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]) && 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                         return ConvertTime (dateTime, FindSystemTimeZoneById (sourceTimeZoneId), FindSystemTimeZoneById (destinationTimeZoneId));
 416                 }
 417
 418                 public static DateTimeOffset ConvertTimeBySystemTimeZoneId (DateTimeOffset dateTimeOffset, string destinationTimeZoneId)
 419                 {
 420                         return ConvertTime (dateTimeOffset, FindSystemTimeZoneById (destinationTimeZoneId));
 421                 }
 422
 423                 private DateTime ConvertTimeFromUtc (DateTime dateTime)
 424                 {
 425                         if (dateTime.Kind == DateTimeKind.Local)
 426                                 throw new ArgumentException ("Kind property of dateTime is Local");
 427
 428                         if (this == TimeZoneInfo.Utc)
 429                                 return DateTime.SpecifyKind (dateTime, DateTimeKind.Utc);
 430
 431                         var utcOffset = GetUtcOffset (dateTime);
 432
 433                         var kind = (this == TimeZoneInfo.Local)? DateTimeKind.Local : DateTimeKind.Unspecified;
 434
 435                         DateTime result;
 436                         if (!TryAddTicks (dateTime, utcOffset.Ticks, out result, kind))
 437                                 return DateTime.SpecifyKind (DateTime.MaxValue, kind);
 438
 439                         return result;
 440                 }
 441
 442                 public static DateTime ConvertTimeFromUtc (DateTime dateTime, TimeZoneInfo destinationTimeZone)
 443                 {
 444                         if (destinationTimeZone == null)
 445                                 throw new ArgumentNullException ("destinationTimeZone");
 446
 447                         return destinationTimeZone.ConvertTimeFromUtc (dateTime);
 448                 }
 449
 450                 public static DateTime ConvertTimeToUtc (DateTime dateTime)
 451                 {
 452                         if (dateTime.Kind == DateTimeKind.Utc)
 453                                 return dateTime;
 454
 455                         return ConvertTimeToUtc (dateTime, TimeZoneInfo.Local);
 456                 }
 457
 458                 static internal DateTime ConvertTimeToUtc(DateTime dateTime, TimeZoneInfoOptions flags)
 459                 {
 460                         return ConvertTimeToUtc (dateTime, TimeZoneInfo.Local, flags);
 461                 }
 462
 463                 public static DateTime ConvertTimeToUtc (DateTime dateTime, TimeZoneInfo sourceTimeZone)
 464                 {
 465                         return ConvertTimeToUtc (dateTime, sourceTimeZone, TimeZoneInfoOptions.None);
 466                 }
 467
 468                 static DateTime ConvertTimeToUtc (DateTime dateTime, TimeZoneInfo sourceTimeZone, TimeZoneInfoOptions flags)
 469                 {
 470                         if ((flags & TimeZoneInfoOptions.NoThrowOnInvalidTime) == 0) {
 471                                 if (sourceTimeZone == null)
 472                                         throw new ArgumentNullException ("sourceTimeZone");
 473
 474                                 if (dateTime.Kind == DateTimeKind.Utc && sourceTimeZone != TimeZoneInfo.Utc)
 475                                         throw new ArgumentException ("Kind property of dateTime is Utc but the sourceTimeZone does not equal TimeZoneInfo.Utc");
 476
 477                                 if (dateTime.Kind == DateTimeKind.Local && sourceTimeZone != TimeZoneInfo.Local)
 478                                         throw new ArgumentException ("Kind property of dateTime is Local but the sourceTimeZone does not equal TimeZoneInfo.Local");
 479
 480                                 if (sourceTimeZone.IsInvalidTime (dateTime))
 481                                         throw new ArgumentException ("dateTime parameter is an invalid time");
 482                         }
 483
 484                         if (dateTime.Kind == DateTimeKind.Utc)
 485                                 return dateTime;
 486
 487                         bool isDst;
 488                         var utcOffset = sourceTimeZone.GetUtcOffset (dateTime, out isDst);
 489
 490                         DateTime utcDateTime;
 491                         TryAddTicks (dateTime, -utcOffset.Ticks, out utcDateTime, DateTimeKind.Utc);
 492                         return utcDateTime;
 493                 }
 494
 495                 static internal TimeSpan GetDateTimeNowUtcOffsetFromUtc(DateTime time, out Boolean isAmbiguousLocalDst)
 496                 {
 497                         bool isDaylightSavings;
 498                         return GetUtcOffsetFromUtc(time, TimeZoneInfo.Local, out isDaylightSavings, out isAmbiguousLocalDst);
 499                 }
 500
 501                 public static TimeZoneInfo CreateCustomTimeZone (string id, TimeSpan baseUtcOffset, string displayName, string standardDisplayName)
 502                 {
 503                         return CreateCustomTimeZone (id, baseUtcOffset, displayName, standardDisplayName, null, null, true);
 504                 }
 505
 506                 public static TimeZoneInfo CreateCustomTimeZone (string id, TimeSpan baseUtcOffset, string displayName, string standardDisplayName, string daylightDisplayName, TimeZoneInfo.AdjustmentRule [] adjustmentRules)
 507                 {
 508                         return CreateCustomTimeZone (id, baseUtcOffset, displayName, standardDisplayName, daylightDisplayName, adjustmentRules, false);
 509                 }
 510
 511                 public static TimeZoneInfo CreateCustomTimeZone ( string id, TimeSpan baseUtcOffset, string displayName, string standardDisplayName, string daylightDisplayName, TimeZoneInfo.AdjustmentRule [] adjustmentRules, bool disableDaylightSavingTime)
 512                 {
 513                         return new TimeZoneInfo (id, baseUtcOffset, displayName, standardDisplayName, daylightDisplayName, adjustmentRules, disableDaylightSavingTime);
 514                 }
 515
 516                 public override bool Equals (object obj)
 517                 {
 518                         return Equals (obj as TimeZoneInfo);
 519                 }
 520
 521                 public bool Equals (TimeZoneInfo other)
 522                 {
 523                         if (other == null)
 524                                 return false;
 525
 526                         return other.Id == this.Id && HasSameRules (other);
 527                 }
 528
 529                 public static TimeZoneInfo FindSystemTimeZoneById (string id)
 530                 {
 531                         //FIXME: this method should check for cached values in systemTimeZones
 532                         if (id == null)
 533                                 throw new ArgumentNullException ("id");
 534 #if !NET_2_1
 535                         if (TimeZoneKey != null)
 536                         {
 537                                 if (id == "Coordinated Universal Time")
 538                                         id = "UTC"; //windows xp exception for "StandardName" property
 539                                 RegistryKey key = TimeZoneKey.OpenSubKey (id, false);
 540                                 if (key == null)
 541                                         throw new TimeZoneNotFoundException ();
 542                                 return FromRegistryKey(id, key);
 543                         }
 544 #endif
 545                         // Local requires special logic that already exists in the Local property (bug #326)
 546                         if (id == "Local")
 547                                 return Local;
 548
 549                         return FindSystemTimeZoneByIdCore (id);
 550                 }
 551
 552 #if LIBC
 553                 private static TimeZoneInfo FindSystemTimeZoneByFileName (string id, string filepath)
 554                 {
 555                         if (!File.Exists (filepath))
 556                                 throw new TimeZoneNotFoundException ();
 557
 558                         using (FileStream stream = File.OpenRead (filepath)) {
 559                                 return BuildFromStream (id, stream);
 560                         }
 561                 }
 562 #endif
 563
 564 #if !NET_2_1
 565                 private static TimeZoneInfo FromRegistryKey (string id, RegistryKey key)
 566                 {
 567                         byte [] reg_tzi = (byte []) key.GetValue ("TZI");
 568
 569                         if (reg_tzi == null)
 570                                 throw new InvalidTimeZoneException ();
 571
 572                         int bias = BitConverter.ToInt32 (reg_tzi, 0);
 573                         TimeSpan baseUtcOffset = new TimeSpan (0, -bias, 0);
 574
 575                         string display_name = (string) key.GetValue ("Display");
 576                         string standard_name = (string) key.GetValue ("Std");
 577                         string daylight_name = (string) key.GetValue ("Dlt");
 578
 579                         List<AdjustmentRule> adjustmentRules = new List<AdjustmentRule> ();
 580
 581                         RegistryKey dst_key = key.OpenSubKey ("Dynamic DST", false);
 582                         if (dst_key != null) {
 583                                 int first_year = (int) dst_key.GetValue ("FirstEntry");
 584                                 int last_year = (int) dst_key.GetValue ("LastEntry");
 585                                 int year;
 586
 587                                 for (year=first_year; year<=last_year; year++) {
 588                                         byte [] dst_tzi = (byte []) dst_key.GetValue (year.ToString ());
 589                                         if (dst_tzi != null) {
 590                                                 int start_year = year == first_year ? 1 : year;
 591                                                 int end_year = year == last_year ? 9999 : year;
 592                                                 ParseRegTzi(adjustmentRules, start_year, end_year, dst_tzi);
 593                                         }
 594                                 }
 595                         }
 596                         else
 597                                 ParseRegTzi(adjustmentRules, 1, 9999, reg_tzi);
 598
 599                         return CreateCustomTimeZone (id, baseUtcOffset, display_name, standard_name, daylight_name, ValidateRules (adjustmentRules).ToArray ());
 600                 }
 601
 602                 private static void ParseRegTzi (List<AdjustmentRule> adjustmentRules, int start_year, int end_year, byte [] buffer)
 603                 {
 604                         //int standard_bias = BitConverter.ToInt32 (buffer, 4); /* not sure how to handle this */
 605                         int daylight_bias = BitConverter.ToInt32 (buffer, 8);
 606
 607                         int standard_year = BitConverter.ToInt16 (buffer, 12);
 608                         int standard_month = BitConverter.ToInt16 (buffer, 14);
 609                         int standard_dayofweek = BitConverter.ToInt16 (buffer, 16);
 610                         int standard_day = BitConverter.ToInt16 (buffer, 18);
 611                         int standard_hour = BitConverter.ToInt16 (buffer, 20);
 612                         int standard_minute = BitConverter.ToInt16 (buffer, 22);
 613                         int standard_second = BitConverter.ToInt16 (buffer, 24);
 614                         int standard_millisecond = BitConverter.ToInt16 (buffer, 26);
 615
 616                         int daylight_year = BitConverter.ToInt16 (buffer, 28);
 617                         int daylight_month = BitConverter.ToInt16 (buffer, 30);
 618                         int daylight_dayofweek = BitConverter.ToInt16 (buffer, 32);
 619                         int daylight_day = BitConverter.ToInt16 (buffer, 34);
 620                         int daylight_hour = BitConverter.ToInt16 (buffer, 36);
 621                         int daylight_minute = BitConverter.ToInt16 (buffer, 38);
 622                         int daylight_second = BitConverter.ToInt16 (buffer, 40);
 623                         int daylight_millisecond = BitConverter.ToInt16 (buffer, 42);
 624
 625                         if (standard_month == 0 || daylight_month == 0)
 626                                 return;
 627
 628                         DateTime start_date;
 629                         DateTime start_timeofday = new DateTime (1, 1, 1, daylight_hour, daylight_minute, daylight_second, daylight_millisecond);
 630                         TransitionTime start_transition_time;
 631
 632                         if (daylight_year == 0) {
 633                                 start_date = new DateTime (start_year, 1, 1);
 634                                 start_transition_time = TransitionTime.CreateFloatingDateRule (
 635                                         start_timeofday, daylight_month, daylight_day,
 636                                         (DayOfWeek) daylight_dayofweek);
 637                         }
 638                         else {
 639                                 start_date = new DateTime (daylight_year, daylight_month, daylight_day,
 640                                         daylight_hour, daylight_minute, daylight_second, daylight_millisecond);
 641                                 start_transition_time = TransitionTime.CreateFixedDateRule (
 642                                         start_timeofday, daylight_month, daylight_day);
 643                         }
 644
 645                         DateTime end_date;
 646                         DateTime end_timeofday = new DateTime (1, 1, 1, standard_hour, standard_minute, standard_second, standard_millisecond);
 647                         TransitionTime end_transition_time;
 648
 649                         if (standard_year == 0) {
 650                                 end_date = new DateTime (end_year, 12, 31);
 651                                 end_transition_time = TransitionTime.CreateFloatingDateRule (
 652                                         end_timeofday, standard_month, standard_day,
 653                                         (DayOfWeek) standard_dayofweek);
 654                         }
 655                         else {
 656                                 end_date = new DateTime (standard_year, standard_month, standard_day,
 657                                         standard_hour, standard_minute, standard_second, standard_millisecond);
 658                                 end_transition_time = TransitionTime.CreateFixedDateRule (
 659                                         end_timeofday, standard_month, standard_day);
 660                         }
 661
 662                         TimeSpan daylight_delta = new TimeSpan(0, -daylight_bias, 0);
 663
 664                         adjustmentRules.Add (AdjustmentRule.CreateAdjustmentRule (
 665                                 start_date, end_date, daylight_delta,
 666                                 start_transition_time, end_transition_time));
 667                 }
 668 #endif
 669
 670                 public AdjustmentRule [] GetAdjustmentRules ()
 671                 {
 672                         if (!supportsDaylightSavingTime || adjustmentRules == null)
 673                                 return new AdjustmentRule [0];
 674                         else
 675                                 return (AdjustmentRule []) adjustmentRules.Clone ();
 676                 }
 677
 678                 public TimeSpan [] GetAmbiguousTimeOffsets (DateTime dateTime)
 679                 {
 680                         if (!IsAmbiguousTime (dateTime))
 681                                 throw new ArgumentException ("dateTime is not an ambiguous time");
 682
 683                         AdjustmentRule rule = GetApplicableRule (dateTime);
 684                         if (rule != null)
 685                                 return new TimeSpan[] {baseUtcOffset, baseUtcOffset + rule.DaylightDelta};
 686                         else
 687                                 return new TimeSpan[] {baseUtcOffset, baseUtcOffset};
 688                 }
 689
 690                 public TimeSpan [] GetAmbiguousTimeOffsets (DateTimeOffset dateTimeOffset)
 691                 {
 692                         if (!IsAmbiguousTime (dateTimeOffset))
 693                                 throw new ArgumentException ("dateTimeOffset is not an ambiguous time");
 694
 695                         throw new NotImplementedException ();
 696                 }
 697
 698                 public override int GetHashCode ()
 699                 {
 700                         int hash_code = Id.GetHashCode ();
 701                         foreach (AdjustmentRule rule in GetAdjustmentRules ())
 702                                 hash_code ^= rule.GetHashCode ();
 703                         return hash_code;
 704                 }
 705
 706                 void ISerializable.GetObjectData (SerializationInfo info, StreamingContext context)
 707                 {
 708                         if (info == null)
 709                                 throw new ArgumentNullException ("info");
 710                         info.AddValue ("Id", id);
 711                         info.AddValue ("DisplayName", displayName);
 712                         info.AddValue ("StandardName", standardDisplayName);
 713                         info.AddValue ("DaylightName", daylightDisplayName);
 714                         info.AddValue ("BaseUtcOffset", baseUtcOffset);
 715                         info.AddValue ("AdjustmentRules", adjustmentRules);
 716                         info.AddValue ("SupportsDaylightSavingTime", SupportsDaylightSavingTime);
 717                 }
 718
 719                 static ReadOnlyCollection<TimeZoneInfo> systemTimeZones;
 720
 721                 public static ReadOnlyCollection<TimeZoneInfo> GetSystemTimeZones ()
 722                 {
 723                         if (systemTimeZones == null) {
 724                                 var tz = new List<TimeZoneInfo> ();
 725                                 GetSystemTimeZonesCore (tz);
 726                                 Interlocked.CompareExchange (ref systemTimeZones, new ReadOnlyCollection<TimeZoneInfo> (tz), null);
 727                         }
 728
 729                         return systemTimeZones;
 730                 }
 731
 732                 public TimeSpan GetUtcOffset (DateTime dateTime)
 733                 {
 734                         bool isDST;
 735                         return GetUtcOffset (dateTime, out isDST);
 736                 }
 737
 738                 public TimeSpan GetUtcOffset (DateTimeOffset dateTimeOffset)
 739                 {
 740                         bool isDST;
 741                         return GetUtcOffset (dateTimeOffset.UtcDateTime, out isDST);
 742                 }
 743
 744                 private TimeSpan GetUtcOffset (DateTime dateTime, out bool isDST)
 745                 {
 746                         isDST = false;
 747
 748                         TimeZoneInfo tz = this;
 749                         if (dateTime.Kind == DateTimeKind.Utc)
 750                                 tz = TimeZoneInfo.Utc;
 751
 752                         if (dateTime.Kind == DateTimeKind.Local)
 753                                 tz = TimeZoneInfo.Local;
 754
 755                         bool isTzDst;
 756                         var tzOffset = GetUtcOffsetHelper (dateTime, tz, out isTzDst);
 757
 758                         if (tz == this) {
 759                                 isDST = isTzDst;
 760                                 return tzOffset;
 761                         }
 762
 763                         DateTime utcDateTime;
 764                         if (!TryAddTicks (dateTime, -tzOffset.Ticks, out utcDateTime, DateTimeKind.Utc))
 765                                 return BaseUtcOffset;
 766
 767                         return GetUtcOffsetHelper (utcDateTime, this, out isDST);
 768                 }
 769
 770                 // This is an helper method used by the method above, do not use this on its own.
 771                 private static TimeSpan GetUtcOffsetHelper (DateTime dateTime, TimeZoneInfo tz, out bool isDST)
 772                 {
 773                         if (dateTime.Kind == DateTimeKind.Local && tz != TimeZoneInfo.Local)
 774                                 throw new Exception ();
 775
 776                         isDST = false;
 777
 778                         if (tz == TimeZoneInfo.Utc)
 779                                 return TimeSpan.Zero;
 780
 781                         TimeSpan offset;
 782                         if (tz.TryGetTransitionOffset(dateTime, out offset, out isDST))
 783                                 return offset;
 784
 785                         if (dateTime.Kind == DateTimeKind.Utc) {
 786                                 var utcRule = tz.GetApplicableRule (dateTime);
 787                                 if (utcRule != null && tz.IsInDST (utcRule, dateTime)) {
 788                                         isDST = true;
 789                                         return tz.BaseUtcOffset + utcRule.DaylightDelta;
 790                                 }
 791
 792                                 return tz.BaseUtcOffset;
 793                         }
 794
 795                         DateTime stdUtcDateTime;
 796                         if (!TryAddTicks (dateTime, -tz.BaseUtcOffset.Ticks, out stdUtcDateTime, DateTimeKind.Utc))
 797                                 return tz.BaseUtcOffset;
 798
 799                         var tzRule = tz.GetApplicableRule (stdUtcDateTime);
 800
 801                         DateTime dstUtcDateTime = DateTime.MinValue;
 802                         if (tzRule != null) {
 803                                 if (!TryAddTicks (stdUtcDateTime, -tzRule.DaylightDelta.Ticks, out dstUtcDateTime, DateTimeKind.Utc))
 804                                         return tz.BaseUtcOffset;
 805                         }
 806
 807                         if (tzRule != null && tz.IsInDST (tzRule, stdUtcDateTime) && tz.IsInDST (tzRule, dstUtcDateTime)) {
 808                                 isDST = true;
 809                                 return tz.BaseUtcOffset + tzRule.DaylightDelta;
 810                         }
 811
 812                         return tz.BaseUtcOffset;
 813                 }
 814
 815                 public bool HasSameRules (TimeZoneInfo other)
 816                 {
 817                         if (other == null)
 818                                 throw new ArgumentNullException ("other");
 819
 820                         if ((this.adjustmentRules == null) != (other.adjustmentRules == null))
 821                                 return false;
 822
 823                         if (this.adjustmentRules == null)
 824                                 return true;
 825
 826                         if (this.BaseUtcOffset != other.BaseUtcOffset)
 827                                 return false;
 828
 829                         if (this.adjustmentRules.Length != other.adjustmentRules.Length)
 830                                 return false;
 831
 832                         for (int i = 0; i < adjustmentRules.Length; i++) {
 833                                 if (! (this.adjustmentRules [i]).Equals (other.adjustmentRules [i]))
 834                                         return false;
 835                         }
 836
 837                         return true;
 838                 }
 839
 840                 public bool IsAmbiguousTime (DateTime dateTime)
 841                 {
 842                         if (dateTime.Kind == DateTimeKind.Local && IsInvalidTime (dateTime))
 843                                 throw new ArgumentException ("Kind is Local and time is Invalid");
 844
 845                         if (this == TimeZoneInfo.Utc)
 846                                 return false;
 847
 848                         if (dateTime.Kind == DateTimeKind.Utc)
 849                                 dateTime = ConvertTimeFromUtc (dateTime);
 850
 851                         if (dateTime.Kind == DateTimeKind.Local && this != TimeZoneInfo.Local)
 852                                 dateTime = ConvertTime (dateTime, TimeZoneInfo.Local, this);
 853
 854                         AdjustmentRule rule = GetApplicableRule (dateTime);
 855                         if (rule != null) {
 856                                 DateTime tpoint = TransitionPoint (rule.DaylightTransitionEnd, dateTime.Year);
 857                                 if (dateTime > tpoint - rule.DaylightDelta  && dateTime <= tpoint)
 858                                         return true;
 859                         }
 860
 861                         return false;
 862                 }
 863
 864                 public bool IsAmbiguousTime (DateTimeOffset dateTimeOffset)
 865                 {
 866                         throw new NotImplementedException ();
 867                 }
 868
 869                 private bool IsInDST (AdjustmentRule rule, DateTime dateTime)
 870                 {
 871                         // Check whether we're in the dateTime year's DST period
 872                         if (IsInDSTForYear (rule, dateTime, dateTime.Year))
 873                                 return true;
 874
 875                         // We might be in the dateTime previous year's DST period
 876                         return IsInDSTForYear (rule, dateTime, dateTime.Year - 1);
 877                 }
 878
 879                 bool IsInDSTForYear (AdjustmentRule rule, DateTime dateTime, int year)
 880                 {
 881                         DateTime DST_start = TransitionPoint (rule.DaylightTransitionStart, year);
 882                         DateTime DST_end = TransitionPoint (rule.DaylightTransitionEnd, year + ((rule.DaylightTransitionStart.Month < rule.DaylightTransitionEnd.Month) ? 0 : 1));
 883                         if (dateTime.Kind == DateTimeKind.Utc) {
 884                                 DST_start -= BaseUtcOffset;
 885                                 DST_end -= (BaseUtcOffset + rule.DaylightDelta);
 886                         }
 887
 888                         return (dateTime >= DST_start && dateTime < DST_end);
 889                 }
 890
 891                 public bool IsDaylightSavingTime (DateTime dateTime)
 892                 {
 893                         if (dateTime.Kind == DateTimeKind.Local && IsInvalidTime (dateTime))
 894                                 throw new ArgumentException ("dateTime is invalid and Kind is Local");
 895
 896                         if (this == TimeZoneInfo.Utc)
 897                                 return false;
 898
 899                         if (!SupportsDaylightSavingTime)
 900                                 return false;
 901
 902                         bool isDst;
 903                         GetUtcOffset (dateTime, out isDst);
 904
 905                         return isDst;
 906                 }
 907
 908                 internal bool IsDaylightSavingTime (DateTime dateTime, TimeZoneInfoOptions flags)
 909                 {
 910                         return IsDaylightSavingTime (dateTime);
 911                 }
 912
 913                 public bool IsDaylightSavingTime (DateTimeOffset dateTimeOffset)
 914                 {
 915                         throw new NotImplementedException ();
 916                 }
 917
 918                 internal DaylightTime GetDaylightChanges (int year)
 919                 {
 920                         DateTime start = DateTime.MinValue, end = DateTime.MinValue;
 921                         TimeSpan delta = new TimeSpan ();
 922
 923                         if (transitions != null) {
 924                                 end = DateTime.MaxValue;
 925                                 for (var i =  transitions.Count - 1; i >= 0; i--) {
 926                                         var pair = transitions [i];
 927                                         DateTime ttime = pair.Key;
 928                                         TimeType ttype = pair.Value;
 929
 930                                         if (ttime.Year > year)
 931                                                 continue;
 932                                         if (ttime.Year < year)
 933                                                 break;
 934
 935                                         if (ttype.IsDst) {
 936                                                 // DaylightTime.Delta is relative to the current BaseUtcOffset.
 937                                                 delta =  new TimeSpan (0, 0, ttype.Offset) - BaseUtcOffset;
 938                                                 start = ttime;
 939                                         } else {
 940                                                 end = ttime;
 941                                         }
 942                                 }
 943
 944                                 // DaylightTime.Start is relative to the Standard time.
 945                                 if (!TryAddTicks (start, BaseUtcOffset.Ticks, out start))
 946                                         start = DateTime.MinValue;
 947
 948                                 // DaylightTime.End is relative to the DST time.
 949                                 if (!TryAddTicks (end, BaseUtcOffset.Ticks + delta.Ticks, out end))
 950                                         end = DateTime.MinValue;
 951                         } else {
 952                                 AdjustmentRule first = null, last = null;
 953
 954                                 foreach (var rule in GetAdjustmentRules ()) {
 955                                         if (rule.DateStart.Year != year && rule.DateEnd.Year != year)
 956                                                 continue;
 957                                         if (rule.DateStart.Year == year)
 958                                                 first = rule;
 959                                         if (rule.DateEnd.Year == year)
 960                                                 last = rule;
 961                                 }
 962
 963                                 if (first == null || last == null)
 964                                         return new DaylightTime (new DateTime (), new DateTime (), new TimeSpan ());
 965
 966                                 start = TransitionPoint (first.DaylightTransitionStart, year);
 967                                 end = TransitionPoint (last.DaylightTransitionEnd, year);
 968                                 delta = first.DaylightDelta;
 969                         }
 970
 971                         if (start == DateTime.MinValue || end == DateTime.MinValue)
 972                                 return new DaylightTime (new DateTime (), new DateTime (), new TimeSpan ());
 973
 974                         return new DaylightTime (start, end, delta);
 975                 }
 976
 977                 public bool IsInvalidTime (DateTime dateTime)
 978                 {
 979                         if (dateTime.Kind == DateTimeKind.Utc)
 980                                 return false;
 981                         if (dateTime.Kind == DateTimeKind.Local && this != Local)
 982                                 return false;
 983
 984                         AdjustmentRule rule = GetApplicableRule (dateTime);
 985                         if (rule != null) {
 986                                 DateTime tpoint = TransitionPoint (rule.DaylightTransitionStart, dateTime.Year);
 987                                 if (dateTime >= tpoint && dateTime < tpoint + rule.DaylightDelta)
 988                                         return true;
 989                         }
 990
 991                         return false;
 992                 }
 993
 994                 void IDeserializationCallback.OnDeserialization (object sender)
 995                 {
 996                         try {
 997                                         TimeZoneInfo.Validate (id, baseUtcOffset, adjustmentRules);
 998                                 } catch (ArgumentException ex) {
 999                                         throw new SerializationException ("invalid serialization data", ex);
1000                                 }
1001                 }
1002
1003                 private static void Validate (string id, TimeSpan baseUtcOffset, AdjustmentRule [] adjustmentRules)
1004                 {
1005                         if (id == null)
1006                                 throw new ArgumentNullException ("id");
1007
1008                         if (id == String.Empty)
1009                                 throw new ArgumentException ("id parameter is an empty string");
1010
1011                         if (baseUtcOffset.Ticks % TimeSpan.TicksPerMinute != 0)
1012                                 throw new ArgumentException ("baseUtcOffset parameter does not represent a whole number of minutes");
1013
1014                         if (baseUtcOffset > new TimeSpan (14, 0, 0) || baseUtcOffset < new TimeSpan (-14, 0, 0))
1015                                 throw new ArgumentOutOfRangeException ("baseUtcOffset parameter is greater than 14 hours or less than -14 hours");
1016
1017 #if STRICT
1018                         if (id.Length > 32)
1019                                 throw new ArgumentException ("id parameter shouldn't be longer than 32 characters");
1020 #endif
1021
1022                         if (adjustmentRules != null && adjustmentRules.Length != 0) {
1023                                 AdjustmentRule prev = null;
1024                                 foreach (AdjustmentRule current in adjustmentRules) {
1025                                         if (current == null)
1026                                                 throw new InvalidTimeZoneException ("one or more elements in adjustmentRules are null");
1027
1028                                         if ((baseUtcOffset + current.DaylightDelta < new TimeSpan (-14, 0, 0)) ||
1029                                                         (baseUtcOffset + current.DaylightDelta > new TimeSpan (14, 0, 0)))
1030                                                 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;");
1031
1032                                         if (prev != null && prev.DateStart > current.DateStart)
1033                                                 throw new InvalidTimeZoneException ("adjustment rules specified in adjustmentRules parameter are not in chronological order");
1034
1035                                         if (prev != null && prev.DateEnd > current.DateStart)
1036                                                 throw new InvalidTimeZoneException ("some adjustment rules in the adjustmentRules parameter overlap");
1037
1038                                         if (prev != null && prev.DateEnd == current.DateStart)
1039                                                 throw new InvalidTimeZoneException ("a date can have multiple adjustment rules applied to it");
1040
1041                                         prev = current;
1042                                 }
1043                         }
1044                 }
1045
1046                 public override string ToString ()
1047                 {
1048                         return DisplayName;
1049                 }
1050
1051                 private TimeZoneInfo (SerializationInfo info, StreamingContext context)
1052                 {
1053                         if (info == null)
1054                                 throw new ArgumentNullException ("info");
1055                         id = (string) info.GetValue ("Id", typeof (string));
1056                         displayName = (string) info.GetValue ("DisplayName", typeof (string));
1057                         standardDisplayName = (string) info.GetValue ("StandardName", typeof (string));
1058                         daylightDisplayName = (string) info.GetValue ("DaylightName", typeof (string));
1059                         baseUtcOffset = (TimeSpan) info.GetValue ("BaseUtcOffset", typeof (TimeSpan));
1060                         adjustmentRules = (TimeZoneInfo.AdjustmentRule []) info.GetValue ("AdjustmentRules", typeof (TimeZoneInfo.AdjustmentRule []));
1061                         supportsDaylightSavingTime = (bool) info.GetValue ("SupportsDaylightSavingTime", typeof (bool));
1062                 }
1063
1064                 private TimeZoneInfo (string id, TimeSpan baseUtcOffset, string displayName, string standardDisplayName, string daylightDisplayName, TimeZoneInfo.AdjustmentRule [] adjustmentRules, bool disableDaylightSavingTime)
1065                 {
1066                         if (id == null)
1067                                 throw new ArgumentNullException ("id");
1068
1069                         if (id == String.Empty)
1070                                 throw new ArgumentException ("id parameter is an empty string");
1071
1072                         if (baseUtcOffset.Ticks % TimeSpan.TicksPerMinute != 0)
1073                                 throw new ArgumentException ("baseUtcOffset parameter does not represent a whole number of minutes");
1074
1075                         if (baseUtcOffset > new TimeSpan (14, 0, 0) || baseUtcOffset < new TimeSpan (-14, 0, 0))
1076                                 throw new ArgumentOutOfRangeException ("baseUtcOffset parameter is greater than 14 hours or less than -14 hours");
1077
1078 #if STRICT
1079                         if (id.Length > 32)
1080                                 throw new ArgumentException ("id parameter shouldn't be longer than 32 characters");
1081 #endif
1082
1083                         bool supportsDaylightSavingTime = !disableDaylightSavingTime;
1084
1085                         if (adjustmentRules != null && adjustmentRules.Length != 0) {
1086                                 AdjustmentRule prev = null;
1087                                 foreach (AdjustmentRule current in adjustmentRules) {
1088                                         if (current == null)
1089                                                 throw new InvalidTimeZoneException ("one or more elements in adjustmentRules are null");
1090
1091                                         if ((baseUtcOffset + current.DaylightDelta < new TimeSpan (-14, 0, 0)) ||
1092                                                         (baseUtcOffset + current.DaylightDelta > new TimeSpan (14, 0, 0)))
1093                                                 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;");
1094
1095                                         if (prev != null && prev.DateStart > current.DateStart)
1096                                                 throw new InvalidTimeZoneException ("adjustment rules specified in adjustmentRules parameter are not in chronological order");
1097
1098                                         if (prev != null && prev.DateEnd > current.DateStart)
1099                                                 throw new InvalidTimeZoneException ("some adjustment rules in the adjustmentRules parameter overlap");
1100
1101                                         if (prev != null && prev.DateEnd == current.DateStart)
1102                                                 throw new InvalidTimeZoneException ("a date can have multiple adjustment rules applied to it");
1103
1104                                         prev = current;
1105                                 }
1106                         } else {
1107                                 supportsDaylightSavingTime = false;
1108                         }
1109
1110                         this.id = id;
1111                         this.baseUtcOffset = baseUtcOffset;
1112                         this.displayName = displayName ?? id;
1113                         this.standardDisplayName = standardDisplayName ?? id;
1114                         this.daylightDisplayName = daylightDisplayName;
1115                         this.supportsDaylightSavingTime = supportsDaylightSavingTime;
1116                         this.adjustmentRules = adjustmentRules;
1117                 }
1118
1119                 private AdjustmentRule GetApplicableRule (DateTime dateTime)
1120                 {
1121                         //Applicable rules are in standard time
1122                         DateTime date = dateTime;
1123
1124                         if (dateTime.Kind == DateTimeKind.Local && this != TimeZoneInfo.Local) {
1125                                 if (!TryAddTicks (date.ToUniversalTime (), BaseUtcOffset.Ticks, out date))
1126                                         return null;
1127                         } else if (dateTime.Kind == DateTimeKind.Utc && this != TimeZoneInfo.Utc) {
1128                                 if (!TryAddTicks (date, BaseUtcOffset.Ticks, out date))
1129                                         return null;
1130                         }
1131
1132                         // get the date component of the datetime
1133                         date = date.Date;
1134
1135                         if (adjustmentRules != null) {
1136                                 foreach (AdjustmentRule rule in adjustmentRules) {
1137                                         if (rule.DateStart > date)
1138                                                 return null;
1139                                         if (rule.DateEnd < date)
1140                                                 continue;
1141                                         return rule;
1142                                 }
1143                         }
1144                         return null;
1145                 }
1146
1147                 private bool TryGetTransitionOffset (DateTime dateTime, out TimeSpan offset,out bool isDst)
1148                 {
1149                         offset = BaseUtcOffset;
1150                         isDst = false;
1151
1152                         if (transitions == null)
1153                                 return false;
1154
1155                         //Transitions are in UTC
1156                         DateTime date = dateTime;
1157
1158                         if (dateTime.Kind == DateTimeKind.Local && this != TimeZoneInfo.Local) {
1159                                 if (!TryAddTicks (date.ToUniversalTime (), BaseUtcOffset.Ticks, out date, DateTimeKind.Utc))
1160                                         return false;
1161                         }
1162
1163                         if (dateTime.Kind != DateTimeKind.Utc) {
1164                                 if (!TryAddTicks (date, -BaseUtcOffset.Ticks, out date, DateTimeKind.Utc))
1165                                         return false;
1166                         }
1167
1168                         for (var i =  transitions.Count - 1; i >= 0; i--) {
1169                                 var pair = transitions [i];
1170                                 DateTime ttime = pair.Key;
1171                                 TimeType ttype = pair.Value;
1172
1173                                 if (ttime > date)
1174                                         continue;
1175
1176                                 offset =  new TimeSpan (0, 0, ttype.Offset);
1177                                 isDst = ttype.IsDst;
1178
1179                                 return true;
1180                         }
1181
1182                         return false;
1183                 }
1184
1185                 private static DateTime TransitionPoint (TransitionTime transition, int year)
1186                 {
1187                         if (transition.IsFixedDateRule)
1188                                 return new DateTime (year, transition.Month, transition.Day) + transition.TimeOfDay.TimeOfDay;
1189
1190                         DayOfWeek first = (new DateTime (year, transition.Month, 1)).DayOfWeek;
1191                         int day = 1 + (transition.Week - 1) * 7 + (transition.DayOfWeek - first + 7) % 7;
1192                         if (day >  DateTime.DaysInMonth (year, transition.Month))
1193                                 day -= 7;
1194                         if (day < 1)
1195                                 day += 7;
1196                         return new DateTime (year, transition.Month, day) + transition.TimeOfDay.TimeOfDay;
1197                 }
1198
1199                 static List<AdjustmentRule> ValidateRules (List<AdjustmentRule> adjustmentRules)
1200                 {
1201                         AdjustmentRule prev = null;
1202                         foreach (AdjustmentRule current in adjustmentRules.ToArray ()) {
1203                                 if (prev != null && prev.DateEnd > current.DateStart) {
1204                                         adjustmentRules.Remove (current);
1205                                 }
1206                                 prev = current;
1207                         }
1208                         return adjustmentRules;
1209                 }
1210
1211 #if LIBC || MONOTOUCH
1212                 const int BUFFER_SIZE = 16384; //Big enough for any tz file (on Oct 2008, all tz files are under 10k)
1213
1214                 private static TimeZoneInfo BuildFromStream (string id, Stream stream)
1215                 {
1216                         byte [] buffer = new byte [BUFFER_SIZE];
1217                         int length = stream.Read (buffer, 0, BUFFER_SIZE);
1218
1219                         if (!ValidTZFile (buffer, length))
1220                                 throw new InvalidTimeZoneException ("TZ file too big for the buffer");
1221
1222                         try {
1223                                 return ParseTZBuffer (id, buffer, length);
1224                         } catch (Exception e) {
1225                                 throw new InvalidTimeZoneException (e.Message);
1226                         }
1227                 }
1228
1229                 private static bool ValidTZFile (byte [] buffer, int length)
1230                 {
1231                         StringBuilder magic = new StringBuilder ();
1232
1233                         for (int i = 0; i < 4; i++)
1234                                 magic.Append ((char)buffer [i]);
1235
1236                         if (magic.ToString () != "TZif")
1237                                 return false;
1238
1239                         if (length >= BUFFER_SIZE)
1240                                 return false;
1241
1242                         return true;
1243                 }
1244
1245                 static int SwapInt32 (int i)
1246                 {
1247                         return (((i >> 24) & 0xff)
1248                                 | ((i >> 8) & 0xff00)
1249                                 | ((i << 8) & 0xff0000)
1250                                 | (((i & 0xff) << 24)));
1251                 }
1252
1253                 static int ReadBigEndianInt32 (byte [] buffer, int start)
1254                 {
1255                         int i = BitConverter.ToInt32 (buffer, start);
1256                         if (!BitConverter.IsLittleEndian)
1257                                 return i;
1258
1259                         return SwapInt32 (i);
1260                 }
1261
1262                 private static TimeZoneInfo ParseTZBuffer (string id, byte [] buffer, int length)
1263                 {
1264                         //Reading the header. 4 bytes for magic, 16 are reserved
1265                         int ttisgmtcnt = ReadBigEndianInt32 (buffer, 20);
1266                         int ttisstdcnt = ReadBigEndianInt32 (buffer, 24);
1267                         int leapcnt = ReadBigEndianInt32 (buffer, 28);
1268                         int timecnt = ReadBigEndianInt32 (buffer, 32);
1269                         int typecnt = ReadBigEndianInt32 (buffer, 36);
1270                         int charcnt = ReadBigEndianInt32 (buffer, 40);
1271
1272                         if (length < 44 + timecnt * 5 + typecnt * 6 + charcnt + leapcnt * 8 + ttisstdcnt + ttisgmtcnt)
1273                                 throw new InvalidTimeZoneException ();
1274
1275                         Dictionary<int, string> abbreviations = ParseAbbreviations (buffer, 44 + 4 * timecnt + timecnt + 6 * typecnt, charcnt);
1276                         Dictionary<int, TimeType> time_types = ParseTimesTypes (buffer, 44 + 4 * timecnt + timecnt, typecnt, abbreviations);
1277                         List<KeyValuePair<DateTime, TimeType>> transitions = ParseTransitions (buffer, 44, timecnt, time_types);
1278
1279                         if (time_types.Count == 0)
1280                                 throw new InvalidTimeZoneException ();
1281
1282                         if (time_types.Count == 1 && ((TimeType)time_types[0]).IsDst)
1283                                 throw new InvalidTimeZoneException ();
1284
1285                         TimeSpan baseUtcOffset = new TimeSpan (0);
1286                         TimeSpan dstDelta = new TimeSpan (0);
1287                         string standardDisplayName = null;
1288                         string daylightDisplayName = null;
1289                         bool dst_observed = false;
1290                         DateTime dst_start = DateTime.MinValue;
1291                         List<AdjustmentRule> adjustmentRules = new List<AdjustmentRule> ();
1292                         bool storeTransition = false;
1293
1294                         for (int i = 0; i < transitions.Count; i++) {
1295                                 var pair = transitions [i];
1296                                 DateTime ttime = pair.Key;
1297                                 TimeType ttype = pair.Value;
1298                                 if (!ttype.IsDst) {
1299                                         if (standardDisplayName != ttype.Name)
1300                                                 standardDisplayName = ttype.Name;
1301                                         if (baseUtcOffset.TotalSeconds != ttype.Offset) {
1302                                                 baseUtcOffset = new TimeSpan (0, 0, ttype.Offset);
1303                                                 if (adjustmentRules.Count > 0) // We ignore AdjustmentRules but store transitions.
1304                                                         storeTransition = true;
1305                                                 adjustmentRules = new List<AdjustmentRule> ();
1306                                                 dst_observed = false;
1307                                         }
1308                                         if (dst_observed) {
1309                                                 //FIXME: check additional fields for this:
1310                                                 //most of the transitions are expressed in GMT
1311                                                 dst_start += baseUtcOffset;
1312                                                 DateTime dst_end = ttime + baseUtcOffset + dstDelta;
1313
1314                                                 //some weird timezone (America/Phoenix) have end dates on Jan 1st
1315                                                 if (dst_end.Date == new DateTime (dst_end.Year, 1, 1) && dst_end.Year > dst_start.Year)
1316                                                         dst_end -= new TimeSpan (24, 0, 0);
1317
1318                                                 /*
1319                                                  * AdjustmentRule specifies a DST period that starts and ends within a year.
1320                                                  * When we have a DST period longer than a year, the generated AdjustmentRule may not be usable.
1321                                                  * Thus we fallback to the transitions.
1322                                                  */
1323                                                 if (dst_start.AddYears (1) < dst_end)
1324                                                         storeTransition = true;
1325
1326                                                 DateTime dateStart, dateEnd;
1327                                                 if (dst_start.Month < 7)
1328                                                         dateStart = new DateTime (dst_start.Year, 1, 1);
1329                                                 else
1330                                                         dateStart = new DateTime (dst_start.Year, 7, 1);
1331
1332                                                 if (dst_end.Month >= 7)
1333                                                         dateEnd = new DateTime (dst_end.Year, 12, 31);
1334                                                 else
1335                                                         dateEnd = new DateTime (dst_end.Year, 6, 30);
1336
1337
1338                                                 TransitionTime transition_start = TransitionTime.CreateFixedDateRule (new DateTime (1, 1, 1) + dst_start.TimeOfDay, dst_start.Month, dst_start.Day);
1339                                                 TransitionTime transition_end = TransitionTime.CreateFixedDateRule (new DateTime (1, 1, 1) + dst_end.TimeOfDay, dst_end.Month, dst_end.Day);
1340                                                 if  (transition_start != transition_end) //y, that happened in Argentina in 1943-1946
1341                                                         adjustmentRules.Add (AdjustmentRule.CreateAdjustmentRule (dateStart, dateEnd, dstDelta, transition_start, transition_end));
1342                                         }
1343                                         dst_observed = false;
1344                                 } else {
1345                                         if (daylightDisplayName != ttype.Name)
1346                                                 daylightDisplayName = ttype.Name;
1347                                         if (dstDelta.TotalSeconds != ttype.Offset - baseUtcOffset.TotalSeconds) {
1348                                                 // Round to nearest minute, since it's not possible to create an adjustment rule
1349                                                 // with sub-minute precision ("The TimeSpan parameter cannot be specified more precisely than whole minutes.")
1350                                                 // This happens for instance with Europe/Dublin, which had an offset of 34 minutes and 39 seconds in 1916.
1351                                                 dstDelta = new TimeSpan (0, 0, ttype.Offset) - baseUtcOffset;
1352                                                 if (dstDelta.Ticks % TimeSpan.TicksPerMinute != 0)
1353                                                         dstDelta = TimeSpan.FromMinutes ((long) (dstDelta.TotalMinutes + 0.5f));
1354                                         }
1355
1356                                         dst_start = ttime;
1357                                         dst_observed = true;
1358                                 }
1359                         }
1360
1361                         TimeZoneInfo tz;
1362                         if (adjustmentRules.Count == 0 && !storeTransition) {
1363                                 TimeType t = (TimeType)time_types [0];
1364                                 if (standardDisplayName == null) {
1365                                         standardDisplayName = t.Name;
1366                                         baseUtcOffset = new TimeSpan (0, 0, t.Offset);
1367                                 }
1368                                 tz = CreateCustomTimeZone (id, baseUtcOffset, id, standardDisplayName);
1369                         } else {
1370                                 tz = CreateCustomTimeZone (id, baseUtcOffset, id, standardDisplayName, daylightDisplayName, ValidateRules (adjustmentRules).ToArray ());
1371                         }
1372
1373                         if (storeTransition && transitions.Count > 0) {
1374                                 tz.transitions = transitions;
1375                                 tz.supportsDaylightSavingTime = true;
1376                         }
1377
1378                         return tz;
1379                 }
1380
1381                 static Dictionary<int, string> ParseAbbreviations (byte [] buffer, int index, int count)
1382                 {
1383                         var abbrevs = new Dictionary<int, string> ();
1384                         int abbrev_index = 0;
1385                         var sb = new StringBuilder ();
1386                         for (int i = 0; i < count; i++) {
1387                                 char c = (char) buffer [index + i];
1388                                 if (c != '\0')
1389                                         sb.Append (c);
1390                                 else {
1391                                         abbrevs.Add (abbrev_index, sb.ToString ());
1392                                         //Adding all the substrings too, as it seems to be used, at least for Africa/Windhoek
1393                                         //j == sb.Length empty substring also needs to be added #31432
1394                                         for (int j = 1; j <= sb.Length; j++)
1395                                                 abbrevs.Add (abbrev_index + j, sb.ToString (j, sb.Length - j));
1396                                         abbrev_index = i + 1;
1397                                         sb = new StringBuilder ();
1398                                 }
1399                         }
1400                         return abbrevs;
1401                 }
1402
1403                 static Dictionary<int, TimeType> ParseTimesTypes (byte [] buffer, int index, int count, Dictionary<int, string> abbreviations)
1404                 {
1405                         var types = new Dictionary<int, TimeType> (count);
1406                         for (int i = 0; i < count; i++) {
1407                                 int offset = ReadBigEndianInt32 (buffer, index + 6 * i);
1408                                 byte is_dst = buffer [index + 6 * i + 4];
1409                                 byte abbrev = buffer [index + 6 * i + 5];
1410                                 types.Add (i, new TimeType (offset, (is_dst != 0), abbreviations [(int)abbrev]));
1411                         }
1412                         return types;
1413                 }
1414
1415                 static List<KeyValuePair<DateTime, TimeType>> ParseTransitions (byte [] buffer, int index, int count, Dictionary<int, TimeType> time_types)
1416                 {
1417                         var list = new List<KeyValuePair<DateTime, TimeType>> (count);
1418                         for (int i = 0; i < count; i++) {
1419                                 int unixtime = ReadBigEndianInt32 (buffer, index + 4 * i);
1420                                 DateTime ttime = DateTimeFromUnixTime (unixtime);
1421                                 byte ttype = buffer [index + 4 * count + i];
1422                                 list.Add (new KeyValuePair<DateTime, TimeType> (ttime, time_types [(int)ttype]));
1423                         }
1424                         return list;
1425                 }
1426
1427                 static DateTime DateTimeFromUnixTime (long unix_time)
1428                 {
1429                         DateTime date_time = new DateTime (1970, 1, 1);
1430                         return date_time.AddSeconds (unix_time);
1431                 }
1432
1433 #region reference sources
1434                 // Shortcut for TimeZoneInfo.Local.GetUtcOffset
1435                 internal static TimeSpan GetLocalUtcOffset(DateTime dateTime, TimeZoneInfoOptions flags)
1436                 {
1437                         bool dst;
1438                         return Local.GetUtcOffset (dateTime, out dst);
1439                 }
1440
1441                 internal TimeSpan GetUtcOffset(DateTime dateTime, TimeZoneInfoOptions flags)
1442                 {
1443                         bool dst;
1444                         return GetUtcOffset (dateTime, out dst);
1445                 }
1446
1447                 static internal TimeSpan GetUtcOffsetFromUtc (DateTime time, TimeZoneInfo zone, out Boolean isDaylightSavings, out Boolean isAmbiguousLocalDst)
1448                 {
1449                         isDaylightSavings = false;
1450                         isAmbiguousLocalDst = false;
1451                         TimeSpan baseOffset = zone.BaseUtcOffset;
1452
1453                         if (zone.IsAmbiguousTime (time)) {
1454                                 isAmbiguousLocalDst = true;
1455                                 return baseOffset;
1456                         }
1457
1458                         return zone.GetUtcOffset (time, out isDaylightSavings);
1459                 }
1460 #endregion
1461         }
1462
1463         struct TimeType {
1464                 public readonly int Offset;
1465                 public readonly bool IsDst;
1466                 public string Name;
1467
1468                 public TimeType (int offset, bool is_dst, string abbrev)
1469                 {
1470                         this.Offset = offset;
1471                         this.IsDst = is_dst;
1472                         this.Name = abbrev;
1473                 }
1474
1475                 public override string ToString ()
1476                 {
1477                         return "offset: " + Offset + "s, is_dst: " + IsDst + ", zone name: " + Name;
1478                 }
1479 #else
1480         }
1481 #endif
1482         }
1483 }