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