Code:
/ DotNET / DotNET / 8.0 / untmp / whidbey / REDBITS / ndp / clr / src / BCL / System / CurrentTimeZone.cs / 3 / CurrentTimeZone.cs
// ==++== // // Copyright (c) Microsoft Corporation. All rights reserved. // // ==--== /*============================================================ ** ** Class: CurrentTimeZone ** ** ** Purpose: ** This class represents the current system timezone. It is ** the only meaningful implementation of the TimeZone class ** available in this version. ** ** The only TimeZone that we support in version 1 is the ** CurrentTimeZone as determined by the system timezone. ** ** ============================================================*/ namespace System { using System; using System.Text; using System.Threading; using System.Collections; using System.Globalization; using System.Runtime.CompilerServices; // // Currently, this is the only supported timezone. // The values of the timezone is from the current system timezone setting in the // control panel. // [Serializable()] internal class CurrentSystemTimeZone : TimeZone { // < private const long TicksPerMillisecond = 10000; private const long TicksPerSecond = TicksPerMillisecond * 1000; private const long TicksPerMinute = TicksPerSecond * 60; // The per-year information is cached in in this instance value. As a result it can // be cleaned up by CultureInfo.ClearCachedData, which will clear the instance of this object private Hashtable m_CachedDaylightChanges = new Hashtable(); // Standard offset in ticks to the Universal time if // no daylight saving is in used. // E.g. the offset for PST (Pacific Standard time) should be -8 * 60 * 60 * 1000 * 10000. // (1 millisecond = 10000 ticks) private long m_ticksOffset; private String m_standardName; private String m_daylightName; internal CurrentSystemTimeZone() { m_ticksOffset = nativeGetTimeZoneMinuteOffset() * TicksPerMinute; m_standardName = null; m_daylightName = null; } public override String StandardName { get { if (m_standardName == null) { m_standardName = nativeGetStandardName(); } return (m_standardName); } } public override String DaylightName { get { if (m_daylightName == null) { m_daylightName = nativeGetDaylightName(); if (m_daylightName == null) { m_daylightName = this.StandardName; } } return (m_daylightName); } } internal long GetUtcOffsetFromUniversalTime(DateTime time, ref Boolean isAmbiguousLocalDst) { // Get the daylight changes for the year of the specified time. TimeSpan offset = new TimeSpan(m_ticksOffset); DaylightTime daylightTime = GetDaylightChanges(time.Year); isAmbiguousLocalDst= false; if (daylightTime == null || daylightTime.Delta.Ticks == 0) { return offset.Ticks; } // The start and end times represent the range of universal times that are in DST for that year. // Within that there is an ambiguous hour, usually right at the end, but at the beginning in // the unusual case of a negative daylight savings delta. DateTime startTime = daylightTime.Start - offset; DateTime endTime = daylightTime.End - offset - daylightTime.Delta; DateTime ambiguousStart; DateTime ambiguousEnd; if (daylightTime.Delta.Ticks > 0) { ambiguousStart = endTime - daylightTime.Delta; ambiguousEnd = endTime; } else { ambiguousStart = startTime; ambiguousEnd = startTime - daylightTime.Delta; } Boolean isDst = false; if (startTime > endTime) { // In southern hemisphere, the daylight saving time starts later in the year, and ends in the beginning of next year. // Note, the summer in the southern hemisphere begins late in the year. isDst = (time < endTime || time >= startTime); } else { // In northern hemisphere, the daylight saving time starts in the middle of the year. isDst = (time>=startTime && time= ambiguousStart && time < ambiguousEnd ) { isAmbiguousLocalDst = true; } } return offset.Ticks; } public override DateTime ToLocalTime(DateTime time) { if (time.Kind == DateTimeKind.Local) { return time; } Boolean isAmbiguousLocalDst = false; Int64 offset = GetUtcOffsetFromUniversalTime(time, ref isAmbiguousLocalDst); long tick = time.Ticks + offset; if (tick>DateTime.MaxTicks) { return new DateTime(DateTime.MaxTicks, DateTimeKind.Local); } if (tick 9999) { throw new ArgumentOutOfRangeException("year", String.Format(CultureInfo.CurrentCulture, Environment.GetResourceString("ArgumentOutOfRange_Range"), 1, 9999)); } Object objYear = (Object)year; if (!m_CachedDaylightChanges.Contains(objYear)) { BCLDebug.Log("Getting TimeZone information for: " + objYear); lock (InternalSyncObject) { if (!m_CachedDaylightChanges.Contains(objYear)) { // // rawData is an array of 17 short (16 bit) numbers. // The first 8 numbers contains the // year/month/day/dayOfWeek/hour/minute/second/millisecond for the starting time of daylight saving time. // The next 8 numbers contains the // year/month/day/dayOfWeek/hour/minute/second/millisecond for the ending time of daylight saving time. // The last short number is the delta to the standard offset in minutes. // short[] rawData = nativeGetDaylightChanges(); if (rawData == null) { // // If rawData is null, it means that daylight saving time is not used // in this timezone. So keep currentDaylightChanges as the empty array. // m_CachedDaylightChanges.Add(objYear, new DaylightTime(DateTime.MinValue, DateTime.MinValue, TimeSpan.Zero)); } else { DateTime start; DateTime end; TimeSpan delta; // // Store the start of daylight saving time. // start = GetDayOfWeek( year, (rawData[0] != 0), rawData[1], rawData[2], rawData[3], rawData[4], rawData[5], rawData[6], rawData[7]); // // Store the end of daylight saving time. // end = GetDayOfWeek( year, (rawData[8] != 0), rawData[9], rawData[10], rawData[11], rawData[12], rawData[13], rawData[14], rawData[15]); delta = new TimeSpan(rawData[16] * TicksPerMinute); DaylightTime currentDaylightChanges = new DaylightTime(start, end, delta); m_CachedDaylightChanges.Add(objYear, currentDaylightChanges); } } } } DaylightTime result = (DaylightTime)m_CachedDaylightChanges[objYear]; return result; } public override TimeSpan GetUtcOffset(DateTime time) { if (time.Kind == DateTimeKind.Utc) { return TimeSpan.Zero; } else { return new TimeSpan(TimeZone.CalculateUtcOffset(time, GetDaylightChanges(time.Year)).Ticks + m_ticksOffset); } } // // Return the (numberOfSunday)th day of week in a particular year/month. // private static DateTime GetDayOfWeek(int year, bool fixedDate, int month, int targetDayOfWeek, int numberOfSunday, int hour, int minute, int second, int millisecond) { DateTime time; if (fixedDate) { // // Create a Fixed-Date transition time based on the supplied parameters // For Fixed-Dated transition times, the 'numberOfSunday' parameter actually // represents the day of the month. // // if the day is out of range for the month then use the last day of the month int day = DateTime.DaysInMonth(year, month); time = new DateTime(year, month, (day < numberOfSunday) ? day : numberOfSunday, hour, minute, second, millisecond, DateTimeKind.Local); } else if (numberOfSunday <= 4) { // // Get the (numberOfSunday)th Sunday. // time = new DateTime(year, month, 1, hour, minute, second, millisecond, DateTimeKind.Local); int dayOfWeek = (int)time.DayOfWeek; int delta = targetDayOfWeek - dayOfWeek; if (delta < 0) { delta += 7; } delta += 7 * (numberOfSunday - 1); if (delta > 0) { time = time.AddDays(delta); } } else { // // If numberOfSunday is greater than 4, we will get the last sunday. // Calendar cal = GregorianCalendar.GetDefaultInstance(); time = new DateTime(year, month, cal.GetDaysInMonth(year, month), hour, minute, second, millisecond, DateTimeKind.Local); // This is the day of week for the last day of the month. int dayOfWeek = (int)time.DayOfWeek; int delta = dayOfWeek - targetDayOfWeek; if (delta < 0) { delta += 7; } if (delta > 0) { time = time.AddDays(-delta); } } return (time); } [MethodImplAttribute(MethodImplOptions.InternalCall)] internal extern static int nativeGetTimeZoneMinuteOffset(); [MethodImplAttribute(MethodImplOptions.InternalCall)] internal extern static String nativeGetDaylightName(); [MethodImplAttribute(MethodImplOptions.InternalCall)] internal extern static String nativeGetStandardName(); [MethodImplAttribute(MethodImplOptions.InternalCall)] internal extern static short[] nativeGetDaylightChanges(); } // class CurrentSystemTimeZone }
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