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.Runtime.InteropServices;
  37 using System.Text;
  38 using System.Globalization;
  39 using System.IO;
  40
  41 using Microsoft.Win32;
  42
  43 namespace System
  44 {
  45         partial class TimeZoneInfo
  46         {
  47                 TimeSpan baseUtcOffset;
  48                 public TimeSpan BaseUtcOffset {
  49                         get { return baseUtcOffset; }
  50                 }
  51
  52                 string daylightDisplayName;
  53                 public string DaylightName {
  54                         get {
  55                                 return supportsDaylightSavingTime
  56                                         ? daylightDisplayName
  57                                         : string.Empty;
  58                         }
  59                 }
  60
  61                 string displayName;
  62                 public string DisplayName {
  63                         get { return displayName; }
  64                 }
  65
  66                 string id;
  67                 public string Id {
  68                         get { return id; }
  69                 }
  70
  71                 static TimeZoneInfo local;
  72                 public static TimeZoneInfo Local {
  73                         get {
  74                                 var l = local;
  75                                 if (l == null) {
  76                                         l = CreateLocal ();
  77                                         if (l == null)
  78                                                 throw new TimeZoneNotFoundException ();
  79
  80                                         if (Interlocked.CompareExchange (ref local, l, null) != null)
  81                                                 l = local;
  82                                 }
  83
  84                                 return l;
  85                         }
  86                 }
  87
  88                 /*
  89                         TimeZone transitions are stored when there is a change on the base offset.
  90                 */
  91                 private List<KeyValuePair<DateTime, TimeType>> transitions;
  92
  93                 private static bool readlinkNotFound;
  94
  95                 [DllImport ("libc")]
  96                 private static extern int readlink (string path, byte[] buffer, int buflen);
  97
  98                 private static string readlink (string path)
  99                 {
 100                         if (readlinkNotFound)
 101                                 return null;
 102
 103                         byte[] buf = new byte [512];
 104                         int ret;
 105
 106                         try {
 107                                 ret = readlink (path, buf, buf.Length);
 108                         } catch (DllNotFoundException e) {
 109                                 readlinkNotFound = true;
 110                                 return null;
 111                         } catch (EntryPointNotFoundException e) {
 112                                 readlinkNotFound = true;
 113                                 return null;
 114                         }
 115
 116                         if (ret == -1) return null;
 117                         char[] cbuf = new char [512];
 118                         int chars = System.Text.Encoding.Default.GetChars (buf, 0, ret, cbuf, 0);
 119                         return new String (cbuf, 0, chars);
 120                 }
 121
 122                 private static bool TryGetNameFromPath (string path, out string name)
 123                 {
 124                         name = null;
 125                         var linkPath = readlink (path);
 126                         if (linkPath != null) {
 127                                 if (Path.IsPathRooted(linkPath))
 128                                         path = linkPath;
 129                                 else
 130                                         path = Path.Combine(Path.GetDirectoryName(path), linkPath);
 131                         }
 132
 133                         path = Path.GetFullPath (path);
 134
 135                         if (string.IsNullOrEmpty (TimeZoneDirectory))
 136                                 return false;
 137
 138                         var baseDir = TimeZoneDirectory;
 139                         if (baseDir [baseDir.Length-1] != Path.DirectorySeparatorChar)
 140                                 baseDir += Path.DirectorySeparatorChar;
 141
 142                         if (!path.StartsWith (baseDir, StringComparison.InvariantCulture))
 143                                 return false;
 144
 145                         name = path.Substring (baseDir.Length);
 146                         if (name == "localtime")
 147                                 name = "Local";
 148
 149                         return true;
 150                 }
 151
 152 #if !MOBILE || MOBILE_STATIC
 153                 static TimeZoneInfo CreateLocal ()
 154                 {
 155 #if !MOBILE_STATIC
 156                         if (IsWindows && LocalZoneKey != null) {
 157                                 string name = (string)LocalZoneKey.GetValue ("TimeZoneKeyName");
 158                                 if (name == null)
 159                                         name = (string)LocalZoneKey.GetValue ("StandardName"); // windows xp
 160                                 name = TrimSpecial (name);
 161                                 if (name != null)
 162                                         return TimeZoneInfo.FindSystemTimeZoneById (name);
 163                         }
 164 #endif
 165
 166                         var tz = Environment.GetEnvironmentVariable ("TZ");
 167                         if (tz != null) {
 168                                 if (tz == String.Empty)
 169                                         return Utc;
 170                                 try {
 171                                         return FindSystemTimeZoneByFileName (tz, Path.Combine (TimeZoneDirectory, tz));
 172                                 } catch {
 173                                         return Utc;
 174                                 }
 175                         }
 176
 177                         var tzFilePaths = new string [] {
 178                                 "/etc/localtime",
 179                                 Path.Combine (TimeZoneDirectory, "localtime")};
 180
 181                         foreach (var tzFilePath in tzFilePaths) {
 182                                 try {
 183                                         string tzName = null;
 184                                         if (!TryGetNameFromPath (tzFilePath, out tzName))
 185                                                 tzName = "Local";
 186                                         return FindSystemTimeZoneByFileName (tzName, tzFilePath);
 187                                 } catch (TimeZoneNotFoundException) {
 188                                         continue;
 189                                 }
 190                         }
 191
 192                         return Utc;
 193                 }
 194
 195                 static TimeZoneInfo FindSystemTimeZoneByIdCore (string id)
 196                 {
 197 #if LIBC
 198                         string filepath = Path.Combine (TimeZoneDirectory, id);
 199                         return FindSystemTimeZoneByFileName (id, filepath);
 200 #else
 201                         throw new NotImplementedException ();
 202 #endif
 203                 }
 204
 205                 static void GetSystemTimeZonesCore (List<TimeZoneInfo> systemTimeZones)
 206                 {
 207 #if !MOBILE_STATIC
 208                         if (TimeZoneKey != null) {
 209                                 foreach (string id in TimeZoneKey.GetSubKeyNames ()) {
 210                                         try {
 211                                                 systemTimeZones.Add (FindSystemTimeZoneById (id));
 212                                         } catch {}
 213                                 }
 214
 215                                 return;
 216                         }
 217 #endif
 218
 219 #if LIBC
 220                         string[] continents = new string [] {"Africa", "America", "Antarctica", "Arctic", "Asia", "Atlantic", "Australia", "Brazil", "Canada", "Chile", "Europe", "Indian", "Mexico", "Mideast", "Pacific", "US"};
 221                         foreach (string continent in continents) {
 222                                 try {
 223                                         foreach (string zonepath in Directory.GetFiles (Path.Combine (TimeZoneDirectory, continent))) {
 224                                                 try {
 225                                                         string id = String.Format ("{0}/{1}", continent, Path.GetFileName (zonepath));
 226                                                         systemTimeZones.Add (FindSystemTimeZoneById (id));
 227                                                 } catch (ArgumentNullException) {
 228                                                 } catch (TimeZoneNotFoundException) {
 229                                                 } catch (InvalidTimeZoneException) {
 230                                                 } catch (Exception) {
 231                                                         throw;
 232                                                 }
 233                                         }
 234                                 } catch {}
 235                         }
 236 #else
 237                         throw new NotImplementedException ("This method is not implemented for this platform");
 238 #endif
 239                 }
 240 #endif
 241
 242                 string standardDisplayName;
 243                 public string StandardName {
 244                         get { return standardDisplayName; }
 245                 }
 246
 247                 bool supportsDaylightSavingTime;
 248                 public bool SupportsDaylightSavingTime {
 249                         get  { return supportsDaylightSavingTime; }
 250                 }
 251
 252                 static TimeZoneInfo utc;
 253                 public static TimeZoneInfo Utc {
 254                         get {
 255                                 if (utc == null)
 256                                         utc = CreateCustomTimeZone ("UTC", new TimeSpan (0), "UTC", "UTC");
 257                                 return utc;
 258                         }
 259                 }
 260 #if LIBC
 261                 static string timeZoneDirectory;
 262                 static string TimeZoneDirectory {
 263                         get {
 264                                 if (timeZoneDirectory == null)
 265                                         timeZoneDirectory = "/usr/share/zoneinfo";
 266                                 return timeZoneDirectory;
 267                         }
 268                         set {
 269                                 ClearCachedData ();
 270                                 timeZoneDirectory = value;
 271                         }
 272                 }
 273 #endif
 274                 private AdjustmentRule [] adjustmentRules;
 275
 276 #if !NET_2_1 || MOBILE_STATIC
 277                 /// <summary>
 278                 /// Determine whether windows of not (taken Stephane Delcroix's code)
 279                 /// </summary>
 280                 private static bool IsWindows
 281                 {
 282                         get {
 283                                 int platform = (int) Environment.OSVersion.Platform;
 284                                 return ((platform != 4) && (platform != 6) && (platform != 128));
 285                         }
 286                 }
 287
 288                 /// <summary>
 289                 /// Needed to trim misc garbage in MS registry keys
 290                 /// </summary>
 291                 private static string TrimSpecial (string str)
 292                 {
 293                         if (str == null)
 294                                 return str;
 295                         var Istart = 0;
 296                         while (Istart < str.Length && !char.IsLetterOrDigit(str[Istart])) Istart++;
 297                         var Iend = str.Length - 1;
 298                         while (Iend > Istart && !char.IsLetterOrDigit(str[Iend])) Iend--;
 299
 300                         return str.Substring (Istart, Iend-Istart+1);
 301                 }
 302
 303 #if !MOBILE_STATIC
 304                 static RegistryKey timeZoneKey;
 305                 static RegistryKey TimeZoneKey {
 306                         get {
 307                                 if (timeZoneKey != null)
 308                                         return timeZoneKey;
 309                                 if (!IsWindows)
 310                                         return null;
 311
 312                                 return timeZoneKey = Registry.LocalMachine.OpenSubKey (
 313                                         "SOFTWARE\\Microsoft\\Windows NT\\CurrentVersion\\Time Zones",
 314                                         false);
 315                         }
 316                 }
 317
 318                 static RegistryKey localZoneKey;
 319                 static RegistryKey LocalZoneKey {
 320                         get {
 321                                 if (localZoneKey != null)
 322                                         return localZoneKey;
 323
 324                                 if (!IsWindows)
 325                                         return null;
 326
 327                                 return localZoneKey = Registry.LocalMachine.OpenSubKey (
 328                                         "SYSTEM\\CurrentControlSet\\Control\\TimeZoneInformation", false);
 329                         }
 330                 }
 331 #endif
 332 #endif
 333
 334                 private static bool TryAddTicks (DateTime date, long ticks, out DateTime result, DateTimeKind kind = DateTimeKind.Unspecified)
 335                 {
 336                         var resultTicks = date.Ticks + ticks;
 337                         if (resultTicks < DateTime.MinValue.Ticks) {
 338                                 result = DateTime.SpecifyKind (DateTime.MinValue, kind);
 339                                 return false;
 340                         }
 341
 342                         if (resultTicks > DateTime.MaxValue.Ticks) {
 343                                 result = DateTime.SpecifyKind (DateTime.MaxValue, kind);
 344                                 return false;
 345                         }
 346
 347                         result = new DateTime (resultTicks, kind);
 348                         return true;
 349                 }
 350
 351                 public static void ClearCachedData ()
 352                 {
 353                         local = null;
 354                         utc = null;
 355                         systemTimeZones = null;
 356                 }
 357
 358                 public static DateTime ConvertTime (DateTime dateTime, TimeZoneInfo destinationTimeZone)
 359                 {
 360                         return ConvertTime (dateTime, dateTime.Kind == DateTimeKind.Utc ? TimeZoneInfo.Utc : TimeZoneInfo.Local, destinationTimeZone);
 361                 }
 362
 363                 public static DateTime ConvertTime (DateTime dateTime, TimeZoneInfo sourceTimeZone, TimeZoneInfo destinationTimeZone)
 364                 {
 365                         if (sourceTimeZone == null)
 366                                 throw new ArgumentNullException ("sourceTimeZone");
 367
 368                         if (destinationTimeZone == null)
 369                                 throw new ArgumentNullException ("destinationTimeZone");
 370
 371                         if (dateTime.Kind == DateTimeKind.Local && sourceTimeZone != TimeZoneInfo.Local)
 372                                 throw new ArgumentException ("Kind property of dateTime is Local but the sourceTimeZone does not equal TimeZoneInfo.Local");
 373
 374                         if (dateTime.Kind == DateTimeKind.Utc && sourceTimeZone != TimeZoneInfo.Utc)
 375                                 throw new ArgumentException ("Kind property of dateTime is Utc but the sourceTimeZone does not equal TimeZoneInfo.Utc");
 376
 377                         if (sourceTimeZone.IsInvalidTime (dateTime))
 378                                 throw new ArgumentException ("dateTime parameter is an invalid time");
 379
 380                         if (dateTime.Kind == DateTimeKind.Local && sourceTimeZone == TimeZoneInfo.Local && destinationTimeZone == TimeZoneInfo.Local)
 381                                 return dateTime;
 382
 383                         DateTime utc = ConvertTimeToUtc (dateTime, sourceTimeZone);
 384
 385                         if (destinationTimeZone != TimeZoneInfo.Utc) {
 386                                 utc = ConvertTimeFromUtc (utc, destinationTimeZone);
 387                                 if (dateTime.Kind == DateTimeKind.Unspecified)
 388                                         return DateTime.SpecifyKind (utc, DateTimeKind.Unspecified);
 389                         }
 390
 391                         return utc;
 392                 }
 393
 394                 public static DateTimeOffset ConvertTime(DateTimeOffset dateTimeOffset, TimeZoneInfo destinationTimeZone)
 395                 {
 396                         if (destinationTimeZone == null)
 397                                 throw new ArgumentNullException("destinationTimeZone");
 398
 399                         var utcDateTime = dateTimeOffset.UtcDateTime;
 400
 401                         bool isDst;
 402                         var utcOffset =  destinationTimeZone.GetUtcOffset(utcDateTime, out isDst);
 403
 404                         return new DateTimeOffset(DateTime.SpecifyKind(utcDateTime, DateTimeKind.Unspecified) + utcOffset, utcOffset);
 405                 }
 406
 407                 public static DateTime ConvertTimeBySystemTimeZoneId (DateTime dateTime, string destinationTimeZoneId)
 408                 {
 409                         return ConvertTime (dateTime, FindSystemTimeZoneById (destinationTimeZoneId));
 410                 }
 411
 412                 public static DateTime ConvertTimeBySystemTimeZoneId (DateTime dateTime, string sourceTimeZoneId, string destinationTimeZoneId)
 413                 {
 414                         return ConvertTime (dateTime, FindSystemTimeZoneById (sourceTimeZoneId), FindSystemTimeZoneById (destinationTimeZoneId));
 415                 }
 416
 417                 public static DateTimeOffset ConvertTimeBySystemTimeZoneId (DateTimeOffset dateTimeOffset, string destinationTimeZoneId)
 418                 {
 419                         return ConvertTime (dateTimeOffset, FindSystemTimeZoneById (destinationTimeZoneId));
 420                 }
 421
 422                 private DateTime ConvertTimeFromUtc (DateTime dateTime)
 423                 {
 424                         if (dateTime.Kind == DateTimeKind.Local)
 425                                 throw new ArgumentException ("Kind property of dateTime is Local");
 426
 427                         if (this == TimeZoneInfo.Utc)
 428                                 return DateTime.SpecifyKind (dateTime, DateTimeKind.Utc);
 429
 430                         var utcOffset = GetUtcOffset (dateTime);
 431
 432                         var kind = (this == TimeZoneInfo.Local)? DateTimeKind.Local : DateTimeKind.Unspecified;
 433
 434                         DateTime result;
 435                         if (!TryAddTicks (dateTime, utcOffset.Ticks, out result, kind))
 436                                 return DateTime.SpecifyKind (DateTime.MaxValue, kind);
 437
 438                         return result;
 439                 }
 440
 441                 public static DateTime ConvertTimeFromUtc (DateTime dateTime, TimeZoneInfo destinationTimeZone)
 442                 {
 443                         if (destinationTimeZone == null)
 444                                 throw new ArgumentNullException ("destinationTimeZone");
 445
 446                         return destinationTimeZone.ConvertTimeFromUtc (dateTime);
 447                 }
 448
 449                 public static DateTime ConvertTimeToUtc (DateTime dateTime)
 450                 {
 451                         if (dateTime.Kind == DateTimeKind.Utc)
 452                                 return dateTime;
 453
 454                         return ConvertTimeToUtc (dateTime, TimeZoneInfo.Local);
 455                 }
 456
 457                 static internal DateTime ConvertTimeToUtc(DateTime dateTime, TimeZoneInfoOptions flags)
 458                 {
 459                         return ConvertTimeToUtc (dateTime, TimeZoneInfo.Local, flags);
 460                 }
 461
 462                 public static DateTime ConvertTimeToUtc (DateTime dateTime, TimeZoneInfo sourceTimeZone)
 463                 {
 464                         return ConvertTimeToUtc (dateTime, sourceTimeZone, TimeZoneInfoOptions.None);
 465                 }
 466
 467                 static DateTime ConvertTimeToUtc (DateTime dateTime, TimeZoneInfo sourceTimeZone, TimeZoneInfoOptions flags)
 468                 {
 469                         if ((flags & TimeZoneInfoOptions.NoThrowOnInvalidTime) == 0) {
 470                                 if (sourceTimeZone == null)
 471                                         throw new ArgumentNullException ("sourceTimeZone");
 472
 473                                 if (dateTime.Kind == DateTimeKind.Utc && sourceTimeZone != TimeZoneInfo.Utc)
 474                                         throw new ArgumentException ("Kind property of dateTime is Utc but the sourceTimeZone does not equal TimeZoneInfo.Utc");
 475
 476                                 if (dateTime.Kind == DateTimeKind.Local && sourceTimeZone != TimeZoneInfo.Local)
 477                                         throw new ArgumentException ("Kind property of dateTime is Local but the sourceTimeZone does not equal TimeZoneInfo.Local");
 478
 479                                 if (sourceTimeZone.IsInvalidTime (dateTime))
 480                                         throw new ArgumentException ("dateTime parameter is an invalid time");
 481                         }
 482
 483                         if (dateTime.Kind == DateTimeKind.Utc)
 484                                 return dateTime;
 485
 486                         bool isDst;
 487                         var utcOffset = sourceTimeZone.GetUtcOffset (dateTime, out isDst);
 488
 489                         DateTime utcDateTime;
 490                         TryAddTicks (dateTime, -utcOffset.Ticks, out utcDateTime, DateTimeKind.Utc);
 491                         return utcDateTime;
 492                 }
 493
 494                 static internal TimeSpan GetDateTimeNowUtcOffsetFromUtc(DateTime time, out Boolean isAmbiguousLocalDst)
 495                 {
 496                         bool isDaylightSavings;
 497                         return GetUtcOffsetFromUtc(time, TimeZoneInfo.Local, out isDaylightSavings, out isAmbiguousLocalDst);
 498                 }
 499
 500                 public static TimeZoneInfo CreateCustomTimeZone (string id, TimeSpan baseUtcOffset, string displayName, string standardDisplayName)
 501                 {
 502                         return CreateCustomTimeZone (id, baseUtcOffset, displayName, standardDisplayName, null, null, true);
 503                 }
 504
 505                 public static TimeZoneInfo CreateCustomTimeZone (string id, TimeSpan baseUtcOffset, string displayName, string standardDisplayName, string daylightDisplayName, TimeZoneInfo.AdjustmentRule [] adjustmentRules)
 506                 {
 507                         return CreateCustomTimeZone (id, baseUtcOffset, displayName, standardDisplayName, daylightDisplayName, adjustmentRules, false);
 508                 }
 509
 510                 public static TimeZoneInfo CreateCustomTimeZone ( string id, TimeSpan baseUtcOffset, string displayName, string standardDisplayName, string daylightDisplayName, TimeZoneInfo.AdjustmentRule [] adjustmentRules, bool disableDaylightSavingTime)
 511                 {
 512                         return new TimeZoneInfo (id, baseUtcOffset, displayName, standardDisplayName, daylightDisplayName, adjustmentRules, disableDaylightSavingTime);
 513                 }
 514
 515                 public override bool Equals (object obj)
 516                 {
 517                         return Equals (obj as TimeZoneInfo);
 518                 }
 519
 520                 public bool Equals (TimeZoneInfo other)
 521                 {
 522                         if (other == null)
 523                                 return false;
 524
 525                         return other.Id == this.Id && HasSameRules (other);
 526                 }
 527
 528                 public static TimeZoneInfo FindSystemTimeZoneById (string id)
 529                 {
 530                         //FIXME: this method should check for cached values in systemTimeZones
 531                         if (id == null)
 532                                 throw new ArgumentNullException ("id");
 533 #if !NET_2_1
 534                         if (TimeZoneKey != null)
 535                         {
 536                                 if (id == "Coordinated Universal Time")
 537                                         id = "UTC"; //windows xp exception for "StandardName" property
 538                                 RegistryKey key = TimeZoneKey.OpenSubKey (id, false);
 539                                 if (key == null)
 540                                         throw new TimeZoneNotFoundException ();
 541                                 return FromRegistryKey(id, key);
 542                         }
 543 #endif
 544                         // Local requires special logic that already exists in the Local property (bug #326)
 545                         if (id == "Local")
 546                                 return Local;
 547
 548                         return FindSystemTimeZoneByIdCore (id);
 549                 }
 550
 551 #if LIBC
 552                 private static TimeZoneInfo FindSystemTimeZoneByFileName (string id, string filepath)
 553                 {
 554                         if (!File.Exists (filepath))
 555                                 throw new TimeZoneNotFoundException ();
 556
 557                         using (FileStream stream = File.OpenRead (filepath)) {
 558                                 return BuildFromStream (id, stream);
 559                         }
 560                 }
 561 #endif
 562
 563 #if !NET_2_1
 564                 private static TimeZoneInfo FromRegistryKey (string id, RegistryKey key)
 565                 {
 566                         byte [] reg_tzi = (byte []) key.GetValue ("TZI");
 567
 568                         if (reg_tzi == null)
 569                                 throw new InvalidTimeZoneException ();
 570
 571                         int bias = BitConverter.ToInt32 (reg_tzi, 0);
 572                         TimeSpan baseUtcOffset = new TimeSpan (0, -bias, 0);
 573
 574                         string display_name = (string) key.GetValue ("Display");
 575                         string standard_name = (string) key.GetValue ("Std");
 576                         string daylight_name = (string) key.GetValue ("Dlt");
 577
 578                         List<AdjustmentRule> adjustmentRules = new List<AdjustmentRule> ();
 579
 580                         RegistryKey dst_key = key.OpenSubKey ("Dynamic DST", false);
 581                         if (dst_key != null) {
 582                                 int first_year = (int) dst_key.GetValue ("FirstEntry");
 583                                 int last_year = (int) dst_key.GetValue ("LastEntry");
 584                                 int year;
 585
 586                                 for (year=first_year; year<=last_year; year++) {
 587                                         byte [] dst_tzi = (byte []) dst_key.GetValue (year.ToString ());
 588                                         if (dst_tzi != null) {
 589                                                 int start_year = year == first_year ? 1 : year;
 590                                                 int end_year = year == last_year ? 9999 : year;
 591                                                 ParseRegTzi(adjustmentRules, start_year, end_year, dst_tzi);
 592                                         }
 593                                 }
 594                         }
 595                         else
 596                                 ParseRegTzi(adjustmentRules, 1, 9999, reg_tzi);
 597
 598                         return CreateCustomTimeZone (id, baseUtcOffset, display_name, standard_name, daylight_name, ValidateRules (adjustmentRules).ToArray ());
 599                 }
 600
 601                 private static void ParseRegTzi (List<AdjustmentRule> adjustmentRules, int start_year, int end_year, byte [] buffer)
 602                 {
 603                         //int standard_bias = BitConverter.ToInt32 (buffer, 4); /* not sure how to handle this */
 604                         int daylight_bias = BitConverter.ToInt32 (buffer, 8);
 605
 606                         int standard_year = BitConverter.ToInt16 (buffer, 12);
 607                         int standard_month = BitConverter.ToInt16 (buffer, 14);
 608                         int standard_dayofweek = BitConverter.ToInt16 (buffer, 16);
 609                         int standard_day = BitConverter.ToInt16 (buffer, 18);
 610                         int standard_hour = BitConverter.ToInt16 (buffer, 20);
 611                         int standard_minute = BitConverter.ToInt16 (buffer, 22);
 612                         int standard_second = BitConverter.ToInt16 (buffer, 24);
 613                         int standard_millisecond = BitConverter.ToInt16 (buffer, 26);
 614
 615                         int daylight_year = BitConverter.ToInt16 (buffer, 28);
 616                         int daylight_month = BitConverter.ToInt16 (buffer, 30);
 617                         int daylight_dayofweek = BitConverter.ToInt16 (buffer, 32);
 618                         int daylight_day = BitConverter.ToInt16 (buffer, 34);
 619                         int daylight_hour = BitConverter.ToInt16 (buffer, 36);
 620                         int daylight_minute = BitConverter.ToInt16 (buffer, 38);
 621                         int daylight_second = BitConverter.ToInt16 (buffer, 40);
 622                         int daylight_millisecond = BitConverter.ToInt16 (buffer, 42);
 623
 624                         if (standard_month == 0 || daylight_month == 0)
 625                                 return;
 626
 627                         DateTime start_date;
 628                         DateTime start_timeofday = new DateTime (1, 1, 1, daylight_hour, daylight_minute, daylight_second, daylight_millisecond);
 629                         TransitionTime start_transition_time;
 630
 631                         if (daylight_year == 0) {
 632                                 start_date = new DateTime (start_year, 1, 1);
 633                                 start_transition_time = TransitionTime.CreateFloatingDateRule (
 634                                         start_timeofday, daylight_month, daylight_day,
 635                                         (DayOfWeek) daylight_dayofweek);
 636                         }
 637                         else {
 638                                 start_date = new DateTime (daylight_year, daylight_month, daylight_day,
 639                                         daylight_hour, daylight_minute, daylight_second, daylight_millisecond);
 640                                 start_transition_time = TransitionTime.CreateFixedDateRule (
 641                                         start_timeofday, daylight_month, daylight_day);
 642                         }
 643
 644                         DateTime end_date;
 645                         DateTime end_timeofday = new DateTime (1, 1, 1, standard_hour, standard_minute, standard_second, standard_millisecond);
 646                         TransitionTime end_transition_time;
 647
 648                         if (standard_year == 0) {
 649                                 end_date = new DateTime (end_year, 12, 31);
 650                                 end_transition_time = TransitionTime.CreateFloatingDateRule (
 651                                         end_timeofday, standard_month, standard_day,
 652                                         (DayOfWeek) standard_dayofweek);
 653                         }
 654                         else {
 655                                 end_date = new DateTime (standard_year, standard_month, standard_day,
 656                                         standard_hour, standard_minute, standard_second, standard_millisecond);
 657                                 end_transition_time = TransitionTime.CreateFixedDateRule (
 658                                         end_timeofday, standard_month, standard_day);
 659                         }
 660
 661                         TimeSpan daylight_delta = new TimeSpan(0, -daylight_bias, 0);
 662
 663                         adjustmentRules.Add (AdjustmentRule.CreateAdjustmentRule (
 664                                 start_date, end_date, daylight_delta,
 665                                 start_transition_time, end_transition_time));
 666                 }
 667 #endif
 668
 669                 public AdjustmentRule [] GetAdjustmentRules ()
 670                 {
 671                         if (!supportsDaylightSavingTime || adjustmentRules == null)
 672                                 return new AdjustmentRule [0];
 673                         else
 674                                 return (AdjustmentRule []) adjustmentRules.Clone ();
 675                 }
 676
 677                 public TimeSpan [] GetAmbiguousTimeOffsets (DateTime dateTime)
 678                 {
 679                         if (!IsAmbiguousTime (dateTime))
 680                                 throw new ArgumentException ("dateTime is not an ambiguous time");
 681
 682                         AdjustmentRule rule = GetApplicableRule (dateTime);
 683                         if (rule != null)
 684                                 return new TimeSpan[] {baseUtcOffset, baseUtcOffset + rule.DaylightDelta};
 685                         else
 686                                 return new TimeSpan[] {baseUtcOffset, baseUtcOffset};
 687                 }
 688
 689                 public TimeSpan [] GetAmbiguousTimeOffsets (DateTimeOffset dateTimeOffset)
 690                 {
 691                         if (!IsAmbiguousTime (dateTimeOffset))
 692                                 throw new ArgumentException ("dateTimeOffset is not an ambiguous time");
 693
 694                         throw new NotImplementedException ();
 695                 }
 696
 697                 public override int GetHashCode ()
 698                 {
 699                         int hash_code = Id.GetHashCode ();
 700                         foreach (AdjustmentRule rule in GetAdjustmentRules ())
 701                                 hash_code ^= rule.GetHashCode ();
 702                         return hash_code;
 703                 }
 704
 705                 void ISerializable.GetObjectData (SerializationInfo info, StreamingContext context)
 706                 {
 707                         if (info == null)
 708                                 throw new ArgumentNullException ("info");
 709                         info.AddValue ("Id", id);
 710                         info.AddValue ("DisplayName", displayName);
 711                         info.AddValue ("StandardName", standardDisplayName);
 712                         info.AddValue ("DaylightName", daylightDisplayName);
 713                         info.AddValue ("BaseUtcOffset", baseUtcOffset);
 714                         info.AddValue ("AdjustmentRules", adjustmentRules);
 715                         info.AddValue ("SupportsDaylightSavingTime", SupportsDaylightSavingTime);
 716                 }
 717
 718                 static ReadOnlyCollection<TimeZoneInfo> systemTimeZones;
 719
 720                 public static ReadOnlyCollection<TimeZoneInfo> GetSystemTimeZones ()
 721                 {
 722                         if (systemTimeZones == null) {
 723                                 var tz = new List<TimeZoneInfo> ();
 724                                 GetSystemTimeZonesCore (tz);
 725                                 Interlocked.CompareExchange (ref systemTimeZones, new ReadOnlyCollection<TimeZoneInfo> (tz), null);
 726                         }
 727
 728                         return systemTimeZones;
 729                 }
 730
 731                 public TimeSpan GetUtcOffset (DateTime dateTime)
 732                 {
 733                         bool isDST;
 734                         return GetUtcOffset (dateTime, out isDST);
 735                 }
 736
 737                 public TimeSpan GetUtcOffset (DateTimeOffset dateTimeOffset)
 738                 {
 739                         bool isDST;
 740                         return GetUtcOffset (dateTimeOffset.UtcDateTime, out isDST);
 741                 }
 742
 743                 private TimeSpan GetUtcOffset (DateTime dateTime, out bool isDST)
 744                 {
 745                         isDST = false;
 746
 747                         TimeZoneInfo tz = this;
 748                         if (dateTime.Kind == DateTimeKind.Utc)
 749                                 tz = TimeZoneInfo.Utc;
 750
 751                         if (dateTime.Kind == DateTimeKind.Local)
 752                                 tz = TimeZoneInfo.Local;
 753
 754                         bool isTzDst;
 755                         var tzOffset = GetUtcOffsetHelper (dateTime, tz, out isTzDst);
 756
 757                         if (tz == this) {
 758                                 isDST = isTzDst;
 759                                 return tzOffset;
 760                         }
 761
 762                         DateTime utcDateTime;
 763                         if (!TryAddTicks (dateTime, -tzOffset.Ticks, out utcDateTime, DateTimeKind.Utc))
 764                                 return BaseUtcOffset;
 765
 766                         return GetUtcOffsetHelper (utcDateTime, this, out isDST);
 767                 }
 768
 769                 // This is an helper method used by the method above, do not use this on its own.
 770                 private static TimeSpan GetUtcOffsetHelper (DateTime dateTime, TimeZoneInfo tz, out bool isDST)
 771                 {
 772                         if (dateTime.Kind == DateTimeKind.Local && tz != TimeZoneInfo.Local)
 773                                 throw new Exception ();
 774
 775                         isDST = false;
 776
 777                         if (tz == TimeZoneInfo.Utc)
 778                                 return TimeSpan.Zero;
 779
 780                         TimeSpan offset;
 781                         if (tz.TryGetTransitionOffset(dateTime, out offset, out isDST))
 782                                 return offset;
 783
 784                         if (dateTime.Kind == DateTimeKind.Utc) {
 785                                 var utcRule = tz.GetApplicableRule (dateTime);
 786                                 if (utcRule != null && tz.IsInDST (utcRule, dateTime)) {
 787                                         isDST = true;
 788                                         return tz.BaseUtcOffset + utcRule.DaylightDelta;
 789                                 }
 790
 791                                 return tz.BaseUtcOffset;
 792                         }
 793
 794                         DateTime stdUtcDateTime;
 795                         if (!TryAddTicks (dateTime, -tz.BaseUtcOffset.Ticks, out stdUtcDateTime, DateTimeKind.Utc))
 796                                 return tz.BaseUtcOffset;
 797
 798                         var tzRule = tz.GetApplicableRule (stdUtcDateTime);
 799
 800                         DateTime dstUtcDateTime = DateTime.MinValue;
 801                         if (tzRule != null) {
 802                                 if (!TryAddTicks (stdUtcDateTime, -tzRule.DaylightDelta.Ticks, out dstUtcDateTime, DateTimeKind.Utc))
 803                                         return tz.BaseUtcOffset;
 804                         }
 805
 806                         if (tzRule != null && tz.IsInDST (tzRule, stdUtcDateTime) && tz.IsInDST (tzRule, dstUtcDateTime)) {
 807                                 isDST = true;
 808                                 return tz.BaseUtcOffset + tzRule.DaylightDelta;
 809                         }
 810
 811                         return tz.BaseUtcOffset;
 812                 }
 813
 814                 public bool HasSameRules (TimeZoneInfo other)
 815                 {
 816                         if (other == null)
 817                                 throw new ArgumentNullException ("other");
 818
 819                         if ((this.adjustmentRules == null) != (other.adjustmentRules == null))
 820                                 return false;
 821
 822                         if (this.adjustmentRules == null)
 823                                 return true;
 824
 825                         if (this.BaseUtcOffset != other.BaseUtcOffset)
 826                                 return false;
 827
 828                         if (this.adjustmentRules.Length != other.adjustmentRules.Length)
 829                                 return false;
 830
 831                         for (int i = 0; i < adjustmentRules.Length; i++) {
 832                                 if (! (this.adjustmentRules [i]).Equals (other.adjustmentRules [i]))
 833                                         return false;
 834                         }
 835
 836                         return true;
 837                 }
 838
 839                 public bool IsAmbiguousTime (DateTime dateTime)
 840                 {
 841                         if (dateTime.Kind == DateTimeKind.Local && IsInvalidTime (dateTime))
 842                                 throw new ArgumentException ("Kind is Local and time is Invalid");
 843
 844                         if (this == TimeZoneInfo.Utc)
 845                                 return false;
 846
 847                         if (dateTime.Kind == DateTimeKind.Utc)
 848                                 dateTime = ConvertTimeFromUtc (dateTime);
 849
 850                         if (dateTime.Kind == DateTimeKind.Local && this != TimeZoneInfo.Local)
 851                                 dateTime = ConvertTime (dateTime, TimeZoneInfo.Local, this);
 852
 853                         AdjustmentRule rule = GetApplicableRule (dateTime);
 854                         if (rule != null) {
 855                                 DateTime tpoint = TransitionPoint (rule.DaylightTransitionEnd, dateTime.Year);
 856                                 if (dateTime > tpoint - rule.DaylightDelta  && dateTime <= tpoint)
 857                                         return true;
 858                         }
 859
 860                         return false;
 861                 }
 862
 863                 public bool IsAmbiguousTime (DateTimeOffset dateTimeOffset)
 864                 {
 865                         throw new NotImplementedException ();
 866                 }
 867
 868                 private bool IsInDST (AdjustmentRule rule, DateTime dateTime)
 869                 {
 870                         // Check whether we're in the dateTime year's DST period
 871                         if (IsInDSTForYear (rule, dateTime, dateTime.Year))
 872                                 return true;
 873
 874                         // We might be in the dateTime previous year's DST period
 875                         return IsInDSTForYear (rule, dateTime, dateTime.Year - 1);
 876                 }
 877
 878                 bool IsInDSTForYear (AdjustmentRule rule, DateTime dateTime, int year)
 879                 {
 880                         DateTime DST_start = TransitionPoint (rule.DaylightTransitionStart, year);
 881                         DateTime DST_end = TransitionPoint (rule.DaylightTransitionEnd, year + ((rule.DaylightTransitionStart.Month < rule.DaylightTransitionEnd.Month) ? 0 : 1));
 882                         if (dateTime.Kind == DateTimeKind.Utc) {
 883                                 DST_start -= BaseUtcOffset;
 884                                 DST_end -= (BaseUtcOffset + rule.DaylightDelta);
 885                         }
 886
 887                         return (dateTime >= DST_start && dateTime < DST_end);
 888                 }
 889
 890                 public bool IsDaylightSavingTime (DateTime dateTime)
 891                 {
 892                         if (dateTime.Kind == DateTimeKind.Local && IsInvalidTime (dateTime))
 893                                 throw new ArgumentException ("dateTime is invalid and Kind is Local");
 894
 895                         if (this == TimeZoneInfo.Utc)
 896                                 return false;
 897
 898                         if (!SupportsDaylightSavingTime)
 899                                 return false;
 900
 901                         bool isDst;
 902                         GetUtcOffset (dateTime, out isDst);
 903
 904                         return isDst;
 905                 }
 906
 907                 internal bool IsDaylightSavingTime (DateTime dateTime, TimeZoneInfoOptions flags)
 908                 {
 909                         return IsDaylightSavingTime (dateTime);
 910                 }
 911
 912                 public bool IsDaylightSavingTime (DateTimeOffset dateTimeOffset)
 913                 {
 914                         throw new NotImplementedException ();
 915                 }
 916
 917                 internal DaylightTime GetDaylightChanges (int year)
 918                 {
 919                         DateTime start = DateTime.MinValue, end = DateTime.MinValue;
 920                         TimeSpan delta = new TimeSpan ();
 921
 922                         if (transitions != null) {
 923                                 end = DateTime.MaxValue;
 924                                 for (var i =  transitions.Count - 1; i >= 0; i--) {
 925                                         var pair = transitions [i];
 926                                         DateTime ttime = pair.Key;
 927                                         TimeType ttype = pair.Value;
 928
 929                                         if (ttime.Year > year)
 930                                                 continue;
 931                                         if (ttime.Year < year)
 932                                                 break;
 933
 934                                         if (ttype.IsDst) {
 935                                                 // DaylightTime.Delta is relative to the current BaseUtcOffset.
 936                                                 delta =  new TimeSpan (0, 0, ttype.Offset) - BaseUtcOffset;
 937                                                 start = ttime;
 938                                         } else {
 939                                                 end = ttime;
 940                                         }
 941                                 }
 942
 943                                 // DaylightTime.Start is relative to the Standard time.
 944                                 if (!TryAddTicks (start, BaseUtcOffset.Ticks, out start))
 945                                         start = DateTime.MinValue;
 946
 947                                 // DaylightTime.End is relative to the DST time.
 948                                 if (!TryAddTicks (end, BaseUtcOffset.Ticks + delta.Ticks, out end))
 949                                         end = DateTime.MinValue;
 950                         } else {
 951                                 AdjustmentRule first = null, last = null;
 952
 953                                 foreach (var rule in GetAdjustmentRules ()) {
 954                                         if (rule.DateStart.Year != year && rule.DateEnd.Year != year)
 955                                                 continue;
 956                                         if (rule.DateStart.Year == year)
 957                                                 first = rule;
 958                                         if (rule.DateEnd.Year == year)
 959                                                 last = rule;
 960                                 }
 961
 962                                 if (first == null || last == null)
 963                                         return new DaylightTime (new DateTime (), new DateTime (), new TimeSpan ());
 964
 965                                 start = TransitionPoint (first.DaylightTransitionStart, year);
 966                                 end = TransitionPoint (last.DaylightTransitionEnd, year);
 967                                 delta = first.DaylightDelta;
 968                         }
 969
 970                         if (start == DateTime.MinValue || end == DateTime.MinValue)
 971                                 return new DaylightTime (new DateTime (), new DateTime (), new TimeSpan ());
 972
 973                         return new DaylightTime (start, end, delta);
 974                 }
 975
 976                 public bool IsInvalidTime (DateTime dateTime)
 977                 {
 978                         if (dateTime.Kind == DateTimeKind.Utc)
 979                                 return false;
 980                         if (dateTime.Kind == DateTimeKind.Local && this != Local)
 981                                 return false;
 982
 983                         AdjustmentRule rule = GetApplicableRule (dateTime);
 984                         if (rule != null) {
 985                                 DateTime tpoint = TransitionPoint (rule.DaylightTransitionStart, dateTime.Year);
 986                                 if (dateTime >= tpoint && dateTime < tpoint + rule.DaylightDelta)
 987                                         return true;
 988                         }
 989
 990                         return false;
 991                 }
 992
 993                 void IDeserializationCallback.OnDeserialization (object sender)
 994                 {
 995                         try {
 996                                         TimeZoneInfo.Validate (id, baseUtcOffset, adjustmentRules);
 997                                 } catch (ArgumentException ex) {
 998                                         throw new SerializationException ("invalid serialization data", ex);
 999                                 }
1000                 }
1001
1002                 private static void Validate (string id, TimeSpan baseUtcOffset, AdjustmentRule [] adjustmentRules)
1003                 {
1004                         if (id == null)
1005                                 throw new ArgumentNullException ("id");
1006
1007                         if (id == String.Empty)
1008                                 throw new ArgumentException ("id parameter is an empty string");
1009
1010                         if (baseUtcOffset.Ticks % TimeSpan.TicksPerMinute != 0)
1011                                 throw new ArgumentException ("baseUtcOffset parameter does not represent a whole number of minutes");
1012
1013                         if (baseUtcOffset > new TimeSpan (14, 0, 0) || baseUtcOffset < new TimeSpan (-14, 0, 0))
1014                                 throw new ArgumentOutOfRangeException ("baseUtcOffset parameter is greater than 14 hours or less than -14 hours");
1015
1016 #if STRICT
1017                         if (id.Length > 32)
1018                                 throw new ArgumentException ("id parameter shouldn't be longer than 32 characters");
1019 #endif
1020
1021                         if (adjustmentRules != null && adjustmentRules.Length != 0) {
1022                                 AdjustmentRule prev = null;
1023                                 foreach (AdjustmentRule current in adjustmentRules) {
1024                                         if (current == null)
1025                                                 throw new InvalidTimeZoneException ("one or more elements in adjustmentRules are null");
1026
1027                                         if ((baseUtcOffset + current.DaylightDelta < new TimeSpan (-14, 0, 0)) ||
1028                                                         (baseUtcOffset + current.DaylightDelta > new TimeSpan (14, 0, 0)))
1029                                                 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;");
1030
1031                                         if (prev != null && prev.DateStart > current.DateStart)
1032                                                 throw new InvalidTimeZoneException ("adjustment rules specified in adjustmentRules parameter are not in chronological order");
1033
1034                                         if (prev != null && prev.DateEnd > current.DateStart)
1035                                                 throw new InvalidTimeZoneException ("some adjustment rules in the adjustmentRules parameter overlap");
1036
1037                                         if (prev != null && prev.DateEnd == current.DateStart)
1038                                                 throw new InvalidTimeZoneException ("a date can have multiple adjustment rules applied to it");
1039
1040                                         prev = current;
1041                                 }
1042                         }
1043                 }
1044
1045                 public override string ToString ()
1046                 {
1047                         return DisplayName;
1048                 }
1049
1050                 private TimeZoneInfo (SerializationInfo info, StreamingContext context)
1051                 {
1052                         if (info == null)
1053                                 throw new ArgumentNullException ("info");
1054                         id = (string) info.GetValue ("Id", typeof (string));
1055                         displayName = (string) info.GetValue ("DisplayName", typeof (string));
1056                         standardDisplayName = (string) info.GetValue ("StandardName", typeof (string));
1057                         daylightDisplayName = (string) info.GetValue ("DaylightName", typeof (string));
1058                         baseUtcOffset = (TimeSpan) info.GetValue ("BaseUtcOffset", typeof (TimeSpan));
1059                         adjustmentRules = (TimeZoneInfo.AdjustmentRule []) info.GetValue ("AdjustmentRules", typeof (TimeZoneInfo.AdjustmentRule []));
1060                         supportsDaylightSavingTime = (bool) info.GetValue ("SupportsDaylightSavingTime", typeof (bool));
1061                 }
1062
1063                 private TimeZoneInfo (string id, TimeSpan baseUtcOffset, string displayName, string standardDisplayName, string daylightDisplayName, TimeZoneInfo.AdjustmentRule [] adjustmentRules, bool disableDaylightSavingTime)
1064                 {
1065                         if (id == null)
1066                                 throw new ArgumentNullException ("id");
1067
1068                         if (id == String.Empty)
1069                                 throw new ArgumentException ("id parameter is an empty string");
1070
1071                         if (baseUtcOffset.Ticks % TimeSpan.TicksPerMinute != 0)
1072                                 throw new ArgumentException ("baseUtcOffset parameter does not represent a whole number of minutes");
1073
1074                         if (baseUtcOffset > new TimeSpan (14, 0, 0) || baseUtcOffset < new TimeSpan (-14, 0, 0))
1075                                 throw new ArgumentOutOfRangeException ("baseUtcOffset parameter is greater than 14 hours or less than -14 hours");
1076
1077 #if STRICT
1078                         if (id.Length > 32)
1079                                 throw new ArgumentException ("id parameter shouldn't be longer than 32 characters");
1080 #endif
1081
1082                         bool supportsDaylightSavingTime = !disableDaylightSavingTime;
1083
1084                         if (adjustmentRules != null && adjustmentRules.Length != 0) {
1085                                 AdjustmentRule prev = null;
1086                                 foreach (AdjustmentRule current in adjustmentRules) {
1087                                         if (current == null)
1088                                                 throw new InvalidTimeZoneException ("one or more elements in adjustmentRules are null");
1089
1090                                         if ((baseUtcOffset + current.DaylightDelta < new TimeSpan (-14, 0, 0)) ||
1091                                                         (baseUtcOffset + current.DaylightDelta > new TimeSpan (14, 0, 0)))
1092                                                 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;");
1093
1094                                         if (prev != null && prev.DateStart > current.DateStart)
1095                                                 throw new InvalidTimeZoneException ("adjustment rules specified in adjustmentRules parameter are not in chronological order");
1096
1097                                         if (prev != null && prev.DateEnd > current.DateStart)
1098                                                 throw new InvalidTimeZoneException ("some adjustment rules in the adjustmentRules parameter overlap");
1099
1100                                         if (prev != null && prev.DateEnd == current.DateStart)
1101                                                 throw new InvalidTimeZoneException ("a date can have multiple adjustment rules applied to it");
1102
1103                                         prev = current;
1104                                 }
1105                         } else {
1106                                 supportsDaylightSavingTime = false;
1107                         }
1108
1109                         this.id = id;
1110                         this.baseUtcOffset = baseUtcOffset;
1111                         this.displayName = displayName ?? id;
1112                         this.standardDisplayName = standardDisplayName ?? id;
1113                         this.daylightDisplayName = daylightDisplayName;
1114                         this.supportsDaylightSavingTime = supportsDaylightSavingTime;
1115                         this.adjustmentRules = adjustmentRules;
1116                 }
1117
1118                 private AdjustmentRule GetApplicableRule (DateTime dateTime)
1119                 {
1120                         //Applicable rules are in standard time
1121                         DateTime date = dateTime;
1122
1123                         if (dateTime.Kind == DateTimeKind.Local && this != TimeZoneInfo.Local) {
1124                                 if (!TryAddTicks (date.ToUniversalTime (), BaseUtcOffset.Ticks, out date))
1125                                         return null;
1126                         } else if (dateTime.Kind == DateTimeKind.Utc && this != TimeZoneInfo.Utc) {
1127                                 if (!TryAddTicks (date, BaseUtcOffset.Ticks, out date))
1128                                         return null;
1129                         }
1130
1131                         // get the date component of the datetime
1132                         date = date.Date;
1133
1134                         if (adjustmentRules != null) {
1135                                 foreach (AdjustmentRule rule in adjustmentRules) {
1136                                         if (rule.DateStart > date)
1137                                                 return null;
1138                                         if (rule.DateEnd < date)
1139                                                 continue;
1140                                         return rule;
1141                                 }
1142                         }
1143                         return null;
1144                 }
1145
1146                 private bool TryGetTransitionOffset (DateTime dateTime, out TimeSpan offset,out bool isDst)
1147                 {
1148                         offset = BaseUtcOffset;
1149                         isDst = false;
1150
1151                         if (transitions == null)
1152                                 return false;
1153
1154                         //Transitions are in UTC
1155                         DateTime date = dateTime;
1156
1157                         if (dateTime.Kind == DateTimeKind.Local && this != TimeZoneInfo.Local) {
1158                                 if (!TryAddTicks (date.ToUniversalTime (), BaseUtcOffset.Ticks, out date, DateTimeKind.Utc))
1159                                         return false;
1160                         }
1161
1162                         if (dateTime.Kind != DateTimeKind.Utc) {
1163                                 if (!TryAddTicks (date, -BaseUtcOffset.Ticks, out date, DateTimeKind.Utc))
1164                                         return false;
1165                         }
1166
1167                         for (var i =  transitions.Count - 1; i >= 0; i--) {
1168                                 var pair = transitions [i];
1169                                 DateTime ttime = pair.Key;
1170                                 TimeType ttype = pair.Value;
1171
1172                                 if (ttime > date)
1173                                         continue;
1174
1175                                 offset =  new TimeSpan (0, 0, ttype.Offset);
1176                                 isDst = ttype.IsDst;
1177
1178                                 return true;
1179                         }
1180
1181                         return false;
1182                 }
1183
1184                 private static DateTime TransitionPoint (TransitionTime transition, int year)
1185                 {
1186                         if (transition.IsFixedDateRule)
1187                                 return new DateTime (year, transition.Month, transition.Day) + transition.TimeOfDay.TimeOfDay;
1188
1189                         DayOfWeek first = (new DateTime (year, transition.Month, 1)).DayOfWeek;
1190                         int day = 1 + (transition.Week - 1) * 7 + (transition.DayOfWeek - first + 7) % 7;
1191                         if (day >  DateTime.DaysInMonth (year, transition.Month))
1192                                 day -= 7;
1193                         if (day < 1)
1194                                 day += 7;
1195                         return new DateTime (year, transition.Month, day) + transition.TimeOfDay.TimeOfDay;
1196                 }
1197
1198                 static List<AdjustmentRule> ValidateRules (List<AdjustmentRule> adjustmentRules)
1199                 {
1200                         AdjustmentRule prev = null;
1201                         foreach (AdjustmentRule current in adjustmentRules.ToArray ()) {
1202                                 if (prev != null && prev.DateEnd > current.DateStart) {
1203                                         adjustmentRules.Remove (current);
1204                                 }
1205                                 prev = current;
1206                         }
1207                         return adjustmentRules;
1208                 }
1209
1210 #if LIBC || MONOTOUCH
1211                 const int BUFFER_SIZE = 16384; //Big enough for any tz file (on Oct 2008, all tz files are under 10k)
1212
1213                 private static TimeZoneInfo BuildFromStream (string id, Stream stream)
1214                 {
1215                         byte [] buffer = new byte [BUFFER_SIZE];
1216                         int length = stream.Read (buffer, 0, BUFFER_SIZE);
1217
1218                         if (!ValidTZFile (buffer, length))
1219                                 throw new InvalidTimeZoneException ("TZ file too big for the buffer");
1220
1221                         try {
1222                                 return ParseTZBuffer (id, buffer, length);
1223                         } catch (Exception e) {
1224                                 throw new InvalidTimeZoneException (e.Message);
1225                         }
1226                 }
1227
1228                 private static bool ValidTZFile (byte [] buffer, int length)
1229                 {
1230                         StringBuilder magic = new StringBuilder ();
1231
1232                         for (int i = 0; i < 4; i++)
1233                                 magic.Append ((char)buffer [i]);
1234
1235                         if (magic.ToString () != "TZif")
1236                                 return false;
1237
1238                         if (length >= BUFFER_SIZE)
1239                                 return false;
1240
1241                         return true;
1242                 }
1243
1244                 static int SwapInt32 (int i)
1245                 {
1246                         return (((i >> 24) & 0xff)
1247                                 | ((i >> 8) & 0xff00)
1248                                 | ((i << 8) & 0xff0000)
1249                                 | (((i & 0xff) << 24)));
1250                 }
1251
1252                 static int ReadBigEndianInt32 (byte [] buffer, int start)
1253                 {
1254                         int i = BitConverter.ToInt32 (buffer, start);
1255                         if (!BitConverter.IsLittleEndian)
1256                                 return i;
1257
1258                         return SwapInt32 (i);
1259                 }
1260
1261                 private static TimeZoneInfo ParseTZBuffer (string id, byte [] buffer, int length)
1262                 {
1263                         //Reading the header. 4 bytes for magic, 16 are reserved
1264                         int ttisgmtcnt = ReadBigEndianInt32 (buffer, 20);
1265                         int ttisstdcnt = ReadBigEndianInt32 (buffer, 24);
1266                         int leapcnt = ReadBigEndianInt32 (buffer, 28);
1267                         int timecnt = ReadBigEndianInt32 (buffer, 32);
1268                         int typecnt = ReadBigEndianInt32 (buffer, 36);
1269                         int charcnt = ReadBigEndianInt32 (buffer, 40);
1270
1271                         if (length < 44 + timecnt * 5 + typecnt * 6 + charcnt + leapcnt * 8 + ttisstdcnt + ttisgmtcnt)
1272                                 throw new InvalidTimeZoneException ();
1273
1274                         Dictionary<int, string> abbreviations = ParseAbbreviations (buffer, 44 + 4 * timecnt + timecnt + 6 * typecnt, charcnt);
1275                         Dictionary<int, TimeType> time_types = ParseTimesTypes (buffer, 44 + 4 * timecnt + timecnt, typecnt, abbreviations);
1276                         List<KeyValuePair<DateTime, TimeType>> transitions = ParseTransitions (buffer, 44, timecnt, time_types);
1277
1278                         if (time_types.Count == 0)
1279                                 throw new InvalidTimeZoneException ();
1280
1281                         if (time_types.Count == 1 && ((TimeType)time_types[0]).IsDst)
1282                                 throw new InvalidTimeZoneException ();
1283
1284                         TimeSpan baseUtcOffset = new TimeSpan (0);
1285                         TimeSpan dstDelta = new TimeSpan (0);
1286                         string standardDisplayName = null;
1287                         string daylightDisplayName = null;
1288                         bool dst_observed = false;
1289                         DateTime dst_start = DateTime.MinValue;
1290                         List<AdjustmentRule> adjustmentRules = new List<AdjustmentRule> ();
1291                         bool storeTransition = false;
1292
1293                         for (int i = 0; i < transitions.Count; i++) {
1294                                 var pair = transitions [i];
1295                                 DateTime ttime = pair.Key;
1296                                 TimeType ttype = pair.Value;
1297                                 if (!ttype.IsDst) {
1298                                         if (standardDisplayName != ttype.Name)
1299                                                 standardDisplayName = ttype.Name;
1300                                         if (baseUtcOffset.TotalSeconds != ttype.Offset) {
1301                                                 baseUtcOffset = new TimeSpan (0, 0, ttype.Offset);
1302                                                 if (adjustmentRules.Count > 0) // We ignore AdjustmentRules but store transitions.
1303                                                         storeTransition = true;
1304                                                 adjustmentRules = new List<AdjustmentRule> ();
1305                                                 dst_observed = false;
1306                                         }
1307                                         if (dst_observed) {
1308                                                 //FIXME: check additional fields for this:
1309                                                 //most of the transitions are expressed in GMT
1310                                                 dst_start += baseUtcOffset;
1311                                                 DateTime dst_end = ttime + baseUtcOffset + dstDelta;
1312
1313                                                 //some weird timezone (America/Phoenix) have end dates on Jan 1st
1314                                                 if (dst_end.Date == new DateTime (dst_end.Year, 1, 1) && dst_end.Year > dst_start.Year)
1315                                                         dst_end -= new TimeSpan (24, 0, 0);
1316
1317                                                 /*
1318                                                  * AdjustmentRule specifies a DST period that starts and ends within a year.
1319                                                  * When we have a DST period longer than a year, the generated AdjustmentRule may not be usable.
1320                                                  * Thus we fallback to the transitions.
1321                                                  */
1322                                                 if (dst_start.AddYears (1) < dst_end)
1323                                                         storeTransition = true;
1324
1325                                                 DateTime dateStart, dateEnd;
1326                                                 if (dst_start.Month < 7)
1327                                                         dateStart = new DateTime (dst_start.Year, 1, 1);
1328                                                 else
1329                                                         dateStart = new DateTime (dst_start.Year, 7, 1);
1330
1331                                                 if (dst_end.Month >= 7)
1332                                                         dateEnd = new DateTime (dst_end.Year, 12, 31);
1333                                                 else
1334                                                         dateEnd = new DateTime (dst_end.Year, 6, 30);
1335
1336
1337                                                 TransitionTime transition_start = TransitionTime.CreateFixedDateRule (new DateTime (1, 1, 1) + dst_start.TimeOfDay, dst_start.Month, dst_start.Day);
1338                                                 TransitionTime transition_end = TransitionTime.CreateFixedDateRule (new DateTime (1, 1, 1) + dst_end.TimeOfDay, dst_end.Month, dst_end.Day);
1339                                                 if  (transition_start != transition_end) //y, that happened in Argentina in 1943-1946
1340                                                         adjustmentRules.Add (AdjustmentRule.CreateAdjustmentRule (dateStart, dateEnd, dstDelta, transition_start, transition_end));
1341                                         }
1342                                         dst_observed = false;
1343                                 } else {
1344                                         if (daylightDisplayName != ttype.Name)
1345                                                 daylightDisplayName = ttype.Name;
1346                                         if (dstDelta.TotalSeconds != ttype.Offset - baseUtcOffset.TotalSeconds) {
1347                                                 // Round to nearest minute, since it's not possible to create an adjustment rule
1348                                                 // with sub-minute precision ("The TimeSpan parameter cannot be specified more precisely than whole minutes.")
1349                                                 // This happens for instance with Europe/Dublin, which had an offset of 34 minutes and 39 seconds in 1916.
1350                                                 dstDelta = new TimeSpan (0, 0, ttype.Offset) - baseUtcOffset;
1351                                                 if (dstDelta.Ticks % TimeSpan.TicksPerMinute != 0)
1352                                                         dstDelta = TimeSpan.FromMinutes ((long) (dstDelta.TotalMinutes + 0.5f));
1353                                         }
1354
1355                                         dst_start = ttime;
1356                                         dst_observed = true;
1357                                 }
1358                         }
1359
1360                         TimeZoneInfo tz;
1361                         if (adjustmentRules.Count == 0 && !storeTransition) {
1362                                 TimeType t = (TimeType)time_types [0];
1363                                 if (standardDisplayName == null) {
1364                                         standardDisplayName = t.Name;
1365                                         baseUtcOffset = new TimeSpan (0, 0, t.Offset);
1366                                 }
1367                                 tz = CreateCustomTimeZone (id, baseUtcOffset, id, standardDisplayName);
1368                         } else {
1369                                 tz = CreateCustomTimeZone (id, baseUtcOffset, id, standardDisplayName, daylightDisplayName, ValidateRules (adjustmentRules).ToArray ());
1370                         }
1371
1372                         if (storeTransition && transitions.Count > 0) {
1373                                 tz.transitions = transitions;
1374                                 tz.supportsDaylightSavingTime = true;
1375                         }
1376
1377                         return tz;
1378                 }
1379
1380                 static Dictionary<int, string> ParseAbbreviations (byte [] buffer, int index, int count)
1381                 {
1382                         var abbrevs = new Dictionary<int, string> ();
1383                         int abbrev_index = 0;
1384                         var sb = new StringBuilder ();
1385                         for (int i = 0; i < count; i++) {
1386                                 char c = (char) buffer [index + i];
1387                                 if (c != '\0')
1388                                         sb.Append (c);
1389                                 else {
1390                                         abbrevs.Add (abbrev_index, sb.ToString ());
1391                                         //Adding all the substrings too, as it seems to be used, at least for Africa/Windhoek
1392                                         //j == sb.Length empty substring also needs to be added #31432
1393                                         for (int j = 1; j <= sb.Length; j++)
1394                                                 abbrevs.Add (abbrev_index + j, sb.ToString (j, sb.Length - j));
1395                                         abbrev_index = i + 1;
1396                                         sb = new StringBuilder ();
1397                                 }
1398                         }
1399                         return abbrevs;
1400                 }
1401
1402                 static Dictionary<int, TimeType> ParseTimesTypes (byte [] buffer, int index, int count, Dictionary<int, string> abbreviations)
1403                 {
1404                         var types = new Dictionary<int, TimeType> (count);
1405                         for (int i = 0; i < count; i++) {
1406                                 int offset = ReadBigEndianInt32 (buffer, index + 6 * i);
1407                                 byte is_dst = buffer [index + 6 * i + 4];
1408                                 byte abbrev = buffer [index + 6 * i + 5];
1409                                 types.Add (i, new TimeType (offset, (is_dst != 0), abbreviations [(int)abbrev]));
1410                         }
1411                         return types;
1412                 }
1413
1414                 static List<KeyValuePair<DateTime, TimeType>> ParseTransitions (byte [] buffer, int index, int count, Dictionary<int, TimeType> time_types)
1415                 {
1416                         var list = new List<KeyValuePair<DateTime, TimeType>> (count);
1417                         for (int i = 0; i < count; i++) {
1418                                 int unixtime = ReadBigEndianInt32 (buffer, index + 4 * i);
1419                                 DateTime ttime = DateTimeFromUnixTime (unixtime);
1420                                 byte ttype = buffer [index + 4 * count + i];
1421                                 list.Add (new KeyValuePair<DateTime, TimeType> (ttime, time_types [(int)ttype]));
1422                         }
1423                         return list;
1424                 }
1425
1426                 static DateTime DateTimeFromUnixTime (long unix_time)
1427                 {
1428                         DateTime date_time = new DateTime (1970, 1, 1);
1429                         return date_time.AddSeconds (unix_time);
1430                 }
1431
1432 #region reference sources
1433                 // Shortcut for TimeZoneInfo.Local.GetUtcOffset
1434                 internal static TimeSpan GetLocalUtcOffset(DateTime dateTime, TimeZoneInfoOptions flags)
1435                 {
1436                         bool dst;
1437                         return Local.GetUtcOffset (dateTime, out dst);
1438                 }
1439
1440                 internal TimeSpan GetUtcOffset(DateTime dateTime, TimeZoneInfoOptions flags)
1441                 {
1442                         bool dst;
1443                         return GetUtcOffset (dateTime, out dst);
1444                 }
1445
1446                 static internal TimeSpan GetUtcOffsetFromUtc (DateTime time, TimeZoneInfo zone, out Boolean isDaylightSavings, out Boolean isAmbiguousLocalDst)
1447                 {
1448                         isDaylightSavings = false;
1449                         isAmbiguousLocalDst = false;
1450                         TimeSpan baseOffset = zone.BaseUtcOffset;
1451
1452                         if (zone.IsAmbiguousTime (time)) {
1453                                 isAmbiguousLocalDst = true;
1454                                 return baseOffset;
1455                         }
1456
1457                         return zone.GetUtcOffset (time, out isDaylightSavings);
1458                 }
1459 #endregion
1460         }
1461
1462         struct TimeType {
1463                 public readonly int Offset;
1464                 public readonly bool IsDst;
1465                 public string Name;
1466
1467                 public TimeType (int offset, bool is_dst, string abbrev)
1468                 {
1469                         this.Offset = offset;
1470                         this.IsDst = is_dst;
1471                         this.Name = abbrev;
1472                 }
1473
1474                 public override string ToString ()
1475                 {
1476                         return "offset: " + Offset + "s, is_dst: " + IsDst + ", zone name: " + Name;
1477                 }
1478 #else
1479         }
1480 #endif
1481         }
1482 }