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.Default;
 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);
 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 static TimeZoneInfo FromSerializedString (string source)
 576                 {
 577                         throw new NotImplementedException ();
 578                 }
 579
 580                 public AdjustmentRule [] GetAdjustmentRules ()
 581                 {
 582                         if (!supportsDaylightSavingTime)
 583                                 return new AdjustmentRule [0];
 584                         else
 585                                 return (AdjustmentRule []) adjustmentRules.Clone ();
 586                 }
 587
 588                 public TimeSpan [] GetAmbiguousTimeOffsets (DateTime dateTime)
 589                 {
 590                         if (!IsAmbiguousTime (dateTime))
 591                                 throw new ArgumentException ("dateTime is not an ambiguous time");
 592
 593                         AdjustmentRule rule = GetApplicableRule (dateTime);
 594                         if (rule != null)
 595                                 return new TimeSpan[] {baseUtcOffset, baseUtcOffset + rule.DaylightDelta};
 596                         else
 597                                 return new TimeSpan[] {baseUtcOffset, baseUtcOffset};
 598                 }
 599
 600                 public TimeSpan [] GetAmbiguousTimeOffsets (DateTimeOffset dateTimeOffset)
 601                 {
 602                         if (!IsAmbiguousTime (dateTimeOffset))
 603                                 throw new ArgumentException ("dateTimeOffset is not an ambiguous time");
 604
 605                         throw new NotImplementedException ();
 606                 }
 607
 608                 public override int GetHashCode ()
 609                 {
 610                         int hash_code = Id.GetHashCode ();
 611                         foreach (AdjustmentRule rule in GetAdjustmentRules ())
 612                                 hash_code ^= rule.GetHashCode ();
 613                         return hash_code;
 614                 }
 615
 616 #if NET_4_0
 617                 void ISerializable.GetObjectData (SerializationInfo info, StreamingContext context)
 618 #else
 619                 public void GetObjectData (SerializationInfo info, StreamingContext context)
 620 #endif
 621                 {
 622                         if (info == null)
 623                                 throw new ArgumentNullException ("info");
 624                         info.AddValue ("Id", id);
 625                         info.AddValue ("DisplayName", displayName);
 626                         info.AddValue ("StandardName", standardDisplayName);
 627                         info.AddValue ("DaylightName", daylightDisplayName);
 628                         info.AddValue ("BaseUtcOffset", baseUtcOffset);
 629                         info.AddValue ("AdjustmentRules", adjustmentRules);
 630                         info.AddValue ("SupportsDaylightSavingTime", SupportsDaylightSavingTime);
 631                 }
 632
 633                 //FIXME: change this to a generic Dictionary and allow caching for FindSystemTimeZoneById
 634                 private static List<TimeZoneInfo> systemTimeZones;
 635                 public static ReadOnlyCollection<TimeZoneInfo> GetSystemTimeZones ()
 636                 {
 637                         if (systemTimeZones == null) {
 638                                 systemTimeZones = new List<TimeZoneInfo> ();
 639 #if !NET_2_1
 640                                 if (TimeZoneKey != null) {
 641                                         foreach (string id in TimeZoneKey.GetSubKeyNames ()) {
 642                                                 try {
 643                                                         systemTimeZones.Add (FindSystemTimeZoneById (id));
 644                                                 } catch {}
 645                                         }
 646
 647                                         return new ReadOnlyCollection<TimeZoneInfo> (systemTimeZones);
 648                                 }
 649 #endif
 650 #if MONODROID
 651                         foreach (string id in AndroidTimeZones.GetAvailableIds ()) {
 652                                 var tz = AndroidTimeZones.GetTimeZone (id);
 653                                 if (tz != null)
 654                                         systemTimeZones.Add (tz);
 655                         }
 656 #elif MONOTOUCH
 657                                 if (systemTimeZones.Count == 0) {
 658                                         foreach (string name in GetMonoTouchNames ()) {
 659                                                 using (Stream stream = GetMonoTouchData (name)) {
 660                                                         systemTimeZones.Add (BuildFromStream (name, stream));
 661                                                 }
 662                                         }
 663                                 }
 664 #elif LIBC
 665                                 string[] continents = new string [] {"Africa", "America", "Antarctica", "Arctic", "Asia", "Atlantic", "Brazil", "Canada", "Chile", "Europe", "Indian", "Mexico", "Mideast", "Pacific", "US"};
 666                                 foreach (string continent in continents) {
 667                                         try {
 668                                                 foreach (string zonepath in Directory.GetFiles (Path.Combine (TimeZoneDirectory, continent))) {
 669                                                         try {
 670                                                                 string id = String.Format ("{0}/{1}", continent, Path.GetFileName (zonepath));
 671                                                                 systemTimeZones.Add (FindSystemTimeZoneById (id));
 672                                                         } catch (ArgumentNullException) {
 673                                                         } catch (TimeZoneNotFoundException) {
 674                                                         } catch (InvalidTimeZoneException) {
 675                                                         } catch (Exception) {
 676                                                                 throw;
 677                                                         }
 678                                                 }
 679                                         } catch {}
 680                                 }
 681 #else
 682                                 throw new NotImplementedException ("This method is not implemented for this platform");
 683 #endif
 684                         }
 685                         return new ReadOnlyCollection<TimeZoneInfo> (systemTimeZones);
 686                 }
 687
 688                 public TimeSpan GetUtcOffset (DateTime dateTime)
 689                 {
 690                         if (IsDaylightSavingTime (dateTime)) {
 691                                 AdjustmentRule rule = GetApplicableRule (dateTime);
 692                                 if (rule != null)
 693                                         return BaseUtcOffset + rule.DaylightDelta;
 694                         }
 695
 696                         return BaseUtcOffset;
 697                 }
 698
 699                 public TimeSpan GetUtcOffset (DateTimeOffset dateTimeOffset)
 700                 {
 701                         throw new NotImplementedException ();
 702                 }
 703
 704                 public bool HasSameRules (TimeZoneInfo other)
 705                 {
 706                         if (other == null)
 707                                 throw new ArgumentNullException ("other");
 708
 709                         if ((this.adjustmentRules == null) != (other.adjustmentRules == null))
 710                                 return false;
 711
 712                         if (this.adjustmentRules == null)
 713                                 return true;
 714
 715                         if (this.BaseUtcOffset != other.BaseUtcOffset)
 716                                 return false;
 717
 718                         if (this.adjustmentRules.Length != other.adjustmentRules.Length)
 719                                 return false;
 720
 721                         for (int i = 0; i < adjustmentRules.Length; i++) {
 722                                 if (! (this.adjustmentRules [i]).Equals (other.adjustmentRules [i]))
 723                                         return false;
 724                         }
 725
 726                         return true;
 727                 }
 728
 729                 public bool IsAmbiguousTime (DateTime dateTime)
 730                 {
 731                         if (dateTime.Kind == DateTimeKind.Local && IsInvalidTime (dateTime))
 732                                 throw new ArgumentException ("Kind is Local and time is Invalid");
 733
 734                         if (this == TimeZoneInfo.Utc)
 735                                 return false;
 736
 737                         if (dateTime.Kind == DateTimeKind.Utc)
 738                                 dateTime = ConvertTimeFromUtc (dateTime);
 739
 740                         if (dateTime.Kind == DateTimeKind.Local && this != TimeZoneInfo.Local)
 741                                 dateTime = ConvertTime (dateTime, TimeZoneInfo.Local, this);
 742
 743                         AdjustmentRule rule = GetApplicableRule (dateTime);
 744                         if (rule != null) {
 745                                 DateTime tpoint = TransitionPoint (rule.DaylightTransitionEnd, dateTime.Year);
 746                                 if (dateTime > tpoint - rule.DaylightDelta  && dateTime <= tpoint)
 747                                         return true;
 748                         }
 749
 750                         return false;
 751                 }
 752
 753                 public bool IsAmbiguousTime (DateTimeOffset dateTimeOffset)
 754                 {
 755                         throw new NotImplementedException ();
 756                 }
 757
 758                 bool IsInDSTForYear (AdjustmentRule rule, DateTime dateTime, int year)
 759                 {
 760                         DateTime DST_start = TransitionPoint (rule.DaylightTransitionStart, year);
 761                         DateTime DST_end = TransitionPoint (rule.DaylightTransitionEnd, year + ((rule.DaylightTransitionStart.Month < rule.DaylightTransitionEnd.Month) ? 0 : 1));
 762                         if (dateTime.Kind == DateTimeKind.Utc) {
 763                                 DST_start -= BaseUtcOffset;
 764                                 DST_end -= (BaseUtcOffset + rule.DaylightDelta);
 765                         }
 766
 767                         return (dateTime >= DST_start && dateTime < DST_end);
 768                 }
 769
 770                 public bool IsDaylightSavingTime (DateTime dateTime)
 771                 {
 772                         if (dateTime.Kind == DateTimeKind.Local && IsInvalidTime (dateTime))
 773                                 throw new ArgumentException ("dateTime is invalid and Kind is Local");
 774
 775                         if (this == TimeZoneInfo.Utc)
 776                                 return false;
 777
 778                         if (!SupportsDaylightSavingTime)
 779                                 return false;
 780
 781                         //FIXME: do not rely on DateTime implementation !
 782                         if ((dateTime.Kind == DateTimeKind.Local || dateTime.Kind == DateTimeKind.Unspecified) && this == TimeZoneInfo.Local)
 783                                 return dateTime.IsDaylightSavingTime ();
 784
 785                         //FIXME: do not rely on DateTime implementation !
 786                         if (dateTime.Kind == DateTimeKind.Local && this != TimeZoneInfo.Utc)
 787                                 return IsDaylightSavingTime (DateTime.SpecifyKind (dateTime.ToUniversalTime (), DateTimeKind.Utc));
 788
 789                         AdjustmentRule rule = GetApplicableRule (dateTime.Date);
 790                         if (rule == null)
 791                                 return false;
 792
 793                         // Check whether we're in the dateTime year's DST period
 794                         if (IsInDSTForYear (rule, dateTime, dateTime.Year))
 795                                 return true;
 796
 797                         // We might be in the dateTime previous year's DST period
 798                         return IsInDSTForYear (rule, dateTime, dateTime.Year - 1);
 799                 }
 800
 801                 public bool IsDaylightSavingTime (DateTimeOffset dateTimeOffset)
 802                 {
 803                         throw new NotImplementedException ();
 804                 }
 805
 806                 public bool IsInvalidTime (DateTime dateTime)
 807                 {
 808                         if (dateTime.Kind == DateTimeKind.Utc)
 809                                 return false;
 810                         if (dateTime.Kind == DateTimeKind.Local && this != Local)
 811                                 return false;
 812
 813                         AdjustmentRule rule = GetApplicableRule (dateTime);
 814                         if (rule != null) {
 815                                 DateTime tpoint = TransitionPoint (rule.DaylightTransitionStart, dateTime.Year);
 816                                 if (dateTime >= tpoint && dateTime < tpoint + rule.DaylightDelta)
 817                                         return true;
 818                         }
 819
 820                         return false;
 821                 }
 822
 823 #if NET_4_0
 824                 void IDeserializationCallback.OnDeserialization (object sender)
 825 #else
 826                 public void OnDeserialization (object sender)
 827 #endif
 828                 {
 829                         try {
 830                                         TimeZoneInfo.Validate (id, baseUtcOffset, adjustmentRules);
 831                                 } catch (ArgumentException ex) {
 832                                         throw new SerializationException ("invalid serialization data", ex);
 833                                 }
 834                 }
 835
 836                 private static void Validate (string id, TimeSpan baseUtcOffset, AdjustmentRule [] adjustmentRules)
 837                 {
 838                         if (id == null)
 839                                 throw new ArgumentNullException ("id");
 840
 841                         if (id == String.Empty)
 842                                 throw new ArgumentException ("id parameter is an empty string");
 843
 844                         if (baseUtcOffset.Ticks % TimeSpan.TicksPerMinute != 0)
 845                                 throw new ArgumentException ("baseUtcOffset parameter does not represent a whole number of minutes");
 846
 847                         if (baseUtcOffset > new TimeSpan (14, 0, 0) || baseUtcOffset < new TimeSpan (-14, 0, 0))
 848                                 throw new ArgumentOutOfRangeException ("baseUtcOffset parameter is greater than 14 hours or less than -14 hours");
 849
 850 #if STRICT
 851                         if (id.Length > 32)
 852                                 throw new ArgumentException ("id parameter shouldn't be longer than 32 characters");
 853 #endif
 854
 855                         if (adjustmentRules != null && adjustmentRules.Length != 0) {
 856                                 AdjustmentRule prev = null;
 857                                 foreach (AdjustmentRule current in adjustmentRules) {
 858                                         if (current == null)
 859                                                 throw new InvalidTimeZoneException ("one or more elements in adjustmentRules are null");
 860
 861                                         if ((baseUtcOffset + current.DaylightDelta < new TimeSpan (-14, 0, 0)) ||
 862                                                         (baseUtcOffset + current.DaylightDelta > new TimeSpan (14, 0, 0)))
 863                                                 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;");
 864
 865                                         if (prev != null && prev.DateStart > current.DateStart)
 866                                                 throw new InvalidTimeZoneException ("adjustment rules specified in adjustmentRules parameter are not in chronological order");
 867
 868                                         if (prev != null && prev.DateEnd > current.DateStart)
 869                                                 throw new InvalidTimeZoneException ("some adjustment rules in the adjustmentRules parameter overlap");
 870
 871                                         if (prev != null && prev.DateEnd == current.DateStart)
 872                                                 throw new InvalidTimeZoneException ("a date can have multiple adjustment rules applied to it");
 873
 874                                         prev = current;
 875                                 }
 876                         }
 877                 }
 878
 879                 public string ToSerializedString ()
 880                 {
 881                         throw new NotImplementedException ();
 882                 }
 883
 884                 public override string ToString ()
 885                 {
 886                         return DisplayName;
 887                 }
 888
 889                 private TimeZoneInfo (SerializationInfo info, StreamingContext context)
 890                 {
 891                         if (info == null)
 892                                 throw new ArgumentNullException ("info");
 893                         id = (string) info.GetValue ("Id", typeof (string));
 894                         displayName = (string) info.GetValue ("DisplayName", typeof (string));
 895                         standardDisplayName = (string) info.GetValue ("StandardName", typeof (string));
 896                         daylightDisplayName = (string) info.GetValue ("DaylightName", typeof (string));
 897                         baseUtcOffset = (TimeSpan) info.GetValue ("BaseUtcOffset", typeof (TimeSpan));
 898                         adjustmentRules = (TimeZoneInfo.AdjustmentRule []) info.GetValue ("AdjustmentRules", typeof (TimeZoneInfo.AdjustmentRule []));
 899                         supportsDaylightSavingTime = (bool) info.GetValue ("SupportsDaylightSavingTime", typeof (bool));
 900                 }
 901
 902                 private TimeZoneInfo (string id, TimeSpan baseUtcOffset, string displayName, string standardDisplayName, string daylightDisplayName, TimeZoneInfo.AdjustmentRule [] adjustmentRules, bool disableDaylightSavingTime)
 903                 {
 904                         if (id == null)
 905                                 throw new ArgumentNullException ("id");
 906
 907                         if (id == String.Empty)
 908                                 throw new ArgumentException ("id parameter is an empty string");
 909
 910                         if (baseUtcOffset.Ticks % TimeSpan.TicksPerMinute != 0)
 911                                 throw new ArgumentException ("baseUtcOffset parameter does not represent a whole number of minutes");
 912
 913                         if (baseUtcOffset > new TimeSpan (14, 0, 0) || baseUtcOffset < new TimeSpan (-14, 0, 0))
 914                                 throw new ArgumentOutOfRangeException ("baseUtcOffset parameter is greater than 14 hours or less than -14 hours");
 915
 916 #if STRICT
 917                         if (id.Length > 32)
 918                                 throw new ArgumentException ("id parameter shouldn't be longer than 32 characters");
 919 #endif
 920
 921                         bool supportsDaylightSavingTime = !disableDaylightSavingTime;
 922
 923                         if (adjustmentRules != null && adjustmentRules.Length != 0) {
 924                                 AdjustmentRule prev = null;
 925                                 foreach (AdjustmentRule current in adjustmentRules) {
 926                                         if (current == null)
 927                                                 throw new InvalidTimeZoneException ("one or more elements in adjustmentRules are null");
 928
 929                                         if ((baseUtcOffset + current.DaylightDelta < new TimeSpan (-14, 0, 0)) ||
 930                                                         (baseUtcOffset + current.DaylightDelta > new TimeSpan (14, 0, 0)))
 931                                                 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;");
 932
 933                                         if (prev != null && prev.DateStart > current.DateStart)
 934                                                 throw new InvalidTimeZoneException ("adjustment rules specified in adjustmentRules parameter are not in chronological order");
 935
 936                                         if (prev != null && prev.DateEnd > current.DateStart)
 937                                                 throw new InvalidTimeZoneException ("some adjustment rules in the adjustmentRules parameter overlap");
 938
 939                                         if (prev != null && prev.DateEnd == current.DateStart)
 940                                                 throw new InvalidTimeZoneException ("a date can have multiple adjustment rules applied to it");
 941
 942                                         prev = current;
 943                                 }
 944                         } else {
 945                                 supportsDaylightSavingTime = false;
 946                         }
 947
 948                         this.id = id;
 949                         this.baseUtcOffset = baseUtcOffset;
 950                         this.displayName = displayName ?? id;
 951                         this.standardDisplayName = standardDisplayName ?? id;
 952                         this.daylightDisplayName = daylightDisplayName;
 953                         this.supportsDaylightSavingTime = supportsDaylightSavingTime;
 954                         this.adjustmentRules = adjustmentRules;
 955                 }
 956
 957                 private AdjustmentRule GetApplicableRule (DateTime dateTime)
 958                 {
 959                         //Transitions are always in standard time
 960                         DateTime date = dateTime;
 961
 962                         if (dateTime.Kind == DateTimeKind.Local && this != TimeZoneInfo.Local)
 963                                 date = date.ToUniversalTime () + BaseUtcOffset;
 964
 965                         if (dateTime.Kind == DateTimeKind.Utc && this != TimeZoneInfo.Utc)
 966                                 date = date + BaseUtcOffset;
 967
 968                         if (adjustmentRules != null) {
 969                                 foreach (AdjustmentRule rule in adjustmentRules) {
 970                                         if (rule.DateStart > date.Date)
 971                                                 return null;
 972                                         if (rule.DateEnd < date.Date)
 973                                                 continue;
 974                                         return rule;
 975                                 }
 976                         }
 977                         return null;
 978                 }
 979
 980                 private static DateTime TransitionPoint (TransitionTime transition, int year)
 981                 {
 982                         if (transition.IsFixedDateRule)
 983                                 return new DateTime (year, transition.Month, transition.Day) + transition.TimeOfDay.TimeOfDay;
 984
 985                         DayOfWeek first = (new DateTime (year, transition.Month, 1)).DayOfWeek;
 986                         int day = 1 + (transition.Week - 1) * 7 + (transition.DayOfWeek - first) % 7;
 987                         if (day >  DateTime.DaysInMonth (year, transition.Month))
 988                                 day -= 7;
 989                         return new DateTime (year, transition.Month, day) + transition.TimeOfDay.TimeOfDay;
 990                 }
 991
 992                 static List<AdjustmentRule> ValidateRules (List<AdjustmentRule> adjustmentRules)
 993                 {
 994                         AdjustmentRule prev = null;
 995                         foreach (AdjustmentRule current in adjustmentRules.ToArray ()) {
 996                                 if (prev != null && prev.DateEnd > current.DateStart) {
 997                                         adjustmentRules.Remove (current);
 998                                 }
 999                                 prev = current;
1000                         }
1001                         return adjustmentRules;
1002                 }
1003
1004 #if LIBC || MONODROID
1005                 private static bool ValidTZFile (byte [] buffer, int length)
1006                 {
1007                         StringBuilder magic = new StringBuilder ();
1008
1009                         for (int i = 0; i < 4; i++)
1010                                 magic.Append ((char)buffer [i]);
1011
1012                         if (magic.ToString () != "TZif")
1013                                 return false;
1014
1015                         if (length >= BUFFER_SIZE)
1016                                 return false;
1017
1018                         return true;
1019                 }
1020
1021                 static int SwapInt32 (int i)
1022                 {
1023                         return (((i >> 24) & 0xff)
1024                                 | ((i >> 8) & 0xff00)
1025                                 | ((i << 8) & 0xff0000)
1026                                 | ((i << 24)));
1027                 }
1028
1029                 static int ReadBigEndianInt32 (byte [] buffer, int start)
1030                 {
1031                         int i = BitConverter.ToInt32 (buffer, start);
1032                         if (!BitConverter.IsLittleEndian)
1033                                 return i;
1034
1035                         return SwapInt32 (i);
1036                 }
1037
1038                 private static TimeZoneInfo ParseTZBuffer (string id, byte [] buffer, int length)
1039                 {
1040                         //Reading the header. 4 bytes for magic, 16 are reserved
1041                         int ttisgmtcnt = ReadBigEndianInt32 (buffer, 20);
1042                         int ttisstdcnt = ReadBigEndianInt32 (buffer, 24);
1043                         int leapcnt = ReadBigEndianInt32 (buffer, 28);
1044                         int timecnt = ReadBigEndianInt32 (buffer, 32);
1045                         int typecnt = ReadBigEndianInt32 (buffer, 36);
1046                         int charcnt = ReadBigEndianInt32 (buffer, 40);
1047
1048                         if (length < 44 + timecnt * 5 + typecnt * 6 + charcnt + leapcnt * 8 + ttisstdcnt + ttisgmtcnt)
1049                                 throw new InvalidTimeZoneException ();
1050
1051                         Dictionary<int, string> abbreviations = ParseAbbreviations (buffer, 44 + 4 * timecnt + timecnt + 6 * typecnt, charcnt);
1052                         Dictionary<int, TimeType> time_types = ParseTimesTypes (buffer, 44 + 4 * timecnt + timecnt, typecnt, abbreviations);
1053                         List<KeyValuePair<DateTime, TimeType>> transitions = ParseTransitions (buffer, 44, timecnt, time_types);
1054
1055                         if (time_types.Count == 0)
1056                                 throw new InvalidTimeZoneException ();
1057
1058                         if (time_types.Count == 1 && ((TimeType)time_types[0]).IsDst)
1059                                 throw new InvalidTimeZoneException ();
1060
1061                         TimeSpan baseUtcOffset = new TimeSpan (0);
1062                         TimeSpan dstDelta = new TimeSpan (0);
1063                         string standardDisplayName = null;
1064                         string daylightDisplayName = null;
1065                         bool dst_observed = false;
1066                         DateTime dst_start = DateTime.MinValue;
1067                         List<AdjustmentRule> adjustmentRules = new List<AdjustmentRule> ();
1068
1069                         for (int i = 0; i < transitions.Count; i++) {
1070                                 var pair = transitions [i];
1071                                 DateTime ttime = pair.Key;
1072                                 TimeType ttype = pair.Value;
1073                                 if (!ttype.IsDst) {
1074                                         if (standardDisplayName != ttype.Name || baseUtcOffset.TotalSeconds != ttype.Offset) {
1075                                                 standardDisplayName = ttype.Name;
1076                                                 daylightDisplayName = null;
1077                                                 baseUtcOffset = new TimeSpan (0, 0, ttype.Offset);
1078                                                 adjustmentRules = new List<AdjustmentRule> ();
1079                                                 dst_observed = false;
1080                                         }
1081                                         if (dst_observed) {
1082                                                 //FIXME: check additional fields for this:
1083                                                 //most of the transitions are expressed in GMT
1084                                                 dst_start += baseUtcOffset;
1085                                                 DateTime dst_end = ttime + baseUtcOffset + dstDelta;
1086
1087                                                 //some weird timezone (America/Phoenix) have end dates on Jan 1st
1088                                                 if (dst_end.Date == new DateTime (dst_end.Year, 1, 1) && dst_end.Year > dst_start.Year)
1089                                                         dst_end -= new TimeSpan (24, 0, 0);
1090
1091                                                 DateTime dateStart, dateEnd;
1092                                                 if (dst_start.Month < 7)
1093                                                         dateStart = new DateTime (dst_start.Year, 1, 1);
1094                                                 else
1095                                                         dateStart = new DateTime (dst_start.Year, 7, 1);
1096
1097                                                 if (dst_end.Month >= 7)
1098                                                         dateEnd = new DateTime (dst_end.Year, 12, 31);
1099                                                 else
1100                                                         dateEnd = new DateTime (dst_end.Year, 6, 30);
1101
1102
1103                                                 TransitionTime transition_start = TransitionTime.CreateFixedDateRule (new DateTime (1, 1, 1) + dst_start.TimeOfDay, dst_start.Month, dst_start.Day);
1104                                                 TransitionTime transition_end = TransitionTime.CreateFixedDateRule (new DateTime (1, 1, 1) + dst_end.TimeOfDay, dst_end.Month, dst_end.Day);
1105                                                 if  (transition_start != transition_end) //y, that happened in Argentina in 1943-1946
1106                                                         adjustmentRules.Add (AdjustmentRule.CreateAdjustmentRule (dateStart, dateEnd, dstDelta, transition_start, transition_end));
1107                                         }
1108                                         dst_observed = false;
1109                                 } else {
1110                                         if (daylightDisplayName != ttype.Name || dstDelta.TotalSeconds != ttype.Offset - baseUtcOffset.TotalSeconds) {
1111                                                 daylightDisplayName = ttype.Name;
1112                                                 dstDelta = new TimeSpan(0, 0, ttype.Offset) - baseUtcOffset;
1113                                         }
1114                                         dst_start = ttime;
1115                                         dst_observed = true;
1116                                 }
1117                         }
1118
1119                         if (adjustmentRules.Count == 0) {
1120                                 TimeType t = (TimeType)time_types [0];
1121                                 if (standardDisplayName == null) {
1122                                         standardDisplayName = t.Name;
1123                                         baseUtcOffset = new TimeSpan (0, 0, t.Offset);
1124                                 }
1125                                 return CreateCustomTimeZone (id, baseUtcOffset, id, standardDisplayName);
1126                         } else {
1127                                 return CreateCustomTimeZone (id, baseUtcOffset, id, standardDisplayName, daylightDisplayName, ValidateRules (adjustmentRules).ToArray ());
1128                         }
1129                 }
1130
1131                 static Dictionary<int, string> ParseAbbreviations (byte [] buffer, int index, int count)
1132                 {
1133                         var abbrevs = new Dictionary<int, string> ();
1134                         int abbrev_index = 0;
1135                         var sb = new StringBuilder ();
1136                         for (int i = 0; i < count; i++) {
1137                                 char c = (char) buffer [index + i];
1138                                 if (c != '\0')
1139                                         sb.Append (c);
1140                                 else {
1141                                         abbrevs.Add (abbrev_index, sb.ToString ());
1142                                         //Adding all the substrings too, as it seems to be used, at least for Africa/Windhoek
1143                                         for (int j = 1; j < sb.Length; j++)
1144                                                 abbrevs.Add (abbrev_index + j, sb.ToString (j, sb.Length - j));
1145                                         abbrev_index = i + 1;
1146                                         sb = new StringBuilder ();
1147                                 }
1148                         }
1149                         return abbrevs;
1150                 }
1151
1152                 static Dictionary<int, TimeType> ParseTimesTypes (byte [] buffer, int index, int count, Dictionary<int, string> abbreviations)
1153                 {
1154                         var types = new Dictionary<int, TimeType> (count);
1155                         for (int i = 0; i < count; i++) {
1156                                 int offset = ReadBigEndianInt32 (buffer, index + 6 * i);
1157                                 byte is_dst = buffer [index + 6 * i + 4];
1158                                 byte abbrev = buffer [index + 6 * i + 5];
1159                                 types.Add (i, new TimeType (offset, (is_dst != 0), abbreviations [(int)abbrev]));
1160                         }
1161                         return types;
1162                 }
1163
1164                 static List<KeyValuePair<DateTime, TimeType>> ParseTransitions (byte [] buffer, int index, int count, Dictionary<int, TimeType> time_types)
1165                 {
1166                         var list = new List<KeyValuePair<DateTime, TimeType>> (count);
1167                         for (int i = 0; i < count; i++) {
1168                                 int unixtime = ReadBigEndianInt32 (buffer, index + 4 * i);
1169                                 DateTime ttime = DateTimeFromUnixTime (unixtime);
1170                                 byte ttype = buffer [index + 4 * count + i];
1171                                 list.Add (new KeyValuePair<DateTime, TimeType> (ttime, time_types [(int)ttype]));
1172                         }
1173                         return list;
1174                 }
1175
1176                 static DateTime DateTimeFromUnixTime (long unix_time)
1177                 {
1178                         DateTime date_time = new DateTime (1970, 1, 1);
1179                         return date_time.AddSeconds (unix_time);
1180                 }
1181         }
1182
1183         struct TimeType {
1184                 public readonly int Offset;
1185                 public readonly bool IsDst;
1186                 public string Name;
1187
1188                 public TimeType (int offset, bool is_dst, string abbrev)
1189                 {
1190                         this.Offset = offset;
1191                         this.IsDst = is_dst;
1192                         this.Name = abbrev;
1193                 }
1194
1195                 public override string ToString ()
1196                 {
1197                         return "offset: " + Offset + "s, is_dst: " + IsDst + ", zone name: " + Name;
1198                 }
1199 #else
1200         }
1201 #endif
1202         }
1203 }
1204
1205 #endif