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) {
 109                                 readlinkNotFound = true;
 110                                 return null;
 111                         } catch (EntryPointNotFoundException) {
 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 !MOBILE || 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]) && str[Iend] != ')') // zone name can include parentheses like "Central Standard Time (Mexico)"
 299                                 Iend--;
 300
 301                         return str.Substring (Istart, Iend-Istart+1);
 302                 }
 303
 304 #if !MOBILE_STATIC
 305                 static RegistryKey timeZoneKey;
 306                 static RegistryKey TimeZoneKey {
 307                         get {
 308                                 if (timeZoneKey != null)
 309                                         return timeZoneKey;
 310                                 if (!IsWindows)
 311                                         return null;
 312
 313                                 return timeZoneKey = Registry.LocalMachine.OpenSubKey (
 314                                         "SOFTWARE\\Microsoft\\Windows NT\\CurrentVersion\\Time Zones",
 315                                         false);
 316                         }
 317                 }
 318
 319                 static RegistryKey localZoneKey;
 320                 static RegistryKey LocalZoneKey {
 321                         get {
 322                                 if (localZoneKey != null)
 323                                         return localZoneKey;
 324
 325                                 if (!IsWindows)
 326                                         return null;
 327
 328                                 return localZoneKey = Registry.LocalMachine.OpenSubKey (
 329                                         "SYSTEM\\CurrentControlSet\\Control\\TimeZoneInformation", false);
 330                         }
 331                 }
 332 #endif
 333 #endif
 334
 335                 private static bool TryAddTicks (DateTime date, long ticks, out DateTime result, DateTimeKind kind = DateTimeKind.Unspecified)
 336                 {
 337                         var resultTicks = date.Ticks + ticks;
 338                         if (resultTicks < DateTime.MinValue.Ticks) {
 339                                 result = DateTime.SpecifyKind (DateTime.MinValue, kind);
 340                                 return false;
 341                         }
 342
 343                         if (resultTicks > DateTime.MaxValue.Ticks) {
 344                                 result = DateTime.SpecifyKind (DateTime.MaxValue, kind);
 345                                 return false;
 346                         }
 347
 348                         result = new DateTime (resultTicks, kind);
 349                         return true;
 350                 }
 351
 352                 public static void ClearCachedData ()
 353                 {
 354                         local = null;
 355                         utc = null;
 356                         systemTimeZones = null;
 357                 }
 358
 359                 public static DateTime ConvertTime (DateTime dateTime, TimeZoneInfo destinationTimeZone)
 360                 {
 361                         return ConvertTime (dateTime, dateTime.Kind == DateTimeKind.Utc ? TimeZoneInfo.Utc : TimeZoneInfo.Local, destinationTimeZone);
 362                 }
 363
 364                 public static DateTime ConvertTime (DateTime dateTime, TimeZoneInfo sourceTimeZone, TimeZoneInfo destinationTimeZone)
 365                 {
 366                         if (sourceTimeZone == null)
 367                                 throw new ArgumentNullException ("sourceTimeZone");
 368
 369                         if (destinationTimeZone == null)
 370                                 throw new ArgumentNullException ("destinationTimeZone");
 371
 372                         if (dateTime.Kind == DateTimeKind.Local && sourceTimeZone != TimeZoneInfo.Local)
 373                                 throw new ArgumentException ("Kind property of dateTime is Local but the sourceTimeZone does not equal TimeZoneInfo.Local");
 374
 375                         if (dateTime.Kind == DateTimeKind.Utc && sourceTimeZone != TimeZoneInfo.Utc)
 376                                 throw new ArgumentException ("Kind property of dateTime is Utc but the sourceTimeZone does not equal TimeZoneInfo.Utc");
 377
 378                         if (sourceTimeZone.IsInvalidTime (dateTime))
 379                                 throw new ArgumentException ("dateTime parameter is an invalid time");
 380
 381                         if (dateTime.Kind == DateTimeKind.Local && sourceTimeZone == TimeZoneInfo.Local && destinationTimeZone == TimeZoneInfo.Local)
 382                                 return dateTime;
 383
 384                         DateTime utc = ConvertTimeToUtc (dateTime, sourceTimeZone);
 385
 386                         if (destinationTimeZone != TimeZoneInfo.Utc) {
 387                                 utc = ConvertTimeFromUtc (utc, destinationTimeZone);
 388                                 if (dateTime.Kind == DateTimeKind.Unspecified)
 389                                         return DateTime.SpecifyKind (utc, DateTimeKind.Unspecified);
 390                         }
 391
 392                         return utc;
 393                 }
 394
 395                 public static DateTimeOffset ConvertTime(DateTimeOffset dateTimeOffset, TimeZoneInfo destinationTimeZone)
 396                 {
 397                         if (destinationTimeZone == null)
 398                                 throw new ArgumentNullException("destinationTimeZone");
 399
 400                         var utcDateTime = dateTimeOffset.UtcDateTime;
 401
 402                         bool isDst;
 403                         var utcOffset =  destinationTimeZone.GetUtcOffset(utcDateTime, out isDst);
 404
 405                         return new DateTimeOffset(DateTime.SpecifyKind(utcDateTime, DateTimeKind.Unspecified) + utcOffset, utcOffset);
 406                 }
 407
 408                 public static DateTime ConvertTimeBySystemTimeZoneId (DateTime dateTime, string destinationTimeZoneId)
 409                 {
 410                         return ConvertTime (dateTime, FindSystemTimeZoneById (destinationTimeZoneId));
 411                 }
 412
 413                 public static DateTime ConvertTimeBySystemTimeZoneId (DateTime dateTime, string sourceTimeZoneId, string destinationTimeZoneId)
 414                 {
 415                         TimeZoneInfo source_tz;
 416                         if (dateTime.Kind == DateTimeKind.Utc && sourceTimeZoneId == TimeZoneInfo.Utc.Id) {
 417                                 source_tz = Utc;
 418                         } else {
 419                                 source_tz = FindSystemTimeZoneById (sourceTimeZoneId);
 420                         }
 421
 422                         return ConvertTime (dateTime, source_tz, FindSystemTimeZoneById (destinationTimeZoneId));
 423                 }
 424
 425                 public static DateTimeOffset ConvertTimeBySystemTimeZoneId (DateTimeOffset dateTimeOffset, string destinationTimeZoneId)
 426                 {
 427                         return ConvertTime (dateTimeOffset, FindSystemTimeZoneById (destinationTimeZoneId));
 428                 }
 429
 430                 private DateTime ConvertTimeFromUtc (DateTime dateTime)
 431                 {
 432                         if (dateTime.Kind == DateTimeKind.Local)
 433                                 throw new ArgumentException ("Kind property of dateTime is Local");
 434
 435                         if (this == TimeZoneInfo.Utc)
 436                                 return DateTime.SpecifyKind (dateTime, DateTimeKind.Utc);
 437
 438                         var utcOffset = GetUtcOffset (dateTime);
 439
 440                         var kind = (this == TimeZoneInfo.Local)? DateTimeKind.Local : DateTimeKind.Unspecified;
 441
 442                         DateTime result;
 443                         if (!TryAddTicks (dateTime, utcOffset.Ticks, out result, kind))
 444                                 return DateTime.SpecifyKind (DateTime.MaxValue, kind);
 445
 446                         return result;
 447                 }
 448
 449                 public static DateTime ConvertTimeFromUtc (DateTime dateTime, TimeZoneInfo destinationTimeZone)
 450                 {
 451                         if (destinationTimeZone == null)
 452                                 throw new ArgumentNullException ("destinationTimeZone");
 453
 454                         return destinationTimeZone.ConvertTimeFromUtc (dateTime);
 455                 }
 456
 457                 public static DateTime ConvertTimeToUtc (DateTime dateTime)
 458                 {
 459                         if (dateTime.Kind == DateTimeKind.Utc)
 460                                 return dateTime;
 461
 462                         return ConvertTimeToUtc (dateTime, TimeZoneInfo.Local);
 463                 }
 464
 465                 static internal DateTime ConvertTimeToUtc(DateTime dateTime, TimeZoneInfoOptions flags)
 466                 {
 467                         return ConvertTimeToUtc (dateTime, TimeZoneInfo.Local, flags);
 468                 }
 469
 470                 public static DateTime ConvertTimeToUtc (DateTime dateTime, TimeZoneInfo sourceTimeZone)
 471                 {
 472                         return ConvertTimeToUtc (dateTime, sourceTimeZone, TimeZoneInfoOptions.None);
 473                 }
 474
 475                 static DateTime ConvertTimeToUtc (DateTime dateTime, TimeZoneInfo sourceTimeZone, TimeZoneInfoOptions flags)
 476                 {
 477                         if ((flags & TimeZoneInfoOptions.NoThrowOnInvalidTime) == 0) {
 478                                 if (sourceTimeZone == null)
 479                                         throw new ArgumentNullException ("sourceTimeZone");
 480
 481                                 if (dateTime.Kind == DateTimeKind.Utc && sourceTimeZone != TimeZoneInfo.Utc)
 482                                         throw new ArgumentException ("Kind property of dateTime is Utc but the sourceTimeZone does not equal TimeZoneInfo.Utc");
 483
 484                                 if (dateTime.Kind == DateTimeKind.Local && sourceTimeZone != TimeZoneInfo.Local)
 485                                         throw new ArgumentException ("Kind property of dateTime is Local but the sourceTimeZone does not equal TimeZoneInfo.Local");
 486
 487                                 if (sourceTimeZone.IsInvalidTime (dateTime))
 488                                         throw new ArgumentException ("dateTime parameter is an invalid time");
 489                         }
 490
 491                         if (dateTime.Kind == DateTimeKind.Utc)
 492                                 return dateTime;
 493
 494                         bool isDst;
 495                         var utcOffset = sourceTimeZone.GetUtcOffset (dateTime, out isDst);
 496
 497                         DateTime utcDateTime;
 498                         TryAddTicks (dateTime, -utcOffset.Ticks, out utcDateTime, DateTimeKind.Utc);
 499                         return utcDateTime;
 500                 }
 501
 502                 static internal TimeSpan GetDateTimeNowUtcOffsetFromUtc(DateTime time, out Boolean isAmbiguousLocalDst)
 503                 {
 504                         bool isDaylightSavings;
 505                         return GetUtcOffsetFromUtc(time, TimeZoneInfo.Local, out isDaylightSavings, out isAmbiguousLocalDst);
 506                 }
 507
 508                 public static TimeZoneInfo CreateCustomTimeZone (string id, TimeSpan baseUtcOffset, string displayName, string standardDisplayName)
 509                 {
 510                         return CreateCustomTimeZone (id, baseUtcOffset, displayName, standardDisplayName, null, null, true);
 511                 }
 512
 513                 public static TimeZoneInfo CreateCustomTimeZone (string id, TimeSpan baseUtcOffset, string displayName, string standardDisplayName, string daylightDisplayName, TimeZoneInfo.AdjustmentRule [] adjustmentRules)
 514                 {
 515                         return CreateCustomTimeZone (id, baseUtcOffset, displayName, standardDisplayName, daylightDisplayName, adjustmentRules, false);
 516                 }
 517
 518                 public static TimeZoneInfo CreateCustomTimeZone ( string id, TimeSpan baseUtcOffset, string displayName, string standardDisplayName, string daylightDisplayName, TimeZoneInfo.AdjustmentRule [] adjustmentRules, bool disableDaylightSavingTime)
 519                 {
 520                         return new TimeZoneInfo (id, baseUtcOffset, displayName, standardDisplayName, daylightDisplayName, adjustmentRules, disableDaylightSavingTime);
 521                 }
 522
 523                 public override bool Equals (object obj)
 524                 {
 525                         return Equals (obj as TimeZoneInfo);
 526                 }
 527
 528                 public bool Equals (TimeZoneInfo other)
 529                 {
 530                         if (other == null)
 531                                 return false;
 532
 533                         return other.Id == this.Id && HasSameRules (other);
 534                 }
 535
 536                 public static TimeZoneInfo FindSystemTimeZoneById (string id)
 537                 {
 538                         //FIXME: this method should check for cached values in systemTimeZones
 539                         if (id == null)
 540                                 throw new ArgumentNullException ("id");
 541 #if !MOBILE
 542                         if (TimeZoneKey != null)
 543                         {
 544                                 if (id == "Coordinated Universal Time")
 545                                         id = "UTC"; //windows xp exception for "StandardName" property
 546                                 RegistryKey key = TimeZoneKey.OpenSubKey (id, false);
 547                                 if (key == null)
 548                                         throw new TimeZoneNotFoundException ();
 549                                 return FromRegistryKey(id, key);
 550                         }
 551 #endif
 552                         // Local requires special logic that already exists in the Local property (bug #326)
 553                         if (id == "Local")
 554                                 return Local;
 555
 556                         return FindSystemTimeZoneByIdCore (id);
 557                 }
 558
 559 #if LIBC
 560                 private static TimeZoneInfo FindSystemTimeZoneByFileName (string id, string filepath)
 561                 {
 562                         if (!File.Exists (filepath))
 563                                 throw new TimeZoneNotFoundException ();
 564
 565                         using (FileStream stream = File.OpenRead (filepath)) {
 566                                 return BuildFromStream (id, stream);
 567                         }
 568                 }
 569 #endif
 570
 571 #if !MOBILE
 572                 private static TimeZoneInfo FromRegistryKey (string id, RegistryKey key)
 573                 {
 574                         byte [] reg_tzi = (byte []) key.GetValue ("TZI");
 575
 576                         if (reg_tzi == null)
 577                                 throw new InvalidTimeZoneException ();
 578
 579                         int bias = BitConverter.ToInt32 (reg_tzi, 0);
 580                         TimeSpan baseUtcOffset = new TimeSpan (0, -bias, 0);
 581
 582                         string display_name = (string) key.GetValue ("Display");
 583                         string standard_name = (string) key.GetValue ("Std");
 584                         string daylight_name = (string) key.GetValue ("Dlt");
 585
 586                         List<AdjustmentRule> adjustmentRules = new List<AdjustmentRule> ();
 587
 588                         RegistryKey dst_key = key.OpenSubKey ("Dynamic DST", false);
 589                         if (dst_key != null) {
 590                                 int first_year = (int) dst_key.GetValue ("FirstEntry");
 591                                 int last_year = (int) dst_key.GetValue ("LastEntry");
 592                                 int year;
 593
 594                                 for (year=first_year; year<=last_year; year++) {
 595                                         byte [] dst_tzi = (byte []) dst_key.GetValue (year.ToString ());
 596                                         if (dst_tzi != null) {
 597                                                 int start_year = year == first_year ? 1 : year;
 598                                                 int end_year = year == last_year ? 9999 : year;
 599                                                 ParseRegTzi(adjustmentRules, start_year, end_year, dst_tzi);
 600                                         }
 601                                 }
 602                         }
 603                         else
 604                                 ParseRegTzi(adjustmentRules, 1, 9999, reg_tzi);
 605
 606                         return CreateCustomTimeZone (id, baseUtcOffset, display_name, standard_name, daylight_name, ValidateRules (adjustmentRules).ToArray ());
 607                 }
 608
 609                 private static void ParseRegTzi (List<AdjustmentRule> adjustmentRules, int start_year, int end_year, byte [] buffer)
 610                 {
 611                         //int standard_bias = BitConverter.ToInt32 (buffer, 4); /* not sure how to handle this */
 612                         int daylight_bias = BitConverter.ToInt32 (buffer, 8);
 613
 614                         int standard_year = BitConverter.ToInt16 (buffer, 12);
 615                         int standard_month = BitConverter.ToInt16 (buffer, 14);
 616                         int standard_dayofweek = BitConverter.ToInt16 (buffer, 16);
 617                         int standard_day = BitConverter.ToInt16 (buffer, 18);
 618                         int standard_hour = BitConverter.ToInt16 (buffer, 20);
 619                         int standard_minute = BitConverter.ToInt16 (buffer, 22);
 620                         int standard_second = BitConverter.ToInt16 (buffer, 24);
 621                         int standard_millisecond = BitConverter.ToInt16 (buffer, 26);
 622
 623                         int daylight_year = BitConverter.ToInt16 (buffer, 28);
 624                         int daylight_month = BitConverter.ToInt16 (buffer, 30);
 625                         int daylight_dayofweek = BitConverter.ToInt16 (buffer, 32);
 626                         int daylight_day = BitConverter.ToInt16 (buffer, 34);
 627                         int daylight_hour = BitConverter.ToInt16 (buffer, 36);
 628                         int daylight_minute = BitConverter.ToInt16 (buffer, 38);
 629                         int daylight_second = BitConverter.ToInt16 (buffer, 40);
 630                         int daylight_millisecond = BitConverter.ToInt16 (buffer, 42);
 631
 632                         if (standard_month == 0 || daylight_month == 0)
 633                                 return;
 634
 635                         DateTime start_date;
 636                         DateTime start_timeofday = new DateTime (1, 1, 1, daylight_hour, daylight_minute, daylight_second, daylight_millisecond);
 637                         TransitionTime start_transition_time;
 638
 639                         if (daylight_year == 0) {
 640                                 start_date = new DateTime (start_year, 1, 1);
 641                                 start_transition_time = TransitionTime.CreateFloatingDateRule (
 642                                         start_timeofday, daylight_month, daylight_day,
 643                                         (DayOfWeek) daylight_dayofweek);
 644                         }
 645                         else {
 646                                 start_date = new DateTime (daylight_year, daylight_month, daylight_day,
 647                                         daylight_hour, daylight_minute, daylight_second, daylight_millisecond);
 648                                 start_transition_time = TransitionTime.CreateFixedDateRule (
 649                                         start_timeofday, daylight_month, daylight_day);
 650                         }
 651
 652                         DateTime end_date;
 653                         DateTime end_timeofday = new DateTime (1, 1, 1, standard_hour, standard_minute, standard_second, standard_millisecond);
 654                         TransitionTime end_transition_time;
 655
 656                         if (standard_year == 0) {
 657                                 end_date = new DateTime (end_year, 12, 31);
 658                                 end_transition_time = TransitionTime.CreateFloatingDateRule (
 659                                         end_timeofday, standard_month, standard_day,
 660                                         (DayOfWeek) standard_dayofweek);
 661                         }
 662                         else {
 663                                 end_date = new DateTime (standard_year, standard_month, standard_day,
 664                                         standard_hour, standard_minute, standard_second, standard_millisecond);
 665                                 end_transition_time = TransitionTime.CreateFixedDateRule (
 666                                         end_timeofday, standard_month, standard_day);
 667                         }
 668
 669                         TimeSpan daylight_delta = new TimeSpan(0, -daylight_bias, 0);
 670
 671                         adjustmentRules.Add (AdjustmentRule.CreateAdjustmentRule (
 672                                 start_date, end_date, daylight_delta,
 673                                 start_transition_time, end_transition_time));
 674                 }
 675 #endif
 676
 677                 public AdjustmentRule [] GetAdjustmentRules ()
 678                 {
 679                         if (!supportsDaylightSavingTime || adjustmentRules == null)
 680                                 return new AdjustmentRule [0];
 681                         else
 682                                 return (AdjustmentRule []) adjustmentRules.Clone ();
 683                 }
 684
 685                 public TimeSpan [] GetAmbiguousTimeOffsets (DateTime dateTime)
 686                 {
 687                         if (!IsAmbiguousTime (dateTime))
 688                                 throw new ArgumentException ("dateTime is not an ambiguous time");
 689
 690                         AdjustmentRule rule = GetApplicableRule (dateTime);
 691                         if (rule != null)
 692                                 return new TimeSpan[] {baseUtcOffset, baseUtcOffset + rule.DaylightDelta};
 693                         else
 694                                 return new TimeSpan[] {baseUtcOffset, baseUtcOffset};
 695                 }
 696
 697                 public TimeSpan [] GetAmbiguousTimeOffsets (DateTimeOffset dateTimeOffset)
 698                 {
 699                         if (!IsAmbiguousTime (dateTimeOffset))
 700                                 throw new ArgumentException ("dateTimeOffset is not an ambiguous time");
 701
 702                         throw new NotImplementedException ();
 703                 }
 704
 705                 public override int GetHashCode ()
 706                 {
 707                         int hash_code = Id.GetHashCode ();
 708                         foreach (AdjustmentRule rule in GetAdjustmentRules ())
 709                                 hash_code ^= rule.GetHashCode ();
 710                         return hash_code;
 711                 }
 712
 713                 void ISerializable.GetObjectData (SerializationInfo info, StreamingContext context)
 714                 {
 715                         if (info == null)
 716                                 throw new ArgumentNullException ("info");
 717                         info.AddValue ("Id", id);
 718                         info.AddValue ("DisplayName", displayName);
 719                         info.AddValue ("StandardName", standardDisplayName);
 720                         info.AddValue ("DaylightName", daylightDisplayName);
 721                         info.AddValue ("BaseUtcOffset", baseUtcOffset);
 722                         info.AddValue ("AdjustmentRules", adjustmentRules);
 723                         info.AddValue ("SupportsDaylightSavingTime", SupportsDaylightSavingTime);
 724                 }
 725
 726                 static ReadOnlyCollection<TimeZoneInfo> systemTimeZones;
 727
 728                 public static ReadOnlyCollection<TimeZoneInfo> GetSystemTimeZones ()
 729                 {
 730                         if (systemTimeZones == null) {
 731                                 var tz = new List<TimeZoneInfo> ();
 732                                 GetSystemTimeZonesCore (tz);
 733                                 Interlocked.CompareExchange (ref systemTimeZones, new ReadOnlyCollection<TimeZoneInfo> (tz), null);
 734                         }
 735
 736                         return systemTimeZones;
 737                 }
 738
 739                 public TimeSpan GetUtcOffset (DateTime dateTime)
 740                 {
 741                         bool isDST;
 742                         return GetUtcOffset (dateTime, out isDST);
 743                 }
 744
 745                 public TimeSpan GetUtcOffset (DateTimeOffset dateTimeOffset)
 746                 {
 747                         bool isDST;
 748                         return GetUtcOffset (dateTimeOffset.UtcDateTime, out isDST);
 749                 }
 750
 751                 private TimeSpan GetUtcOffset (DateTime dateTime, out bool isDST)
 752                 {
 753                         isDST = false;
 754
 755                         TimeZoneInfo tz = this;
 756                         if (dateTime.Kind == DateTimeKind.Utc)
 757                                 tz = TimeZoneInfo.Utc;
 758
 759                         if (dateTime.Kind == DateTimeKind.Local)
 760                                 tz = TimeZoneInfo.Local;
 761
 762                         bool isTzDst;
 763                         var tzOffset = GetUtcOffsetHelper (dateTime, tz, out isTzDst);
 764
 765                         if (tz == this) {
 766                                 isDST = isTzDst;
 767                                 return tzOffset;
 768                         }
 769
 770                         DateTime utcDateTime;
 771                         if (!TryAddTicks (dateTime, -tzOffset.Ticks, out utcDateTime, DateTimeKind.Utc))
 772                                 return BaseUtcOffset;
 773
 774                         return GetUtcOffsetHelper (utcDateTime, this, out isDST);
 775                 }
 776
 777                 // This is an helper method used by the method above, do not use this on its own.
 778                 private static TimeSpan GetUtcOffsetHelper (DateTime dateTime, TimeZoneInfo tz, out bool isDST)
 779                 {
 780                         if (dateTime.Kind == DateTimeKind.Local && tz != TimeZoneInfo.Local)
 781                                 throw new Exception ();
 782
 783                         isDST = false;
 784
 785                         if (tz == TimeZoneInfo.Utc)
 786                                 return TimeSpan.Zero;
 787
 788                         TimeSpan offset;
 789                         if (tz.TryGetTransitionOffset(dateTime, out offset, out isDST))
 790                                 return offset;
 791
 792                         if (dateTime.Kind == DateTimeKind.Utc) {
 793                                 var utcRule = tz.GetApplicableRule (dateTime);
 794                                 if (utcRule != null && tz.IsInDST (utcRule, dateTime)) {
 795                                         isDST = true;
 796                                         return tz.BaseUtcOffset + utcRule.DaylightDelta;
 797                                 }
 798
 799                                 return tz.BaseUtcOffset;
 800                         }
 801
 802                         DateTime stdUtcDateTime;
 803                         if (!TryAddTicks (dateTime, -tz.BaseUtcOffset.Ticks, out stdUtcDateTime, DateTimeKind.Utc))
 804                                 return tz.BaseUtcOffset;
 805
 806                         var tzRule = tz.GetApplicableRule (stdUtcDateTime);
 807
 808                         DateTime dstUtcDateTime = DateTime.MinValue;
 809                         if (tzRule != null) {
 810                                 if (!TryAddTicks (stdUtcDateTime, -tzRule.DaylightDelta.Ticks, out dstUtcDateTime, DateTimeKind.Utc))
 811                                         return tz.BaseUtcOffset;
 812                         }
 813
 814                         if (tzRule != null && tz.IsInDST (tzRule, stdUtcDateTime)) {
 815                                 // Replicate what .NET does when given a time which falls into the hour which is lost when
 816                                 // DST starts. isDST should always be true but the offset should be BaseUtcOffset without the
 817                                 // DST delta while in that hour.
 818                                 isDST = true;
 819                                 if (tz.IsInDST (tzRule, dstUtcDateTime)) {
 820                                         return tz.BaseUtcOffset + tzRule.DaylightDelta;
 821                                 } else {
 822                                         return tz.BaseUtcOffset;
 823                                 }
 824                         }
 825
 826                         return tz.BaseUtcOffset;
 827                 }
 828
 829                 public bool HasSameRules (TimeZoneInfo other)
 830                 {
 831                         if (other == null)
 832                                 throw new ArgumentNullException ("other");
 833
 834                         if ((this.adjustmentRules == null) != (other.adjustmentRules == null))
 835                                 return false;
 836
 837                         if (this.adjustmentRules == null)
 838                                 return true;
 839
 840                         if (this.BaseUtcOffset != other.BaseUtcOffset)
 841                                 return false;
 842
 843                         if (this.adjustmentRules.Length != other.adjustmentRules.Length)
 844                                 return false;
 845
 846                         for (int i = 0; i < adjustmentRules.Length; i++) {
 847                                 if (! (this.adjustmentRules [i]).Equals (other.adjustmentRules [i]))
 848                                         return false;
 849                         }
 850
 851                         return true;
 852                 }
 853
 854                 public bool IsAmbiguousTime (DateTime dateTime)
 855                 {
 856                         if (dateTime.Kind == DateTimeKind.Local && IsInvalidTime (dateTime))
 857                                 throw new ArgumentException ("Kind is Local and time is Invalid");
 858
 859                         if (this == TimeZoneInfo.Utc)
 860                                 return false;
 861
 862                         if (dateTime.Kind == DateTimeKind.Utc)
 863                                 dateTime = ConvertTimeFromUtc (dateTime);
 864
 865                         if (dateTime.Kind == DateTimeKind.Local && this != TimeZoneInfo.Local)
 866                                 dateTime = ConvertTime (dateTime, TimeZoneInfo.Local, this);
 867
 868                         AdjustmentRule rule = GetApplicableRule (dateTime);
 869                         if (rule != null) {
 870                                 DateTime tpoint = TransitionPoint (rule.DaylightTransitionEnd, dateTime.Year);
 871                                 if (dateTime > tpoint - rule.DaylightDelta  && dateTime <= tpoint)
 872                                         return true;
 873                         }
 874
 875                         return false;
 876                 }
 877
 878                 public bool IsAmbiguousTime (DateTimeOffset dateTimeOffset)
 879                 {
 880                         throw new NotImplementedException ();
 881                 }
 882
 883                 private bool IsInDST (AdjustmentRule rule, DateTime dateTime)
 884                 {
 885                         // Check whether we're in the dateTime year's DST period
 886                         if (IsInDSTForYear (rule, dateTime, dateTime.Year))
 887                                 return true;
 888
 889                         // We might be in the dateTime previous year's DST period
 890                         return dateTime.Year > 1 && IsInDSTForYear (rule, dateTime, dateTime.Year - 1);
 891                 }
 892
 893                 bool IsInDSTForYear (AdjustmentRule rule, DateTime dateTime, int year)
 894                 {
 895                         DateTime DST_start = TransitionPoint (rule.DaylightTransitionStart, year);
 896                         DateTime DST_end = TransitionPoint (rule.DaylightTransitionEnd, year + ((rule.DaylightTransitionStart.Month < rule.DaylightTransitionEnd.Month) ? 0 : 1));
 897                         if (dateTime.Kind == DateTimeKind.Utc) {
 898                                 DST_start -= BaseUtcOffset;
 899                                 DST_end -= (BaseUtcOffset + rule.DaylightDelta);
 900                         }
 901
 902                         return (dateTime >= DST_start && dateTime < DST_end);
 903                 }
 904
 905                 public bool IsDaylightSavingTime (DateTime dateTime)
 906                 {
 907                         if (dateTime.Kind == DateTimeKind.Local && IsInvalidTime (dateTime))
 908                                 throw new ArgumentException ("dateTime is invalid and Kind is Local");
 909
 910                         if (this == TimeZoneInfo.Utc)
 911                                 return false;
 912
 913                         if (!SupportsDaylightSavingTime)
 914                                 return false;
 915
 916                         bool isDst;
 917                         GetUtcOffset (dateTime, out isDst);
 918
 919                         return isDst;
 920                 }
 921
 922                 internal bool IsDaylightSavingTime (DateTime dateTime, TimeZoneInfoOptions flags)
 923                 {
 924                         return IsDaylightSavingTime (dateTime);
 925                 }
 926
 927                 public bool IsDaylightSavingTime (DateTimeOffset dateTimeOffset)
 928                 {
 929                         return IsDaylightSavingTime (dateTimeOffset.DateTime);
 930                 }
 931
 932                 internal DaylightTime GetDaylightChanges (int year)
 933                 {
 934                         DateTime start = DateTime.MinValue, end = DateTime.MinValue;
 935                         TimeSpan delta = new TimeSpan ();
 936
 937                         if (transitions != null) {
 938                                 end = DateTime.MaxValue;
 939                                 for (var i =  transitions.Count - 1; i >= 0; i--) {
 940                                         var pair = transitions [i];
 941                                         DateTime ttime = pair.Key;
 942                                         TimeType ttype = pair.Value;
 943
 944                                         if (ttime.Year > year)
 945                                                 continue;
 946                                         if (ttime.Year < year)
 947                                                 break;
 948
 949                                         if (ttype.IsDst) {
 950                                                 // DaylightTime.Delta is relative to the current BaseUtcOffset.
 951                                                 delta =  new TimeSpan (0, 0, ttype.Offset) - BaseUtcOffset;
 952                                                 start = ttime;
 953                                         } else {
 954                                                 end = ttime;
 955                                         }
 956                                 }
 957
 958                                 // DaylightTime.Start is relative to the Standard time.
 959                                 if (!TryAddTicks (start, BaseUtcOffset.Ticks, out start))
 960                                         start = DateTime.MinValue;
 961
 962                                 // DaylightTime.End is relative to the DST time.
 963                                 if (!TryAddTicks (end, BaseUtcOffset.Ticks + delta.Ticks, out end))
 964                                         end = DateTime.MinValue;
 965                         } else {
 966                                 AdjustmentRule first = null, last = null;
 967
 968                                 // Rule start/end dates are either very specific or very broad depending on the platform
 969                                 //   2015-10-04..2016-04-03 - Rule for a time zone in southern hemisphere on non-Windows platforms
 970                                 //   2016-03-27..2016-10-03 - Rule for a time zone in northern hemisphere on non-Windows platforms
 971                                 //   0001-01-01..9999-12-31 - Rule for a time zone on Windows
 972
 973                                 foreach (var rule in GetAdjustmentRules ()) {
 974                                         if (rule.DateStart.Year > year || rule.DateEnd.Year < year)
 975                                                 continue;
 976                                         if (rule.DateStart.Year <= year && (first == null || rule.DateStart.Year > first.DateStart.Year))
 977                                                 first = rule;
 978                                         if (rule.DateEnd.Year >= year && (last == null || rule.DateEnd.Year < last.DateEnd.Year))
 979                                                 last = rule;
 980                                 }
 981
 982                                 if (first == null || last == null)
 983                                         return new DaylightTime (new DateTime (), new DateTime (), new TimeSpan ());
 984
 985                                 start = TransitionPoint (first.DaylightTransitionStart, year);
 986                                 end = TransitionPoint (last.DaylightTransitionEnd, year);
 987                                 delta = first.DaylightDelta;
 988                         }
 989
 990                         if (start == DateTime.MinValue || end == DateTime.MinValue)
 991                                 return new DaylightTime (new DateTime (), new DateTime (), new TimeSpan ());
 992
 993                         return new DaylightTime (start, end, delta);
 994                 }
 995
 996                 public bool IsInvalidTime (DateTime dateTime)
 997                 {
 998                         if (dateTime.Kind == DateTimeKind.Utc)
 999                                 return false;
1000                         if (dateTime.Kind == DateTimeKind.Local && this != Local)
1001                                 return false;
1002
1003                         AdjustmentRule rule = GetApplicableRule (dateTime);
1004                         if (rule != null) {
1005                                 DateTime tpoint = TransitionPoint (rule.DaylightTransitionStart, dateTime.Year);
1006                                 if (dateTime >= tpoint && dateTime < tpoint + rule.DaylightDelta)
1007                                         return true;
1008                         }
1009
1010                         return false;
1011                 }
1012
1013                 void IDeserializationCallback.OnDeserialization (object sender)
1014                 {
1015                         try {
1016                                         TimeZoneInfo.Validate (id, baseUtcOffset, adjustmentRules);
1017                                 } catch (ArgumentException ex) {
1018                                         throw new SerializationException ("invalid serialization data", ex);
1019                                 }
1020                 }
1021
1022                 private static void Validate (string id, TimeSpan baseUtcOffset, AdjustmentRule [] adjustmentRules)
1023                 {
1024                         if (id == null)
1025                                 throw new ArgumentNullException ("id");
1026
1027                         if (id == String.Empty)
1028                                 throw new ArgumentException ("id parameter is an empty string");
1029
1030                         if (baseUtcOffset.Ticks % TimeSpan.TicksPerMinute != 0)
1031                                 throw new ArgumentException ("baseUtcOffset parameter does not represent a whole number of minutes");
1032
1033                         if (baseUtcOffset > new TimeSpan (14, 0, 0) || baseUtcOffset < new TimeSpan (-14, 0, 0))
1034                                 throw new ArgumentOutOfRangeException ("baseUtcOffset parameter is greater than 14 hours or less than -14 hours");
1035
1036 #if STRICT
1037                         if (id.Length > 32)
1038                                 throw new ArgumentException ("id parameter shouldn't be longer than 32 characters");
1039 #endif
1040
1041                         if (adjustmentRules != null && adjustmentRules.Length != 0) {
1042                                 AdjustmentRule prev = null;
1043                                 foreach (AdjustmentRule current in adjustmentRules) {
1044                                         if (current == null)
1045                                                 throw new InvalidTimeZoneException ("one or more elements in adjustmentRules are null");
1046
1047                                         if ((baseUtcOffset + current.DaylightDelta < new TimeSpan (-14, 0, 0)) ||
1048                                                         (baseUtcOffset + current.DaylightDelta > new TimeSpan (14, 0, 0)))
1049                                                 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;");
1050
1051                                         if (prev != null && prev.DateStart > current.DateStart)
1052                                                 throw new InvalidTimeZoneException ("adjustment rules specified in adjustmentRules parameter are not in chronological order");
1053
1054                                         if (prev != null && prev.DateEnd > current.DateStart)
1055                                                 throw new InvalidTimeZoneException ("some adjustment rules in the adjustmentRules parameter overlap");
1056
1057                                         if (prev != null && prev.DateEnd == current.DateStart)
1058                                                 throw new InvalidTimeZoneException ("a date can have multiple adjustment rules applied to it");
1059
1060                                         prev = current;
1061                                 }
1062                         }
1063                 }
1064
1065                 public override string ToString ()
1066                 {
1067                         return DisplayName;
1068                 }
1069
1070                 private TimeZoneInfo (SerializationInfo info, StreamingContext context)
1071                 {
1072                         if (info == null)
1073                                 throw new ArgumentNullException ("info");
1074                         id = (string) info.GetValue ("Id", typeof (string));
1075                         displayName = (string) info.GetValue ("DisplayName", typeof (string));
1076                         standardDisplayName = (string) info.GetValue ("StandardName", typeof (string));
1077                         daylightDisplayName = (string) info.GetValue ("DaylightName", typeof (string));
1078                         baseUtcOffset = (TimeSpan) info.GetValue ("BaseUtcOffset", typeof (TimeSpan));
1079                         adjustmentRules = (TimeZoneInfo.AdjustmentRule []) info.GetValue ("AdjustmentRules", typeof (TimeZoneInfo.AdjustmentRule []));
1080                         supportsDaylightSavingTime = (bool) info.GetValue ("SupportsDaylightSavingTime", typeof (bool));
1081                 }
1082
1083                 private TimeZoneInfo (string id, TimeSpan baseUtcOffset, string displayName, string standardDisplayName, string daylightDisplayName, TimeZoneInfo.AdjustmentRule [] adjustmentRules, bool disableDaylightSavingTime)
1084                 {
1085                         if (id == null)
1086                                 throw new ArgumentNullException ("id");
1087
1088                         if (id == String.Empty)
1089                                 throw new ArgumentException ("id parameter is an empty string");
1090
1091                         if (baseUtcOffset.Ticks % TimeSpan.TicksPerMinute != 0)
1092                                 throw new ArgumentException ("baseUtcOffset parameter does not represent a whole number of minutes");
1093
1094                         if (baseUtcOffset > new TimeSpan (14, 0, 0) || baseUtcOffset < new TimeSpan (-14, 0, 0))
1095                                 throw new ArgumentOutOfRangeException ("baseUtcOffset parameter is greater than 14 hours or less than -14 hours");
1096
1097 #if STRICT
1098                         if (id.Length > 32)
1099                                 throw new ArgumentException ("id parameter shouldn't be longer than 32 characters");
1100 #endif
1101
1102                         bool supportsDaylightSavingTime = !disableDaylightSavingTime;
1103
1104                         if (adjustmentRules != null && adjustmentRules.Length != 0) {
1105                                 AdjustmentRule prev = null;
1106                                 foreach (AdjustmentRule current in adjustmentRules) {
1107                                         if (current == null)
1108                                                 throw new InvalidTimeZoneException ("one or more elements in adjustmentRules are null");
1109
1110                                         if ((baseUtcOffset + current.DaylightDelta < new TimeSpan (-14, 0, 0)) ||
1111                                                         (baseUtcOffset + current.DaylightDelta > new TimeSpan (14, 0, 0)))
1112                                                 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;");
1113
1114                                         if (prev != null && prev.DateStart > current.DateStart)
1115                                                 throw new InvalidTimeZoneException ("adjustment rules specified in adjustmentRules parameter are not in chronological order");
1116
1117                                         if (prev != null && prev.DateEnd > current.DateStart)
1118                                                 throw new InvalidTimeZoneException ("some adjustment rules in the adjustmentRules parameter overlap");
1119
1120                                         if (prev != null && prev.DateEnd == current.DateStart)
1121                                                 throw new InvalidTimeZoneException ("a date can have multiple adjustment rules applied to it");
1122
1123                                         prev = current;
1124                                 }
1125                         } else {
1126                                 supportsDaylightSavingTime = false;
1127                         }
1128
1129                         this.id = id;
1130                         this.baseUtcOffset = baseUtcOffset;
1131                         this.displayName = displayName ?? id;
1132                         this.standardDisplayName = standardDisplayName ?? id;
1133                         this.daylightDisplayName = daylightDisplayName;
1134                         this.supportsDaylightSavingTime = supportsDaylightSavingTime;
1135                         this.adjustmentRules = adjustmentRules;
1136                 }
1137
1138                 private AdjustmentRule GetApplicableRule (DateTime dateTime)
1139                 {
1140                         //Applicable rules are in standard time
1141                         DateTime date = dateTime;
1142
1143                         if (dateTime.Kind == DateTimeKind.Local && this != TimeZoneInfo.Local) {
1144                                 if (!TryAddTicks (date.ToUniversalTime (), BaseUtcOffset.Ticks, out date))
1145                                         return null;
1146                         } else if (dateTime.Kind == DateTimeKind.Utc && this != TimeZoneInfo.Utc) {
1147                                 if (!TryAddTicks (date, BaseUtcOffset.Ticks, out date))
1148                                         return null;
1149                         }
1150
1151                         // get the date component of the datetime
1152                         date = date.Date;
1153
1154                         if (adjustmentRules != null) {
1155                                 foreach (AdjustmentRule rule in adjustmentRules) {
1156                                         if (rule.DateStart > date)
1157                                                 return null;
1158                                         if (rule.DateEnd < date)
1159                                                 continue;
1160                                         return rule;
1161                                 }
1162                         }
1163                         return null;
1164                 }
1165
1166                 private bool TryGetTransitionOffset (DateTime dateTime, out TimeSpan offset,out bool isDst)
1167                 {
1168                         offset = BaseUtcOffset;
1169                         isDst = false;
1170
1171                         if (transitions == null)
1172                                 return false;
1173
1174                         //Transitions are in UTC
1175                         DateTime date = dateTime;
1176
1177                         if (dateTime.Kind == DateTimeKind.Local && this != TimeZoneInfo.Local) {
1178                                 if (!TryAddTicks (date.ToUniversalTime (), BaseUtcOffset.Ticks, out date, DateTimeKind.Utc))
1179                                         return false;
1180                         }
1181
1182                         if (dateTime.Kind != DateTimeKind.Utc) {
1183                                 if (!TryAddTicks (date, -BaseUtcOffset.Ticks, out date, DateTimeKind.Utc))
1184                                         return false;
1185                         }
1186
1187                         var inDelta = false;
1188                         for (var i =  transitions.Count - 1; i >= 0; i--) {
1189                                 var pair = transitions [i];
1190                                 DateTime ttime = pair.Key;
1191                                 TimeType ttype = pair.Value;
1192
1193                                 var delta =  new TimeSpan (0, 0, ttype.Offset) - BaseUtcOffset;
1194
1195                                 if ((ttime + delta) > date) {
1196                                         inDelta = ttime <= date;
1197                                         continue;
1198                                 }
1199
1200                                 offset =  new TimeSpan (0, 0, ttype.Offset);
1201                                 if (inDelta) {
1202                                         // Replicate what .NET does when given a time which falls into the hour which is lost when
1203                                         // DST starts. isDST should be true but the offset should be the non-DST offset.
1204                                         isDst = transitions [i - 1].Value.IsDst;
1205                                 } else {
1206                                         isDst = ttype.IsDst;
1207                                 }
1208
1209                                 return true;
1210                         }
1211
1212                         return false;
1213                 }
1214
1215                 private static DateTime TransitionPoint (TransitionTime transition, int year)
1216                 {
1217                         if (transition.IsFixedDateRule)
1218                                 return new DateTime (year, transition.Month, transition.Day) + transition.TimeOfDay.TimeOfDay;
1219
1220                         DayOfWeek first = (new DateTime (year, transition.Month, 1)).DayOfWeek;
1221                         int day = 1 + (transition.Week - 1) * 7 + (transition.DayOfWeek - first + 7) % 7;
1222                         if (day >  DateTime.DaysInMonth (year, transition.Month))
1223                                 day -= 7;
1224                         if (day < 1)
1225                                 day += 7;
1226                         return new DateTime (year, transition.Month, day) + transition.TimeOfDay.TimeOfDay;
1227                 }
1228
1229                 static List<AdjustmentRule> ValidateRules (List<AdjustmentRule> adjustmentRules)
1230                 {
1231                         AdjustmentRule prev = null;
1232                         foreach (AdjustmentRule current in adjustmentRules.ToArray ()) {
1233                                 if (prev != null && prev.DateEnd > current.DateStart) {
1234                                         adjustmentRules.Remove (current);
1235                                 }
1236                                 prev = current;
1237                         }
1238                         return adjustmentRules;
1239                 }
1240
1241 #if LIBC || MONOTOUCH
1242                 const int BUFFER_SIZE = 16384; //Big enough for any tz file (on Oct 2008, all tz files are under 10k)
1243
1244                 private static TimeZoneInfo BuildFromStream (string id, Stream stream)
1245                 {
1246                         byte [] buffer = new byte [BUFFER_SIZE];
1247                         int length = stream.Read (buffer, 0, BUFFER_SIZE);
1248
1249                         if (!ValidTZFile (buffer, length))
1250                                 throw new InvalidTimeZoneException ("TZ file too big for the buffer");
1251
1252                         try {
1253                                 return ParseTZBuffer (id, buffer, length);
1254                         } catch (InvalidTimeZoneException) {
1255                                 throw;
1256                         } catch (Exception e) {
1257                                 throw new InvalidTimeZoneException ("Time zone information file contains invalid data", e);
1258                         }
1259                 }
1260
1261                 private static bool ValidTZFile (byte [] buffer, int length)
1262                 {
1263                         StringBuilder magic = new StringBuilder ();
1264
1265                         for (int i = 0; i < 4; i++)
1266                                 magic.Append ((char)buffer [i]);
1267
1268                         if (magic.ToString () != "TZif")
1269                                 return false;
1270
1271                         if (length >= BUFFER_SIZE)
1272                                 return false;
1273
1274                         return true;
1275                 }
1276
1277                 static int SwapInt32 (int i)
1278                 {
1279                         return (((i >> 24) & 0xff)
1280                                 | ((i >> 8) & 0xff00)
1281                                 | ((i << 8) & 0xff0000)
1282                                 | (((i & 0xff) << 24)));
1283                 }
1284
1285                 static int ReadBigEndianInt32 (byte [] buffer, int start)
1286                 {
1287                         int i = BitConverter.ToInt32 (buffer, start);
1288                         if (!BitConverter.IsLittleEndian)
1289                                 return i;
1290
1291                         return SwapInt32 (i);
1292                 }
1293
1294                 private static TimeZoneInfo ParseTZBuffer (string id, byte [] buffer, int length)
1295                 {
1296                         //Reading the header. 4 bytes for magic, 16 are reserved
1297                         int ttisgmtcnt = ReadBigEndianInt32 (buffer, 20);
1298                         int ttisstdcnt = ReadBigEndianInt32 (buffer, 24);
1299                         int leapcnt = ReadBigEndianInt32 (buffer, 28);
1300                         int timecnt = ReadBigEndianInt32 (buffer, 32);
1301                         int typecnt = ReadBigEndianInt32 (buffer, 36);
1302                         int charcnt = ReadBigEndianInt32 (buffer, 40);
1303
1304                         if (length < 44 + timecnt * 5 + typecnt * 6 + charcnt + leapcnt * 8 + ttisstdcnt + ttisgmtcnt)
1305                                 throw new InvalidTimeZoneException ();
1306
1307                         Dictionary<int, string> abbreviations = ParseAbbreviations (buffer, 44 + 4 * timecnt + timecnt + 6 * typecnt, charcnt);
1308                         Dictionary<int, TimeType> time_types = ParseTimesTypes (buffer, 44 + 4 * timecnt + timecnt, typecnt, abbreviations);
1309                         List<KeyValuePair<DateTime, TimeType>> transitions = ParseTransitions (buffer, 44, timecnt, time_types);
1310
1311                         if (time_types.Count == 0)
1312                                 throw new InvalidTimeZoneException ();
1313
1314                         if (time_types.Count == 1 && time_types[0].IsDst)
1315                                 throw new InvalidTimeZoneException ();
1316
1317                         TimeSpan baseUtcOffset = new TimeSpan (0);
1318                         TimeSpan dstDelta = new TimeSpan (0);
1319                         string standardDisplayName = null;
1320                         string daylightDisplayName = null;
1321                         bool dst_observed = false;
1322                         DateTime dst_start = DateTime.MinValue;
1323                         List<AdjustmentRule> adjustmentRules = new List<AdjustmentRule> ();
1324                         bool storeTransition = false;
1325
1326                         for (int i = 0; i < transitions.Count; i++) {
1327                                 var pair = transitions [i];
1328                                 DateTime ttime = pair.Key;
1329                                 TimeType ttype = pair.Value;
1330                                 if (!ttype.IsDst) {
1331                                         if (standardDisplayName != ttype.Name)
1332                                                 standardDisplayName = ttype.Name;
1333                                         if (baseUtcOffset.TotalSeconds != ttype.Offset) {
1334                                                 baseUtcOffset = new TimeSpan (0, 0, ttype.Offset);
1335                                                 if (adjustmentRules.Count > 0) // We ignore AdjustmentRules but store transitions.
1336                                                         storeTransition = true;
1337                                                 adjustmentRules = new List<AdjustmentRule> ();
1338                                                 dst_observed = false;
1339                                         }
1340                                         if (dst_observed) {
1341                                                 //FIXME: check additional fields for this:
1342                                                 //most of the transitions are expressed in GMT
1343                                                 dst_start += baseUtcOffset;
1344                                                 DateTime dst_end = ttime + baseUtcOffset + dstDelta;
1345
1346                                                 //some weird timezone (America/Phoenix) have end dates on Jan 1st
1347                                                 if (dst_end.Date == new DateTime (dst_end.Year, 1, 1) && dst_end.Year > dst_start.Year)
1348                                                         dst_end -= new TimeSpan (24, 0, 0);
1349
1350                                                 /*
1351                                                  * AdjustmentRule specifies a DST period that starts and ends within a year.
1352                                                  * When we have a DST period longer than a year, the generated AdjustmentRule may not be usable.
1353                                                  * Thus we fallback to the transitions.
1354                                                  */
1355                                                 if (dst_start.AddYears (1) < dst_end)
1356                                                         storeTransition = true;
1357
1358                                                 DateTime dateStart, dateEnd;
1359                                                 if (dst_start.Month < 7)
1360                                                         dateStart = new DateTime (dst_start.Year, 1, 1);
1361                                                 else
1362                                                         dateStart = new DateTime (dst_start.Year, 7, 1);
1363
1364                                                 if (dst_end.Month >= 7)
1365                                                         dateEnd = new DateTime (dst_end.Year, 12, 31);
1366                                                 else
1367                                                         dateEnd = new DateTime (dst_end.Year, 6, 30);
1368
1369
1370                                                 TransitionTime transition_start = TransitionTime.CreateFixedDateRule (new DateTime (1, 1, 1) + dst_start.TimeOfDay, dst_start.Month, dst_start.Day);
1371                                                 TransitionTime transition_end = TransitionTime.CreateFixedDateRule (new DateTime (1, 1, 1) + dst_end.TimeOfDay, dst_end.Month, dst_end.Day);
1372                                                 if  (transition_start != transition_end) //y, that happened in Argentina in 1943-1946
1373                                                         adjustmentRules.Add (AdjustmentRule.CreateAdjustmentRule (dateStart, dateEnd, dstDelta, transition_start, transition_end));
1374                                         }
1375                                         dst_observed = false;
1376                                 } else {
1377                                         if (daylightDisplayName != ttype.Name)
1378                                                 daylightDisplayName = ttype.Name;
1379                                         if (dstDelta.TotalSeconds != ttype.Offset - baseUtcOffset.TotalSeconds) {
1380                                                 // Round to nearest minute, since it's not possible to create an adjustment rule
1381                                                 // with sub-minute precision ("The TimeSpan parameter cannot be specified more precisely than whole minutes.")
1382                                                 // This happens for instance with Europe/Dublin, which had an offset of 34 minutes and 39 seconds in 1916.
1383                                                 dstDelta = new TimeSpan (0, 0, ttype.Offset) - baseUtcOffset;
1384                                                 if (dstDelta.Ticks % TimeSpan.TicksPerMinute != 0)
1385                                                         dstDelta = TimeSpan.FromMinutes ((long) (dstDelta.TotalMinutes + 0.5f));
1386                                         }
1387
1388                                         dst_start = ttime;
1389                                         dst_observed = true;
1390                                 }
1391                         }
1392
1393                         TimeZoneInfo tz;
1394                         if (adjustmentRules.Count == 0 && !storeTransition) {
1395                                 if (standardDisplayName == null) {
1396                                         var t = time_types [0];
1397                                         standardDisplayName = t.Name;
1398                                         baseUtcOffset = new TimeSpan (0, 0, t.Offset);
1399                                 }
1400                                 tz = CreateCustomTimeZone (id, baseUtcOffset, id, standardDisplayName);
1401                         } else {
1402                                 tz = CreateCustomTimeZone (id, baseUtcOffset, id, standardDisplayName, daylightDisplayName, ValidateRules (adjustmentRules).ToArray ());
1403                         }
1404
1405                         if (storeTransition && transitions.Count > 0) {
1406                                 tz.transitions = transitions;
1407                                 tz.supportsDaylightSavingTime = true;
1408                         }
1409
1410                         return tz;
1411                 }
1412
1413                 static Dictionary<int, string> ParseAbbreviations (byte [] buffer, int index, int count)
1414                 {
1415                         var abbrevs = new Dictionary<int, string> ();
1416                         int abbrev_index = 0;
1417                         var sb = new StringBuilder ();
1418                         for (int i = 0; i < count; i++) {
1419                                 char c = (char) buffer [index + i];
1420                                 if (c != '\0')
1421                                         sb.Append (c);
1422                                 else {
1423                                         abbrevs.Add (abbrev_index, sb.ToString ());
1424                                         //Adding all the substrings too, as it seems to be used, at least for Africa/Windhoek
1425                                         //j == sb.Length empty substring also needs to be added #31432
1426                                         for (int j = 1; j <= sb.Length; j++)
1427                                                 abbrevs.Add (abbrev_index + j, sb.ToString (j, sb.Length - j));
1428                                         abbrev_index = i + 1;
1429                                         sb = new StringBuilder ();
1430                                 }
1431                         }
1432                         return abbrevs;
1433                 }
1434
1435                 static Dictionary<int, TimeType> ParseTimesTypes (byte [] buffer, int index, int count, Dictionary<int, string> abbreviations)
1436                 {
1437                         var types = new Dictionary<int, TimeType> (count);
1438                         for (int i = 0; i < count; i++) {
1439                                 int offset = ReadBigEndianInt32 (buffer, index + 6 * i);
1440
1441                                 //
1442                                 // The official tz database contains timezone with GMT offsets
1443                                 // not only in whole hours/minutes but in seconds. This happens for years
1444                                 // before 1901. For example
1445                                 //
1446                                 // NAME                 GMTOFF   RULES  FORMAT  UNTIL
1447                                 // Europe/Madrid        -0:14:44 -      LMT     1901 Jan  1  0:00s
1448                                 //
1449                                 // .NET as of 4.6.2 cannot handle that and uses hours/minutes only, so
1450                                 // we remove seconds to not crash later
1451                                 //
1452                                 offset = (offset / 60) * 60;
1453
1454                                 byte is_dst = buffer [index + 6 * i + 4];
1455                                 byte abbrev = buffer [index + 6 * i + 5];
1456                                 types.Add (i, new TimeType (offset, (is_dst != 0), abbreviations [(int)abbrev]));
1457                         }
1458                         return types;
1459                 }
1460
1461                 static List<KeyValuePair<DateTime, TimeType>> ParseTransitions (byte [] buffer, int index, int count, Dictionary<int, TimeType> time_types)
1462                 {
1463                         var list = new List<KeyValuePair<DateTime, TimeType>> (count);
1464                         for (int i = 0; i < count; i++) {
1465                                 int unixtime = ReadBigEndianInt32 (buffer, index + 4 * i);
1466                                 DateTime ttime = DateTimeFromUnixTime (unixtime);
1467                                 byte ttype = buffer [index + 4 * count + i];
1468                                 list.Add (new KeyValuePair<DateTime, TimeType> (ttime, time_types [(int)ttype]));
1469                         }
1470                         return list;
1471                 }
1472
1473                 static DateTime DateTimeFromUnixTime (long unix_time)
1474                 {
1475                         DateTime date_time = new DateTime (1970, 1, 1);
1476                         return date_time.AddSeconds (unix_time);
1477                 }
1478
1479 #region reference sources
1480                 // Shortcut for TimeZoneInfo.Local.GetUtcOffset
1481                 internal static TimeSpan GetLocalUtcOffset(DateTime dateTime, TimeZoneInfoOptions flags)
1482                 {
1483                         bool dst;
1484                         return Local.GetUtcOffset (dateTime, out dst);
1485                 }
1486
1487                 internal TimeSpan GetUtcOffset(DateTime dateTime, TimeZoneInfoOptions flags)
1488                 {
1489                         bool dst;
1490                         return GetUtcOffset (dateTime, out dst);
1491                 }
1492
1493                 static internal TimeSpan GetUtcOffsetFromUtc (DateTime time, TimeZoneInfo zone, out Boolean isDaylightSavings, out Boolean isAmbiguousLocalDst)
1494                 {
1495                         isDaylightSavings = false;
1496                         isAmbiguousLocalDst = false;
1497                         TimeSpan baseOffset = zone.BaseUtcOffset;
1498
1499                         if (zone.IsAmbiguousTime (time)) {
1500                                 isAmbiguousLocalDst = true;
1501                                 return baseOffset;
1502                         }
1503
1504                         return zone.GetUtcOffset (time, out isDaylightSavings);
1505                 }
1506 #endregion
1507         }
1508
1509         class TimeType {
1510                 public readonly int Offset;
1511                 public readonly bool IsDst;
1512                 public string Name;
1513
1514                 public TimeType (int offset, bool is_dst, string abbrev)
1515                 {
1516                         this.Offset = offset;
1517                         this.IsDst = is_dst;
1518                         this.Name = abbrev;
1519                 }
1520
1521                 public override string ToString ()
1522                 {
1523                         return "offset: " + Offset + "s, is_dst: " + IsDst + ", zone name: " + Name;
1524                 }
1525 #else
1526         }
1527 #endif
1528         }
1529 }