System.Data.SQLite
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Overview
Comment:Improve handling of out-of-range Julian Day values.
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SHA1: c559792dba4cff18e8af99127eb0a12e57c02b72
User & Date: mistachkin 2014-10-31 22:40:47
Context
2014-10-31
23:36
Completely remove use of DateTime.FromOADate and DateTime.ToOADate methods. Improve comments. Now passes existing tests. More tests are still necessary. check-in: 36b4f89052 user: mistachkin tags: newJulianDay
22:40
Improve handling of out-of-range Julian Day values. check-in: c559792dba user: mistachkin tags: newJulianDay
21:36
Add experimental port of the Julian Day handling functions from the SQLite core library. Still needs tests. Pursuant to [3e783eecbe]. check-in: fe17cded54 user: mistachkin tags: newJulianDay
Changes
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Changes to System.Data.SQLite/SQLiteConvert.cs.

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    private static readonly double OleAutomationEpochAsJulianDay = 2415018.5;

    /// <summary>
    /// The format string for DateTime values when using the InvariantCulture or CurrentCulture formats.
    /// </summary>
    private const string FullFormat = "yyyy-MM-ddTHH:mm:ss.fffffffK";













    /// <summary>
    /// An array of ISO-8601 DateTime formats that we support parsing.
    /// </summary>
    private static string[] _datetimeFormats = new string[] {
      "THHmmssK",
      "THHmmK",
      "HH:mm:ss.FFFFFFFK",
................................................................................


    #endregion

    #region DateTime Conversion Functions
    #region New Julian Day Conversion Methods
    /// <summary>


















    /// Converts a Julian Day number to a <see cref="DateTime" />.
    /// This function was copied from the "date.c" file belonging
    /// to the SQLite core library.
    /// </summary>
    /// <param name="jd">
    /// The Julian Day number to convert.
    /// </param>




    /// <returns>
    /// A <see cref="DateTime" /> value that contains the year, month, and day
    /// values that are closest to the specified Julian Day value.
    /// </returns>
    private static DateTime computeYMD(
        long jd

        )
    {



        int Z, A, B, C, D, E, X1;

        Z = (int)((jd + 43200000) / 86400000);
        A = (int)((Z - 1867216.25) / 36524.25);
        A = Z + 1 + A - (A / 4);
        B = A + 1524;
        C = (int)((B - 122.1) / 365.25);
................................................................................

        int day, month, year;

        day = B - D - X1;
        month = E < 14 ? E - 1 : E - 13;
        year = month > 2 ? C - 4716 : C - 4715;



        return new DateTime(year, month, day);





    }

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

    /// <summary>
    /// Converts a Julian Day number to a <see cref="DateTime" />.
    /// This function was copied from the "date.c" file belonging
    /// to the SQLite core library.
    /// </summary>
    /// <param name="jd">
    /// The Julian Day number to convert.




    /// </param>
    /// <returns>
    /// A <see cref="DateTime" /> value that contains the hour, minute, and
    /// second values that are closest to the specified Julian Day value.
    /// </returns>
    private static DateTime computeHMS(
        long jd

        )
    {



        int s;

        s = (int)((jd + 43200000) % 86400000);

        double seconds;

        seconds = s / 1000.0;
................................................................................

        minute = s / 60;
        seconds += s - minute * 60;

        int second = (int)Math.Truncate(seconds);
        int millisecond = (int)((seconds - second) * 1000.0);



        DateTime minValue = DateTime.MinValue;

        return new DateTime(
            minValue.Year, minValue.Month, minValue.Day,
            hour, minute, second, millisecond);





    }

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

    /// <summary>
    /// Converts a <see cref="DateTime" /> to a Julian Day number.
    /// This function was copied from the "date.c" file belonging
    /// to the SQLite core library.




    /// </summary>
    /// <param name="dateTime">
    /// The <see cref="DateTime" /> value to convert.




    /// </param>
    /// <returns>
    /// The nearest Julian Day number corresponding to the specified
    /// <see cref="DateTime" /> value.
    /// </returns>
    private static long computeJD(
        DateTime dateTime
        )
    {
        int Y, M, D;







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    private static readonly double OleAutomationEpochAsJulianDay = 2415018.5;

    /// <summary>
    /// The format string for DateTime values when using the InvariantCulture or CurrentCulture formats.
    /// </summary>
    private const string FullFormat = "yyyy-MM-ddTHH:mm:ss.fffffffK";

    /// <summary>
    /// This is the minimum Julian Day value supported by this library
    /// (148731163200000).
    /// </summary>
    private static readonly long MinimumJD = computeJD(DateTime.MinValue);

    /// <summary>
    /// This is the maximum Julian Day value supported by this library
    /// (464269060799000).
    /// </summary>
    private static readonly long MaximumJD = computeJD(DateTime.MaxValue);

    /// <summary>
    /// An array of ISO-8601 DateTime formats that we support parsing.
    /// </summary>
    private static string[] _datetimeFormats = new string[] {
      "THHmmssK",
      "THHmmK",
      "HH:mm:ss.FFFFFFFK",
................................................................................


    #endregion

    #region DateTime Conversion Functions
    #region New Julian Day Conversion Methods
    /// <summary>
    /// Checks if the specified <see cref="Int64" /> is within the
    /// supported range for a Julian Day value.
    /// </summary>
    /// <param name="jd">
    /// The Julian Day value to check.
    /// </param>
    /// <returns>
    /// Non-zero if the specified Julian Day value is in the supported
    /// range; otherwise, zero.
    /// </returns>
    private static bool isValidJD(
        long jd
        )
    {
        return ((jd >= MinimumJD) && (jd <= MaximumJD));
    }

    /// <summary>
    /// Converts a Julian Day value to a <see cref="DateTime" />.
    /// This function was copied from the "date.c" file belonging
    /// to the SQLite core library.
    /// </summary>
    /// <param name="jd">
    /// The Julian Day value to convert.
    /// </param>
    /// <param name="badValue">
    /// The <see cref="DateTime" /> value to return in the event that the
    /// Julian Day is out of the supported range.
    /// </param>
    /// <returns>
    /// A <see cref="DateTime" /> value that contains the year, month, and
    /// day values that are closest to the specified Julian Day value.
    /// </returns>
    private static DateTime computeYMD(
        long jd,
        DateTime badValue
        )
    {
        if (!isValidJD(jd))
            return badValue;

        int Z, A, B, C, D, E, X1;

        Z = (int)((jd + 43200000) / 86400000);
        A = (int)((Z - 1867216.25) / 36524.25);
        A = Z + 1 + A - (A / 4);
        B = A + 1524;
        C = (int)((B - 122.1) / 365.25);
................................................................................

        int day, month, year;

        day = B - D - X1;
        month = E < 14 ? E - 1 : E - 13;
        year = month > 2 ? C - 4716 : C - 4715;

        try
        {
            return new DateTime(year, month, day);
        }
        catch
        {
            return badValue;
        }
    }

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

    /// <summary>
    /// Converts a Julian Day value to a <see cref="DateTime" />.
    /// This function was copied from the "date.c" file belonging
    /// to the SQLite core library.
    /// </summary>
    /// <param name="jd">
    /// The Julian Day value to convert.
    /// </param>
    /// <param name="badValue">
    /// The <see cref="DateTime" /> value to return in the event that the
    /// Julian Day value is out of the supported range.
    /// </param>
    /// <returns>
    /// A <see cref="DateTime" /> value that contains the hour, minute, and
    /// second values that are closest to the specified Julian Day value.
    /// </returns>
    private static DateTime computeHMS(
        long jd,
        DateTime badValue
        )
    {
        if (!isValidJD(jd))
            return badValue;

        int s;

        s = (int)((jd + 43200000) % 86400000);

        double seconds;

        seconds = s / 1000.0;
................................................................................

        minute = s / 60;
        seconds += s - minute * 60;

        int second = (int)Math.Truncate(seconds);
        int millisecond = (int)((seconds - second) * 1000.0);

        try
        {
            DateTime minValue = DateTime.MinValue;

            return new DateTime(
                minValue.Year, minValue.Month, minValue.Day,
                hour, minute, second, millisecond);
        }
        catch
        {
            return badValue;
        }
    }

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

    /// <summary>
    /// Converts a <see cref="DateTime" /> to a Julian Day value.
    /// This function was copied from the "date.c" file belonging
    /// to the SQLite core library.  Since the range of Julian Day
    /// values supported by this method includes all possible valid
    /// values of a <see cref="DateTime" /> value, it should be
    /// impossible for this method to raise an exception or return
    /// an undefined result.
    /// </summary>
    /// <param name="dateTime">
    /// The <see cref="DateTime" /> value to convert.  This value
    /// will be within the range of <see cref="DateTime.MinValue" />
    /// (00:00:00.0000000, January 1, 0001) to
    /// <see cref="DateTime.MaxValue" /> (23:59:59.9999999, December
    /// 31, 9999).
    /// </param>
    /// <returns>
    /// The nearest Julian Day value corresponding to the specified
    /// <see cref="DateTime" /> value.
    /// </returns>
    private static long computeJD(
        DateTime dateTime
        )
    {
        int Y, M, D;