(pVtab, e.ToString());
            }

            return SQLiteErrorCode.Error;
        }

        ///////////////////////////////////////////////////////////////////////

        /// <summary>
        /// See the <see cref="ISQLiteNativeModule.xDisconnect" /> method.
        /// </summary>
        /// <param name="pVtab">
        /// See the <see cref="ISQLiteNativeModule.xDisconnect" /> method.
        /// </param>
        /// <returns>
        /// See the <see cref="ISQLiteNativeModule.xDisconnect" /> method.
        /// </returns>
        private SQLiteErrorCode xDisconnect(
            IntPtr pVtab
            )
        {
            return DestroyOrDisconnect(false, pVtab);
        }

        ///////////////////////////////////////////////////////////////////////

        /// <summary>
        /// See the <see cref="ISQLiteNativeModule.xDestroy" /> method.
        /// </summary>
        /// <param name="pVtab">
        /// See the <see cref="ISQLiteNativeModule.xDestroy" /> method.
        /// </param>
        /// <returns>
        /// See the <see cref="ISQLiteNativeModule.xDestroy" /> method.
        /// </returns>
        private SQLiteErrorCode xDestroy(
            IntPtr pVtab
            )
        {
            return DestroyOrDisconnect(true, pVtab);
        }

        ///////////////////////////////////////////////////////////////////////

        /// <summary>
        /// See the <see cref="ISQLiteNativeModule.xOpen" /> method.
        /// </summary>
        /// <param name="pVtab">
        /// See the <see cref="ISQLiteNativeModule.xOpen" /> method.
        /// </param>
        /// <param name="pCursor">
        /// See the <see cref="ISQLiteNativeModule.xOpen" /> method.
        /// </param>
        /// <returns>
        /// See the <see cref="ISQLiteNativeModule.xOpen" /> method.
        /// </returns>
        private SQLiteErrorCode xOpen(
            IntPtr pVtab,
            ref IntPtr pCursor
            )
        {
            try
            {
                SQLiteVirtualTable table = TableFromIntPtr(pVtab);

                if (table != null)
                {
                    SQLiteVirtualTableCursor cursor = null;

                    if (Open(table, ref cursor) == SQLiteErrorCode.Ok)
                    {
                        if (cursor != null)
                        {
                            pCursor = CursorToIntPtr(cursor);

                            if (pCursor != IntPtr.Zero)
                            {
                                return SQLiteErrorCode.Ok;
                            }
                            else
                            {
                                SetTableError(pVtab,
                                    "no native cursor was created");
                            }
                        }
                        else
                        {
                            SetTableError(pVtab,
                                "no managed cursor was created");
                        }
                    }
                }
            }
            catch (Exception e) /* NOTE: Must catch ALL. */
            {
                SetTableError(pVtab, e.ToString());
            }

            return SQLiteErrorCode.Error;
        }

        ///////////////////////////////////////////////////////////////////////

        /// <summary>
        /// See the <see cref="ISQLiteNativeModule.xClose" /> method.
        /// </summary>
        /// <param name="pCursor">
        /// See the <see cref="ISQLiteNativeModule.xClose" /> method.
        /// </param>
        /// <returns>
        /// See the <see cref="ISQLiteNativeModule.xClose" /> method.
        /// </returns>
        private SQLiteErrorCode xClose(
            IntPtr pCursor
            )
        {
            IntPtr pVtab = IntPtr.Zero;

            try
            {
                pVtab = TableFromCursor(pCursor);

                SQLiteVirtualTableCursor cursor = CursorFromIntPtr(
                    pVtab, pCursor);

                if (cursor != null)
                {
                    if (Close(cursor) == SQLiteErrorCode.Ok)
                    {
                        if (cursors != null)
                            cursors.Remove(pCursor);

                        return SQLiteErrorCode.Ok;
                    }
                }
            }
            catch (Exception e) /* NOTE: Must catch ALL. */
            {
                SetTableError(pVtab, e.ToString());
            }
            finally
            {
                FreeCursor(pCursor);
            }

            return SQLiteErrorCode.Error;
        }

        ///////////////////////////////////////////////////////////////////////

        /// <summary>
        /// See the <see cref="ISQLiteNativeModule.xFilter" /> method.
        /// </summary>
        /// <param name="pCursor">
        /// See the <see cref="ISQLiteNativeModule.xFilter" /> method.
        /// </param>
        /// <param name="idxNum">
        /// See the <see cref="ISQLiteNativeModule.xFilter" /> method.
        /// </param>
        /// <param name="idxStr">
        /// See the <see cref="ISQLiteNativeModule.xFilter" /> method.
        /// </param>
        /// <param name="argc">
        /// See the <see cref="ISQLiteNativeModule.xFilter" /> method.
        /// </param>
        /// <param name="argv">
        /// See the <see cref="ISQLiteNativeModule.xFilter" /> method.
        /// </param>
        /// <returns>
        /// See the <see cref="ISQLiteNativeModule.xFilter" /> method.
        /// </returns>
        private SQLiteErrorCode xFilter(
            IntPtr pCursor,
            int idxNum,
            IntPtr idxStr,
            int argc,
            IntPtr argv
            )
        {
            IntPtr pVtab = IntPtr.Zero;

            try
            {
                pVtab = TableFromCursor(pCursor);

                SQLiteVirtualTableCursor cursor = CursorFromIntPtr(
                    pVtab, pCursor);

                if (cursor != null)
                {
                    if (Filter(cursor, idxNum,
                            SQLiteString.StringFromUtf8IntPtr(idxStr),
                            SQLiteValue.ArrayFromSizeAndIntPtr(argc,
                                argv)) == SQLiteErrorCode.Ok)
                    {
                        return SQLiteErrorCode.Ok;
                    }
                }
            }
            catch (Exception e) /* NOTE: Must catch ALL. */
            {
                SetTableError(pVtab, e.ToString());
            }

            return SQLiteErrorCode.Error;
        }

        ///////////////////////////////////////////////////////////////////////

        /// <summary>
        /// See the <see cref="ISQLiteNativeModule.xNext" /> method.
        /// </summary>
        /// <param name="pCursor">
        /// See the <see cref="ISQLiteNativeModule.xNext" /> method.
        /// </param>
        /// <returns>
        /// See the <see cref="ISQLiteNativeModule.xNext" /> method.
        /// </returns>
        private SQLiteErrorCode xNext(
            IntPtr pCursor
            )
        {
            IntPtr pVtab = IntPtr.Zero;

            try
            {
                pVtab = TableFromCursor(pCursor);

                SQLiteVirtualTableCursor cursor = CursorFromIntPtr(
                    pVtab, pCursor);

                if (cursor != null)
                {
                    if (Next(cursor) == SQLiteErrorCode.Ok)
                        return SQLiteErrorCode.Ok;
                }
            }
            catch (Exception e) /* NOTE: Must catch ALL. */
            {
                SetTableError(pVtab, e.ToString());
            }

            return SQLiteErrorCode.Error;
        }

        ///////////////////////////////////////////////////////////////////////

        /// <summary>
        /// See the <see cref="ISQLiteNativeModule.xEof" /> method.
        /// </summary>
        /// <param name="pCursor">
        /// See the <see cref="ISQLiteNativeModule.xEof" /> method.
        /// </param>
        /// <returns>
        /// See the <see cref="ISQLiteNativeModule.xEof" /> method.
        /// </returns>
        private int xEof(
            IntPtr pCursor
            )
        {
            IntPtr pVtab = IntPtr.Zero;

            try
            {
                pVtab = TableFromCursor(pCursor);

                SQLiteVirtualTableCursor cursor = CursorFromIntPtr(
                    pVtab, pCursor);

                if (cursor != null)
                    return Eof(cursor) ? 1 : 0;
            }
            catch (Exception e) /* NOTE: Must catch ALL. */
            {
                SetTableError(pVtab, e.ToString());
            }

            return 1; /* NOTE: On any error, return "no more rows". */
        }

        ///////////////////////////////////////////////////////////////////////

        /// <summary>
        /// See the <see cref="ISQLiteNativeModule.xColumn" /> method.
        /// </summary>
        /// <param name="pCursor">
        /// See the <see cref="ISQLiteNativeModule.xColumn" /> method.
        /// </param>
        /// <param name="pContext">
        /// See the <see cref="ISQLiteNativeModule.xColumn" /> method.
        /// </param>
        /// <param name="index">
        /// See the <see cref="ISQLiteNativeModule.xColumn" /> method.
        /// </param>
        /// <returns>
        /// See the <see cref="ISQLiteNativeModule.xColumn" /> method.
        /// </returns>
        private SQLiteErrorCode xColumn(
            IntPtr pCursor,
            IntPtr pContext,
            int index
            )
        {
            IntPtr pVtab = IntPtr.Zero;

            try
            {
                pVtab = TableFromCursor(pCursor);

                SQLiteVirtualTableCursor cursor = CursorFromIntPtr(
                    pVtab, pCursor);

                if (cursor != null)
                {
                    SQLiteContext context = new SQLiteContext(pContext);

                    return Column(cursor, context, index);
                }
            }
            catch (Exception e) /* NOTE: Must catch ALL. */
            {
                SetTableError(pVtab, e.ToString());
            }

            return SQLiteErrorCode.Error;
        }

        ///////////////////////////////////////////////////////////////////////

        /// <summary>
        /// See the <see cref="ISQLiteNativeModule.xRowId" /> method.
        /// </summary>
        /// <param name="pCursor">
        /// See the <see cref="ISQLiteNativeModule.xRowId" /> method.
        /// </param>
        /// <param name="rowId">
        /// See the <see cref="ISQLiteNativeModule.xRowId" /> method.
        /// </param>
        /// <returns>
        /// See the <see cref="ISQLiteNativeModule.xRowId" /> method.
        /// </returns>
        private SQLiteErrorCode xRowId(
            IntPtr pCursor,
            ref long rowId
            )
        {
            IntPtr pVtab = IntPtr.Zero;

            try
            {
                pVtab = TableFromCursor(pCursor);

                SQLiteVirtualTableCursor cursor = CursorFromIntPtr(
                    pVtab, pCursor);

                if (cursor != null)
                    return RowId(cursor, ref rowId);
            }
            catch (Exception e) /* NOTE: Must catch ALL. */
            {
                SetTableError(pVtab, e.ToString());
            }

            return SQLiteErrorCode.Error;
        }

        ///////////////////////////////////////////////////////////////////////

        /// <summary>
        /// See the <see cref="ISQLiteNativeModule.xUpdate" /> method.
        /// </summary>
        /// <param name="pVtab">
        /// See the <see cref="ISQLiteNativeModule.xUpdate" /> method.
        /// </param>
        /// <param name="argc">
        /// See the <see cref="ISQLiteNativeModule.xUpdate" /> method.
        /// </param>
        /// <param name="argv">
        /// See the <see cref="ISQLiteNativeModule.xUpdate" /> method.
        /// </param>
        /// <param name="rowId">
        /// See the <see cref="ISQLiteNativeModule.xUpdate" /> method.
        /// </param>
        /// <returns>
        /// See the <see cref="ISQLiteNativeModule.xUpdate" /> method.
        /// </returns>
        private SQLiteErrorCode xUpdate(
            IntPtr pVtab,
            int argc,
            IntPtr argv,
            ref long rowId
            )
        {
            try
            {
                SQLiteVirtualTable table = TableFromIntPtr(pVtab);

                if (table != null)
                {
                    return Update(table,
                        SQLiteValue.ArrayFromSizeAndIntPtr(argc, argv),
                        ref rowId);
                }
            }
            catch (Exception e) /* NOTE: Must catch ALL. */
            {
                SetTableError(pVtab, e.ToString());
            }

            return SQLiteErrorCode.Error;
        }

        ///////////////////////////////////////////////////////////////////////

        /// <summary>
        /// See the <see cref="ISQLiteNativeModule.xBegin" /> method.
        /// </summary>
        /// <param name="pVtab">
        /// See the <see cref="ISQLiteNativeModule.xBegin" /> method.
        /// </param>
        /// <returns>
        /// See the <see cref="ISQLiteNativeModule.xBegin" /> method.
        /// </returns>
        private SQLiteErrorCode xBegin(
            IntPtr pVtab
            )
        {
            try
            {
                SQLiteVirtualTable table = TableFromIntPtr(pVtab);

                if (table != null)
                    return Begin(table);
            }
            catch (Exception e) /* NOTE: Must catch ALL. */
            {
                SetTableError(pVtab, e.ToString());
            }

            return SQLiteErrorCode.Error;
        }

        ///////////////////////////////////////////////////////////////////////

        /// <summary>
        /// See the <see cref="ISQLiteNativeModule.xSync" /> method.
        /// </summary>
        /// <param name="pVtab">
        /// See the <see cref="ISQLiteNativeModule.xSync" /> method.
        /// </param>
        /// <returns>
        /// See the <see cref="ISQLiteNativeModule.xSync" /> method.
        /// </returns>
        private SQLiteErrorCode xSync(
            IntPtr pVtab
            )
        {
            try
            {
                SQLiteVirtualTable table = TableFromIntPtr(pVtab);

                if (table != null)
                    return Sync(table);
            }
            catch (Exception e) /* NOTE: Must catch ALL. */
            {
                SetTableError(pVtab, e.ToString());
            }

            return SQLiteErrorCode.Error;
        }

        ///////////////////////////////////////////////////////////////////////

        /// <summary>
        /// See the <see cref="ISQLiteNativeModule.xCommit" /> method.
        /// </summary>
        /// <param name="pVtab">
        /// See the <see cref="ISQLiteNativeModule.xCommit" /> method.
        /// </param>
        /// <returns>
        /// See the <see cref="ISQLiteNativeModule.xCommit" /> method.
        /// </returns>
        private SQLiteErrorCode xCommit(
            IntPtr pVtab
            )
        {
            try
            {
                SQLiteVirtualTable table = TableFromIntPtr(pVtab);

                if (table != null)
                    return Commit(table);
            }
            catch (Exception e) /* NOTE: Must catch ALL. */
            {
                SetTableError(pVtab, e.ToString());
            }

            return SQLiteErrorCode.Error;
        }

        ///////////////////////////////////////////////////////////////////////

        /// <summary>
        /// See the <see cref="ISQLiteNativeModule.xRollback" /> method.
        /// </summary>
        /// <param name="pVtab">
        /// See the <see cref="ISQLiteNativeModule.xRollback" /> method.
        /// </param>
        /// <returns>
        /// See the <see cref="ISQLiteNativeModule.xRollback" /> method.
        /// </returns>
        private SQLiteErrorCode xRollback(
            IntPtr pVtab
            )
        {
            try
            {
                SQLiteVirtualTable table = TableFromIntPtr(pVtab);

                if (table != null)
                    return Rollback(table);
            }
            catch (Exception e) /* NOTE: Must catch ALL. */
            {
                SetTableError(pVtab, e.ToString());
            }

            return SQLiteErrorCode.Error;
        }

        ///////////////////////////////////////////////////////////////////////

        /// <summary>
        /// See the <see cref="ISQLiteNativeModule.xFindFunction" /> method.
        /// </summary>
        /// <param name="pVtab">
        /// See the <see cref="ISQLiteNativeModule.xFindFunction" /> method.
        /// </param>
        /// <param name="nArg">
        /// See the <see cref="ISQLiteNativeModule.xFindFunction" /> method.
        /// </param>
        /// <param name="zName">
        /// See the <see cref="ISQLiteNativeModule.xFindFunction" /> method.
        /// </param>
        /// <param name="callback">
        /// See the <see cref="ISQLiteNativeModule.xFindFunction" /> method.
        /// </param>
        /// <param name="pClientData">
        /// See the <see cref="ISQLiteNativeModule.xFindFunction" /> method.
        /// </param>
        /// <returns>
        /// See the <see cref="ISQLiteNativeModule.xFindFunction" /> method.
        /// </returns>
        private int xFindFunction(
            IntPtr pVtab,
            int nArg,
            IntPtr zName,
            ref SQLiteCallback callback,
            ref IntPtr pClientData
            )
        {
            try
            {
                SQLiteVirtualTable table = TableFromIntPtr(pVtab);

                if (table != null)
                {
                    string name = SQLiteString.StringFromUtf8IntPtr(zName);
                    SQLiteFunction function = null;

                    if (FindFunction(
                            table, nArg, name, ref function, ref pClientData))
                    {
                        if (function != null)
                        {
                            string key = GetFunctionKey(nArg, name, function);

                            functions[key] = function;
                            callback = function.ScalarCallback;

                            return 1;
                        }
                        else
                        {
                            SetTableError(pVtab, "no function was created");
                        }
                    }
                }
            }
            catch (Exception e) /* NOTE: Must catch ALL. */
            {
                SetTableError(pVtab, e.ToString());
            }

            return 0; /* NOTE: On any error, return "no such function". */
        }

        ///////////////////////////////////////////////////////////////////////

        /// <summary>
        /// See the <see cref="ISQLiteNativeModule.xRename" /> method.
        /// </summary>
        /// <param name="pVtab">
        /// See the <see cref="ISQLiteNativeModule.xRename" /> method.
        /// </param>
        /// <param name="zNew">
        /// See the <see cref="ISQLiteNativeModule.xRename" /> method.
        /// </param>
        /// <returns>
        /// See the <see cref="ISQLiteNativeModule.xRename" /> method.
        /// </returns>
        private SQLiteErrorCode xRename(
            IntPtr pVtab,
            IntPtr zNew
            )
        {
            try
            {
                SQLiteVirtualTable table = TableFromIntPtr(pVtab);

                if (table != null)
                {
                    return Rename(table,
                        SQLiteString.StringFromUtf8IntPtr(zNew));
                }
            }
            catch (Exception e) /* NOTE: Must catch ALL. */
            {
                SetTableError(pVtab, e.ToString());
            }

            return SQLiteErrorCode.Error;
        }

        ///////////////////////////////////////////////////////////////////////

        /// <summary>
        /// See the <see cref="ISQLiteNativeModule.xSavepoint" /> method.
        /// </summary>
        /// <param name="pVtab">
        /// See the <see cref="ISQLiteNativeModule.xSavepoint" /> method.
        /// </param>
        /// <param name="iSavepoint">
        /// See the <see cref="ISQLiteNativeModule.xSavepoint" /> method.
        /// </param>
        /// <returns>
        /// See the <see cref="ISQLiteNativeModule.xSavepoint" /> method.
        /// </returns>
        private SQLiteErrorCode xSavepoint(
            IntPtr pVtab,
            int iSavepoint
            )
        {
            try
            {
                SQLiteVirtualTable table = TableFromIntPtr(pVtab);

                if (table != null)
                    return Savepoint(table, iSavepoint);
            }
            catch (Exception e) /* NOTE: Must catch ALL. */
            {
                SetTableError(pVtab, e.ToString());
            }

            return SQLiteErrorCode.Error;
        }

        ///////////////////////////////////////////////////////////////////////

        /// <summary>
        /// See the <see cref="ISQLiteNativeModule.xRelease" /> method.
        /// </summary>
        /// <param name="pVtab">
        /// See the <see cref="ISQLiteNativeModule.xRelease" /> method.
        /// </param>
        /// <param name="iSavepoint">
        /// See the <see cref="ISQLiteNativeModule.xRelease" /> method.
        /// </param>
        /// <returns>
        /// See the <see cref="ISQLiteNativeModule.xRelease" /> method.
        /// </returns>
        private SQLiteErrorCode xRelease(
            IntPtr pVtab,
            int iSavepoint
            )
        {
            try
            {
                SQLiteVirtualTable table = TableFromIntPtr(pVtab);

                if (table != null)
                    return Release(table, iSavepoint);
            }
            catch (Exception e) /* NOTE: Must catch ALL. */
            {
                SetTableError(pVtab, e.ToString());
            }

            return SQLiteErrorCode.Error;
        }

        ///////////////////////////////////////////////////////////////////////

        /// <summary>
        /// See the <see cref="ISQLiteNativeModule.xRollbackTo" /> method.
        /// </summary>
        /// <param name="pVtab">
        /// See the <see cref="ISQLiteNativeModule.xRollbackTo" /> method.
        /// </param>
        /// <param name="iSavepoint">
        /// See the <see cref="ISQLiteNativeModule.xRollbackTo" /> method.
        /// </param>
        /// <returns>
        /// See the <see cref="ISQLiteNativeModule.xRollbackTo" /> method.
        /// </returns>
        private SQLiteErrorCode xRollbackTo(
            IntPtr pVtab,
            int iSavepoint
            )
        {
            try
            {
                SQLiteVirtualTable table = TableFromIntPtr(pVtab);

                if (table != null)
                    return RollbackTo(table, iSavepoint);
            }
            catch (Exception e) /* NOTE: Must catch ALL. */
            {
                SetTableError(pVtab, e.ToString());
            }

            return SQLiteErrorCode.Error;
        }
        #endregion

        ///////////////////////////////////////////////////////////////////////

        #region ISQLiteManagedModule Members
        private bool declared;
        /// <summary>
        /// Returns non-zero if the schema for the virtual table has been
        /// declared.
        /// </summary>
        public virtual bool Declared
        {
            get { CheckDisposed(); return declared; }
            internal set { declared = value; }
        }

        ///////////////////////////////////////////////////////////////////////

        private string name;
        /// <summary>
        /// Returns the name of the module as it was registered with the SQLite
        /// core library.
        /// </summary>
        public virtual string Name
        {
            get { CheckDisposed(); return name; }
        }

        ///////////////////////////////////////////////////////////////////////

        /// <summary>
        /// This method is called in response to the
        /// <see cref="ISQLiteNativeModule.xCreate" /> method.
        /// </summary>
        /// <param name="connection">
        /// The <see cref="SQLiteConnection" /> object instance associated with
        /// the virtual table.
        /// </param>
        /// <param name="pClientData">
        /// The native user-data pointer associated with this module, as it was
        /// provided to the SQLite core library when the native module instance
        /// was created.
        /// </param>
        /// <param name="arguments">
        /// The module name, database name, virtual table name, and all other
        /// arguments passed to the CREATE VIRTUAL TABLE statement.
        /// </param>
        /// <param name="table">
        /// Upon success, this parameter must be modified to contain the
        /// <see cref="SQLiteVirtualTable" /> object instance associated with
        /// the virtual table.
        /// </param>
        /// <param name="error">
        /// Upon failure, this parameter must be modified to contain an error
        /// message.
        /// </param>
        /// <returns>
        /// A standard SQLite return code.
        /// </returns>
        public abstract SQLiteErrorCode Create(
            SQLiteConnection connection,
            IntPtr pClientData,
            string[] arguments,
            ref SQLiteVirtualTable table,
            ref string error
            );

        ///////////////////////////////////////////////////////////////////////

        /// <summary>
        /// This method is called in response to the
        /// <see cref="ISQLiteNativeModule.xConnect" /> method.
        /// </summary>
        /// <param name="connection">
        /// The <see cref="SQLiteConnection" /> object instance associated with
        /// the virtual table.
        /// </param>
        /// <param name="pClientData">
        /// The native user-data pointer associated with this module, as it was
        /// provided to the SQLite core library when the native module instance
        /// was created.
        /// </param>
        /// <param name="arguments">
        /// The module name, database name, virtual table name, and all other
        /// arguments passed to the CREATE VIRTUAL TABLE statement.
        /// </param>
        /// <param name="table">
        /// Upon success, this parameter must be modified to contain the
        /// <see cref="SQLiteVirtualTable" /> object instance associated with
        /// the virtual table.
        /// </param>
        /// <param name="error">
        /// Upon failure, this parameter must be modified to contain an error
        /// message.
        /// </param>
        /// <returns>
        /// A standard SQLite return code.
        /// </returns>
        public abstract SQLiteErrorCode Connect(
            SQLiteConnection connection,
            IntPtr pClientData,
            string[] arguments,
            ref SQLiteVirtualTable table,
            ref string error
            );

        ///////////////////////////////////////////////////////////////////////

        /// <summary>
        /// This method is called in response to the
        /// <see cref="ISQLiteNativeModule.xBestIndex" /> method.
        /// </summary>
        /// <param name="table">
        /// The <see cref="SQLiteVirtualTable" /> object instance associated
        /// with this virtual table.
        /// </param>
        /// <param name="index">
        /// The <see cref="SQLiteIndex" /> object instance containing all the
        /// data for the inputs and outputs relating to index selection.
        /// </param>
        /// <returns>
        /// A standard SQLite return code.
        /// </returns>
        public abstract SQLiteErrorCode BestIndex(
            SQLiteVirtualTable table,
            SQLiteIndex index
            );

        ///////////////////////////////////////////////////////////////////////

        /// <summary>
        /// This method is called in response to the
        /// <see cref="ISQLiteNativeModule.xDisconnect" /> method.
        /// </summary>
        /// <param name="table">
        /// The <see cref="SQLiteVirtualTable" /> object instance associated
        /// with this virtual table.
        /// </param>
        /// <returns>
        /// A standard SQLite return code.
        /// </returns>
        public abstract SQLiteErrorCode Disconnect(
            SQLiteVirtualTable table
            );

        ///////////////////////////////////////////////////////////////////////

        /// <summary>
        /// This method is called in response to the
        /// <see cref="ISQLiteNativeModule.xDestroy" /> method.
        /// </summary>
        /// <param name="table">
        /// The <see cref="SQLiteVirtualTable" /> object instance associated
        /// with this virtual table.
        /// </param>
        /// <returns>
        /// A standard SQLite return code.
        /// </returns>
        public abstract SQLiteErrorCode Destroy(
            SQLiteVirtualTable table
            );

        ///////////////////////////////////////////////////////////////////////

        /// <summary>
        /// This method is called in response to the
        /// <see cref="ISQLiteNativeModule.xOpen" /> method.
        /// </summary>
        /// <param name="table">
        /// The <see cref="SQLiteVirtualTable" /> object instance associated
        /// with this virtual table.
        /// </param>
        /// <param name="cursor">
        /// Upon success, this parameter must be modified to contain the
        /// <see cref="SQLiteVirtualTableCursor" /> object instance associated
        /// with the newly opened virtual table cursor.
        /// </param>
        /// <returns>
        /// A standard SQLite return code.
        /// </returns>
        public abstract SQLiteErrorCode Open(
            SQLiteVirtualTable table,
            ref SQLiteVirtualTableCursor cursor
            );

        ///////////////////////////////////////////////////////////////////////

        /// <summary>
        /// This method is called in response to the
        /// <see cref="ISQLiteNativeModule.xClose" /> method.
        /// </summary>
        /// <param name="cursor">
        /// The <see cref="SQLiteVirtualTableCursor" /> object instance
        /// associated with the previously opened virtual table cursor to be
        /// used.
        /// </param>
        /// <returns>
        /// A standard SQLite return code.
        /// </returns>
        public abstract SQLiteErrorCode Close(
            SQLiteVirtualTableCursor cursor
            );

        ///////////////////////////////////////////////////////////////////////

        /// <summary>
        /// This method is called in response to the
        /// <see cref="ISQLiteNativeModule.xFilter" /> method.
        /// </summary>
        /// <param name="cursor">
        /// The <see cref="SQLiteVirtualTableCursor" /> object instance
        /// associated with the previously opened virtual table cursor to be
        /// used.
        /// </param>
        /// <param name="indexNumber">
        /// Number used to help identify the selected index.
        /// </param>
        /// <param name="indexString">
        /// String used to help identify the selected index.
        /// </param>
        /// <param name="values">
        /// The values corresponding to each column in the selected index.
        /// </param>
        /// <returns>
        /// A standard SQLite return code.
        /// </returns>
        public abstract SQLiteErrorCode Filter(
            SQLiteVirtualTableCursor cursor,
            int indexNumber,
            string indexString,
            SQLiteValue[] values
            );

        ///////////////////////////////////////////////////////////////////////

        /// <summary>
        /// This method is called in response to the
        /// <see cref="ISQLiteNativeModule.xNext" /> method.
        /// </summary>
        /// <param name="cursor">
        /// The <see cref="SQLiteVirtualTableCursor" /> object instance
        /// associated with the previously opened virtual table cursor to be
        /// used.
        /// </param>
        /// <returns>
        /// A standard SQLite return code.
        /// </returns>
        public abstract SQLiteErrorCode Next(
            SQLiteVirtualTableCursor cursor
            );

        ///////////////////////////////////////////////////////////////////////

        /// <summary>
        /// This method is called in response to the
        /// <see cref="ISQLiteNativeModule.xEof" /> method.
        /// </summary>
        /// <param name="cursor">
        /// The <see cref="SQLiteVirtualTableCursor" /> object instance
        /// associated with the previously opened virtual table cursor to be
        /// used.
        /// </param>
        /// <returns>
        /// Non-zero if no more rows are available; zero otherwise.
        /// </returns>
        public abstract bool Eof(
            SQLiteVirtualTableCursor cursor
            );

        ///////////////////////////////////////////////////////////////////////

        /// <summary>
        /// This method is called in response to the
        /// <see cref="ISQLiteNativeModule.xColumn" /> method.
        /// </summary>
        /// <param name="cursor">
        /// The <see cref="SQLiteVirtualTableCursor" /> object instance
        /// associated with the previously opened virtual table cursor to be
        /// used.
        /// </param>
        /// <param name="context">
        /// The <see cref="SQLiteContext" /> object instance to be used for
        /// returning the specified column value to the SQLite core library.
        /// </param>
        /// <param name="index">
        /// The zero-based index corresponding to the column containing the
        /// value to be returned.
        /// </param>
        /// <returns>
        /// A standard SQLite return code.
        /// </returns>
        public abstract SQLiteErrorCode Column(
            SQLiteVirtualTableCursor cursor,
            SQLiteContext context,
            int index
            );

        ///////////////////////////////////////////////////////////////////////

        /// <summary>
        /// This method is called in response to the
        /// <see cref="ISQLiteNativeModule.xRowId" /> method.
        /// </summary>
        /// <param name="cursor">
        /// The <see cref="SQLiteVirtualTableCursor" /> object instance
        /// associated with the previously opened virtual table cursor to be
        /// used.
        /// </param>
        /// <param name="rowId">
        /// Upon success, this parameter must be modified to contain the unique
        /// integer row identifier for the current row for the specified cursor.
        /// </param>
        /// <returns>
        /// A standard SQLite return code.
        /// </returns>
        public abstract SQLiteErrorCode RowId(
            SQLiteVirtualTableCursor cursor,
            ref long rowId
            );

        ///////////////////////////////////////////////////////////////////////

        /// <summary>
        /// This method is called in response to the
        /// <see cref="ISQLiteNativeModule.xUpdate" /> method.
        /// </summary>
        /// <param name="table">
        /// The <see cref="SQLiteVirtualTable" /> object instance associated
        /// with this virtual table.
        /// </param>
        /// <param name="values">
        /// The array of <see cref="SQLiteValue" /> object instances containing
        /// the new or modified column values, if any.
        /// </param>
        /// <param name="rowId">
        /// Upon success, this parameter must be modified to contain the unique
        /// integer row identifier for the row that was inserted, if any.
        /// </param>
        /// <returns>
        /// A standard SQLite return code.
        /// </returns>
        public abstract SQLiteErrorCode Update(
            SQLiteVirtualTable table,
            SQLiteValue[] values,
            ref long rowId
            );

        ///////////////////////////////////////////////////////////////////////

        /// <summary>
        /// This method is called in response to the
        /// <see cref="ISQLiteNativeModule.xBegin" /> method.
        /// </summary>
        /// <param name="table">
        /// The <see cref="SQLiteVirtualTable" /> object instance associated
        /// with this virtual table.
        /// </param>
        /// <returns>
        /// A standard SQLite return code.
        /// </returns>
        public abstract SQLiteErrorCode Begin(
            SQLiteVirtualTable table
            );

        ///////////////////////////////////////////////////////////////////////

        /// <summary>
        /// This method is called in response to the
        /// <see cref="ISQLiteNativeModule.xSync" /> method.
        /// </summary>
        /// <param name="table">
        /// The <see cref="SQLiteVirtualTable" /> object instance associated
        /// with this virtual table.
        /// </param>
        /// <returns>
        /// A standard SQLite return code.
        /// </returns>
        public abstract SQLiteErrorCode Sync(
            SQLiteVirtualTable table
            );

        ///////////////////////////////////////////////////////////////////////

        /// <summary>
        /// This method is called in response to the
        /// <see cref="ISQLiteNativeModule.xCommit" /> method.
        /// </summary>
        /// <param name="table">
        /// The <see cref="SQLiteVirtualTable" /> object instance associated
        /// with this virtual table.
        /// </param>
        /// <returns>
        /// A standard SQLite return code.
        /// </returns>
        public abstract SQLiteErrorCode Commit(
            SQLiteVirtualTable table
            );

        ///////////////////////////////////////////////////////////////////////

        /// <summary>
        /// This method is called in response to the
        /// <see cref="ISQLiteNativeModule.xRollback" /> method.
        /// </summary>
        /// <param name="table">
        /// The <see cref="SQLiteVirtualTable" /> object instance associated
        /// with this virtual table.
        /// </param>
        /// <returns>
        /// A standard SQLite return code.
        /// </returns>
        public abstract SQLiteErrorCode Rollback(
            SQLiteVirtualTable table
            );

        ///////////////////////////////////////////////////////////////////////

        /// <summary>
        /// This method is called in response to the
        /// <see cref="ISQLiteNativeModule.xFindFunction" /> method.
        /// </summary>
        /// <param name="table">
        /// The <see cref="SQLiteVirtualTable" /> object instance associated
        /// with this virtual table.
        /// </param>
        /// <param name="argumentCount">
        /// The number of arguments to the function being sought.
        /// </param>
        /// <param name="name">
        /// The name of the function being sought.
        /// </param>
        /// <param name="function">
        /// Upon success, this parameter must be modified to contain the
        /// <see cref="SQLiteFunction" /> object instance responsible for
        /// implementing the specified function.
        /// </param>
        /// <param name="pClientData">
        /// Upon success, this parameter must be modified to contain the
        /// native user-data pointer associated with
        /// <paramref name="function" />.
        /// </param>
        /// <returns>
        /// Non-zero if the specified function was found; zero otherwise.
        /// </returns>
        public abstract bool FindFunction(
            SQLiteVirtualTable table,
            int argumentCount,
            string name,
            ref SQLiteFunction function,
            ref IntPtr pClientData
            );

        ///////////////////////////////////////////////////////////////////////

        /// <summary>
        /// This method is called in response to the
        /// <see cref="ISQLiteNativeModule.xRename" /> method.
        /// </summary>
        /// <param name="table">
        /// The <see cref="SQLiteVirtualTable" /> object instance associated
        /// with this virtual table.
        /// </param>
        /// <param name="newName">
        /// The new name for the virtual table.
        /// </param>
        /// <returns>
        /// A standard SQLite return code.
        /// </returns>
        public abstract SQLiteErrorCode Rename(
            SQLiteVirtualTable table,
            string newName
            );

        ///////////////////////////////////////////////////////////////////////

        /// <summary>
        /// This method is called in response to the
        /// <see cref="ISQLiteNativeModule.xSavepoint" /> method.
        /// </summary>
        /// <param name="table">
        /// The <see cref="SQLiteVirtualTable" /> object instance associated
        /// with this virtual table.
        /// </param>
        /// <param name="savepoint">
        /// This is an integer identifier under which the the current state of
        /// the virtual table should be saved.
        /// </param>
        /// <returns>
        /// A standard SQLite return code.
        /// </returns>
        public abstract SQLiteErrorCode Savepoint(
            SQLiteVirtualTable table,
            int savepoint
            );

        ///////////////////////////////////////////////////////////////////////

        /// <summary>
        /// This method is called in response to the
        /// <see cref="ISQLiteNativeModule.xRelease" /> method.
        /// </summary>
        /// <param name="table">
        /// The <see cref="SQLiteVirtualTable" /> object instance associated
        /// with this virtual table.
        /// </param>
        /// <param name="savepoint">
        /// This is an integer used to indicate that any saved states with an
        /// identifier greater than or equal to this should be deleted by the
        /// virtual table.
        /// </param>
        /// <returns>
        /// A standard SQLite return code.
        /// </returns>
        public abstract SQLiteErrorCode Release(
            SQLiteVirtualTable table,
            int savepoint
            );

        ///////////////////////////////////////////////////////////////////////

        /// <summary>
        /// This method is called in response to the
        /// <see cref="ISQLiteNativeModule.xRollbackTo" /> method.
        /// </summary>
        /// <param name="table">
        /// The <see cref="SQLiteVirtualTable" /> object instance associated
        /// with this virtual table.
        /// </param>
        /// <param name="savepoint">
        /// This is an integer identifier used to specify a specific saved
        /// state for the virtual table for it to restore itself back to, which
        /// should also have the effect of deleting all saved states with an
        /// integer identifier greater than this one.
        /// </param>
        /// <returns>
        /// A standard SQLite return code.
        /// </returns>
        public abstract SQLiteErrorCode RollbackTo(
            SQLiteVirtualTable table,
            int savepoint
            );
        #endregion

        ///////////////////////////////////////////////////////////////////////

        #region IDisposable Members
        /// <summary>
        /// Disposes of this object instance.
        /// </summary>
        public void Dispose()
        {
            Dispose(true);
            GC.SuppressFinalize(this);
        }
        #endregion

        ///////////////////////////////////////////////////////////////////////

        #region IDisposable "Pattern" Members
        private bool disposed;
        /// <summary>
        /// Throws an <see cref="ObjectDisposedException" /> if this object
        /// instance has been disposed.
        /// </summary>
        private void CheckDisposed() /* throw */
        {
#if THROW_ON_DISPOSED
            if (disposed)
            {
                throw new ObjectDisposedException(
                    typeof(SQLiteModule).Name);
            }
#endif
        }

        ///////////////////////////////////////////////////////////////////////

        /// <summary>
        /// Disposes of this object instance.
        /// </summary>
        /// <param name="disposing">
        /// Non-zero if this method is being called from the
        /// <see cref="Dispose()" /> method.  Zero if this method is being
        /// called from the finalizer.
        /// </param>
        protected virtual void Dispose(bool disposing)
        {
            if (!disposed)
            {
                if (disposing)
                {
                    ////////////////////////////////////
                    // dispose managed resources here...
                    ////////////////////////////////////

                    if (functions != null)
                        functions.Clear();
                }

                //////////////////////////////////////
                // release unmanaged resources here...
                //////////////////////////////////////

                try
                {
                    if (disposableModule != IntPtr.Zero)
                    {
                        UnsafeNativeMethods.sqlite3_dispose_module(
                            disposableModule);

                        disposableModule = IntPtr.Zero;
                    }
                }
                catch (Exception e)
                {
                    try
                    {
                        if (LogExceptionsNoThrow)
                        {
                            SQLiteLog.LogMessage(SQLiteBase.COR_E_EXCEPTION,
                                HelperMethods.StringFormat(
                                CultureInfo.CurrentCulture,
                                UnsafeNativeMethods.ExceptionMessageFormat,
                                "Dispose", e)); /* throw */
                        }
                    }
                    catch
                    {
                        // do nothing.
                    }
                }
#if PLATFORM_COMPACTFRAMEWORK
                finally
                {
                    if (pNativeModule != IntPtr.Zero)
                    {
                        SQLiteMemory.Free(pNativeModule);
                        pNativeModule = IntPtr.Zero;
                    }
                }
#endif

                disposed = true;
            }
        }
        #endregion

        ///////////////////////////////////////////////////////////////////////

        #region Destructor
        /// <summary>
        /// Finalizes this object instance.
        /// </summary>
        ~SQLiteModule()
        {
            Dispose(false);
        }
        #endregion
    }
    #endregion
}