System.Data.SQLite

  #region Native Library Helper Class
  /// <summary>
  /// This static class provides a thin wrapper around the native library
  /// loading features of the underlying platform.
  /// </summary>
  internal static class NativeLibraryHelper
  {
      #region Private Constants
#if !PLATFORM_COMPACTFRAMEWORK
      /// <summary>
      /// The list of characters used as path delimiters for this platform.
      /// </summary>
      private static readonly char[] PathSeparators = { Path.PathSeparator };

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

      /// <summary>
      /// This is the name of the environment variable containing the POSIX
      /// shared library search path.  The value is assumed to be a list of
      /// directories, delimited by <see cref="Path.PathSeparator" />.
      /// </summary>
      private static readonly string LdLibraryPath = "LD_LIBRARY_PATH";
#endif
      #endregion

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

      #region Private Delegates
      /// <summary>
      /// This delegate is used to wrap the concept of loading a native
      /// library, based on a file name, and returning the loaded module
      /// handle.
      /// </summary>
      /// <param name="fileName">

      {
          return UnsafeNativeMethodsWin32.LoadLibrary(fileName);
      }

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

#if !PLATFORM_COMPACTFRAMEWORK
      /// <summary>
      /// Attempts to determine if a directory exists in a search path.
      /// </summary>
      /// <param name="directory">
      /// The directory to search for.  This is case-sensitive.
      /// </param>
      /// <param name="path">
      /// The search path to inspect.  This is case-sensitive.
      /// </param>
      /// <returns>
      /// Non-zero if the directory exists in the search path; otherwise,
      /// zero.
      /// </returns>
      private static bool IsDirectoryInPath(
          string directory,
          string path
          )
      {
          //
          // NOTE: Nothing meaningful can be done if either of the parameters
          //       are null (or an empty string).  Therefore, return false in
          //       that case.
          //
          if (String.IsNullOrEmpty(directory) || String.IsNullOrEmpty(path))
              return false;

          string[] pathDirectories = path.Split(
              PathSeparators, StringSplitOptions.RemoveEmptyEntries);

          //
          // NOTE: No search can be performed if the list of path directories
          //       is invalid (or empty).  Therefore, just return false.
          //
          if ((pathDirectories == null) || (pathDirectories.Length == 0))
              return false;

          foreach (string pathDirectory in pathDirectories)
          {
              if (String.Equals(
                    pathDirectory, directory, StringComparison.Ordinal))
              {
                  return true;
              }
          }

          return false;
      }

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

      /// <summary>
      /// Ensures that the directory containing the specified file is included
      /// in the POSIX shared library search path via the environment variable
      /// LD_LIBRARY_PATH.
      /// </summary>
      /// <param name="fileName">
      /// The file name of the native library that was successfully loaded.
      /// </param>
      /// <returns>
      /// Non-zero if the POSIX shared library path was updated; otherwise,
      /// zero.
      /// </returns>
      private static bool MaybeUpdateLdLibraryPath(
          string fileName
          )
      {
          string directory = Path.GetDirectoryName(fileName);

          if (!String.IsNullOrEmpty(directory))
          {
              string path = Environment.GetEnvironmentVariable(LdLibraryPath);

              if (!IsDirectoryInPath(directory, path))
              {
                  if (!String.IsNullOrEmpty(path))
                  {
                      path = HelperMethods.StringFormat(
                          CultureInfo.InvariantCulture, "{0}{1}{2}",
                          directory, Path.PathSeparator, path);
                  }
                  else
                  {
                      path = directory;
                  }

                  Environment.SetEnvironmentVariable(LdLibraryPath, path);
                  return true;
              }
          }

          return false;
      }

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

      /// <summary>
      /// Attempts to load the specified native library file using the POSIX
      /// API.
      /// </summary>
      /// <param name="fileName">
      /// The file name of the native library to load.
      /// </param>
      /// <returns>
      /// The native module handle upon success -OR- IntPtr.Zero on failure.
      /// </returns>
      private static IntPtr LoadLibraryPosix(
          string fileName
          )
      {
          IntPtr nativeModuleHandle = UnsafeNativeMethodsPosix.dlopen(
              fileName, UnsafeNativeMethodsPosix.RTLD_DEFAULT);

          if (nativeModuleHandle != IntPtr.Zero)
          {
              if (MaybeUpdateLdLibraryPath(fileName))
              {
                  UnsafeNativeMethodsPosix.dlclose(nativeModuleHandle);
                  nativeModuleHandle = IntPtr.Zero;
              }
          }

          return nativeModuleHandle;
      }
#endif
      #endregion

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

      #region Public Methods