mcs/class/System.Core/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
  34 #if !INSIDE_CORLIB && NET_4_0
  35
  36 [assembly:TypeForwardedTo (typeof(TimeZoneInfo))]
  37
  38 #elif (INSIDE_CORLIB && NET_4_0) || (!INSIDE_CORLIB && (NET_3_5 && !NET_4_0 && !MOBILE))
  39
  40 using System.Collections.Generic;
  41 using System.Collections.ObjectModel;
  42 using System.Runtime.Serialization;
  43 using System.Text;
  44
  45 #if LIBC || MONODROID
  46 using System.IO;
  47 using Mono;
  48 #endif
  49
  50 using Microsoft.Win32;
  51
  52 namespace System
  53 {
  54 #if MOBILE
  55         [TypeForwardedFrom (Consts.AssemblySystem_Core)]
  56 #elif NET_4_0
  57         [TypeForwardedFrom (Consts.AssemblySystemCore_3_5)]
  58 #endif
  59         [SerializableAttribute]
  60         public sealed partial class TimeZoneInfo : IEquatable<TimeZoneInfo>, ISerializable, IDeserializationCallback
  61         {
  62                 TimeSpan baseUtcOffset;
  63                 public TimeSpan BaseUtcOffset {
  64                         get { return baseUtcOffset; }
  65                 }
  66
  67                 string daylightDisplayName;
  68                 public string DaylightName {
  69                         get {
  70                                 return supportsDaylightSavingTime
  71                                         ? daylightDisplayName
  72                                         : string.Empty;
  73                         }
  74                 }
  75
  76                 string displayName;
  77                 public string DisplayName {
  78                         get { return displayName; }
  79                 }
  80
  81                 string id;
  82                 public string Id {
  83                         get { return id; }
  84                 }
  85
  86                 static TimeZoneInfo local;
  87                 public static TimeZoneInfo Local {
  88                         get {
  89                                 var l = local;
  90                                 if (l == null) {
  91                                         l = CreateLocal ();
  92                                         if (l == null)
  93                                                 throw new TimeZoneNotFoundException ();
  94
  95                                         if (Interlocked.CompareExchange (ref local, l, null) != null)
  96                                                 l = local;
  97                                 }
  98
  99                                 return l;
 100                         }
 101                 }
 102
 103                 static TimeZoneInfo CreateLocal ()
 104                 {
 105 #if MONODROID
 106                         return AndroidTimeZones.Local;
 107 #elif MONOTOUCH
 108                         using (Stream stream = GetMonoTouchData (null)) {
 109                                 return BuildFromStream ("Local", stream);
 110                         }
 111 #elif LIBC
 112                         try {
 113                                 return FindSystemTimeZoneByFileName ("Local", "/etc/localtime");
 114                         } catch {
 115                                 try {
 116                                         return FindSystemTimeZoneByFileName ("Local", Path.Combine (TimeZoneDirectory, "localtime"));
 117                                 } catch {
 118                                         return null;
 119                                 }
 120                         }
 121 #else
 122                         if (IsWindows && LocalZoneKey != null) {
 123                                 string name = (string)LocalZoneKey.GetValue ("TimeZoneKeyName");
 124                                 name = TrimSpecial (name);
 125                                 if (name != null)
 126                                         return TimeZoneInfo.FindSystemTimeZoneById (name);
 127                         }
 128
 129                         return null;
 130 #endif
 131                 }
 132
 133                 string standardDisplayName;
 134                 public string StandardName {
 135                         get { return standardDisplayName; }
 136                 }
 137
 138                 bool supportsDaylightSavingTime;
 139                 public bool SupportsDaylightSavingTime {
 140                         get  { return supportsDaylightSavingTime; }
 141                 }
 142
 143                 static TimeZoneInfo utc;
 144                 public static TimeZoneInfo Utc {
 145                         get {
 146                                 if (utc == null)
 147                                         utc = CreateCustomTimeZone ("UTC", new TimeSpan (0), "UTC", "UTC");
 148                                 return utc;
 149                         }
 150                 }
 151 #if LIBC
 152                 static string timeZoneDirectory;
 153                 static string TimeZoneDirectory {
 154                         get {
 155                                 if (timeZoneDirectory == null)
 156                                         timeZoneDirectory = "/usr/share/zoneinfo";
 157                                 return timeZoneDirectory;
 158                         }
 159                         set {
 160                                 ClearCachedData ();
 161                                 timeZoneDirectory = value;
 162                         }
 163                 }
 164 #endif
 165                 private AdjustmentRule [] adjustmentRules;
 166
 167 #if !NET_2_1
 168                 /// <summary>
 169                 /// Determine whether windows of not (taken Stephane Delcroix's code)
 170                 /// </summary>
 171                 private static bool IsWindows
 172                 {
 173                         get {
 174                                 int platform = (int) Environment.OSVersion.Platform;
 175                                 return ((platform != 4) && (platform != 6) && (platform != 128));
 176                         }
 177                 }
 178
 179                 /// <summary>
 180                 /// Needed to trim misc garbage in MS registry keys
 181                 /// </summary>
 182                 private static string TrimSpecial (string str)
 183                 {
 184                         var Istart = 0;
 185                         while (Istart < str.Length && !char.IsLetterOrDigit(str[Istart])) Istart++;
 186                         var Iend = str.Length - 1;
 187                         while (Iend > Istart && !char.IsLetterOrDigit(str[Iend])) Iend--;
 188
 189                         return str.Substring (Istart, Iend-Istart+1);
 190                 }
 191
 192                 static RegistryKey timeZoneKey;
 193                 static RegistryKey TimeZoneKey {
 194                         get {
 195                                 if (timeZoneKey != null)
 196                                         return timeZoneKey;
 197                                 if (!IsWindows)
 198                                         return null;
 199
 200                                 return timeZoneKey = Registry.LocalMachine.OpenSubKey (
 201                                         "SOFTWARE\\Microsoft\\Windows NT\\CurrentVersion\\Time Zones",
 202                                         false);
 203                         }
 204                 }
 205
 206                 static RegistryKey localZoneKey;
 207                 static RegistryKey LocalZoneKey {
 208                         get {
 209                                 if (localZoneKey != null)
 210                                         return localZoneKey;
 211
 212                                 if (!IsWindows)
 213                                         return null;
 214
 215                                 return localZoneKey = Registry.LocalMachine.OpenSubKey (
 216                                         "SYSTEM\\CurrentControlSet\\Control\\TimeZoneInformation", false);
 217                         }
 218                 }
 219 #endif
 220
 221                 public static void ClearCachedData ()
 222                 {
 223                         local = null;
 224                         utc = null;
 225                         systemTimeZones = null;
 226                 }
 227
 228                 public static DateTime ConvertTime (DateTime dateTime, TimeZoneInfo destinationTimeZone)
 229                 {
 230                         return ConvertTime (dateTime, dateTime.Kind == DateTimeKind.Utc ? TimeZoneInfo.Utc : TimeZoneInfo.Local, destinationTimeZone);
 231                 }
 232
 233                 public static DateTime ConvertTime (DateTime dateTime, TimeZoneInfo sourceTimeZone, TimeZoneInfo destinationTimeZone)
 234                 {
 235                         if (sourceTimeZone == null)
 236                                 throw new ArgumentNullException ("sourceTimeZone");
 237
 238                         if (destinationTimeZone == null)
 239                                 throw new ArgumentNullException ("destinationTimeZone");
 240
 241                         if (dateTime.Kind == DateTimeKind.Local && sourceTimeZone != TimeZoneInfo.Local)
 242                                 throw new ArgumentException ("Kind property of dateTime is Local but the sourceTimeZone does not equal TimeZoneInfo.Local");
 243
 244                         if (dateTime.Kind == DateTimeKind.Utc && sourceTimeZone != TimeZoneInfo.Utc)
 245                                 throw new ArgumentException ("Kind property of dateTime is Utc but the sourceTimeZone does not equal TimeZoneInfo.Utc");
 246
 247                         if (sourceTimeZone.IsInvalidTime (dateTime))
 248                                 throw new ArgumentException ("dateTime parameter is an invalid time");
 249
 250                         if (dateTime.Kind == DateTimeKind.Local && sourceTimeZone == TimeZoneInfo.Local && destinationTimeZone == TimeZoneInfo.Local)
 251                                 return dateTime;
 252
 253                         DateTime utc = ConvertTimeToUtc (dateTime);
 254
 255                         if (destinationTimeZone != TimeZoneInfo.Utc) {
 256                                 utc = ConvertTimeFromUtc (utc, destinationTimeZone);
 257                                 if (dateTime.Kind == DateTimeKind.Unspecified)
 258                                         return DateTime.SpecifyKind (utc, DateTimeKind.Unspecified);
 259                         }
 260
 261                         return utc;
 262                 }
 263
 264                 public static DateTimeOffset ConvertTime(DateTimeOffset dateTimeOffset, TimeZoneInfo destinationTimeZone)
 265                 {
 266                         if (destinationTimeZone == null)
 267                                 throw new ArgumentNullException("destinationTimeZone");
 268
 269                         var utcDateTime = dateTimeOffset.UtcDateTime;
 270                         AdjustmentRule rule = destinationTimeZone.GetApplicableRule (utcDateTime);
 271
 272                         if (rule != null && destinationTimeZone.IsDaylightSavingTime(utcDateTime)) {
 273                                 var offset = destinationTimeZone.BaseUtcOffset + rule.DaylightDelta;
 274                                 return new DateTimeOffset(DateTime.SpecifyKind(utcDateTime, DateTimeKind.Unspecified) + offset, offset);
 275                         }
 276                         else {
 277                                 return new DateTimeOffset(DateTime.SpecifyKind(utcDateTime, DateTimeKind.Unspecified) + destinationTimeZone.BaseUtcOffset, destinationTimeZone.BaseUtcOffset);
 278                         }
 279                 }
 280
 281                 public static DateTime ConvertTimeBySystemTimeZoneId (DateTime dateTime, string destinationTimeZoneId)
 282                 {
 283                         return ConvertTime (dateTime, FindSystemTimeZoneById (destinationTimeZoneId));
 284                 }
 285
 286                 public static DateTime ConvertTimeBySystemTimeZoneId (DateTime dateTime, string sourceTimeZoneId, string destinationTimeZoneId)
 287                 {
 288                         return ConvertTime (dateTime, FindSystemTimeZoneById (sourceTimeZoneId), FindSystemTimeZoneById (destinationTimeZoneId));
 289                 }
 290
 291                 public static DateTimeOffset ConvertTimeBySystemTimeZoneId (DateTimeOffset dateTimeOffset, string destinationTimeZoneId)
 292                 {
 293                         return ConvertTime (dateTimeOffset, FindSystemTimeZoneById (destinationTimeZoneId));
 294                 }
 295
 296                 private DateTime ConvertTimeFromUtc (DateTime dateTime)
 297                 {
 298                         if (dateTime.Kind == DateTimeKind.Local)
 299                                 throw new ArgumentException ("Kind property of dateTime is Local");
 300
 301                         if (this == TimeZoneInfo.Utc)
 302                                 return DateTime.SpecifyKind (dateTime, DateTimeKind.Utc);
 303
 304                         //FIXME: do not rely on DateTime implementation !
 305                         if (this == TimeZoneInfo.Local)
 306                         {
 307 #if NET_4_0
 308                                 return dateTime.ToLocalTime ();
 309 #else
 310                                 return DateTime.SpecifyKind (dateTime.ToLocalTime (), DateTimeKind.Unspecified);
 311 #endif
 312                         }
 313
 314
 315                         AdjustmentRule rule = GetApplicableRule (dateTime);
 316                         if (rule != null && IsDaylightSavingTime (DateTime.SpecifyKind (dateTime, DateTimeKind.Utc)))
 317                                 return DateTime.SpecifyKind (dateTime + BaseUtcOffset + rule.DaylightDelta , DateTimeKind.Unspecified);
 318                         else
 319                                 return DateTime.SpecifyKind (dateTime + BaseUtcOffset, DateTimeKind.Unspecified);
 320                 }
 321
 322                 public static DateTime ConvertTimeFromUtc (DateTime dateTime, TimeZoneInfo destinationTimeZone)
 323                 {
 324                         if (destinationTimeZone == null)
 325                                 throw new ArgumentNullException ("destinationTimeZone");
 326
 327                         return destinationTimeZone.ConvertTimeFromUtc (dateTime);
 328                 }
 329
 330                 public static DateTime ConvertTimeToUtc (DateTime dateTime)
 331                 {
 332                         if (dateTime.Kind == DateTimeKind.Utc)
 333                                 return dateTime;
 334
 335                         //FIXME: do not rely on DateTime implementation !
 336                         return DateTime.SpecifyKind (dateTime.ToUniversalTime (), DateTimeKind.Utc);
 337                 }
 338
 339                 public static DateTime ConvertTimeToUtc (DateTime dateTime, TimeZoneInfo sourceTimeZone)
 340                 {
 341                         if (sourceTimeZone == null)
 342                                 throw new ArgumentNullException ("sourceTimeZone");
 343
 344                         if (dateTime.Kind == DateTimeKind.Utc && sourceTimeZone != TimeZoneInfo.Utc)
 345                                 throw new ArgumentException ("Kind property of dateTime is Utc but the sourceTimeZone does not equal TimeZoneInfo.Utc");
 346
 347                         if (dateTime.Kind == DateTimeKind.Local && sourceTimeZone != TimeZoneInfo.Local)
 348                                 throw new ArgumentException ("Kind property of dateTime is Local but the sourceTimeZone does not equal TimeZoneInfo.Local");
 349
 350                         if (sourceTimeZone.IsInvalidTime (dateTime))
 351                                 throw new ArgumentException ("dateTime parameter is an invalid time");
 352
 353                         if (dateTime.Kind == DateTimeKind.Utc && sourceTimeZone == TimeZoneInfo.Utc)
 354                                 return dateTime;
 355
 356                         if (dateTime.Kind == DateTimeKind.Utc)
 357                                 return dateTime;
 358
 359                         if (dateTime.Kind == DateTimeKind.Local)
 360                                 return ConvertTimeToUtc (dateTime);
 361
 362                         if (sourceTimeZone.IsAmbiguousTime (dateTime) || !sourceTimeZone.IsDaylightSavingTime (dateTime))
 363                                 return DateTime.SpecifyKind (dateTime - sourceTimeZone.BaseUtcOffset, DateTimeKind.Utc);
 364                         else {
 365                                 AdjustmentRule rule = sourceTimeZone.GetApplicableRule (dateTime);
 366                                 if (rule != null)
 367                                         return DateTime.SpecifyKind (dateTime - sourceTimeZone.BaseUtcOffset - rule.DaylightDelta, DateTimeKind.Utc);
 368                                 else
 369                                         return DateTime.SpecifyKind (dateTime - sourceTimeZone.BaseUtcOffset, DateTimeKind.Utc);
 370                         }
 371                 }
 372
 373                 public static TimeZoneInfo CreateCustomTimeZone (string id, TimeSpan baseUtcOffset, string displayName, string standardDisplayName)
 374                 {
 375                         return CreateCustomTimeZone (id, baseUtcOffset, displayName, standardDisplayName, null, null, true);
 376                 }
 377
 378                 public static TimeZoneInfo CreateCustomTimeZone (string id, TimeSpan baseUtcOffset, string displayName, string standardDisplayName, string daylightDisplayName, TimeZoneInfo.AdjustmentRule [] adjustmentRules)
 379                 {
 380                         return CreateCustomTimeZone (id, baseUtcOffset, displayName, standardDisplayName, daylightDisplayName, adjustmentRules, false);
 381                 }
 382
 383                 public static TimeZoneInfo CreateCustomTimeZone ( string id, TimeSpan baseUtcOffset, string displayName, string standardDisplayName, string daylightDisplayName, TimeZoneInfo.AdjustmentRule [] adjustmentRules, bool disableDaylightSavingTime)
 384                 {
 385                         return new TimeZoneInfo (id, baseUtcOffset, displayName, standardDisplayName, daylightDisplayName, adjustmentRules, disableDaylightSavingTime);
 386                 }
 387
 388 #if NET_4_5
 389                 public override bool Equals (object obj)
 390                 {
 391                         return Equals (obj as TimeZoneInfo);
 392                 }
 393 #endif
 394
 395                 public bool Equals (TimeZoneInfo other)
 396                 {
 397                         if (other == null)
 398                                 return false;
 399
 400                         return other.Id == this.Id && HasSameRules (other);
 401                 }
 402
 403                 public static TimeZoneInfo FindSystemTimeZoneById (string id)
 404                 {
 405                         //FIXME: this method should check for cached values in systemTimeZones
 406                         if (id == null)
 407                                 throw new ArgumentNullException ("id");
 408 #if !NET_2_1
 409                         if (TimeZoneKey != null)
 410                         {
 411                                 RegistryKey key = TimeZoneKey.OpenSubKey (id, false);
 412                                 if (key == null)
 413                                         throw new TimeZoneNotFoundException ();
 414                                 return FromRegistryKey(id, key);
 415                         }
 416 #endif
 417 #if MONODROID
 418                         var timeZoneInfo = AndroidTimeZones.GetTimeZone (id, id);
 419                         if (timeZoneInfo == null)
 420                                 throw new TimeZoneNotFoundException ();
 421                         return timeZoneInfo;
 422 #else
 423                         // Local requires special logic that already exists in the Local property (bug #326)
 424                         if (id == "Local")
 425                                 return Local;
 426 #if MONOTOUCH
 427                         using (Stream stream = GetMonoTouchData (id)) {
 428                                 return BuildFromStream (id, stream);
 429                         }
 430 #elif LIBC
 431                         string filepath = Path.Combine (TimeZoneDirectory, id);
 432                         return FindSystemTimeZoneByFileName (id, filepath);
 433 #else
 434                         throw new NotImplementedException ();
 435 #endif
 436 #endif
 437                 }
 438
 439 #if LIBC
 440                 private static TimeZoneInfo FindSystemTimeZoneByFileName (string id, string filepath)
 441                 {
 442                         if (!File.Exists (filepath))
 443                                 throw new TimeZoneNotFoundException ();
 444
 445                         using (FileStream stream = File.OpenRead (filepath)) {
 446                                 return BuildFromStream (id, stream);
 447                         }
 448                 }
 449 #endif
 450 #if LIBC || MONOTOUCH
 451                 const int BUFFER_SIZE = 16384; //Big enough for any tz file (on Oct 2008, all tz files are under 10k)
 452
 453                 private static TimeZoneInfo BuildFromStream (string id, Stream stream)
 454                 {
 455                         byte [] buffer = new byte [BUFFER_SIZE];
 456                         int length = stream.Read (buffer, 0, BUFFER_SIZE);
 457
 458                         if (!ValidTZFile (buffer, length))
 459                                 throw new InvalidTimeZoneException ("TZ file too big for the buffer");
 460
 461                         try {
 462                                 return ParseTZBuffer (id, buffer, length);
 463                         } catch (Exception e) {
 464                                 throw new InvalidTimeZoneException (e.Message);
 465                         }
 466                 }
 467 #endif
 468
 469 #if !NET_2_1
 470                 private static TimeZoneInfo FromRegistryKey (string id, RegistryKey key)
 471                 {
 472                         byte [] reg_tzi = (byte []) key.GetValue ("TZI");
 473
 474                         if (reg_tzi == null)
 475                                 throw new InvalidTimeZoneException ();
 476
 477                         int bias = BitConverter.ToInt32 (reg_tzi, 0);
 478                         TimeSpan baseUtcOffset = new TimeSpan (0, -bias, 0);
 479
 480                         string display_name = (string) key.GetValue ("Display");
 481                         string standard_name = (string) key.GetValue ("Std");
 482                         string daylight_name = (string) key.GetValue ("Dlt");
 483
 484                         List<AdjustmentRule> adjustmentRules = new List<AdjustmentRule> ();
 485
 486                         RegistryKey dst_key = key.OpenSubKey ("Dynamic DST", false);
 487                         if (dst_key != null) {
 488                                 int first_year = (int) dst_key.GetValue ("FirstEntry");
 489                                 int last_year = (int) dst_key.GetValue ("LastEntry");
 490                                 int year;
 491
 492                                 for (year=first_year; year<=last_year; year++) {
 493                                         byte [] dst_tzi = (byte []) dst_key.GetValue (year.ToString ());
 494                                         if (dst_tzi != null) {
 495                                                 int start_year = year == first_year ? 1 : year;
 496                                                 int end_year = year == last_year ? 9999 : year;
 497                                                 ParseRegTzi(adjustmentRules, start_year, end_year, dst_tzi);
 498                                         }
 499                                 }
 500                         }
 501                         else
 502                                 ParseRegTzi(adjustmentRules, 1, 9999, reg_tzi);
 503
 504                         return CreateCustomTimeZone (id, baseUtcOffset, display_name, standard_name, daylight_name, ValidateRules (adjustmentRules).ToArray ());
 505                 }
 506
 507                 private static void ParseRegTzi (List<AdjustmentRule> adjustmentRules, int start_year, int end_year, byte [] buffer)
 508                 {
 509                         //int standard_bias = BitConverter.ToInt32 (buffer, 4); /* not sure how to handle this */
 510                         int daylight_bias = BitConverter.ToInt32 (buffer, 8);
 511
 512                         int standard_year = BitConverter.ToInt16 (buffer, 12);
 513                         int standard_month = BitConverter.ToInt16 (buffer, 14);
 514                         int standard_dayofweek = BitConverter.ToInt16 (buffer, 16);
 515                         int standard_day = BitConverter.ToInt16 (buffer, 18);
 516                         int standard_hour = BitConverter.ToInt16 (buffer, 20);
 517                         int standard_minute = BitConverter.ToInt16 (buffer, 22);
 518                         int standard_second = BitConverter.ToInt16 (buffer, 24);
 519                         int standard_millisecond = BitConverter.ToInt16 (buffer, 26);
 520
 521                         int daylight_year = BitConverter.ToInt16 (buffer, 28);
 522                         int daylight_month = BitConverter.ToInt16 (buffer, 30);
 523                         int daylight_dayofweek = BitConverter.ToInt16 (buffer, 32);
 524                         int daylight_day = BitConverter.ToInt16 (buffer, 34);
 525                         int daylight_hour = BitConverter.ToInt16 (buffer, 36);
 526                         int daylight_minute = BitConverter.ToInt16 (buffer, 38);
 527                         int daylight_second = BitConverter.ToInt16 (buffer, 40);
 528                         int daylight_millisecond = BitConverter.ToInt16 (buffer, 42);
 529
 530                         if (standard_month == 0 || daylight_month == 0)
 531                                 return;
 532
 533                         DateTime start_date;
 534                         DateTime start_timeofday = new DateTime (1, 1, 1, daylight_hour, daylight_minute, daylight_second, daylight_millisecond);
 535                         TransitionTime start_transition_time;
 536
 537                         if (daylight_year == 0) {
 538                                 start_date = new DateTime (start_year, 1, 1);
 539                                 start_transition_time = TransitionTime.CreateFloatingDateRule (
 540                                         start_timeofday, daylight_month, daylight_day,
 541                                         (DayOfWeek) daylight_dayofweek);
 542                         }
 543                         else {
 544                                 start_date = new DateTime (daylight_year, daylight_month, daylight_day,
 545                                         daylight_hour, daylight_minute, daylight_second, daylight_millisecond);
 546                                 start_transition_time = TransitionTime.CreateFixedDateRule (
 547                                         start_timeofday, daylight_month, daylight_day);
 548                         }
 549
 550                         DateTime end_date;
 551                         DateTime end_timeofday = new DateTime (1, 1, 1, standard_hour, standard_minute, standard_second, standard_millisecond);
 552                         TransitionTime end_transition_time;
 553
 554                         if (standard_year == 0) {
 555                                 end_date = new DateTime (end_year, 12, 31);
 556                                 end_transition_time = TransitionTime.CreateFloatingDateRule (
 557                                         end_timeofday, standard_month, standard_day,
 558                                         (DayOfWeek) standard_dayofweek);
 559                         }
 560                         else {
 561                                 end_date = new DateTime (standard_year, standard_month, standard_day,
 562                                         standard_hour, standard_minute, standard_second, standard_millisecond);
 563                                 end_transition_time = TransitionTime.CreateFixedDateRule (
 564                                         end_timeofday, standard_month, standard_day);
 565                         }
 566
 567                         TimeSpan daylight_delta = new TimeSpan(0, -daylight_bias, 0);
 568
 569                         adjustmentRules.Add (AdjustmentRule.CreateAdjustmentRule (
 570                                 start_date, end_date, daylight_delta,
 571                                 start_transition_time, end_transition_time));
 572                 }
 573 #endif
 574
 575                 public AdjustmentRule [] GetAdjustmentRules ()
 576                 {
 577                         if (!supportsDaylightSavingTime)
 578                                 return new AdjustmentRule [0];
 579                         else
 580                                 return (AdjustmentRule []) adjustmentRules.Clone ();
 581                 }
 582
 583                 public TimeSpan [] GetAmbiguousTimeOffsets (DateTime dateTime)
 584                 {
 585                         if (!IsAmbiguousTime (dateTime))
 586                                 throw new ArgumentException ("dateTime is not an ambiguous time");
 587
 588                         AdjustmentRule rule = GetApplicableRule (dateTime);
 589                         if (rule != null)
 590                                 return new TimeSpan[] {baseUtcOffset, baseUtcOffset + rule.DaylightDelta};
 591                         else
 592                                 return new TimeSpan[] {baseUtcOffset, baseUtcOffset};
 593                 }
 594
 595                 public TimeSpan [] GetAmbiguousTimeOffsets (DateTimeOffset dateTimeOffset)
 596                 {
 597                         if (!IsAmbiguousTime (dateTimeOffset))
 598                                 throw new ArgumentException ("dateTimeOffset is not an ambiguous time");
 599
 600                         throw new NotImplementedException ();
 601                 }
 602
 603                 public override int GetHashCode ()
 604                 {
 605                         int hash_code = Id.GetHashCode ();
 606                         foreach (AdjustmentRule rule in GetAdjustmentRules ())
 607                                 hash_code ^= rule.GetHashCode ();
 608                         return hash_code;
 609                 }
 610
 611 #if NET_4_0
 612                 void ISerializable.GetObjectData (SerializationInfo info, StreamingContext context)
 613 #else
 614                 public void GetObjectData (SerializationInfo info, StreamingContext context)
 615 #endif
 616                 {
 617                         if (info == null)
 618                                 throw new ArgumentNullException ("info");
 619                         info.AddValue ("Id", id);
 620                         info.AddValue ("DisplayName", displayName);
 621                         info.AddValue ("StandardName", standardDisplayName);
 622                         info.AddValue ("DaylightName", daylightDisplayName);
 623                         info.AddValue ("BaseUtcOffset", baseUtcOffset);
 624                         info.AddValue ("AdjustmentRules", adjustmentRules);
 625                         info.AddValue ("SupportsDaylightSavingTime", SupportsDaylightSavingTime);
 626                 }
 627
 628                 //FIXME: change this to a generic Dictionary and allow caching for FindSystemTimeZoneById
 629                 private static List<TimeZoneInfo> systemTimeZones;
 630                 public static ReadOnlyCollection<TimeZoneInfo> GetSystemTimeZones ()
 631                 {
 632                         if (systemTimeZones == null) {
 633                                 systemTimeZones = new List<TimeZoneInfo> ();
 634 #if !NET_2_1
 635                                 if (TimeZoneKey != null) {
 636                                         foreach (string id in TimeZoneKey.GetSubKeyNames ()) {
 637                                                 try {
 638                                                         systemTimeZones.Add (FindSystemTimeZoneById (id));
 639                                                 } catch {}
 640                                         }
 641
 642                                         return new ReadOnlyCollection<TimeZoneInfo> (systemTimeZones);
 643                                 }
 644 #endif
 645 #if MONODROID
 646                         foreach (string id in AndroidTimeZones.GetAvailableIds ()) {
 647                                 var tz = AndroidTimeZones.GetTimeZone (id, id);
 648                                 if (tz != null)
 649                                         systemTimeZones.Add (tz);
 650                         }
 651 #elif MONOTOUCH
 652                                 if (systemTimeZones.Count == 0) {
 653                                         foreach (string name in GetMonoTouchNames ()) {
 654                                                 using (Stream stream = GetMonoTouchData (name, false)) {
 655                                                         if (stream == null)
 656                                                                 continue;
 657                                                         systemTimeZones.Add (BuildFromStream (name, stream));
 658                                                 }
 659                                         }
 660                                 }
 661 #elif LIBC
 662                                 string[] continents = new string [] {"Africa", "America", "Antarctica", "Arctic", "Asia", "Atlantic", "Brazil", "Canada", "Chile", "Europe", "Indian", "Mexico", "Mideast", "Pacific", "US"};
 663                                 foreach (string continent in continents) {
 664                                         try {
 665                                                 foreach (string zonepath in Directory.GetFiles (Path.Combine (TimeZoneDirectory, continent))) {
 666                                                         try {
 667                                                                 string id = String.Format ("{0}/{1}", continent, Path.GetFileName (zonepath));
 668                                                                 systemTimeZones.Add (FindSystemTimeZoneById (id));
 669                                                         } catch (ArgumentNullException) {
 670                                                         } catch (TimeZoneNotFoundException) {
 671                                                         } catch (InvalidTimeZoneException) {
 672                                                         } catch (Exception) {
 673                                                                 throw;
 674                                                         }
 675                                                 }
 676                                         } catch {}
 677                                 }
 678 #else
 679                                 throw new NotImplementedException ("This method is not implemented for this platform");
 680 #endif
 681                         }
 682                         return new ReadOnlyCollection<TimeZoneInfo> (systemTimeZones);
 683                 }
 684
 685                 public TimeSpan GetUtcOffset (DateTime dateTime)
 686                 {
 687                         if (IsDaylightSavingTime (dateTime)) {
 688                                 AdjustmentRule rule = GetApplicableRule (dateTime);
 689                                 if (rule != null)
 690                                         return BaseUtcOffset + rule.DaylightDelta;
 691                         }
 692
 693                         return BaseUtcOffset;
 694                 }
 695
 696                 public TimeSpan GetUtcOffset (DateTimeOffset dateTimeOffset)
 697                 {
 698                         throw new NotImplementedException ();
 699                 }
 700
 701                 public bool HasSameRules (TimeZoneInfo other)
 702                 {
 703                         if (other == null)
 704                                 throw new ArgumentNullException ("other");
 705
 706                         if ((this.adjustmentRules == null) != (other.adjustmentRules == null))
 707                                 return false;
 708
 709                         if (this.adjustmentRules == null)
 710                                 return true;
 711
 712                         if (this.BaseUtcOffset != other.BaseUtcOffset)
 713                                 return false;
 714
 715                         if (this.adjustmentRules.Length != other.adjustmentRules.Length)
 716                                 return false;
 717
 718                         for (int i = 0; i < adjustmentRules.Length; i++) {
 719                                 if (! (this.adjustmentRules [i]).Equals (other.adjustmentRules [i]))
 720                                         return false;
 721                         }
 722
 723                         return true;
 724                 }
 725
 726                 public bool IsAmbiguousTime (DateTime dateTime)
 727                 {
 728                         if (dateTime.Kind == DateTimeKind.Local && IsInvalidTime (dateTime))
 729                                 throw new ArgumentException ("Kind is Local and time is Invalid");
 730
 731                         if (this == TimeZoneInfo.Utc)
 732                                 return false;
 733
 734                         if (dateTime.Kind == DateTimeKind.Utc)
 735                                 dateTime = ConvertTimeFromUtc (dateTime);
 736
 737                         if (dateTime.Kind == DateTimeKind.Local && this != TimeZoneInfo.Local)
 738                                 dateTime = ConvertTime (dateTime, TimeZoneInfo.Local, this);
 739
 740                         AdjustmentRule rule = GetApplicableRule (dateTime);
 741                         if (rule != null) {
 742                                 DateTime tpoint = TransitionPoint (rule.DaylightTransitionEnd, dateTime.Year);
 743                                 if (dateTime > tpoint - rule.DaylightDelta  && dateTime <= tpoint)
 744                                         return true;
 745                         }
 746
 747                         return false;
 748                 }
 749
 750                 public bool IsAmbiguousTime (DateTimeOffset dateTimeOffset)
 751                 {
 752                         throw new NotImplementedException ();
 753                 }
 754
 755                 bool IsInDSTForYear (AdjustmentRule rule, DateTime dateTime, int year)
 756                 {
 757                         DateTime DST_start = TransitionPoint (rule.DaylightTransitionStart, year);
 758                         DateTime DST_end = TransitionPoint (rule.DaylightTransitionEnd, year + ((rule.DaylightTransitionStart.Month < rule.DaylightTransitionEnd.Month) ? 0 : 1));
 759                         if (dateTime.Kind == DateTimeKind.Utc) {
 760                                 DST_start -= BaseUtcOffset;
 761                                 DST_end -= (BaseUtcOffset + rule.DaylightDelta);
 762                         }
 763
 764                         return (dateTime >= DST_start && dateTime < DST_end);
 765                 }
 766
 767                 public bool IsDaylightSavingTime (DateTime dateTime)
 768                 {
 769                         if (dateTime.Kind == DateTimeKind.Local && IsInvalidTime (dateTime))
 770                                 throw new ArgumentException ("dateTime is invalid and Kind is Local");
 771
 772                         if (this == TimeZoneInfo.Utc)
 773                                 return false;
 774
 775                         if (!SupportsDaylightSavingTime)
 776                                 return false;
 777
 778                         //FIXME: do not rely on DateTime implementation !
 779                         if ((dateTime.Kind == DateTimeKind.Local || dateTime.Kind == DateTimeKind.Unspecified) && this == TimeZoneInfo.Local)
 780                                 return dateTime.IsDaylightSavingTime ();
 781
 782                         //FIXME: do not rely on DateTime implementation !
 783                         if (dateTime.Kind == DateTimeKind.Local && this != TimeZoneInfo.Utc)
 784                                 return IsDaylightSavingTime (DateTime.SpecifyKind (dateTime.ToUniversalTime (), DateTimeKind.Utc));
 785
 786                         AdjustmentRule rule = GetApplicableRule (dateTime.Date);
 787                         if (rule == null)
 788                                 return false;
 789
 790                         // Check whether we're in the dateTime year's DST period
 791                         if (IsInDSTForYear (rule, dateTime, dateTime.Year))
 792                                 return true;
 793
 794                         // We might be in the dateTime previous year's DST period
 795                         return IsInDSTForYear (rule, dateTime, dateTime.Year - 1);
 796                 }
 797
 798                 public bool IsDaylightSavingTime (DateTimeOffset dateTimeOffset)
 799                 {
 800                         throw new NotImplementedException ();
 801                 }
 802
 803                 public bool IsInvalidTime (DateTime dateTime)
 804                 {
 805                         if (dateTime.Kind == DateTimeKind.Utc)
 806                                 return false;
 807                         if (dateTime.Kind == DateTimeKind.Local && this != Local)
 808                                 return false;
 809
 810                         AdjustmentRule rule = GetApplicableRule (dateTime);
 811                         if (rule != null) {
 812                                 DateTime tpoint = TransitionPoint (rule.DaylightTransitionStart, dateTime.Year);
 813                                 if (dateTime >= tpoint && dateTime < tpoint + rule.DaylightDelta)
 814                                         return true;
 815                         }
 816
 817                         return false;
 818                 }
 819
 820 #if NET_4_0
 821                 void IDeserializationCallback.OnDeserialization (object sender)
 822 #else
 823                 public void OnDeserialization (object sender)
 824 #endif
 825                 {
 826                         try {
 827                                         TimeZoneInfo.Validate (id, baseUtcOffset, adjustmentRules);
 828                                 } catch (ArgumentException ex) {
 829                                         throw new SerializationException ("invalid serialization data", ex);
 830                                 }
 831                 }
 832
 833                 private static void Validate (string id, TimeSpan baseUtcOffset, AdjustmentRule [] adjustmentRules)
 834                 {
 835                         if (id == null)
 836                                 throw new ArgumentNullException ("id");
 837
 838                         if (id == String.Empty)
 839                                 throw new ArgumentException ("id parameter is an empty string");
 840
 841                         if (baseUtcOffset.Ticks % TimeSpan.TicksPerMinute != 0)
 842                                 throw new ArgumentException ("baseUtcOffset parameter does not represent a whole number of minutes");
 843
 844                         if (baseUtcOffset > new TimeSpan (14, 0, 0) || baseUtcOffset < new TimeSpan (-14, 0, 0))
 845                                 throw new ArgumentOutOfRangeException ("baseUtcOffset parameter is greater than 14 hours or less than -14 hours");
 846
 847 #if STRICT
 848                         if (id.Length > 32)
 849                                 throw new ArgumentException ("id parameter shouldn't be longer than 32 characters");
 850 #endif
 851
 852                         if (adjustmentRules != null && adjustmentRules.Length != 0) {
 853                                 AdjustmentRule prev = null;
 854                                 foreach (AdjustmentRule current in adjustmentRules) {
 855                                         if (current == null)
 856                                                 throw new InvalidTimeZoneException ("one or more elements in adjustmentRules are null");
 857
 858                                         if ((baseUtcOffset + current.DaylightDelta < new TimeSpan (-14, 0, 0)) ||
 859                                                         (baseUtcOffset + current.DaylightDelta > new TimeSpan (14, 0, 0)))
 860                                                 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;");
 861
 862                                         if (prev != null && prev.DateStart > current.DateStart)
 863                                                 throw new InvalidTimeZoneException ("adjustment rules specified in adjustmentRules parameter are not in chronological order");
 864
 865                                         if (prev != null && prev.DateEnd > current.DateStart)
 866                                                 throw new InvalidTimeZoneException ("some adjustment rules in the adjustmentRules parameter overlap");
 867
 868                                         if (prev != null && prev.DateEnd == current.DateStart)
 869                                                 throw new InvalidTimeZoneException ("a date can have multiple adjustment rules applied to it");
 870
 871                                         prev = current;
 872                                 }
 873                         }
 874                 }
 875
 876                 public override string ToString ()
 877                 {
 878                         return DisplayName;
 879                 }
 880
 881                 private TimeZoneInfo (SerializationInfo info, StreamingContext context)
 882                 {
 883                         if (info == null)
 884                                 throw new ArgumentNullException ("info");
 885                         id = (string) info.GetValue ("Id", typeof (string));
 886                         displayName = (string) info.GetValue ("DisplayName", typeof (string));
 887                         standardDisplayName = (string) info.GetValue ("StandardName", typeof (string));
 888                         daylightDisplayName = (string) info.GetValue ("DaylightName", typeof (string));
 889                         baseUtcOffset = (TimeSpan) info.GetValue ("BaseUtcOffset", typeof (TimeSpan));
 890                         adjustmentRules = (TimeZoneInfo.AdjustmentRule []) info.GetValue ("AdjustmentRules", typeof (TimeZoneInfo.AdjustmentRule []));
 891                         supportsDaylightSavingTime = (bool) info.GetValue ("SupportsDaylightSavingTime", typeof (bool));
 892                 }
 893
 894                 private TimeZoneInfo (string id, TimeSpan baseUtcOffset, string displayName, string standardDisplayName, string daylightDisplayName, TimeZoneInfo.AdjustmentRule [] adjustmentRules, bool disableDaylightSavingTime)
 895                 {
 896                         if (id == null)
 897                                 throw new ArgumentNullException ("id");
 898
 899                         if (id == String.Empty)
 900                                 throw new ArgumentException ("id parameter is an empty string");
 901
 902                         if (baseUtcOffset.Ticks % TimeSpan.TicksPerMinute != 0)
 903                                 throw new ArgumentException ("baseUtcOffset parameter does not represent a whole number of minutes");
 904
 905                         if (baseUtcOffset > new TimeSpan (14, 0, 0) || baseUtcOffset < new TimeSpan (-14, 0, 0))
 906                                 throw new ArgumentOutOfRangeException ("baseUtcOffset parameter is greater than 14 hours or less than -14 hours");
 907
 908 #if STRICT
 909                         if (id.Length > 32)
 910                                 throw new ArgumentException ("id parameter shouldn't be longer than 32 characters");
 911 #endif
 912
 913                         bool supportsDaylightSavingTime = !disableDaylightSavingTime;
 914
 915                         if (adjustmentRules != null && adjustmentRules.Length != 0) {
 916                                 AdjustmentRule prev = null;
 917                                 foreach (AdjustmentRule current in adjustmentRules) {
 918                                         if (current == null)
 919                                                 throw new InvalidTimeZoneException ("one or more elements in adjustmentRules are null");
 920
 921                                         if ((baseUtcOffset + current.DaylightDelta < new TimeSpan (-14, 0, 0)) ||
 922                                                         (baseUtcOffset + current.DaylightDelta > new TimeSpan (14, 0, 0)))
 923                                                 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;");
 924
 925                                         if (prev != null && prev.DateStart > current.DateStart)
 926                                                 throw new InvalidTimeZoneException ("adjustment rules specified in adjustmentRules parameter are not in chronological order");
 927
 928                                         if (prev != null && prev.DateEnd > current.DateStart)
 929                                                 throw new InvalidTimeZoneException ("some adjustment rules in the adjustmentRules parameter overlap");
 930
 931                                         if (prev != null && prev.DateEnd == current.DateStart)
 932                                                 throw new InvalidTimeZoneException ("a date can have multiple adjustment rules applied to it");
 933
 934                                         prev = current;
 935                                 }
 936                         } else {
 937                                 supportsDaylightSavingTime = false;
 938                         }
 939
 940                         this.id = id;
 941                         this.baseUtcOffset = baseUtcOffset;
 942                         this.displayName = displayName ?? id;
 943                         this.standardDisplayName = standardDisplayName ?? id;
 944                         this.daylightDisplayName = daylightDisplayName;
 945                         this.supportsDaylightSavingTime = supportsDaylightSavingTime;
 946                         this.adjustmentRules = adjustmentRules;
 947                 }
 948
 949                 private AdjustmentRule GetApplicableRule (DateTime dateTime)
 950                 {
 951                         //Transitions are always in standard time
 952                         DateTime date = dateTime;
 953
 954                         if (dateTime.Kind == DateTimeKind.Local && this != TimeZoneInfo.Local)
 955                                 date = date.ToUniversalTime () + BaseUtcOffset;
 956
 957                         if (dateTime.Kind == DateTimeKind.Utc && this != TimeZoneInfo.Utc)
 958                                 date = date + BaseUtcOffset;
 959
 960                         if (adjustmentRules != null) {
 961                                 foreach (AdjustmentRule rule in adjustmentRules) {
 962                                         if (rule.DateStart > date.Date)
 963                                                 return null;
 964                                         if (rule.DateEnd < date.Date)
 965                                                 continue;
 966                                         return rule;
 967                                 }
 968                         }
 969                         return null;
 970                 }
 971
 972                 private static DateTime TransitionPoint (TransitionTime transition, int year)
 973                 {
 974                         if (transition.IsFixedDateRule)
 975                                 return new DateTime (year, transition.Month, transition.Day) + transition.TimeOfDay.TimeOfDay;
 976
 977                         DayOfWeek first = (new DateTime (year, transition.Month, 1)).DayOfWeek;
 978                         int day = 1 + (transition.Week - 1) * 7 + (transition.DayOfWeek - first) % 7;
 979                         if (day >  DateTime.DaysInMonth (year, transition.Month))
 980                                 day -= 7;
 981                         if (day < 1)
 982                                 day += 7;
 983                         return new DateTime (year, transition.Month, day) + transition.TimeOfDay.TimeOfDay;
 984                 }
 985
 986                 static List<AdjustmentRule> ValidateRules (List<AdjustmentRule> adjustmentRules)
 987                 {
 988                         AdjustmentRule prev = null;
 989                         foreach (AdjustmentRule current in adjustmentRules.ToArray ()) {
 990                                 if (prev != null && prev.DateEnd > current.DateStart) {
 991                                         adjustmentRules.Remove (current);
 992                                 }
 993                                 prev = current;
 994                         }
 995                         return adjustmentRules;
 996                 }
 997
 998 #if LIBC || MONODROID
 999                 private static bool ValidTZFile (byte [] buffer, int length)
1000                 {
1001                         StringBuilder magic = new StringBuilder ();
1002
1003                         for (int i = 0; i < 4; i++)
1004                                 magic.Append ((char)buffer [i]);
1005
1006                         if (magic.ToString () != "TZif")
1007                                 return false;
1008
1009                         if (length >= BUFFER_SIZE)
1010                                 return false;
1011
1012                         return true;
1013                 }
1014
1015                 static int SwapInt32 (int i)
1016                 {
1017                         return (((i >> 24) & 0xff)
1018                                 | ((i >> 8) & 0xff00)
1019                                 | ((i << 8) & 0xff0000)
1020                                 | ((i << 24)));
1021                 }
1022
1023                 static int ReadBigEndianInt32 (byte [] buffer, int start)
1024                 {
1025                         int i = BitConverter.ToInt32 (buffer, start);
1026                         if (!BitConverter.IsLittleEndian)
1027                                 return i;
1028
1029                         return SwapInt32 (i);
1030                 }
1031
1032                 private static TimeZoneInfo ParseTZBuffer (string id, byte [] buffer, int length)
1033                 {
1034                         //Reading the header. 4 bytes for magic, 16 are reserved
1035                         int ttisgmtcnt = ReadBigEndianInt32 (buffer, 20);
1036                         int ttisstdcnt = ReadBigEndianInt32 (buffer, 24);
1037                         int leapcnt = ReadBigEndianInt32 (buffer, 28);
1038                         int timecnt = ReadBigEndianInt32 (buffer, 32);
1039                         int typecnt = ReadBigEndianInt32 (buffer, 36);
1040                         int charcnt = ReadBigEndianInt32 (buffer, 40);
1041
1042                         if (length < 44 + timecnt * 5 + typecnt * 6 + charcnt + leapcnt * 8 + ttisstdcnt + ttisgmtcnt)
1043                                 throw new InvalidTimeZoneException ();
1044
1045                         Dictionary<int, string> abbreviations = ParseAbbreviations (buffer, 44 + 4 * timecnt + timecnt + 6 * typecnt, charcnt);
1046                         Dictionary<int, TimeType> time_types = ParseTimesTypes (buffer, 44 + 4 * timecnt + timecnt, typecnt, abbreviations);
1047                         List<KeyValuePair<DateTime, TimeType>> transitions = ParseTransitions (buffer, 44, timecnt, time_types);
1048
1049                         if (time_types.Count == 0)
1050                                 throw new InvalidTimeZoneException ();
1051
1052                         if (time_types.Count == 1 && ((TimeType)time_types[0]).IsDst)
1053                                 throw new InvalidTimeZoneException ();
1054
1055                         TimeSpan baseUtcOffset = new TimeSpan (0);
1056                         TimeSpan dstDelta = new TimeSpan (0);
1057                         string standardDisplayName = null;
1058                         string daylightDisplayName = null;
1059                         bool dst_observed = false;
1060                         DateTime dst_start = DateTime.MinValue;
1061                         List<AdjustmentRule> adjustmentRules = new List<AdjustmentRule> ();
1062
1063                         for (int i = 0; i < transitions.Count; i++) {
1064                                 var pair = transitions [i];
1065                                 DateTime ttime = pair.Key;
1066                                 TimeType ttype = pair.Value;
1067                                 if (!ttype.IsDst) {
1068                                         if (standardDisplayName != ttype.Name || baseUtcOffset.TotalSeconds != ttype.Offset) {
1069                                                 standardDisplayName = ttype.Name;
1070                                                 daylightDisplayName = null;
1071                                                 baseUtcOffset = new TimeSpan (0, 0, ttype.Offset);
1072                                                 adjustmentRules = new List<AdjustmentRule> ();
1073                                                 dst_observed = false;
1074                                         }
1075                                         if (dst_observed) {
1076                                                 //FIXME: check additional fields for this:
1077                                                 //most of the transitions are expressed in GMT
1078                                                 dst_start += baseUtcOffset;
1079                                                 DateTime dst_end = ttime + baseUtcOffset + dstDelta;
1080
1081                                                 //some weird timezone (America/Phoenix) have end dates on Jan 1st
1082                                                 if (dst_end.Date == new DateTime (dst_end.Year, 1, 1) && dst_end.Year > dst_start.Year)
1083                                                         dst_end -= new TimeSpan (24, 0, 0);
1084
1085                                                 DateTime dateStart, dateEnd;
1086                                                 if (dst_start.Month < 7)
1087                                                         dateStart = new DateTime (dst_start.Year, 1, 1);
1088                                                 else
1089                                                         dateStart = new DateTime (dst_start.Year, 7, 1);
1090
1091                                                 if (dst_end.Month >= 7)
1092                                                         dateEnd = new DateTime (dst_end.Year, 12, 31);
1093                                                 else
1094                                                         dateEnd = new DateTime (dst_end.Year, 6, 30);
1095
1096
1097                                                 TransitionTime transition_start = TransitionTime.CreateFixedDateRule (new DateTime (1, 1, 1) + dst_start.TimeOfDay, dst_start.Month, dst_start.Day);
1098                                                 TransitionTime transition_end = TransitionTime.CreateFixedDateRule (new DateTime (1, 1, 1) + dst_end.TimeOfDay, dst_end.Month, dst_end.Day);
1099                                                 if  (transition_start != transition_end) //y, that happened in Argentina in 1943-1946
1100                                                         adjustmentRules.Add (AdjustmentRule.CreateAdjustmentRule (dateStart, dateEnd, dstDelta, transition_start, transition_end));
1101                                         }
1102                                         dst_observed = false;
1103                                 } else {
1104                                         if (daylightDisplayName != ttype.Name || dstDelta.TotalSeconds != ttype.Offset - baseUtcOffset.TotalSeconds) {
1105                                                 daylightDisplayName = ttype.Name;
1106                                                 dstDelta = new TimeSpan(0, 0, ttype.Offset) - baseUtcOffset;
1107                                         }
1108                                         dst_start = ttime;
1109                                         dst_observed = true;
1110                                 }
1111                         }
1112
1113                         if (adjustmentRules.Count == 0) {
1114                                 TimeType t = (TimeType)time_types [0];
1115                                 if (standardDisplayName == null) {
1116                                         standardDisplayName = t.Name;
1117                                         baseUtcOffset = new TimeSpan (0, 0, t.Offset);
1118                                 }
1119                                 return CreateCustomTimeZone (id, baseUtcOffset, id, standardDisplayName);
1120                         } else {
1121                                 return CreateCustomTimeZone (id, baseUtcOffset, id, standardDisplayName, daylightDisplayName, ValidateRules (adjustmentRules).ToArray ());
1122                         }
1123                 }
1124
1125                 static Dictionary<int, string> ParseAbbreviations (byte [] buffer, int index, int count)
1126                 {
1127                         var abbrevs = new Dictionary<int, string> ();
1128                         int abbrev_index = 0;
1129                         var sb = new StringBuilder ();
1130                         for (int i = 0; i < count; i++) {
1131                                 char c = (char) buffer [index + i];
1132                                 if (c != '\0')
1133                                         sb.Append (c);
1134                                 else {
1135                                         abbrevs.Add (abbrev_index, sb.ToString ());
1136                                         //Adding all the substrings too, as it seems to be used, at least for Africa/Windhoek
1137                                         for (int j = 1; j < sb.Length; j++)
1138                                                 abbrevs.Add (abbrev_index + j, sb.ToString (j, sb.Length - j));
1139                                         abbrev_index = i + 1;
1140                                         sb = new StringBuilder ();
1141                                 }
1142                         }
1143                         return abbrevs;
1144                 }
1145
1146                 static Dictionary<int, TimeType> ParseTimesTypes (byte [] buffer, int index, int count, Dictionary<int, string> abbreviations)
1147                 {
1148                         var types = new Dictionary<int, TimeType> (count);
1149                         for (int i = 0; i < count; i++) {
1150                                 int offset = ReadBigEndianInt32 (buffer, index + 6 * i);
1151                                 byte is_dst = buffer [index + 6 * i + 4];
1152                                 byte abbrev = buffer [index + 6 * i + 5];
1153                                 types.Add (i, new TimeType (offset, (is_dst != 0), abbreviations [(int)abbrev]));
1154                         }
1155                         return types;
1156                 }
1157
1158                 static List<KeyValuePair<DateTime, TimeType>> ParseTransitions (byte [] buffer, int index, int count, Dictionary<int, TimeType> time_types)
1159                 {
1160                         var list = new List<KeyValuePair<DateTime, TimeType>> (count);
1161                         for (int i = 0; i < count; i++) {
1162                                 int unixtime = ReadBigEndianInt32 (buffer, index + 4 * i);
1163                                 DateTime ttime = DateTimeFromUnixTime (unixtime);
1164                                 byte ttype = buffer [index + 4 * count + i];
1165                                 list.Add (new KeyValuePair<DateTime, TimeType> (ttime, time_types [(int)ttype]));
1166                         }
1167                         return list;
1168                 }
1169
1170                 static DateTime DateTimeFromUnixTime (long unix_time)
1171                 {
1172                         DateTime date_time = new DateTime (1970, 1, 1);
1173                         return date_time.AddSeconds (unix_time);
1174                 }
1175         }
1176
1177         struct TimeType {
1178                 public readonly int Offset;
1179                 public readonly bool IsDst;
1180                 public string Name;
1181
1182                 public TimeType (int offset, bool is_dst, string abbrev)
1183                 {
1184                         this.Offset = offset;
1185                         this.IsDst = is_dst;
1186                         this.Name = abbrev;
1187                 }
1188
1189                 public override string ToString ()
1190                 {
1191                         return "offset: " + Offset + "s, is_dst: " + IsDst + ", zone name: " + Name;
1192                 }
1193 #else
1194         }
1195 #endif
1196         }
1197 }
1198
1199 #endif