mcs/class/System.Core/System/TimeZoneInfo.cs

   1 /*
   2  * System.TimeZoneInfo
   3  *
   4  * Author(s)
   5  *      Stephane Delcroix <stephane@delcroix.org>
   6  *
   7  * Copyright 2011 Xamarin Inc.
   8  *
   9  * Permission is hereby granted, free of charge, to any person obtaining
  10  * a copy of this software and associated documentation files (the
  11  * "Software"), to deal in the Software without restriction, including
  12  * without limitation the rights to use, copy, modify, merge, publish,
  13  * distribute, sublicense, and/or sell copies of the Software, and to
  14  * permit persons to whom the Software is furnished to do so, subject to
  15  * the following conditions:
  16  *
  17  * The above copyright notice and this permission notice shall be
  18  * included in all copies or substantial portions of the Software.
  19  *
  20  * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
  21  * EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
  22  * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
  23  * NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE
  24  * LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION
  25  * OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
  26  * WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
  27  */
  28
  29 using System;
  30 using System.Runtime.CompilerServices;
  31
  32 #if !INSIDE_CORLIB && (NET_4_0 || MOONLIGHT || MOBILE)
  33
  34 [assembly:TypeForwardedTo (typeof(TimeZoneInfo))]
  35
  36 #elif (INSIDE_CORLIB && (NET_4_0 || MOONLIGHT || MOBILE)) || (!INSIDE_CORLIB && (NET_3_5 && !NET_4_0 && !MOBILE))
  37
  38 using System.Collections.Generic;
  39 using System.Collections.ObjectModel;
  40 using System.Runtime.Serialization;
  41 using System.Text;
  42
  43 #if LIBC || MONODROID
  44 using System.IO;
  45 using Mono;
  46 #endif
  47
  48 using Microsoft.Win32;
  49
  50 namespace System
  51 {
  52 #if NET_4_0
  53         [TypeForwardedFrom (Consts.AssemblySystemCore_3_5)]
  54 #elif MOONLIGHT || MOBILE
  55         [TypeForwardedFrom (Consts.AssemblySystem_Core)]
  56 #endif
  57         [SerializableAttribute]
  58         public sealed partial class TimeZoneInfo : IEquatable<TimeZoneInfo>, ISerializable, IDeserializationCallback
  59         {
  60                 TimeSpan baseUtcOffset;
  61                 public TimeSpan BaseUtcOffset {
  62                         get { return baseUtcOffset; }
  63                 }
  64
  65                 string daylightDisplayName;
  66                 public string DaylightName {
  67                         get {
  68                                 return supportsDaylightSavingTime
  69                                         ? daylightDisplayName
  70                                         : string.Empty;
  71                         }
  72                 }
  73
  74                 string displayName;
  75                 public string DisplayName {
  76                         get { return displayName; }
  77                 }
  78
  79                 string id;
  80                 public string Id {
  81                         get { return id; }
  82                 }
  83
  84                 static TimeZoneInfo local;
  85                 public static TimeZoneInfo Local {
  86                         get {
  87                                 if (local == null) {
  88 #if MONODROID
  89                                         local = ZoneInfoDB.Default;
  90 #elif MONOTOUCH
  91                                         using (Stream stream = GetMonoTouchDefault ()) {
  92                                                 local = BuildFromStream ("Local", stream);
  93                                         }
  94 #elif LIBC
  95                                         try {
  96                                                 local = FindSystemTimeZoneByFileName ("Local", "/etc/localtime");
  97                                         } catch {
  98                                                 try {
  99                                                         local = FindSystemTimeZoneByFileName ("Local", Path.Combine (TimeZoneDirectory, "localtime"));
 100                                                 } catch {
 101                                                         throw new TimeZoneNotFoundException ();
 102                                                 }
 103                                         }
 104 #else
 105                                         if (IsWindows && LocalZoneKey != null) {
 106                                                 string name = (string)LocalZoneKey.GetValue ("TimeZoneKeyName");
 107                                                 name = TrimSpecial (name);
 108                                                 if (name != null)
 109                                                         local = TimeZoneInfo.FindSystemTimeZoneById (name);
 110                                         }
 111
 112                                         if (local == null)
 113                                                 throw new TimeZoneNotFoundException ();
 114 #endif
 115                                 }
 116                                 return local;
 117                         }
 118                 }
 119
 120                 string standardDisplayName;
 121                 public string StandardName {
 122                         get { return standardDisplayName; }
 123                 }
 124
 125                 bool supportsDaylightSavingTime;
 126                 public bool SupportsDaylightSavingTime {
 127                         get  { return supportsDaylightSavingTime; }
 128                 }
 129
 130                 static TimeZoneInfo utc;
 131                 public static TimeZoneInfo Utc {
 132                         get {
 133                                 if (utc == null)
 134                                         utc = CreateCustomTimeZone ("UTC", new TimeSpan (0), "UTC", "UTC");
 135                                 return utc;
 136                         }
 137                 }
 138 #if LIBC
 139                 static string timeZoneDirectory;
 140                 static string TimeZoneDirectory {
 141                         get {
 142                                 if (timeZoneDirectory == null)
 143                                         timeZoneDirectory = "/usr/share/zoneinfo";
 144                                 return timeZoneDirectory;
 145                         }
 146                         set {
 147                                 ClearCachedData ();
 148                                 timeZoneDirectory = value;
 149                         }
 150                 }
 151 #endif
 152                 private AdjustmentRule [] adjustmentRules;
 153
 154 #if !NET_2_1
 155                 /// <summary>
 156                 /// Determine whether windows of not (taken Stephane Delcroix's code)
 157                 /// </summary>
 158                 private static bool IsWindows
 159                 {
 160                         get {
 161                                 int platform = (int) Environment.OSVersion.Platform;
 162                                 return ((platform != 4) && (platform != 6) && (platform != 128));
 163                         }
 164                 }
 165
 166                 /// <summary>
 167                 /// Needed to trim misc garbage in MS registry keys
 168                 /// </summary>
 169                 private static string TrimSpecial (string str)
 170                 {
 171                         var Istart = 0;
 172                         while (Istart < str.Length && !char.IsLetterOrDigit(str[Istart])) Istart++;
 173                         var Iend = str.Length - 1;
 174                         while (Iend > Istart && !char.IsLetterOrDigit(str[Iend])) Iend--;
 175
 176                         return str.Substring (Istart, Iend-Istart+1);
 177                 }
 178
 179                 static RegistryKey timeZoneKey;
 180                 static RegistryKey TimeZoneKey {
 181                         get {
 182                                 if (timeZoneKey != null)
 183                                         return timeZoneKey;
 184                                 if (!IsWindows)
 185                                         return null;
 186
 187                                 return timeZoneKey = Registry.LocalMachine.OpenSubKey (
 188                                         "SOFTWARE\\Microsoft\\Windows NT\\CurrentVersion\\Time Zones",
 189                                         false);
 190                         }
 191                 }
 192
 193                 static RegistryKey localZoneKey;
 194                 static RegistryKey LocalZoneKey {
 195                         get {
 196                                 if (localZoneKey != null)
 197                                         return localZoneKey;
 198
 199                                 if (!IsWindows)
 200                                         return null;
 201
 202                                 return localZoneKey = Registry.LocalMachine.OpenSubKey (
 203                                         "SYSTEM\\CurrentControlSet\\Control\\TimeZoneInformation", false);
 204                         }
 205                 }
 206 #endif
 207
 208                 public static void ClearCachedData ()
 209                 {
 210                         local = null;
 211                         utc = null;
 212                         systemTimeZones = null;
 213                 }
 214
 215                 public static DateTime ConvertTime (DateTime dateTime, TimeZoneInfo destinationTimeZone)
 216                 {
 217                         return ConvertTime (dateTime, TimeZoneInfo.Local, destinationTimeZone);
 218                 }
 219
 220                 public static DateTime ConvertTime (DateTime dateTime, TimeZoneInfo sourceTimeZone, TimeZoneInfo destinationTimeZone)
 221                 {
 222                         if (dateTime.Kind == DateTimeKind.Local && sourceTimeZone != TimeZoneInfo.Local)
 223                                 throw new ArgumentException ("Kind property of dateTime is Local but the sourceTimeZone does not equal TimeZoneInfo.Local");
 224
 225                         if (dateTime.Kind == DateTimeKind.Utc && sourceTimeZone != TimeZoneInfo.Utc)
 226                                 throw new ArgumentException ("Kind property of dateTime is Utc but the sourceTimeZone does not equal TimeZoneInfo.Utc");
 227
 228                         if (sourceTimeZone.IsInvalidTime (dateTime))
 229                                 throw new ArgumentException ("dateTime parameter is an invalid time");
 230
 231                         if (sourceTimeZone == null)
 232                                 throw new ArgumentNullException ("sourceTimeZone");
 233
 234                         if (destinationTimeZone == null)
 235                                 throw new ArgumentNullException ("destinationTimeZone");
 236
 237                         if (dateTime.Kind == DateTimeKind.Local && sourceTimeZone == TimeZoneInfo.Local && destinationTimeZone == TimeZoneInfo.Local)
 238                                 return dateTime;
 239
 240                         DateTime utc = ConvertTimeToUtc (dateTime);
 241
 242                         if (destinationTimeZone == TimeZoneInfo.Utc)
 243                                 return utc;
 244
 245                         return ConvertTimeFromUtc (utc, destinationTimeZone);
 246
 247                 }
 248
 249                 public static DateTimeOffset ConvertTime(DateTimeOffset dateTimeOffset, TimeZoneInfo destinationTimeZone)
 250                 {
 251                         if (destinationTimeZone == null)
 252                                 throw new ArgumentNullException("destinationTimeZone");
 253
 254                         var utcDateTime = dateTimeOffset.UtcDateTime;
 255                         AdjustmentRule rule = GetApplicableRule (utcDateTime);
 256
 257                         if (rule != null && destinationTimeZone.IsDaylightSavingTime(utcDateTime)) {
 258                                 var offset = destinationTimeZone.BaseUtcOffset + rule.DaylightDelta;
 259                                 return new DateTimeOffset(DateTime.SpecifyKind(utcDateTime, DateTimeKind.Unspecified) + offset, offset);
 260                         }
 261                         else {
 262                                 return new DateTimeOffset(DateTime.SpecifyKind(utcDateTime, DateTimeKind.Unspecified) + destinationTimeZone.BaseUtcOffset, destinationTimeZone.BaseUtcOffset);
 263                         }
 264                 }
 265
 266                 public static DateTime ConvertTimeBySystemTimeZoneId (DateTime dateTime, string destinationTimeZoneId)
 267                 {
 268                         return ConvertTime (dateTime, FindSystemTimeZoneById (destinationTimeZoneId));
 269                 }
 270
 271                 public static DateTime ConvertTimeBySystemTimeZoneId (DateTime dateTime, string sourceTimeZoneId, string destinationTimeZoneId)
 272                 {
 273                         return ConvertTime (dateTime, FindSystemTimeZoneById (sourceTimeZoneId), FindSystemTimeZoneById (destinationTimeZoneId));
 274                 }
 275
 276                 public static DateTimeOffset ConvertTimeBySystemTimeZoneId (DateTimeOffset dateTimeOffset, string destinationTimeZoneId)
 277                 {
 278                         return ConvertTime (dateTimeOffset, FindSystemTimeZoneById (destinationTimeZoneId));
 279                 }
 280
 281                 private DateTime ConvertTimeFromUtc (DateTime dateTime)
 282                 {
 283                         if (dateTime.Kind == DateTimeKind.Local)
 284                                 throw new ArgumentException ("Kind property of dateTime is Local");
 285
 286                         if (this == TimeZoneInfo.Utc)
 287                                 return DateTime.SpecifyKind (dateTime, DateTimeKind.Utc);
 288
 289                         //FIXME: do not rely on DateTime implementation !
 290                         if (this == TimeZoneInfo.Local)
 291                                 return DateTime.SpecifyKind (dateTime.ToLocalTime (), DateTimeKind.Unspecified);
 292
 293                         AdjustmentRule rule = GetApplicableRule (dateTime);
 294
 295                         if (rule != null && IsDaylightSavingTime (DateTime.SpecifyKind (dateTime, DateTimeKind.Utc)))
 296                                 return DateTime.SpecifyKind (dateTime + BaseUtcOffset + rule.DaylightDelta , DateTimeKind.Unspecified);
 297                         else
 298                                 return DateTime.SpecifyKind (dateTime + BaseUtcOffset, DateTimeKind.Unspecified);
 299                 }
 300
 301                 public static DateTime ConvertTimeFromUtc (DateTime dateTime, TimeZoneInfo destinationTimeZone)
 302                 {
 303                         if (destinationTimeZone == null)
 304                                 throw new ArgumentNullException ("destinationTimeZone");
 305
 306                         return destinationTimeZone.ConvertTimeFromUtc (dateTime);
 307                 }
 308
 309                 public static DateTime ConvertTimeToUtc (DateTime dateTime)
 310                 {
 311                         if (dateTime.Kind == DateTimeKind.Utc)
 312                                 return dateTime;
 313
 314                         //FIXME: do not rely on DateTime implementation !
 315                         return DateTime.SpecifyKind (dateTime.ToUniversalTime (), DateTimeKind.Utc);
 316                 }
 317
 318                 public static DateTime ConvertTimeToUtc (DateTime dateTime, TimeZoneInfo sourceTimeZone)
 319                 {
 320                         if (sourceTimeZone == null)
 321                                 throw new ArgumentNullException ("sourceTimeZone");
 322
 323                         if (dateTime.Kind == DateTimeKind.Utc && sourceTimeZone != TimeZoneInfo.Utc)
 324                                 throw new ArgumentException ("Kind property of dateTime is Utc but the sourceTimeZone does not equal TimeZoneInfo.Utc");
 325
 326                         if (dateTime.Kind == DateTimeKind.Local && sourceTimeZone != TimeZoneInfo.Local)
 327                                 throw new ArgumentException ("Kind property of dateTime is Local but the sourceTimeZone does not equal TimeZoneInfo.Local");
 328
 329                         if (sourceTimeZone.IsInvalidTime (dateTime))
 330                                 throw new ArgumentException ("dateTime parameter is an invalid time");
 331
 332                         if (dateTime.Kind == DateTimeKind.Utc && sourceTimeZone == TimeZoneInfo.Utc)
 333                                 return dateTime;
 334
 335                         if (dateTime.Kind == DateTimeKind.Utc)
 336                                 return dateTime;
 337
 338                         if (dateTime.Kind == DateTimeKind.Local)
 339                                 return ConvertTimeToUtc (dateTime);
 340
 341                         if (sourceTimeZone.IsAmbiguousTime (dateTime) || !sourceTimeZone.IsDaylightSavingTime (dateTime))
 342                                 return DateTime.SpecifyKind (dateTime - sourceTimeZone.BaseUtcOffset, DateTimeKind.Utc);
 343                         else {
 344                                 AdjustmentRule rule = sourceTimeZone.GetApplicableRule (dateTime);
 345                                 if (rule != null)
 346                                         return DateTime.SpecifyKind (dateTime - sourceTimeZone.BaseUtcOffset - rule.DaylightDelta, DateTimeKind.Utc);
 347                                 else
 348                                         return DateTime.SpecifyKind (dateTime - sourceTimeZone.BaseUtcOffset, DateTimeKind.Utc);
 349                         }
 350                 }
 351
 352                 public static TimeZoneInfo CreateCustomTimeZone (string id, TimeSpan baseUtcOffset, string displayName, string standardDisplayName)
 353                 {
 354                         return CreateCustomTimeZone (id, baseUtcOffset, displayName, standardDisplayName, null, null, true);
 355                 }
 356
 357                 public static TimeZoneInfo CreateCustomTimeZone (string id, TimeSpan baseUtcOffset, string displayName, string standardDisplayName, string daylightDisplayName, TimeZoneInfo.AdjustmentRule [] adjustmentRules)
 358                 {
 359                         return CreateCustomTimeZone (id, baseUtcOffset, displayName, standardDisplayName, daylightDisplayName, adjustmentRules, false);
 360                 }
 361
 362                 public static TimeZoneInfo CreateCustomTimeZone ( string id, TimeSpan baseUtcOffset, string displayName, string standardDisplayName, string daylightDisplayName, TimeZoneInfo.AdjustmentRule [] adjustmentRules, bool disableDaylightSavingTime)
 363                 {
 364                         return new TimeZoneInfo (id, baseUtcOffset, displayName, standardDisplayName, daylightDisplayName, adjustmentRules, disableDaylightSavingTime);
 365                 }
 366
 367 #if NET_4_5
 368                 public override bool Equals (object obj)
 369                 {
 370                         return Equals (obj as TimeZoneInfo);
 371                 }
 372 #endif
 373
 374                 public bool Equals (TimeZoneInfo other)
 375                 {
 376                         if (other == null)
 377                                 return false;
 378
 379                         return other.Id == this.Id && HasSameRules (other);
 380                 }
 381
 382                 public static TimeZoneInfo FindSystemTimeZoneById (string id)
 383                 {
 384                         //FIXME: this method should check for cached values in systemTimeZones
 385                         if (id == null)
 386                                 throw new ArgumentNullException ("id");
 387 #if !NET_2_1
 388                         if (TimeZoneKey != null)
 389                         {
 390                                 RegistryKey key = TimeZoneKey.OpenSubKey (id, false);
 391                                 if (key == null)
 392                                         throw new TimeZoneNotFoundException ();
 393                                 return FromRegistryKey(id, key);
 394                         }
 395 #endif
 396 #if MONODROID
 397                         var timeZoneInfo = ZoneInfoDB.GetTimeZone (id);
 398                         if (timeZoneInfo == null)
 399                                 throw new TimeZoneNotFoundException ();
 400                         return timeZoneInfo;
 401 #else
 402                         // Local requires special logic that already exists in the Local property (bug #326)
 403                         if (id == "Local")
 404                                 return Local;
 405 #if MONOTOUCH
 406                         using (Stream stream = GetMonoTouchData (id)) {
 407                                 return BuildFromStream (id, stream);
 408                         }
 409 #elif LIBC
 410                         string filepath = Path.Combine (TimeZoneDirectory, id);
 411                         return FindSystemTimeZoneByFileName (id, filepath);
 412 #else
 413                         throw new NotImplementedException ();
 414 #endif
 415 #endif
 416                 }
 417
 418 #if LIBC
 419                 private static TimeZoneInfo FindSystemTimeZoneByFileName (string id, string filepath)
 420                 {
 421                         if (!File.Exists (filepath))
 422                                 throw new TimeZoneNotFoundException ();
 423
 424                         using (FileStream stream = File.OpenRead (filepath)) {
 425                                 return BuildFromStream (id, stream);
 426                         }
 427                 }
 428 #endif
 429 #if LIBC || MONOTOUCH
 430                 const int BUFFER_SIZE = 16384; //Big enough for any tz file (on Oct 2008, all tz files are under 10k)
 431
 432                 private static TimeZoneInfo BuildFromStream (string id, Stream stream)
 433                 {
 434                         byte [] buffer = new byte [BUFFER_SIZE];
 435                         int length = stream.Read (buffer, 0, BUFFER_SIZE);
 436
 437                         if (!ValidTZFile (buffer, length))
 438                                 throw new InvalidTimeZoneException ("TZ file too big for the buffer");
 439
 440                         try {
 441                                 return ParseTZBuffer (id, buffer, length);
 442                         } catch (Exception e) {
 443                                 throw new InvalidTimeZoneException (e.Message);
 444                         }
 445                 }
 446 #endif
 447
 448 #if !NET_2_1
 449                 private static TimeZoneInfo FromRegistryKey (string id, RegistryKey key)
 450                 {
 451                         byte [] reg_tzi = (byte []) key.GetValue ("TZI");
 452
 453                         if (reg_tzi == null)
 454                                 throw new InvalidTimeZoneException ();
 455
 456                         int bias = BitConverter.ToInt32 (reg_tzi, 0);
 457                         TimeSpan baseUtcOffset = new TimeSpan (0, -bias, 0);
 458
 459                         string display_name = (string) key.GetValue ("Display");
 460                         string standard_name = (string) key.GetValue ("Std");
 461                         string daylight_name = (string) key.GetValue ("Dlt");
 462
 463                         List<AdjustmentRule> adjustmentRules = new List<AdjustmentRule> ();
 464
 465                         RegistryKey dst_key = key.OpenSubKey ("Dynamic DST", false);
 466                         if (dst_key != null) {
 467                                 int first_year = (int) dst_key.GetValue ("FirstEntry");
 468                                 int last_year = (int) dst_key.GetValue ("LastEntry");
 469                                 int year;
 470
 471                                 for (year=first_year; year<=last_year; year++) {
 472                                         byte [] dst_tzi = (byte []) dst_key.GetValue (year.ToString ());
 473                                         if (dst_tzi != null) {
 474                                                 int start_year = year == first_year ? 1 : year;
 475                                                 int end_year = year == last_year ? 9999 : year;
 476                                                 ParseRegTzi(adjustmentRules, start_year, end_year, dst_tzi);
 477                                         }
 478                                 }
 479                         }
 480                         else
 481                                 ParseRegTzi(adjustmentRules, 1, 9999, reg_tzi);
 482
 483                         return CreateCustomTimeZone (id, baseUtcOffset, display_name, standard_name, daylight_name, ValidateRules (adjustmentRules).ToArray ());
 484                 }
 485
 486                 private static void ParseRegTzi (List<AdjustmentRule> adjustmentRules, int start_year, int end_year, byte [] buffer)
 487                 {
 488                         //int standard_bias = BitConverter.ToInt32 (buffer, 4); /* not sure how to handle this */
 489                         int daylight_bias = BitConverter.ToInt32 (buffer, 8);
 490
 491                         int standard_year = BitConverter.ToInt16 (buffer, 12);
 492                         int standard_month = BitConverter.ToInt16 (buffer, 14);
 493                         int standard_dayofweek = BitConverter.ToInt16 (buffer, 16);
 494                         int standard_day = BitConverter.ToInt16 (buffer, 18);
 495                         int standard_hour = BitConverter.ToInt16 (buffer, 20);
 496                         int standard_minute = BitConverter.ToInt16 (buffer, 22);
 497                         int standard_second = BitConverter.ToInt16 (buffer, 24);
 498                         int standard_millisecond = BitConverter.ToInt16 (buffer, 26);
 499
 500                         int daylight_year = BitConverter.ToInt16 (buffer, 28);
 501                         int daylight_month = BitConverter.ToInt16 (buffer, 30);
 502                         int daylight_dayofweek = BitConverter.ToInt16 (buffer, 32);
 503                         int daylight_day = BitConverter.ToInt16 (buffer, 34);
 504                         int daylight_hour = BitConverter.ToInt16 (buffer, 36);
 505                         int daylight_minute = BitConverter.ToInt16 (buffer, 38);
 506                         int daylight_second = BitConverter.ToInt16 (buffer, 40);
 507                         int daylight_millisecond = BitConverter.ToInt16 (buffer, 42);
 508
 509                         if (standard_month == 0 || daylight_month == 0)
 510                                 return;
 511
 512                         DateTime start_date;
 513                         DateTime start_timeofday = new DateTime (1, 1, 1, daylight_hour, daylight_minute, daylight_second, daylight_millisecond);
 514                         TransitionTime start_transition_time;
 515
 516                         if (daylight_year == 0) {
 517                                 start_date = new DateTime (start_year, 1, 1);
 518                                 start_transition_time = TransitionTime.CreateFloatingDateRule (
 519                                         start_timeofday, daylight_month, daylight_day,
 520                                         (DayOfWeek) daylight_dayofweek);
 521                         }
 522                         else {
 523                                 start_date = new DateTime (daylight_year, daylight_month, daylight_day,
 524                                         daylight_hour, daylight_minute, daylight_second, daylight_millisecond);
 525                                 start_transition_time = TransitionTime.CreateFixedDateRule (
 526                                         start_timeofday, daylight_month, daylight_day);
 527                         }
 528
 529                         DateTime end_date;
 530                         DateTime end_timeofday = new DateTime (1, 1, 1, standard_hour, standard_minute, standard_second, standard_millisecond);
 531                         TransitionTime end_transition_time;
 532
 533                         if (standard_year == 0) {
 534                                 end_date = new DateTime (end_year, 12, 31);
 535                                 end_transition_time = TransitionTime.CreateFloatingDateRule (
 536                                         end_timeofday, standard_month, standard_day,
 537                                         (DayOfWeek) standard_dayofweek);
 538                         }
 539                         else {
 540                                 end_date = new DateTime (standard_year, standard_month, standard_day,
 541                                         standard_hour, standard_minute, standard_second, standard_millisecond);
 542                                 end_transition_time = TransitionTime.CreateFixedDateRule (
 543                                         end_timeofday, standard_month, standard_day);
 544                         }
 545
 546                         TimeSpan daylight_delta = new TimeSpan(0, -daylight_bias, 0);
 547
 548                         adjustmentRules.Add (AdjustmentRule.CreateAdjustmentRule (
 549                                 start_date, end_date, daylight_delta,
 550                                 start_transition_time, end_transition_time));
 551                 }
 552 #endif
 553
 554                 public static TimeZoneInfo FromSerializedString (string source)
 555                 {
 556                         throw new NotImplementedException ();
 557                 }
 558
 559                 public AdjustmentRule [] GetAdjustmentRules ()
 560                 {
 561                         if (!supportsDaylightSavingTime)
 562                                 return new AdjustmentRule [0];
 563                         else
 564                                 return (AdjustmentRule []) adjustmentRules.Clone ();
 565                 }
 566
 567                 public TimeSpan [] GetAmbiguousTimeOffsets (DateTime dateTime)
 568                 {
 569                         if (!IsAmbiguousTime (dateTime))
 570                                 throw new ArgumentException ("dateTime is not an ambiguous time");
 571
 572                         AdjustmentRule rule = GetApplicableRule (dateTime);
 573                         if (rule != null)
 574                                 return new TimeSpan[] {baseUtcOffset, baseUtcOffset + rule.DaylightDelta};
 575                         else
 576                                 return new TimeSpan[] {baseUtcOffset, baseUtcOffset};
 577                 }
 578
 579                 public TimeSpan [] GetAmbiguousTimeOffsets (DateTimeOffset dateTimeOffset)
 580                 {
 581                         if (!IsAmbiguousTime (dateTimeOffset))
 582                                 throw new ArgumentException ("dateTimeOffset is not an ambiguous time");
 583
 584                         throw new NotImplementedException ();
 585                 }
 586
 587                 public override int GetHashCode ()
 588                 {
 589                         int hash_code = Id.GetHashCode ();
 590                         foreach (AdjustmentRule rule in GetAdjustmentRules ())
 591                                 hash_code ^= rule.GetHashCode ();
 592                         return hash_code;
 593                 }
 594
 595 #if NET_4_0
 596                 void ISerializable.GetObjectData (SerializationInfo info, StreamingContext context)
 597 #else
 598                 public void GetObjectData (SerializationInfo info, StreamingContext context)
 599 #endif
 600                 {
 601                         throw new NotImplementedException ();
 602                 }
 603
 604                 //FIXME: change this to a generic Dictionary and allow caching for FindSystemTimeZoneById
 605                 private static List<TimeZoneInfo> systemTimeZones;
 606                 public static ReadOnlyCollection<TimeZoneInfo> GetSystemTimeZones ()
 607                 {
 608                         if (systemTimeZones == null) {
 609                                 systemTimeZones = new List<TimeZoneInfo> ();
 610 #if !NET_2_1
 611                                 if (TimeZoneKey != null) {
 612                                         foreach (string id in TimeZoneKey.GetSubKeyNames ()) {
 613                                                 try {
 614                                                         systemTimeZones.Add (FindSystemTimeZoneById (id));
 615                                                 } catch {}
 616                                         }
 617
 618                                         return new ReadOnlyCollection<TimeZoneInfo> (systemTimeZones);
 619                                 }
 620 #endif
 621 #if MONODROID
 622                         foreach (string id in ZoneInfoDB.GetAvailableIds ()) {
 623                                 var tz = ZoneInfoDB.GetTimeZone (id);
 624                                 if (tz != null)
 625                                         systemTimeZones.Add (tz);
 626                         }
 627 #elif MONOTOUCH
 628                                 if (systemTimeZones.Count == 0) {
 629                                         foreach (string name in GetMonoTouchNames ()) {
 630                                                 using (Stream stream = GetMonoTouchData (name)) {
 631                                                         systemTimeZones.Add (BuildFromStream (name, stream));
 632                                                 }
 633                                         }
 634                                 }
 635 #elif LIBC
 636                                 string[] continents = new string [] {"Africa", "America", "Antarctica", "Arctic", "Asia", "Atlantic", "Brazil", "Canada", "Chile", "Europe", "Indian", "Mexico", "Mideast", "Pacific", "US"};
 637                                 foreach (string continent in continents) {
 638                                         try {
 639                                                 foreach (string zonepath in Directory.GetFiles (Path.Combine (TimeZoneDirectory, continent))) {
 640                                                         try {
 641                                                                 string id = String.Format ("{0}/{1}", continent, Path.GetFileName (zonepath));
 642                                                                 systemTimeZones.Add (FindSystemTimeZoneById (id));
 643                                                         } catch (ArgumentNullException) {
 644                                                         } catch (TimeZoneNotFoundException) {
 645                                                         } catch (InvalidTimeZoneException) {
 646                                                         } catch (Exception) {
 647                                                                 throw;
 648                                                         }
 649                                                 }
 650                                         } catch {}
 651                                 }
 652 #else
 653                                 throw new NotImplementedException ("This method is not implemented for this platform");
 654 #endif
 655                         }
 656                         return new ReadOnlyCollection<TimeZoneInfo> (systemTimeZones);
 657                 }
 658
 659                 public TimeSpan GetUtcOffset (DateTime dateTime)
 660                 {
 661                         if (IsDaylightSavingTime (dateTime)) {
 662                                 AdjustmentRule rule = GetApplicableRule (dateTime);
 663                                 if (rule != null)
 664                                         return BaseUtcOffset + rule.DaylightDelta;
 665                         }
 666
 667                         return BaseUtcOffset;
 668                 }
 669
 670                 public TimeSpan GetUtcOffset (DateTimeOffset dateTimeOffset)
 671                 {
 672                         throw new NotImplementedException ();
 673                 }
 674
 675                 public bool HasSameRules (TimeZoneInfo other)
 676                 {
 677                         if (other == null)
 678                                 throw new ArgumentNullException ("other");
 679
 680                         if ((this.adjustmentRules == null) != (other.adjustmentRules == null))
 681                                 return false;
 682
 683                         if (this.adjustmentRules == null)
 684                                 return true;
 685
 686                         if (this.BaseUtcOffset != other.BaseUtcOffset)
 687                                 return false;
 688
 689                         if (this.adjustmentRules.Length != other.adjustmentRules.Length)
 690                                 return false;
 691
 692                         for (int i = 0; i < adjustmentRules.Length; i++) {
 693                                 if (! (this.adjustmentRules [i]).Equals (other.adjustmentRules [i]))
 694                                         return false;
 695                         }
 696
 697                         return true;
 698                 }
 699
 700                 public bool IsAmbiguousTime (DateTime dateTime)
 701                 {
 702                         if (dateTime.Kind == DateTimeKind.Local && IsInvalidTime (dateTime))
 703                                 throw new ArgumentException ("Kind is Local and time is Invalid");
 704
 705                         if (this == TimeZoneInfo.Utc)
 706                                 return false;
 707
 708                         if (dateTime.Kind == DateTimeKind.Utc)
 709                                 dateTime = ConvertTimeFromUtc (dateTime);
 710
 711                         if (dateTime.Kind == DateTimeKind.Local && this != TimeZoneInfo.Local)
 712                                 dateTime = ConvertTime (dateTime, TimeZoneInfo.Local, this);
 713
 714                         AdjustmentRule rule = GetApplicableRule (dateTime);
 715                         if (rule != null) {
 716                                 DateTime tpoint = TransitionPoint (rule.DaylightTransitionEnd, dateTime.Year);
 717                                 if (dateTime > tpoint - rule.DaylightDelta  && dateTime <= tpoint)
 718                                         return true;
 719                         }
 720
 721                         return false;
 722                 }
 723
 724                 public bool IsAmbiguousTime (DateTimeOffset dateTimeOffset)
 725                 {
 726                         throw new NotImplementedException ();
 727                 }
 728
 729                 public bool IsDaylightSavingTime (DateTime dateTime)
 730                 {
 731                         if (dateTime.Kind == DateTimeKind.Local && IsInvalidTime (dateTime))
 732                                 throw new ArgumentException ("dateTime is invalid and Kind is Local");
 733
 734                         if (this == TimeZoneInfo.Utc)
 735                                 return false;
 736
 737                         if (!SupportsDaylightSavingTime)
 738                                 return false;
 739                         //FIXME: do not rely on DateTime implementation !
 740                         if ((dateTime.Kind == DateTimeKind.Local || dateTime.Kind == DateTimeKind.Unspecified) && this == TimeZoneInfo.Local)
 741                                 return dateTime.IsDaylightSavingTime ();
 742
 743                         //FIXME: do not rely on DateTime implementation !
 744                         if (dateTime.Kind == DateTimeKind.Local && this != TimeZoneInfo.Utc)
 745                                 return IsDaylightSavingTime (DateTime.SpecifyKind (dateTime.ToUniversalTime (), DateTimeKind.Utc));
 746
 747                         AdjustmentRule rule = GetApplicableRule (dateTime.Date);
 748                         if (rule == null)
 749                                 return false;
 750
 751                         DateTime DST_start = TransitionPoint (rule.DaylightTransitionStart, dateTime.Year);
 752                         DateTime DST_end = TransitionPoint (rule.DaylightTransitionEnd, dateTime.Year + ((rule.DaylightTransitionStart.Month < rule.DaylightTransitionEnd.Month) ? 0 : 1));
 753                         if (dateTime.Kind == DateTimeKind.Utc) {
 754                                 DST_start -= BaseUtcOffset;
 755                                 DST_end -= (BaseUtcOffset + rule.DaylightDelta);
 756                         }
 757
 758                         return (dateTime >= DST_start && dateTime < DST_end);
 759                 }
 760
 761                 public bool IsDaylightSavingTime (DateTimeOffset dateTimeOffset)
 762                 {
 763                         throw new NotImplementedException ();
 764                 }
 765
 766                 public bool IsInvalidTime (DateTime dateTime)
 767                 {
 768                         if (dateTime.Kind == DateTimeKind.Utc)
 769                                 return false;
 770                         if (dateTime.Kind == DateTimeKind.Local && this != Local)
 771                                 return false;
 772
 773                         AdjustmentRule rule = GetApplicableRule (dateTime);
 774                         if (rule != null) {
 775                                 DateTime tpoint = TransitionPoint (rule.DaylightTransitionStart, dateTime.Year);
 776                                 if (dateTime >= tpoint && dateTime < tpoint + rule.DaylightDelta)
 777                                         return true;
 778                         }
 779
 780                         return false;
 781                 }
 782
 783 #if NET_4_0
 784                 void IDeserializationCallback.OnDeserialization (object sender)
 785 #else
 786                 public void OnDeserialization (object sender)
 787 #endif
 788                 {
 789                         throw new NotImplementedException ();
 790                 }
 791
 792                 public string ToSerializedString ()
 793                 {
 794                         throw new NotImplementedException ();
 795                 }
 796
 797                 public override string ToString ()
 798                 {
 799                         return DisplayName;
 800                 }
 801
 802                 private TimeZoneInfo (string id, TimeSpan baseUtcOffset, string displayName, string standardDisplayName, string daylightDisplayName, TimeZoneInfo.AdjustmentRule [] adjustmentRules, bool disableDaylightSavingTime)
 803                 {
 804                         if (id == null)
 805                                 throw new ArgumentNullException ("id");
 806
 807                         if (id == String.Empty)
 808                                 throw new ArgumentException ("id parameter is an empty string");
 809
 810                         if (baseUtcOffset.Ticks % TimeSpan.TicksPerMinute != 0)
 811                                 throw new ArgumentException ("baseUtcOffset parameter does not represent a whole number of minutes");
 812
 813                         if (baseUtcOffset > new TimeSpan (14, 0, 0) || baseUtcOffset < new TimeSpan (-14, 0, 0))
 814                                 throw new ArgumentOutOfRangeException ("baseUtcOffset parameter is greater than 14 hours or less than -14 hours");
 815
 816 #if STRICT
 817                         if (id.Length > 32)
 818                                 throw new ArgumentException ("id parameter shouldn't be longer than 32 characters");
 819 #endif
 820
 821                         bool supportsDaylightSavingTime = !disableDaylightSavingTime;
 822
 823                         if (adjustmentRules != null && adjustmentRules.Length != 0) {
 824                                 AdjustmentRule prev = null;
 825                                 foreach (AdjustmentRule current in adjustmentRules) {
 826                                         if (current == null)
 827                                                 throw new InvalidTimeZoneException ("one or more elements in adjustmentRules are null");
 828
 829                                         if ((baseUtcOffset + current.DaylightDelta < new TimeSpan (-14, 0, 0)) ||
 830                                                         (baseUtcOffset + current.DaylightDelta > new TimeSpan (14, 0, 0)))
 831                                                 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;");
 832
 833                                         if (prev != null && prev.DateStart > current.DateStart)
 834                                                 throw new InvalidTimeZoneException ("adjustment rules specified in adjustmentRules parameter are not in chronological order");
 835
 836                                         if (prev != null && prev.DateEnd > current.DateStart)
 837                                                 throw new InvalidTimeZoneException ("some adjustment rules in the adjustmentRules parameter overlap");
 838
 839                                         if (prev != null && prev.DateEnd == current.DateStart)
 840                                                 throw new InvalidTimeZoneException ("a date can have multiple adjustment rules applied to it");
 841
 842                                         prev = current;
 843                                 }
 844                         } else {
 845                                 supportsDaylightSavingTime = false;
 846                         }
 847
 848                         this.id = id;
 849                         this.baseUtcOffset = baseUtcOffset;
 850                         this.displayName = displayName ?? id;
 851                         this.standardDisplayName = standardDisplayName ?? id;
 852                         this.daylightDisplayName = daylightDisplayName;
 853                         this.supportsDaylightSavingTime = supportsDaylightSavingTime;
 854                         this.adjustmentRules = adjustmentRules;
 855                 }
 856
 857                 private AdjustmentRule GetApplicableRule (DateTime dateTime)
 858                 {
 859                         //Transitions are always in standard time
 860                         DateTime date = dateTime;
 861
 862                         if (dateTime.Kind == DateTimeKind.Local && this != TimeZoneInfo.Local)
 863                                 date = date.ToUniversalTime () + BaseUtcOffset;
 864
 865                         if (dateTime.Kind == DateTimeKind.Utc && this != TimeZoneInfo.Utc)
 866                                 date = date + BaseUtcOffset;
 867
 868                         if (adjustmentRules != null) {
 869                                 foreach (AdjustmentRule rule in adjustmentRules) {
 870                                         if (rule.DateStart > date.Date)
 871                                                 return null;
 872                                         if (rule.DateEnd < date.Date)
 873                                                 continue;
 874                                         return rule;
 875                                 }
 876                         }
 877                         return null;
 878                 }
 879
 880                 private static DateTime TransitionPoint (TransitionTime transition, int year)
 881                 {
 882                         if (transition.IsFixedDateRule)
 883                                 return new DateTime (year, transition.Month, transition.Day) + transition.TimeOfDay.TimeOfDay;
 884
 885                         DayOfWeek first = (new DateTime (year, transition.Month, 1)).DayOfWeek;
 886                         int day = 1 + (transition.Week - 1) * 7 + (transition.DayOfWeek - first) % 7;
 887                         if (day >  DateTime.DaysInMonth (year, transition.Month))
 888                                 day -= 7;
 889                         return new DateTime (year, transition.Month, day) + transition.TimeOfDay.TimeOfDay;
 890                 }
 891
 892                 static List<AdjustmentRule> ValidateRules (List<AdjustmentRule> adjustmentRules)
 893                 {
 894                         AdjustmentRule prev = null;
 895                         foreach (AdjustmentRule current in adjustmentRules.ToArray ()) {
 896                                 if (prev != null && prev.DateEnd > current.DateStart) {
 897                                         adjustmentRules.Remove (current);
 898                                 }
 899                                 prev = current;
 900                         }
 901                         return adjustmentRules;
 902                 }
 903
 904 #if LIBC || MONODROID
 905                 private static bool ValidTZFile (byte [] buffer, int length)
 906                 {
 907                         StringBuilder magic = new StringBuilder ();
 908
 909                         for (int i = 0; i < 4; i++)
 910                                 magic.Append ((char)buffer [i]);
 911
 912                         if (magic.ToString () != "TZif")
 913                                 return false;
 914
 915                         if (length >= BUFFER_SIZE)
 916                                 return false;
 917
 918                         return true;
 919                 }
 920
 921                 static int SwapInt32 (int i)
 922                 {
 923                         return (((i >> 24) & 0xff)
 924                                 | ((i >> 8) & 0xff00)
 925                                 | ((i << 8) & 0xff0000)
 926                                 | ((i << 24)));
 927                 }
 928
 929                 static int ReadBigEndianInt32 (byte [] buffer, int start)
 930                 {
 931                         int i = BitConverter.ToInt32 (buffer, start);
 932                         if (!BitConverter.IsLittleEndian)
 933                                 return i;
 934
 935                         return SwapInt32 (i);
 936                 }
 937
 938                 private static TimeZoneInfo ParseTZBuffer (string id, byte [] buffer, int length)
 939                 {
 940                         //Reading the header. 4 bytes for magic, 16 are reserved
 941                         int ttisgmtcnt = ReadBigEndianInt32 (buffer, 20);
 942                         int ttisstdcnt = ReadBigEndianInt32 (buffer, 24);
 943                         int leapcnt = ReadBigEndianInt32 (buffer, 28);
 944                         int timecnt = ReadBigEndianInt32 (buffer, 32);
 945                         int typecnt = ReadBigEndianInt32 (buffer, 36);
 946                         int charcnt = ReadBigEndianInt32 (buffer, 40);
 947
 948                         if (length < 44 + timecnt * 5 + typecnt * 6 + charcnt + leapcnt * 8 + ttisstdcnt + ttisgmtcnt)
 949                                 throw new InvalidTimeZoneException ();
 950
 951                         Dictionary<int, string> abbreviations = ParseAbbreviations (buffer, 44 + 4 * timecnt + timecnt + 6 * typecnt, charcnt);
 952                         Dictionary<int, TimeType> time_types = ParseTimesTypes (buffer, 44 + 4 * timecnt + timecnt, typecnt, abbreviations);
 953                         List<KeyValuePair<DateTime, TimeType>> transitions = ParseTransitions (buffer, 44, timecnt, time_types);
 954
 955                         if (time_types.Count == 0)
 956                                 throw new InvalidTimeZoneException ();
 957
 958                         if (time_types.Count == 1 && ((TimeType)time_types[0]).IsDst)
 959                                 throw new InvalidTimeZoneException ();
 960
 961                         TimeSpan baseUtcOffset = new TimeSpan (0);
 962                         TimeSpan dstDelta = new TimeSpan (0);
 963                         string standardDisplayName = null;
 964                         string daylightDisplayName = null;
 965                         bool dst_observed = false;
 966                         DateTime dst_start = DateTime.MinValue;
 967                         List<AdjustmentRule> adjustmentRules = new List<AdjustmentRule> ();
 968
 969                         for (int i = 0; i < transitions.Count; i++) {
 970                                 var pair = transitions [i];
 971                                 DateTime ttime = pair.Key;
 972                                 TimeType ttype = pair.Value;
 973                                 if (!ttype.IsDst) {
 974                                         if (standardDisplayName != ttype.Name || baseUtcOffset.TotalSeconds != ttype.Offset) {
 975                                                 standardDisplayName = ttype.Name;
 976                                                 daylightDisplayName = null;
 977                                                 baseUtcOffset = new TimeSpan (0, 0, ttype.Offset);
 978                                                 adjustmentRules = new List<AdjustmentRule> ();
 979                                                 dst_observed = false;
 980                                         }
 981                                         if (dst_observed) {
 982                                                 //FIXME: check additional fields for this:
 983                                                 //most of the transitions are expressed in GMT
 984                                                 dst_start += baseUtcOffset;
 985                                                 DateTime dst_end = ttime + baseUtcOffset + dstDelta;
 986
 987                                                 //some weird timezone (America/Phoenix) have end dates on Jan 1st
 988                                                 if (dst_end.Date == new DateTime (dst_end.Year, 1, 1) && dst_end.Year > dst_start.Year)
 989                                                         dst_end -= new TimeSpan (24, 0, 0);
 990
 991                                                 DateTime dateStart, dateEnd;
 992                                                 if (dst_start.Month < 7)
 993                                                         dateStart = new DateTime (dst_start.Year, 1, 1);
 994                                                 else
 995                                                         dateStart = new DateTime (dst_start.Year, 7, 1);
 996
 997                                                 if (dst_end.Month >= 7)
 998                                                         dateEnd = new DateTime (dst_end.Year, 12, 31);
 999                                                 else
1000                                                         dateEnd = new DateTime (dst_end.Year, 6, 30);
1001
1002
1003                                                 TransitionTime transition_start = TransitionTime.CreateFixedDateRule (new DateTime (1, 1, 1) + dst_start.TimeOfDay, dst_start.Month, dst_start.Day);
1004                                                 TransitionTime transition_end = TransitionTime.CreateFixedDateRule (new DateTime (1, 1, 1) + dst_end.TimeOfDay, dst_end.Month, dst_end.Day);
1005                                                 if  (transition_start != transition_end) //y, that happened in Argentina in 1943-1946
1006                                                         adjustmentRules.Add (AdjustmentRule.CreateAdjustmentRule (dateStart, dateEnd, dstDelta, transition_start, transition_end));
1007                                         }
1008                                         dst_observed = false;
1009                                 } else {
1010                                         if (daylightDisplayName != ttype.Name || dstDelta.TotalSeconds != ttype.Offset - baseUtcOffset.TotalSeconds) {
1011                                                 daylightDisplayName = ttype.Name;
1012                                                 dstDelta = new TimeSpan(0, 0, ttype.Offset) - baseUtcOffset;
1013                                         }
1014                                         dst_start = ttime;
1015                                         dst_observed = true;
1016                                 }
1017                         }
1018
1019                         if (adjustmentRules.Count == 0) {
1020                                 TimeType t = (TimeType)time_types [0];
1021                                 if (standardDisplayName == null) {
1022                                         standardDisplayName = t.Name;
1023                                         baseUtcOffset = new TimeSpan (0, 0, t.Offset);
1024                                 }
1025                                 return CreateCustomTimeZone (id, baseUtcOffset, id, standardDisplayName);
1026                         } else {
1027                                 return CreateCustomTimeZone (id, baseUtcOffset, id, standardDisplayName, daylightDisplayName, ValidateRules (adjustmentRules).ToArray ());
1028                         }
1029                 }
1030
1031                 static Dictionary<int, string> ParseAbbreviations (byte [] buffer, int index, int count)
1032                 {
1033                         var abbrevs = new Dictionary<int, string> ();
1034                         int abbrev_index = 0;
1035                         var sb = new StringBuilder ();
1036                         for (int i = 0; i < count; i++) {
1037                                 char c = (char) buffer [index + i];
1038                                 if (c != '\0')
1039                                         sb.Append (c);
1040                                 else {
1041                                         abbrevs.Add (abbrev_index, sb.ToString ());
1042                                         //Adding all the substrings too, as it seems to be used, at least for Africa/Windhoek
1043                                         for (int j = 1; j < sb.Length; j++)
1044                                                 abbrevs.Add (abbrev_index + j, sb.ToString (j, sb.Length - j));
1045                                         abbrev_index = i + 1;
1046                                         sb = new StringBuilder ();
1047                                 }
1048                         }
1049                         return abbrevs;
1050                 }
1051
1052                 static Dictionary<int, TimeType> ParseTimesTypes (byte [] buffer, int index, int count, Dictionary<int, string> abbreviations)
1053                 {
1054                         var types = new Dictionary<int, TimeType> (count);
1055                         for (int i = 0; i < count; i++) {
1056                                 int offset = ReadBigEndianInt32 (buffer, index + 6 * i);
1057                                 byte is_dst = buffer [index + 6 * i + 4];
1058                                 byte abbrev = buffer [index + 6 * i + 5];
1059                                 types.Add (i, new TimeType (offset, (is_dst != 0), abbreviations [(int)abbrev]));
1060                         }
1061                         return types;
1062                 }
1063
1064                 static List<KeyValuePair<DateTime, TimeType>> ParseTransitions (byte [] buffer, int index, int count, Dictionary<int, TimeType> time_types)
1065                 {
1066                         var list = new List<KeyValuePair<DateTime, TimeType>> (count);
1067                         for (int i = 0; i < count; i++) {
1068                                 int unixtime = ReadBigEndianInt32 (buffer, index + 4 * i);
1069                                 DateTime ttime = DateTimeFromUnixTime (unixtime);
1070                                 byte ttype = buffer [index + 4 * count + i];
1071                                 list.Add (new KeyValuePair<DateTime, TimeType> (ttime, time_types [(int)ttype]));
1072                         }
1073                         return list;
1074                 }
1075
1076                 static DateTime DateTimeFromUnixTime (long unix_time)
1077                 {
1078                         DateTime date_time = new DateTime (1970, 1, 1);
1079                         return date_time.AddSeconds (unix_time);
1080                 }
1081         }
1082
1083         struct TimeType {
1084                 public readonly int Offset;
1085                 public readonly bool IsDst;
1086                 public string Name;
1087
1088                 public TimeType (int offset, bool is_dst, string abbrev)
1089                 {
1090                         this.Offset = offset;
1091                         this.IsDst = is_dst;
1092                         this.Name = abbrev;
1093                 }
1094
1095                 public override string ToString ()
1096                 {
1097                         return "offset: " + Offset + "s, is_dst: " + IsDst + ", zone name: " + Name;
1098                 }
1099 #else
1100         }
1101 #endif
1102         }
1103 }
1104
1105 #endif