mcs/class/corlib/System/TimeZoneInfo.cs

   1
   2 /*
   3  * System.TimeZoneInfo
   4  *
   5  * Author(s)
   6  *      Stephane Delcroix <stephane@delcroix.org>
   7  *
   8  * Copyright 2011 Xamarin Inc.
   9  *
  10  * Permission is hereby granted, free of charge, to any person obtaining
  11  * a copy of this software and associated documentation files (the
  12  * "Software"), to deal in the Software without restriction, including
  13  * without limitation the rights to use, copy, modify, merge, publish,
  14  * distribute, sublicense, and/or sell copies of the Software, and to
  15  * permit persons to whom the Software is furnished to do so, subject to
  16  * the following conditions:
  17  *
  18  * The above copyright notice and this permission notice shall be
  19  * included in all copies or substantial portions of the Software.
  20  *
  21  * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
  22  * EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
  23  * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
  24  * NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE
  25  * LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION
  26  * OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
  27  * WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
  28  */
  29
  30 using System;
  31 using System.Runtime.CompilerServices;
  32 using System.Threading;
  33 using System.Collections.Generic;
  34 using System.Collections.ObjectModel;
  35 using System.Runtime.Serialization;
  36 using System.Text;
  37 using System.Globalization;
  38 using System.IO;
  39
  40 using Microsoft.Win32;
  41
  42 namespace System
  43 {
  44         partial class TimeZoneInfo
  45         {
  46                 TimeSpan baseUtcOffset;
  47                 public TimeSpan BaseUtcOffset {
  48                         get { return baseUtcOffset; }
  49                 }
  50
  51                 string daylightDisplayName;
  52                 public string DaylightName {
  53                         get {
  54                                 return supportsDaylightSavingTime
  55                                         ? daylightDisplayName
  56                                         : string.Empty;
  57                         }
  58                 }
  59
  60                 string displayName;
  61                 public string DisplayName {
  62                         get { return displayName; }
  63                 }
  64
  65                 string id;
  66                 public string Id {
  67                         get { return id; }
  68                 }
  69
  70                 static TimeZoneInfo local;
  71                 public static TimeZoneInfo Local {
  72                         get {
  73                                 var l = local;
  74                                 if (l == null) {
  75                                         l = CreateLocal ();
  76                                         if (l == null)
  77                                                 throw new TimeZoneNotFoundException ();
  78
  79                                         if (Interlocked.CompareExchange (ref local, l, null) != null)
  80                                                 l = local;
  81                                 }
  82
  83                                 return l;
  84                         }
  85                 }
  86
  87                 /*
  88                         TimeZone transitions are stored when there is a change on the base offset.
  89                 */
  90                 private List<KeyValuePair<DateTime, TimeType>> transitions;
  91
  92 #if !MOBILE || MOBILE_STATIC
  93                 static TimeZoneInfo CreateLocal ()
  94                 {
  95 #if !MOBILE_STATIC
  96                         if (IsWindows && LocalZoneKey != null) {
  97                                 string name = (string)LocalZoneKey.GetValue ("TimeZoneKeyName");
  98                                 if (name == null)
  99                                         name = (string)LocalZoneKey.GetValue ("StandardName"); // windows xp
 100                                 name = TrimSpecial (name);
 101                                 if (name != null)
 102                                         return TimeZoneInfo.FindSystemTimeZoneById (name);
 103                         }
 104 #endif
 105
 106                         var tz = Environment.GetEnvironmentVariable ("TZ");
 107                         if (tz != null) {
 108                                 if (tz == String.Empty)
 109                                         return Utc;
 110                                 try {
 111                                         return FindSystemTimeZoneByFileName (tz, Path.Combine (TimeZoneDirectory, tz));
 112                                 } catch {
 113                                         return Utc;
 114                                 }
 115                         }
 116
 117                         try {
 118                                 return FindSystemTimeZoneByFileName ("Local", "/etc/localtime");
 119                         } catch {
 120                                 try {
 121                                         return FindSystemTimeZoneByFileName ("Local", Path.Combine (TimeZoneDirectory, "localtime"));
 122                                 } catch {
 123                                         return null;
 124                                 }
 125                         }
 126                 }
 127
 128                 static TimeZoneInfo FindSystemTimeZoneByIdCore (string id)
 129                 {
 130 #if LIBC
 131                         string filepath = Path.Combine (TimeZoneDirectory, id);
 132                         return FindSystemTimeZoneByFileName (id, filepath);
 133 #else
 134                         throw new NotImplementedException ();
 135 #endif
 136                 }
 137
 138                 static void GetSystemTimeZones (List<TimeZoneInfo> systemTimeZones)
 139                 {
 140 #if !MOBILE_STATIC
 141                         if (TimeZoneKey != null) {
 142                                 foreach (string id in TimeZoneKey.GetSubKeyNames ()) {
 143                                         try {
 144                                                 systemTimeZones.Add (FindSystemTimeZoneById (id));
 145                                         } catch {}
 146                                 }
 147
 148                                 return;
 149                         }
 150 #endif
 151
 152 #if LIBC
 153                         string[] continents = new string [] {"Africa", "America", "Antarctica", "Arctic", "Asia", "Atlantic", "Brazil", "Canada", "Chile", "Europe", "Indian", "Mexico", "Mideast", "Pacific", "US"};
 154                         foreach (string continent in continents) {
 155                                 try {
 156                                         foreach (string zonepath in Directory.GetFiles (Path.Combine (TimeZoneDirectory, continent))) {
 157                                                 try {
 158                                                         string id = String.Format ("{0}/{1}", continent, Path.GetFileName (zonepath));
 159                                                         systemTimeZones.Add (FindSystemTimeZoneById (id));
 160                                                 } catch (ArgumentNullException) {
 161                                                 } catch (TimeZoneNotFoundException) {
 162                                                 } catch (InvalidTimeZoneException) {
 163                                                 } catch (Exception) {
 164                                                         throw;
 165                                                 }
 166                                         }
 167                                 } catch {}
 168                         }
 169 #else
 170                         throw new NotImplementedException ("This method is not implemented for this platform");
 171 #endif
 172                 }
 173 #endif
 174
 175                 string standardDisplayName;
 176                 public string StandardName {
 177                         get { return standardDisplayName; }
 178                 }
 179
 180                 bool supportsDaylightSavingTime;
 181                 public bool SupportsDaylightSavingTime {
 182                         get  { return supportsDaylightSavingTime; }
 183                 }
 184
 185                 static TimeZoneInfo utc;
 186                 public static TimeZoneInfo Utc {
 187                         get {
 188                                 if (utc == null)
 189                                         utc = CreateCustomTimeZone ("UTC", new TimeSpan (0), "UTC", "UTC");
 190                                 return utc;
 191                         }
 192                 }
 193 #if LIBC
 194                 static string timeZoneDirectory;
 195                 static string TimeZoneDirectory {
 196                         get {
 197                                 if (timeZoneDirectory == null)
 198                                         timeZoneDirectory = "/usr/share/zoneinfo";
 199                                 return timeZoneDirectory;
 200                         }
 201                         set {
 202                                 ClearCachedData ();
 203                                 timeZoneDirectory = value;
 204                         }
 205                 }
 206 #endif
 207                 private AdjustmentRule [] adjustmentRules;
 208
 209 #if !NET_2_1 || MOBILE_STATIC
 210                 /// <summary>
 211                 /// Determine whether windows of not (taken Stephane Delcroix's code)
 212                 /// </summary>
 213                 private static bool IsWindows
 214                 {
 215                         get {
 216                                 int platform = (int) Environment.OSVersion.Platform;
 217                                 return ((platform != 4) && (platform != 6) && (platform != 128));
 218                         }
 219                 }
 220
 221                 /// <summary>
 222                 /// Needed to trim misc garbage in MS registry keys
 223                 /// </summary>
 224                 private static string TrimSpecial (string str)
 225                 {
 226                         if (str == null)
 227                                 return str;
 228                         var Istart = 0;
 229                         while (Istart < str.Length && !char.IsLetterOrDigit(str[Istart])) Istart++;
 230                         var Iend = str.Length - 1;
 231                         while (Iend > Istart && !char.IsLetterOrDigit(str[Iend])) Iend--;
 232
 233                         return str.Substring (Istart, Iend-Istart+1);
 234                 }
 235
 236 #if !MOBILE_STATIC
 237                 static RegistryKey timeZoneKey;
 238                 static RegistryKey TimeZoneKey {
 239                         get {
 240                                 if (timeZoneKey != null)
 241                                         return timeZoneKey;
 242                                 if (!IsWindows)
 243                                         return null;
 244
 245                                 return timeZoneKey = Registry.LocalMachine.OpenSubKey (
 246                                         "SOFTWARE\\Microsoft\\Windows NT\\CurrentVersion\\Time Zones",
 247                                         false);
 248                         }
 249                 }
 250
 251                 static RegistryKey localZoneKey;
 252                 static RegistryKey LocalZoneKey {
 253                         get {
 254                                 if (localZoneKey != null)
 255                                         return localZoneKey;
 256
 257                                 if (!IsWindows)
 258                                         return null;
 259
 260                                 return localZoneKey = Registry.LocalMachine.OpenSubKey (
 261                                         "SYSTEM\\CurrentControlSet\\Control\\TimeZoneInformation", false);
 262                         }
 263                 }
 264 #endif
 265 #endif
 266
 267                 private static bool TryAddTicks (DateTime date, long ticks, out DateTime result, DateTimeKind kind = DateTimeKind.Unspecified)
 268                 {
 269                         var resultTicks = date.Ticks + ticks;
 270                         if (resultTicks < DateTime.MinValue.Ticks || resultTicks > DateTime.MaxValue.Ticks) {
 271                                 result =  default (DateTime);
 272                                 return false;
 273                         }
 274
 275                         result = new DateTime (resultTicks, kind);
 276                         return true;
 277                 }
 278
 279                 public static void ClearCachedData ()
 280                 {
 281                         local = null;
 282                         utc = null;
 283                         systemTimeZones = null;
 284                 }
 285
 286                 public static DateTime ConvertTime (DateTime dateTime, TimeZoneInfo destinationTimeZone)
 287                 {
 288                         return ConvertTime (dateTime, dateTime.Kind == DateTimeKind.Utc ? TimeZoneInfo.Utc : TimeZoneInfo.Local, destinationTimeZone);
 289                 }
 290
 291                 public static DateTime ConvertTime (DateTime dateTime, TimeZoneInfo sourceTimeZone, TimeZoneInfo destinationTimeZone)
 292                 {
 293                         if (sourceTimeZone == null)
 294                                 throw new ArgumentNullException ("sourceTimeZone");
 295
 296                         if (destinationTimeZone == null)
 297                                 throw new ArgumentNullException ("destinationTimeZone");
 298
 299                         if (dateTime.Kind == DateTimeKind.Local && sourceTimeZone != TimeZoneInfo.Local)
 300                                 throw new ArgumentException ("Kind property of dateTime is Local but the sourceTimeZone does not equal TimeZoneInfo.Local");
 301
 302                         if (dateTime.Kind == DateTimeKind.Utc && sourceTimeZone != TimeZoneInfo.Utc)
 303                                 throw new ArgumentException ("Kind property of dateTime is Utc but the sourceTimeZone does not equal TimeZoneInfo.Utc");
 304
 305                         if (sourceTimeZone.IsInvalidTime (dateTime))
 306                                 throw new ArgumentException ("dateTime parameter is an invalid time");
 307
 308                         if (dateTime.Kind == DateTimeKind.Local && sourceTimeZone == TimeZoneInfo.Local && destinationTimeZone == TimeZoneInfo.Local)
 309                                 return dateTime;
 310
 311                         DateTime utc = ConvertTimeToUtc (dateTime, sourceTimeZone);
 312
 313                         if (destinationTimeZone != TimeZoneInfo.Utc) {
 314                                 utc = ConvertTimeFromUtc (utc, destinationTimeZone);
 315                                 if (dateTime.Kind == DateTimeKind.Unspecified)
 316                                         return DateTime.SpecifyKind (utc, DateTimeKind.Unspecified);
 317                         }
 318
 319                         return utc;
 320                 }
 321
 322                 public static DateTimeOffset ConvertTime(DateTimeOffset dateTimeOffset, TimeZoneInfo destinationTimeZone)
 323                 {
 324                         if (destinationTimeZone == null)
 325                                 throw new ArgumentNullException("destinationTimeZone");
 326
 327                         var utcDateTime = dateTimeOffset.UtcDateTime;
 328
 329                         bool isDst;
 330                         var utcOffset =  destinationTimeZone.GetUtcOffset(utcDateTime, out isDst);
 331
 332                         return new DateTimeOffset(DateTime.SpecifyKind(utcDateTime, DateTimeKind.Unspecified) + utcOffset, utcOffset);
 333                 }
 334
 335                 public static DateTime ConvertTimeBySystemTimeZoneId (DateTime dateTime, string destinationTimeZoneId)
 336                 {
 337                         return ConvertTime (dateTime, FindSystemTimeZoneById (destinationTimeZoneId));
 338                 }
 339
 340                 public static DateTime ConvertTimeBySystemTimeZoneId (DateTime dateTime, string sourceTimeZoneId, string destinationTimeZoneId)
 341                 {
 342                         return ConvertTime (dateTime, FindSystemTimeZoneById (sourceTimeZoneId), FindSystemTimeZoneById (destinationTimeZoneId));
 343                 }
 344
 345                 public static DateTimeOffset ConvertTimeBySystemTimeZoneId (DateTimeOffset dateTimeOffset, string destinationTimeZoneId)
 346                 {
 347                         return ConvertTime (dateTimeOffset, FindSystemTimeZoneById (destinationTimeZoneId));
 348                 }
 349
 350                 private DateTime ConvertTimeFromUtc (DateTime dateTime)
 351                 {
 352                         if (dateTime.Kind == DateTimeKind.Local)
 353                                 throw new ArgumentException ("Kind property of dateTime is Local");
 354
 355                         if (this == TimeZoneInfo.Utc)
 356                                 return DateTime.SpecifyKind (dateTime, DateTimeKind.Utc);
 357
 358                         var utcOffset = GetUtcOffset (dateTime);
 359
 360                         var kind = (this == TimeZoneInfo.Local)? DateTimeKind.Local : DateTimeKind.Unspecified;
 361
 362                         DateTime result;
 363                         if (!TryAddTicks (dateTime, utcOffset.Ticks, out result, kind))
 364                                 return DateTime.SpecifyKind (DateTime.MaxValue, kind);
 365
 366                         return result;
 367                 }
 368
 369                 public static DateTime ConvertTimeFromUtc (DateTime dateTime, TimeZoneInfo destinationTimeZone)
 370                 {
 371                         if (destinationTimeZone == null)
 372                                 throw new ArgumentNullException ("destinationTimeZone");
 373
 374                         return destinationTimeZone.ConvertTimeFromUtc (dateTime);
 375                 }
 376
 377                 public static DateTime ConvertTimeToUtc (DateTime dateTime)
 378                 {
 379                         if (dateTime.Kind == DateTimeKind.Utc)
 380                                 return dateTime;
 381
 382                         return ConvertTimeToUtc (dateTime, TimeZoneInfo.Local);
 383                 }
 384
 385                 static internal DateTime ConvertTimeToUtc(DateTime dateTime, TimeZoneInfoOptions flags)
 386                 {
 387                         return ConvertTimeToUtc (dateTime, TimeZoneInfo.Local, flags);
 388                 }
 389
 390                 public static DateTime ConvertTimeToUtc (DateTime dateTime, TimeZoneInfo sourceTimeZone)
 391                 {
 392                         return ConvertTimeToUtc (dateTime, sourceTimeZone, TimeZoneInfoOptions.None);
 393                 }
 394
 395                 static DateTime ConvertTimeToUtc (DateTime dateTime, TimeZoneInfo sourceTimeZone, TimeZoneInfoOptions flags)
 396                 {
 397                         if ((flags & TimeZoneInfoOptions.NoThrowOnInvalidTime) == 0) {
 398                                 if (sourceTimeZone == null)
 399                                         throw new ArgumentNullException ("sourceTimeZone");
 400
 401                                 if (dateTime.Kind == DateTimeKind.Utc && sourceTimeZone != TimeZoneInfo.Utc)
 402                                         throw new ArgumentException ("Kind property of dateTime is Utc but the sourceTimeZone does not equal TimeZoneInfo.Utc");
 403
 404                                 if (dateTime.Kind == DateTimeKind.Local && sourceTimeZone != TimeZoneInfo.Local)
 405                                         throw new ArgumentException ("Kind property of dateTime is Local but the sourceTimeZone does not equal TimeZoneInfo.Local");
 406
 407                                 if (sourceTimeZone.IsInvalidTime (dateTime))
 408                                         throw new ArgumentException ("dateTime parameter is an invalid time");
 409                         }
 410
 411                         if (dateTime.Kind == DateTimeKind.Utc)
 412                                 return dateTime;
 413
 414                         bool isDst;
 415                         var utcOffset = sourceTimeZone.GetUtcOffset (dateTime, out isDst);
 416
 417                         DateTime utcDateTime;
 418                         if (!TryAddTicks (dateTime, -utcOffset.Ticks, out utcDateTime, DateTimeKind.Utc))
 419                                 return DateTime.SpecifyKind (DateTime.MinValue, DateTimeKind.Utc);
 420
 421                         return utcDateTime;
 422                 }
 423
 424                 static internal TimeSpan GetDateTimeNowUtcOffsetFromUtc(DateTime time, out Boolean isAmbiguousLocalDst)
 425                 {
 426                         bool isDaylightSavings;
 427                         return GetUtcOffsetFromUtc(time, TimeZoneInfo.Local, out isDaylightSavings, out isAmbiguousLocalDst);
 428                 }
 429
 430                 public static TimeZoneInfo CreateCustomTimeZone (string id, TimeSpan baseUtcOffset, string displayName, string standardDisplayName)
 431                 {
 432                         return CreateCustomTimeZone (id, baseUtcOffset, displayName, standardDisplayName, null, null, true);
 433                 }
 434
 435                 public static TimeZoneInfo CreateCustomTimeZone (string id, TimeSpan baseUtcOffset, string displayName, string standardDisplayName, string daylightDisplayName, TimeZoneInfo.AdjustmentRule [] adjustmentRules)
 436                 {
 437                         return CreateCustomTimeZone (id, baseUtcOffset, displayName, standardDisplayName, daylightDisplayName, adjustmentRules, false);
 438                 }
 439
 440                 public static TimeZoneInfo CreateCustomTimeZone ( string id, TimeSpan baseUtcOffset, string displayName, string standardDisplayName, string daylightDisplayName, TimeZoneInfo.AdjustmentRule [] adjustmentRules, bool disableDaylightSavingTime)
 441                 {
 442                         return new TimeZoneInfo (id, baseUtcOffset, displayName, standardDisplayName, daylightDisplayName, adjustmentRules, disableDaylightSavingTime);
 443                 }
 444
 445                 public override bool Equals (object obj)
 446                 {
 447                         return Equals (obj as TimeZoneInfo);
 448                 }
 449
 450                 public bool Equals (TimeZoneInfo other)
 451                 {
 452                         if (other == null)
 453                                 return false;
 454
 455                         return other.Id == this.Id && HasSameRules (other);
 456                 }
 457
 458                 public static TimeZoneInfo FindSystemTimeZoneById (string id)
 459                 {
 460                         //FIXME: this method should check for cached values in systemTimeZones
 461                         if (id == null)
 462                                 throw new ArgumentNullException ("id");
 463 #if !NET_2_1
 464                         if (TimeZoneKey != null)
 465                         {
 466                                 if (id == "Coordinated Universal Time")
 467                                         id = "UTC"; //windows xp exception for "StandardName" property
 468                                 RegistryKey key = TimeZoneKey.OpenSubKey (id, false);
 469                                 if (key == null)
 470                                         throw new TimeZoneNotFoundException ();
 471                                 return FromRegistryKey(id, key);
 472                         }
 473 #endif
 474                         // Local requires special logic that already exists in the Local property (bug #326)
 475                         if (id == "Local")
 476                                 return Local;
 477
 478                         return FindSystemTimeZoneByIdCore (id);
 479                 }
 480
 481 #if LIBC
 482                 private static TimeZoneInfo FindSystemTimeZoneByFileName (string id, string filepath)
 483                 {
 484                         if (!File.Exists (filepath))
 485                                 throw new TimeZoneNotFoundException ();
 486
 487                         using (FileStream stream = File.OpenRead (filepath)) {
 488                                 return BuildFromStream (id, stream);
 489                         }
 490                 }
 491 #endif
 492
 493 #if !NET_2_1
 494                 private static TimeZoneInfo FromRegistryKey (string id, RegistryKey key)
 495                 {
 496                         byte [] reg_tzi = (byte []) key.GetValue ("TZI");
 497
 498                         if (reg_tzi == null)
 499                                 throw new InvalidTimeZoneException ();
 500
 501                         int bias = BitConverter.ToInt32 (reg_tzi, 0);
 502                         TimeSpan baseUtcOffset = new TimeSpan (0, -bias, 0);
 503
 504                         string display_name = (string) key.GetValue ("Display");
 505                         string standard_name = (string) key.GetValue ("Std");
 506                         string daylight_name = (string) key.GetValue ("Dlt");
 507
 508                         List<AdjustmentRule> adjustmentRules = new List<AdjustmentRule> ();
 509
 510                         RegistryKey dst_key = key.OpenSubKey ("Dynamic DST", false);
 511                         if (dst_key != null) {
 512                                 int first_year = (int) dst_key.GetValue ("FirstEntry");
 513                                 int last_year = (int) dst_key.GetValue ("LastEntry");
 514                                 int year;
 515
 516                                 for (year=first_year; year<=last_year; year++) {
 517                                         byte [] dst_tzi = (byte []) dst_key.GetValue (year.ToString ());
 518                                         if (dst_tzi != null) {
 519                                                 int start_year = year == first_year ? 1 : year;
 520                                                 int end_year = year == last_year ? 9999 : year;
 521                                                 ParseRegTzi(adjustmentRules, start_year, end_year, dst_tzi);
 522                                         }
 523                                 }
 524                         }
 525                         else
 526                                 ParseRegTzi(adjustmentRules, 1, 9999, reg_tzi);
 527
 528                         return CreateCustomTimeZone (id, baseUtcOffset, display_name, standard_name, daylight_name, ValidateRules (adjustmentRules).ToArray ());
 529                 }
 530
 531                 private static void ParseRegTzi (List<AdjustmentRule> adjustmentRules, int start_year, int end_year, byte [] buffer)
 532                 {
 533                         //int standard_bias = BitConverter.ToInt32 (buffer, 4); /* not sure how to handle this */
 534                         int daylight_bias = BitConverter.ToInt32 (buffer, 8);
 535
 536                         int standard_year = BitConverter.ToInt16 (buffer, 12);
 537                         int standard_month = BitConverter.ToInt16 (buffer, 14);
 538                         int standard_dayofweek = BitConverter.ToInt16 (buffer, 16);
 539                         int standard_day = BitConverter.ToInt16 (buffer, 18);
 540                         int standard_hour = BitConverter.ToInt16 (buffer, 20);
 541                         int standard_minute = BitConverter.ToInt16 (buffer, 22);
 542                         int standard_second = BitConverter.ToInt16 (buffer, 24);
 543                         int standard_millisecond = BitConverter.ToInt16 (buffer, 26);
 544
 545                         int daylight_year = BitConverter.ToInt16 (buffer, 28);
 546                         int daylight_month = BitConverter.ToInt16 (buffer, 30);
 547                         int daylight_dayofweek = BitConverter.ToInt16 (buffer, 32);
 548                         int daylight_day = BitConverter.ToInt16 (buffer, 34);
 549                         int daylight_hour = BitConverter.ToInt16 (buffer, 36);
 550                         int daylight_minute = BitConverter.ToInt16 (buffer, 38);
 551                         int daylight_second = BitConverter.ToInt16 (buffer, 40);
 552                         int daylight_millisecond = BitConverter.ToInt16 (buffer, 42);
 553
 554                         if (standard_month == 0 || daylight_month == 0)
 555                                 return;
 556
 557                         DateTime start_date;
 558                         DateTime start_timeofday = new DateTime (1, 1, 1, daylight_hour, daylight_minute, daylight_second, daylight_millisecond);
 559                         TransitionTime start_transition_time;
 560
 561                         if (daylight_year == 0) {
 562                                 start_date = new DateTime (start_year, 1, 1);
 563                                 start_transition_time = TransitionTime.CreateFloatingDateRule (
 564                                         start_timeofday, daylight_month, daylight_day,
 565                                         (DayOfWeek) daylight_dayofweek);
 566                         }
 567                         else {
 568                                 start_date = new DateTime (daylight_year, daylight_month, daylight_day,
 569                                         daylight_hour, daylight_minute, daylight_second, daylight_millisecond);
 570                                 start_transition_time = TransitionTime.CreateFixedDateRule (
 571                                         start_timeofday, daylight_month, daylight_day);
 572                         }
 573
 574                         DateTime end_date;
 575                         DateTime end_timeofday = new DateTime (1, 1, 1, standard_hour, standard_minute, standard_second, standard_millisecond);
 576                         TransitionTime end_transition_time;
 577
 578                         if (standard_year == 0) {
 579                                 end_date = new DateTime (end_year, 12, 31);
 580                                 end_transition_time = TransitionTime.CreateFloatingDateRule (
 581                                         end_timeofday, standard_month, standard_day,
 582                                         (DayOfWeek) standard_dayofweek);
 583                         }
 584                         else {
 585                                 end_date = new DateTime (standard_year, standard_month, standard_day,
 586                                         standard_hour, standard_minute, standard_second, standard_millisecond);
 587                                 end_transition_time = TransitionTime.CreateFixedDateRule (
 588                                         end_timeofday, standard_month, standard_day);
 589                         }
 590
 591                         TimeSpan daylight_delta = new TimeSpan(0, -daylight_bias, 0);
 592
 593                         adjustmentRules.Add (AdjustmentRule.CreateAdjustmentRule (
 594                                 start_date, end_date, daylight_delta,
 595                                 start_transition_time, end_transition_time));
 596                 }
 597 #endif
 598
 599                 public AdjustmentRule [] GetAdjustmentRules ()
 600                 {
 601                         if (!supportsDaylightSavingTime || adjustmentRules == null)
 602                                 return new AdjustmentRule [0];
 603                         else
 604                                 return (AdjustmentRule []) adjustmentRules.Clone ();
 605                 }
 606
 607                 public TimeSpan [] GetAmbiguousTimeOffsets (DateTime dateTime)
 608                 {
 609                         if (!IsAmbiguousTime (dateTime))
 610                                 throw new ArgumentException ("dateTime is not an ambiguous time");
 611
 612                         AdjustmentRule rule = GetApplicableRule (dateTime);
 613                         if (rule != null)
 614                                 return new TimeSpan[] {baseUtcOffset, baseUtcOffset + rule.DaylightDelta};
 615                         else
 616                                 return new TimeSpan[] {baseUtcOffset, baseUtcOffset};
 617                 }
 618
 619                 public TimeSpan [] GetAmbiguousTimeOffsets (DateTimeOffset dateTimeOffset)
 620                 {
 621                         if (!IsAmbiguousTime (dateTimeOffset))
 622                                 throw new ArgumentException ("dateTimeOffset is not an ambiguous time");
 623
 624                         throw new NotImplementedException ();
 625                 }
 626
 627                 public override int GetHashCode ()
 628                 {
 629                         int hash_code = Id.GetHashCode ();
 630                         foreach (AdjustmentRule rule in GetAdjustmentRules ())
 631                                 hash_code ^= rule.GetHashCode ();
 632                         return hash_code;
 633                 }
 634
 635                 void ISerializable.GetObjectData (SerializationInfo info, StreamingContext context)
 636                 {
 637                         if (info == null)
 638                                 throw new ArgumentNullException ("info");
 639                         info.AddValue ("Id", id);
 640                         info.AddValue ("DisplayName", displayName);
 641                         info.AddValue ("StandardName", standardDisplayName);
 642                         info.AddValue ("DaylightName", daylightDisplayName);
 643                         info.AddValue ("BaseUtcOffset", baseUtcOffset);
 644                         info.AddValue ("AdjustmentRules", adjustmentRules);
 645                         info.AddValue ("SupportsDaylightSavingTime", SupportsDaylightSavingTime);
 646                 }
 647
 648                 static ReadOnlyCollection<TimeZoneInfo> systemTimeZones;
 649
 650                 public static ReadOnlyCollection<TimeZoneInfo> GetSystemTimeZones ()
 651                 {
 652                         if (systemTimeZones == null) {
 653                                 var tz = new List<TimeZoneInfo> ();
 654                                 GetSystemTimeZones (tz);
 655                                 Interlocked.CompareExchange (ref systemTimeZones, new ReadOnlyCollection<TimeZoneInfo> (tz), null);
 656                         }
 657
 658                         return systemTimeZones;
 659                 }
 660
 661                 public TimeSpan GetUtcOffset (DateTime dateTime)
 662                 {
 663                         bool isDST;
 664                         return GetUtcOffset (dateTime, out isDST);
 665                 }
 666
 667                 public TimeSpan GetUtcOffset (DateTimeOffset dateTimeOffset)
 668                 {
 669                         throw new NotImplementedException ();
 670                 }
 671
 672                 private TimeSpan GetUtcOffset (DateTime dateTime, out bool isDST)
 673                 {
 674                         isDST = false;
 675
 676                         TimeZoneInfo tz = this;
 677                         if (dateTime.Kind == DateTimeKind.Utc)
 678                                 tz = TimeZoneInfo.Utc;
 679
 680                         if (dateTime.Kind == DateTimeKind.Local)
 681                                 tz = TimeZoneInfo.Local;
 682
 683                         bool isTzDst;
 684                         var tzOffset = GetUtcOffsetHelper (dateTime, tz, out isTzDst);
 685
 686                         if (tz == this) {
 687                                 isDST = isTzDst;
 688                                 return tzOffset;
 689                         }
 690
 691                         DateTime utcDateTime;
 692                         if (!TryAddTicks (dateTime, -tzOffset.Ticks, out utcDateTime, DateTimeKind.Utc))
 693                                 return BaseUtcOffset;
 694
 695                         return GetUtcOffsetHelper (utcDateTime, this, out isDST);
 696                 }
 697
 698                 // This is an helper method used by the method above, do not use this on its own.
 699                 private static TimeSpan GetUtcOffsetHelper (DateTime dateTime, TimeZoneInfo tz, out bool isDST)
 700                 {
 701                         if (dateTime.Kind == DateTimeKind.Local && tz != TimeZoneInfo.Local)
 702                                 throw new Exception ();
 703
 704                         isDST = false;
 705
 706                         if (tz == TimeZoneInfo.Utc)
 707                                 return TimeSpan.Zero;
 708
 709                         TimeSpan offset;
 710                         if (tz.TryGetTransitionOffset(dateTime, out offset, out isDST))
 711                                 return offset;
 712
 713                         if (dateTime.Kind == DateTimeKind.Utc) {
 714                                 var utcRule = tz.GetApplicableRule (dateTime);
 715                                 if (utcRule != null && tz.IsInDST (utcRule, dateTime)) {
 716                                         isDST = true;
 717                                         return tz.BaseUtcOffset + utcRule.DaylightDelta;
 718                                 }
 719
 720                                 return tz.BaseUtcOffset;
 721                         }
 722
 723                         DateTime stdUtcDateTime;
 724                         if (!TryAddTicks (dateTime, -tz.BaseUtcOffset.Ticks, out stdUtcDateTime, DateTimeKind.Utc))
 725                                 return tz.BaseUtcOffset;
 726
 727                         var tzRule = tz.GetApplicableRule (stdUtcDateTime);
 728
 729                         DateTime dstUtcDateTime = DateTime.MinValue;
 730                         if (tzRule != null) {
 731                                 if (!TryAddTicks (stdUtcDateTime, -tzRule.DaylightDelta.Ticks, out dstUtcDateTime, DateTimeKind.Utc))
 732                                         return tz.BaseUtcOffset;
 733                         }
 734
 735                         if (tzRule != null && tz.IsInDST (tzRule, stdUtcDateTime) && tz.IsInDST (tzRule, dstUtcDateTime)) {
 736                                 isDST = true;
 737                                 return tz.BaseUtcOffset + tzRule.DaylightDelta;
 738                         }
 739
 740                         return tz.BaseUtcOffset;
 741                 }
 742
 743                 public bool HasSameRules (TimeZoneInfo other)
 744                 {
 745                         if (other == null)
 746                                 throw new ArgumentNullException ("other");
 747
 748                         if ((this.adjustmentRules == null) != (other.adjustmentRules == null))
 749                                 return false;
 750
 751                         if (this.adjustmentRules == null)
 752                                 return true;
 753
 754                         if (this.BaseUtcOffset != other.BaseUtcOffset)
 755                                 return false;
 756
 757                         if (this.adjustmentRules.Length != other.adjustmentRules.Length)
 758                                 return false;
 759
 760                         for (int i = 0; i < adjustmentRules.Length; i++) {
 761                                 if (! (this.adjustmentRules [i]).Equals (other.adjustmentRules [i]))
 762                                         return false;
 763                         }
 764
 765                         return true;
 766                 }
 767
 768                 public bool IsAmbiguousTime (DateTime dateTime)
 769                 {
 770                         if (dateTime.Kind == DateTimeKind.Local && IsInvalidTime (dateTime))
 771                                 throw new ArgumentException ("Kind is Local and time is Invalid");
 772
 773                         if (this == TimeZoneInfo.Utc)
 774                                 return false;
 775
 776                         if (dateTime.Kind == DateTimeKind.Utc)
 777                                 dateTime = ConvertTimeFromUtc (dateTime);
 778
 779                         if (dateTime.Kind == DateTimeKind.Local && this != TimeZoneInfo.Local)
 780                                 dateTime = ConvertTime (dateTime, TimeZoneInfo.Local, this);
 781
 782                         AdjustmentRule rule = GetApplicableRule (dateTime);
 783                         if (rule != null) {
 784                                 DateTime tpoint = TransitionPoint (rule.DaylightTransitionEnd, dateTime.Year);
 785                                 if (dateTime > tpoint - rule.DaylightDelta  && dateTime <= tpoint)
 786                                         return true;
 787                         }
 788
 789                         return false;
 790                 }
 791
 792                 public bool IsAmbiguousTime (DateTimeOffset dateTimeOffset)
 793                 {
 794                         throw new NotImplementedException ();
 795                 }
 796
 797                 private bool IsInDST (AdjustmentRule rule, DateTime dateTime)
 798                 {
 799                         // Check whether we're in the dateTime year's DST period
 800                         if (IsInDSTForYear (rule, dateTime, dateTime.Year))
 801                                 return true;
 802
 803                         // We might be in the dateTime previous year's DST period
 804                         return IsInDSTForYear (rule, dateTime, dateTime.Year - 1);
 805                 }
 806
 807                 bool IsInDSTForYear (AdjustmentRule rule, DateTime dateTime, int year)
 808                 {
 809                         DateTime DST_start = TransitionPoint (rule.DaylightTransitionStart, year);
 810                         DateTime DST_end = TransitionPoint (rule.DaylightTransitionEnd, year + ((rule.DaylightTransitionStart.Month < rule.DaylightTransitionEnd.Month) ? 0 : 1));
 811                         if (dateTime.Kind == DateTimeKind.Utc) {
 812                                 DST_start -= BaseUtcOffset;
 813                                 DST_end -= (BaseUtcOffset + rule.DaylightDelta);
 814                         }
 815
 816                         return (dateTime >= DST_start && dateTime < DST_end);
 817                 }
 818
 819                 public bool IsDaylightSavingTime (DateTime dateTime)
 820                 {
 821                         if (dateTime.Kind == DateTimeKind.Local && IsInvalidTime (dateTime))
 822                                 throw new ArgumentException ("dateTime is invalid and Kind is Local");
 823
 824                         if (this == TimeZoneInfo.Utc)
 825                                 return false;
 826
 827                         if (!SupportsDaylightSavingTime)
 828                                 return false;
 829
 830                         bool isDst;
 831                         GetUtcOffset (dateTime, out isDst);
 832
 833                         return isDst;
 834                 }
 835
 836                 internal bool IsDaylightSavingTime (DateTime dateTime, TimeZoneInfoOptions flags)
 837                 {
 838                         return IsDaylightSavingTime (dateTime);
 839                 }
 840
 841                 public bool IsDaylightSavingTime (DateTimeOffset dateTimeOffset)
 842                 {
 843                         throw new NotImplementedException ();
 844                 }
 845
 846                 internal DaylightTime GetDaylightChanges (int year)
 847                 {
 848                         DateTime start = DateTime.MinValue, end = DateTime.MinValue;
 849                         TimeSpan delta = new TimeSpan ();
 850
 851                         if (transitions != null) {
 852                                 end = DateTime.MaxValue;
 853                                 for (var i =  transitions.Count - 1; i >= 0; i--) {
 854                                         var pair = transitions [i];
 855                                         DateTime ttime = pair.Key;
 856                                         TimeType ttype = pair.Value;
 857
 858                                         if (ttime.Year > year)
 859                                                 continue;
 860                                         if (ttime.Year < year)
 861                                                 break;
 862
 863                                         if (ttype.IsDst) {
 864                                                 // DaylightTime.Delta is relative to the current BaseUtcOffset.
 865                                                 delta =  new TimeSpan (0, 0, ttype.Offset) - BaseUtcOffset;
 866                                                 start = ttime;
 867                                         } else {
 868                                                 end = ttime;
 869                                         }
 870                                 }
 871
 872                                 // DaylightTime.Start is relative to the Standard time.
 873                                 if (start != DateTime.MinValue)
 874                                         start += BaseUtcOffset;
 875
 876                                 // DaylightTime.End is relative to the DST time.
 877                                 if (end != DateTime.MinValue)
 878                                         end += BaseUtcOffset + delta;
 879                         } else {
 880                                 AdjustmentRule first = null, last = null;
 881
 882                                 foreach (var rule in GetAdjustmentRules ()) {
 883                                         if (rule.DateStart.Year != year && rule.DateEnd.Year != year)
 884                                                 continue;
 885                                         if (rule.DateStart.Year == year)
 886                                                 first = rule;
 887                                         if (rule.DateEnd.Year == year)
 888                                                 last = rule;
 889                                 }
 890
 891                                 if (first == null || last == null)
 892                                         return new DaylightTime (new DateTime (), new DateTime (), new TimeSpan ());
 893
 894                                 start = TransitionPoint (first.DaylightTransitionStart, year);
 895                                 end = TransitionPoint (last.DaylightTransitionEnd, year);
 896                                 delta = first.DaylightDelta;
 897                         }
 898
 899                         if (start == DateTime.MinValue || end == DateTime.MinValue)
 900                                 return new DaylightTime (new DateTime (), new DateTime (), new TimeSpan ());
 901
 902                         return new DaylightTime (start, end, delta);
 903                 }
 904
 905                 public bool IsInvalidTime (DateTime dateTime)
 906                 {
 907                         if (dateTime.Kind == DateTimeKind.Utc)
 908                                 return false;
 909                         if (dateTime.Kind == DateTimeKind.Local && this != Local)
 910                                 return false;
 911
 912                         AdjustmentRule rule = GetApplicableRule (dateTime);
 913                         if (rule != null) {
 914                                 DateTime tpoint = TransitionPoint (rule.DaylightTransitionStart, dateTime.Year);
 915                                 if (dateTime >= tpoint && dateTime < tpoint + rule.DaylightDelta)
 916                                         return true;
 917                         }
 918
 919                         return false;
 920                 }
 921
 922                 void IDeserializationCallback.OnDeserialization (object sender)
 923                 {
 924                         try {
 925                                         TimeZoneInfo.Validate (id, baseUtcOffset, adjustmentRules);
 926                                 } catch (ArgumentException ex) {
 927                                         throw new SerializationException ("invalid serialization data", ex);
 928                                 }
 929                 }
 930
 931                 private static void Validate (string id, TimeSpan baseUtcOffset, AdjustmentRule [] adjustmentRules)
 932                 {
 933                         if (id == null)
 934                                 throw new ArgumentNullException ("id");
 935
 936                         if (id == String.Empty)
 937                                 throw new ArgumentException ("id parameter is an empty string");
 938
 939                         if (baseUtcOffset.Ticks % TimeSpan.TicksPerMinute != 0)
 940                                 throw new ArgumentException ("baseUtcOffset parameter does not represent a whole number of minutes");
 941
 942                         if (baseUtcOffset > new TimeSpan (14, 0, 0) || baseUtcOffset < new TimeSpan (-14, 0, 0))
 943                                 throw new ArgumentOutOfRangeException ("baseUtcOffset parameter is greater than 14 hours or less than -14 hours");
 944
 945 #if STRICT
 946                         if (id.Length > 32)
 947                                 throw new ArgumentException ("id parameter shouldn't be longer than 32 characters");
 948 #endif
 949
 950                         if (adjustmentRules != null && adjustmentRules.Length != 0) {
 951                                 AdjustmentRule prev = null;
 952                                 foreach (AdjustmentRule current in adjustmentRules) {
 953                                         if (current == null)
 954                                                 throw new InvalidTimeZoneException ("one or more elements in adjustmentRules are null");
 955
 956                                         if ((baseUtcOffset + current.DaylightDelta < new TimeSpan (-14, 0, 0)) ||
 957                                                         (baseUtcOffset + current.DaylightDelta > new TimeSpan (14, 0, 0)))
 958                                                 throw new InvalidTimeZoneException ("Sum of baseUtcOffset and DaylightDelta of one or more object in adjustmentRules array is greater than 14 or less than -14 hours;");
 959
 960                                         if (prev != null && prev.DateStart > current.DateStart)
 961                                                 throw new InvalidTimeZoneException ("adjustment rules specified in adjustmentRules parameter are not in chronological order");
 962
 963                                         if (prev != null && prev.DateEnd > current.DateStart)
 964                                                 throw new InvalidTimeZoneException ("some adjustment rules in the adjustmentRules parameter overlap");
 965
 966                                         if (prev != null && prev.DateEnd == current.DateStart)
 967                                                 throw new InvalidTimeZoneException ("a date can have multiple adjustment rules applied to it");
 968
 969                                         prev = current;
 970                                 }
 971                         }
 972                 }
 973
 974                 public override string ToString ()
 975                 {
 976                         return DisplayName;
 977                 }
 978
 979                 private TimeZoneInfo (SerializationInfo info, StreamingContext context)
 980                 {
 981                         if (info == null)
 982                                 throw new ArgumentNullException ("info");
 983                         id = (string) info.GetValue ("Id", typeof (string));
 984                         displayName = (string) info.GetValue ("DisplayName", typeof (string));
 985                         standardDisplayName = (string) info.GetValue ("StandardName", typeof (string));
 986                         daylightDisplayName = (string) info.GetValue ("DaylightName", typeof (string));
 987                         baseUtcOffset = (TimeSpan) info.GetValue ("BaseUtcOffset", typeof (TimeSpan));
 988                         adjustmentRules = (TimeZoneInfo.AdjustmentRule []) info.GetValue ("AdjustmentRules", typeof (TimeZoneInfo.AdjustmentRule []));
 989                         supportsDaylightSavingTime = (bool) info.GetValue ("SupportsDaylightSavingTime", typeof (bool));
 990                 }
 991
 992                 private TimeZoneInfo (string id, TimeSpan baseUtcOffset, string displayName, string standardDisplayName, string daylightDisplayName, TimeZoneInfo.AdjustmentRule [] adjustmentRules, bool disableDaylightSavingTime)
 993                 {
 994                         if (id == null)
 995                                 throw new ArgumentNullException ("id");
 996
 997                         if (id == String.Empty)
 998                                 throw new ArgumentException ("id parameter is an empty string");
 999
1000                         if (baseUtcOffset.Ticks % TimeSpan.TicksPerMinute != 0)
1001                                 throw new ArgumentException ("baseUtcOffset parameter does not represent a whole number of minutes");
1002
1003                         if (baseUtcOffset > new TimeSpan (14, 0, 0) || baseUtcOffset < new TimeSpan (-14, 0, 0))
1004                                 throw new ArgumentOutOfRangeException ("baseUtcOffset parameter is greater than 14 hours or less than -14 hours");
1005
1006 #if STRICT
1007                         if (id.Length > 32)
1008                                 throw new ArgumentException ("id parameter shouldn't be longer than 32 characters");
1009 #endif
1010
1011                         bool supportsDaylightSavingTime = !disableDaylightSavingTime;
1012
1013                         if (adjustmentRules != null && adjustmentRules.Length != 0) {
1014                                 AdjustmentRule prev = null;
1015                                 foreach (AdjustmentRule current in adjustmentRules) {
1016                                         if (current == null)
1017                                                 throw new InvalidTimeZoneException ("one or more elements in adjustmentRules are null");
1018
1019                                         if ((baseUtcOffset + current.DaylightDelta < new TimeSpan (-14, 0, 0)) ||
1020                                                         (baseUtcOffset + current.DaylightDelta > new TimeSpan (14, 0, 0)))
1021                                                 throw new InvalidTimeZoneException ("Sum of baseUtcOffset and DaylightDelta of one or more object in adjustmentRules array is greater than 14 or less than -14 hours;");
1022
1023                                         if (prev != null && prev.DateStart > current.DateStart)
1024                                                 throw new InvalidTimeZoneException ("adjustment rules specified in adjustmentRules parameter are not in chronological order");
1025
1026                                         if (prev != null && prev.DateEnd > current.DateStart)
1027                                                 throw new InvalidTimeZoneException ("some adjustment rules in the adjustmentRules parameter overlap");
1028
1029                                         if (prev != null && prev.DateEnd == current.DateStart)
1030                                                 throw new InvalidTimeZoneException ("a date can have multiple adjustment rules applied to it");
1031
1032                                         prev = current;
1033                                 }
1034                         } else {
1035                                 supportsDaylightSavingTime = false;
1036                         }
1037
1038                         this.id = id;
1039                         this.baseUtcOffset = baseUtcOffset;
1040                         this.displayName = displayName ?? id;
1041                         this.standardDisplayName = standardDisplayName ?? id;
1042                         this.daylightDisplayName = daylightDisplayName;
1043                         this.supportsDaylightSavingTime = supportsDaylightSavingTime;
1044                         this.adjustmentRules = adjustmentRules;
1045                 }
1046
1047                 private AdjustmentRule GetApplicableRule (DateTime dateTime)
1048                 {
1049                         //Applicable rules are in standard time
1050                         DateTime date = dateTime;
1051
1052                         if (dateTime.Kind == DateTimeKind.Local && this != TimeZoneInfo.Local) {
1053                                 if (!TryAddTicks (date.ToUniversalTime (), BaseUtcOffset.Ticks, out date))
1054                                         return null;
1055                         } else if (dateTime.Kind == DateTimeKind.Utc && this != TimeZoneInfo.Utc) {
1056                                 if (!TryAddTicks (date, BaseUtcOffset.Ticks, out date))
1057                                         return null;
1058                         }
1059
1060                         // get the date component of the datetime
1061                         date = date.Date;
1062
1063                         if (adjustmentRules != null) {
1064                                 foreach (AdjustmentRule rule in adjustmentRules) {
1065                                         if (rule.DateStart > date)
1066                                                 return null;
1067                                         if (rule.DateEnd < date)
1068                                                 continue;
1069                                         return rule;
1070                                 }
1071                         }
1072                         return null;
1073                 }
1074
1075                 private bool TryGetTransitionOffset (DateTime dateTime, out TimeSpan offset,out bool isDst)
1076                 {
1077                         offset = BaseUtcOffset;
1078                         isDst = false;
1079
1080                         if (transitions == null)
1081                                 return false;
1082
1083                         //Transitions are in UTC
1084                         DateTime date = dateTime;
1085
1086                         if (dateTime.Kind == DateTimeKind.Local && this != TimeZoneInfo.Local) {
1087                                 if (!TryAddTicks (date.ToUniversalTime (), BaseUtcOffset.Ticks, out date, DateTimeKind.Utc))
1088                                         return false;
1089                         }
1090
1091                         if (dateTime.Kind != DateTimeKind.Utc) {
1092                                 if (!TryAddTicks (date, -BaseUtcOffset.Ticks, out date, DateTimeKind.Utc))
1093                                         return false;
1094                         }
1095
1096                         for (var i =  transitions.Count - 1; i >= 0; i--) {
1097                                 var pair = transitions [i];
1098                                 DateTime ttime = pair.Key;
1099                                 TimeType ttype = pair.Value;
1100
1101                                 if (ttime > date)
1102                                         continue;
1103
1104                                 offset =  new TimeSpan (0, 0, ttype.Offset);
1105                                 isDst = ttype.IsDst;
1106
1107                                 return true;
1108                         }
1109
1110                         return false;
1111                 }
1112
1113                 private static DateTime TransitionPoint (TransitionTime transition, int year)
1114                 {
1115                         if (transition.IsFixedDateRule)
1116                                 return new DateTime (year, transition.Month, transition.Day) + transition.TimeOfDay.TimeOfDay;
1117
1118                         DayOfWeek first = (new DateTime (year, transition.Month, 1)).DayOfWeek;
1119                         int day = 1 + (transition.Week - 1) * 7 + (transition.DayOfWeek - first + 7) % 7;
1120                         if (day >  DateTime.DaysInMonth (year, transition.Month))
1121                                 day -= 7;
1122                         if (day < 1)
1123                                 day += 7;
1124                         return new DateTime (year, transition.Month, day) + transition.TimeOfDay.TimeOfDay;
1125                 }
1126
1127                 static List<AdjustmentRule> ValidateRules (List<AdjustmentRule> adjustmentRules)
1128                 {
1129                         AdjustmentRule prev = null;
1130                         foreach (AdjustmentRule current in adjustmentRules.ToArray ()) {
1131                                 if (prev != null && prev.DateEnd > current.DateStart) {
1132                                         adjustmentRules.Remove (current);
1133                                 }
1134                                 prev = current;
1135                         }
1136                         return adjustmentRules;
1137                 }
1138
1139 #if LIBC || MONOTOUCH
1140                 const int BUFFER_SIZE = 16384; //Big enough for any tz file (on Oct 2008, all tz files are under 10k)
1141
1142                 private static TimeZoneInfo BuildFromStream (string id, Stream stream)
1143                 {
1144                         byte [] buffer = new byte [BUFFER_SIZE];
1145                         int length = stream.Read (buffer, 0, BUFFER_SIZE);
1146
1147                         if (!ValidTZFile (buffer, length))
1148                                 throw new InvalidTimeZoneException ("TZ file too big for the buffer");
1149
1150                         try {
1151                                 return ParseTZBuffer (id, buffer, length);
1152                         } catch (Exception e) {
1153                                 throw new InvalidTimeZoneException (e.Message);
1154                         }
1155                 }
1156
1157                 private static bool ValidTZFile (byte [] buffer, int length)
1158                 {
1159                         StringBuilder magic = new StringBuilder ();
1160
1161                         for (int i = 0; i < 4; i++)
1162                                 magic.Append ((char)buffer [i]);
1163
1164                         if (magic.ToString () != "TZif")
1165                                 return false;
1166
1167                         if (length >= BUFFER_SIZE)
1168                                 return false;
1169
1170                         return true;
1171                 }
1172
1173                 static int SwapInt32 (int i)
1174                 {
1175                         return (((i >> 24) & 0xff)
1176                                 | ((i >> 8) & 0xff00)
1177                                 | ((i << 8) & 0xff0000)
1178                                 | ((i << 24)));
1179                 }
1180
1181                 static int ReadBigEndianInt32 (byte [] buffer, int start)
1182                 {
1183                         int i = BitConverter.ToInt32 (buffer, start);
1184                         if (!BitConverter.IsLittleEndian)
1185                                 return i;
1186
1187                         return SwapInt32 (i);
1188                 }
1189
1190                 private static TimeZoneInfo ParseTZBuffer (string id, byte [] buffer, int length)
1191                 {
1192                         //Reading the header. 4 bytes for magic, 16 are reserved
1193                         int ttisgmtcnt = ReadBigEndianInt32 (buffer, 20);
1194                         int ttisstdcnt = ReadBigEndianInt32 (buffer, 24);
1195                         int leapcnt = ReadBigEndianInt32 (buffer, 28);
1196                         int timecnt = ReadBigEndianInt32 (buffer, 32);
1197                         int typecnt = ReadBigEndianInt32 (buffer, 36);
1198                         int charcnt = ReadBigEndianInt32 (buffer, 40);
1199
1200                         if (length < 44 + timecnt * 5 + typecnt * 6 + charcnt + leapcnt * 8 + ttisstdcnt + ttisgmtcnt)
1201                                 throw new InvalidTimeZoneException ();
1202
1203                         Dictionary<int, string> abbreviations = ParseAbbreviations (buffer, 44 + 4 * timecnt + timecnt + 6 * typecnt, charcnt);
1204                         Dictionary<int, TimeType> time_types = ParseTimesTypes (buffer, 44 + 4 * timecnt + timecnt, typecnt, abbreviations);
1205                         List<KeyValuePair<DateTime, TimeType>> transitions = ParseTransitions (buffer, 44, timecnt, time_types);
1206
1207                         if (time_types.Count == 0)
1208                                 throw new InvalidTimeZoneException ();
1209
1210                         if (time_types.Count == 1 && ((TimeType)time_types[0]).IsDst)
1211                                 throw new InvalidTimeZoneException ();
1212
1213                         TimeSpan baseUtcOffset = new TimeSpan (0);
1214                         TimeSpan dstDelta = new TimeSpan (0);
1215                         string standardDisplayName = null;
1216                         string daylightDisplayName = null;
1217                         bool dst_observed = false;
1218                         DateTime dst_start = DateTime.MinValue;
1219                         List<AdjustmentRule> adjustmentRules = new List<AdjustmentRule> ();
1220                         bool storeTransition = false;
1221
1222                         for (int i = 0; i < transitions.Count; i++) {
1223                                 var pair = transitions [i];
1224                                 DateTime ttime = pair.Key;
1225                                 TimeType ttype = pair.Value;
1226                                 if (!ttype.IsDst) {
1227                                         if (standardDisplayName != ttype.Name)
1228                                                 standardDisplayName = ttype.Name;
1229                                         if (baseUtcOffset.TotalSeconds != ttype.Offset) {
1230                                                 baseUtcOffset = new TimeSpan (0, 0, ttype.Offset);
1231                                                 if (adjustmentRules.Count > 0) // We ignore AdjustmentRules but store transitions.
1232                                                         storeTransition = true;
1233                                                 adjustmentRules = new List<AdjustmentRule> ();
1234                                                 dst_observed = false;
1235                                         }
1236                                         if (dst_observed) {
1237                                                 //FIXME: check additional fields for this:
1238                                                 //most of the transitions are expressed in GMT
1239                                                 dst_start += baseUtcOffset;
1240                                                 DateTime dst_end = ttime + baseUtcOffset + dstDelta;
1241
1242                                                 //some weird timezone (America/Phoenix) have end dates on Jan 1st
1243                                                 if (dst_end.Date == new DateTime (dst_end.Year, 1, 1) && dst_end.Year > dst_start.Year)
1244                                                         dst_end -= new TimeSpan (24, 0, 0);
1245
1246                                                 /*
1247                                                  * AdjustmentRule specifies a DST period that starts and ends within a year.
1248                                                  * When we have a DST period longer than a year, the generated AdjustmentRule may not be usable.
1249                                                  * Thus we fallback to the transitions.
1250                                                  */
1251                                                 if (dst_start.AddYears (1) < dst_end)
1252                                                         storeTransition = true;
1253
1254                                                 DateTime dateStart, dateEnd;
1255                                                 if (dst_start.Month < 7)
1256                                                         dateStart = new DateTime (dst_start.Year, 1, 1);
1257                                                 else
1258                                                         dateStart = new DateTime (dst_start.Year, 7, 1);
1259
1260                                                 if (dst_end.Month >= 7)
1261                                                         dateEnd = new DateTime (dst_end.Year, 12, 31);
1262                                                 else
1263                                                         dateEnd = new DateTime (dst_end.Year, 6, 30);
1264
1265
1266                                                 TransitionTime transition_start = TransitionTime.CreateFixedDateRule (new DateTime (1, 1, 1) + dst_start.TimeOfDay, dst_start.Month, dst_start.Day);
1267                                                 TransitionTime transition_end = TransitionTime.CreateFixedDateRule (new DateTime (1, 1, 1) + dst_end.TimeOfDay, dst_end.Month, dst_end.Day);
1268                                                 if  (transition_start != transition_end) //y, that happened in Argentina in 1943-1946
1269                                                         adjustmentRules.Add (AdjustmentRule.CreateAdjustmentRule (dateStart, dateEnd, dstDelta, transition_start, transition_end));
1270                                         }
1271                                         dst_observed = false;
1272                                 } else {
1273                                         if (daylightDisplayName != ttype.Name)
1274                                                 daylightDisplayName = ttype.Name;
1275                                         if (dstDelta.TotalSeconds != ttype.Offset - baseUtcOffset.TotalSeconds) {
1276                                                 // Round to nearest minute, since it's not possible to create an adjustment rule
1277                                                 // with sub-minute precision ("The TimeSpan parameter cannot be specified more precisely than whole minutes.")
1278                                                 // This happens for instance with Europe/Dublin, which had an offset of 34 minutes and 39 seconds in 1916.
1279                                                 dstDelta = new TimeSpan (0, 0, ttype.Offset) - baseUtcOffset;
1280                                                 if (dstDelta.Ticks % TimeSpan.TicksPerMinute != 0)
1281                                                         dstDelta = TimeSpan.FromMinutes ((long) (dstDelta.TotalMinutes + 0.5f));
1282                                         }
1283
1284                                         dst_start = ttime;
1285                                         dst_observed = true;
1286                                 }
1287                         }
1288
1289                         TimeZoneInfo tz;
1290                         if (adjustmentRules.Count == 0 && !storeTransition) {
1291                                 TimeType t = (TimeType)time_types [0];
1292                                 if (standardDisplayName == null) {
1293                                         standardDisplayName = t.Name;
1294                                         baseUtcOffset = new TimeSpan (0, 0, t.Offset);
1295                                 }
1296                                 tz = CreateCustomTimeZone (id, baseUtcOffset, id, standardDisplayName);
1297                         } else {
1298                                 tz = CreateCustomTimeZone (id, baseUtcOffset, id, standardDisplayName, daylightDisplayName, ValidateRules (adjustmentRules).ToArray ());
1299                         }
1300
1301                         if (storeTransition && transitions.Count > 0) {
1302                                 tz.transitions = transitions;
1303                                 tz.supportsDaylightSavingTime = true;
1304                         }
1305
1306                         return tz;
1307                 }
1308
1309                 static Dictionary<int, string> ParseAbbreviations (byte [] buffer, int index, int count)
1310                 {
1311                         var abbrevs = new Dictionary<int, string> ();
1312                         int abbrev_index = 0;
1313                         var sb = new StringBuilder ();
1314                         for (int i = 0; i < count; i++) {
1315                                 char c = (char) buffer [index + i];
1316                                 if (c != '\0')
1317                                         sb.Append (c);
1318                                 else {
1319                                         abbrevs.Add (abbrev_index, sb.ToString ());
1320                                         //Adding all the substrings too, as it seems to be used, at least for Africa/Windhoek
1321                                         for (int j = 1; j < sb.Length; j++)
1322                                                 abbrevs.Add (abbrev_index + j, sb.ToString (j, sb.Length - j));
1323                                         abbrev_index = i + 1;
1324                                         sb = new StringBuilder ();
1325                                 }
1326                         }
1327                         return abbrevs;
1328                 }
1329
1330                 static Dictionary<int, TimeType> ParseTimesTypes (byte [] buffer, int index, int count, Dictionary<int, string> abbreviations)
1331                 {
1332                         var types = new Dictionary<int, TimeType> (count);
1333                         for (int i = 0; i < count; i++) {
1334                                 int offset = ReadBigEndianInt32 (buffer, index + 6 * i);
1335                                 byte is_dst = buffer [index + 6 * i + 4];
1336                                 byte abbrev = buffer [index + 6 * i + 5];
1337                                 types.Add (i, new TimeType (offset, (is_dst != 0), abbreviations [(int)abbrev]));
1338                         }
1339                         return types;
1340                 }
1341
1342                 static List<KeyValuePair<DateTime, TimeType>> ParseTransitions (byte [] buffer, int index, int count, Dictionary<int, TimeType> time_types)
1343                 {
1344                         var list = new List<KeyValuePair<DateTime, TimeType>> (count);
1345                         for (int i = 0; i < count; i++) {
1346                                 int unixtime = ReadBigEndianInt32 (buffer, index + 4 * i);
1347                                 DateTime ttime = DateTimeFromUnixTime (unixtime);
1348                                 byte ttype = buffer [index + 4 * count + i];
1349                                 list.Add (new KeyValuePair<DateTime, TimeType> (ttime, time_types [(int)ttype]));
1350                         }
1351                         return list;
1352                 }
1353
1354                 static DateTime DateTimeFromUnixTime (long unix_time)
1355                 {
1356                         DateTime date_time = new DateTime (1970, 1, 1);
1357                         return date_time.AddSeconds (unix_time);
1358                 }
1359
1360 #region reference sources
1361                 // Shortcut for TimeZoneInfo.Local.GetUtcOffset
1362                 internal static TimeSpan GetLocalUtcOffset(DateTime dateTime, TimeZoneInfoOptions flags)
1363                 {
1364                         bool dst;
1365                         return Local.GetUtcOffset (dateTime, out dst);
1366                 }
1367
1368                 internal TimeSpan GetUtcOffset(DateTime dateTime, TimeZoneInfoOptions flags)
1369                 {
1370                         bool dst;
1371                         return GetUtcOffset (dateTime, out dst);
1372                 }
1373
1374                 static internal TimeSpan GetUtcOffsetFromUtc (DateTime time, TimeZoneInfo zone, out Boolean isDaylightSavings, out Boolean isAmbiguousLocalDst)
1375                 {
1376                         isDaylightSavings = false;
1377                         isAmbiguousLocalDst = false;
1378                         TimeSpan baseOffset = zone.BaseUtcOffset;
1379
1380                         if (zone.IsAmbiguousTime (time)) {
1381                                 isAmbiguousLocalDst = true;
1382                                 return baseOffset;
1383                         }
1384
1385                         return zone.GetUtcOffset (time, out isDaylightSavings);
1386                 }
1387 #endregion
1388         }
1389
1390         struct TimeType {
1391                 public readonly int Offset;
1392                 public readonly bool IsDst;
1393                 public string Name;
1394
1395                 public TimeType (int offset, bool is_dst, string abbrev)
1396                 {
1397                         this.Offset = offset;
1398                         this.IsDst = is_dst;
1399                         this.Name = abbrev;
1400                 }
1401
1402                 public override string ToString ()
1403                 {
1404                         return "offset: " + Offset + "s, is_dst: " + IsDst + ", zone name: " + Name;
1405                 }
1406 #else
1407         }
1408 #endif
1409         }
1410 }