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