// ==++==
//
//
// Copyright (c) 2006 Microsoft Corporation. All rights reserved.
//
// The use and distribution terms for this software are contained in the file
// named license.txt, which can be found in the root of this distribution.
// By using this software in any fashion, you are agreeing to be bound by the
// terms of this license.
//
// You must not remove this notice, or any other, from this software.
//
//
// ==--==
/*============================================================
**
** 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<endTime);
}
if (isDst) {
offset += daylightTime.Delta;
// See if the resulting local time becomes ambiguous. This must be captured here or the
// DateTime will not be able to round-trip back to UTC accurately.
if (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<DateTime.MinTicks) {
return new DateTime(DateTime.MinTicks, DateTimeKind.Local);
}
return new DateTime(tick, DateTimeKind.Local, isAmbiguousLocalDst);
}
// Private object for locking instead of locking on a public type for SQL reliability work.
private static Object s_InternalSyncObject;
private static Object InternalSyncObject {
get {
if (s_InternalSyncObject == null) {
Object o = new Object();
Interlocked.CompareExchange(ref s_InternalSyncObject, o, null);
}
return s_InternalSyncObject;
}
}
public override DaylightTime GetDaylightChanges(int year) {
if (year < 1 || year > 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[1], rawData[2],
rawData[3],
rawData[4], rawData[5], rawData[6], rawData[7]);
//
// Store the end of daylight saving time.
//
end = GetDayOfWeek( year, 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, int month, int targetDayOfWeek, int numberOfSunday, int hour, int minute, int second, int millisecond) {
DateTime time;
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
}
