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_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 #if NET_4_0 || !INSIDE_CORLIB
  61         public
  62 #endif
  63         sealed partial class TimeZoneInfo : IEquatable<TimeZoneInfo>, ISerializable, IDeserializationCallback
  64         {
  65                 TimeSpan baseUtcOffset;
  66                 public TimeSpan BaseUtcOffset {
  67                         get { return baseUtcOffset; }
  68                 }
  69
  70                 string daylightDisplayName;
  71                 public string DaylightName {
  72                         get {
  73                                 return supportsDaylightSavingTime
  74                                         ? daylightDisplayName
  75                                         : string.Empty;
  76                         }
  77                 }
  78
  79                 string displayName;
  80                 public string DisplayName {
  81                         get { return displayName; }
  82                 }
  83
  84                 string id;
  85                 public string Id {
  86                         get { return id; }
  87                 }
  88
  89                 static TimeZoneInfo local;
  90                 public static TimeZoneInfo Local {
  91                         get {
  92                                 var l = local;
  93                                 if (l == null) {
  94                                         l = CreateLocal ();
  95                                         if (l == null)
  96                                                 throw new TimeZoneNotFoundException ();
  97
  98                                         if (Interlocked.CompareExchange (ref local, l, null) != null)
  99                                                 l = local;
 100                                 }
 101
 102                                 return l;
 103                         }
 104                 }
 105
 106                 /*
 107                         TimeZone transitions are stored when there is a change on the base offset.
 108                 */
 109                 private List<KeyValuePair<DateTime, TimeType>> transitions;
 110
 111                 static TimeZoneInfo CreateLocal ()
 112                 {
 113 #if MONODROID
 114                         return AndroidTimeZones.Local;
 115 #elif MONOTOUCH
 116                         using (Stream stream = GetMonoTouchData (null)) {
 117                                 return BuildFromStream ("Local", stream);
 118                         }
 119 #elif LIBC
 120                         var tz = Environment.GetEnvironmentVariable ("TZ");
 121                         if (tz != null) {
 122                                 if (tz == String.Empty)
 123                                         return Utc;
 124                                 try {
 125                                         return FindSystemTimeZoneByFileName (tz, Path.Combine (TimeZoneDirectory, tz));
 126                                 } catch {
 127                                         return Utc;
 128                                 }
 129                         }
 130
 131                         try {
 132                                 return FindSystemTimeZoneByFileName ("Local", "/etc/localtime");
 133                         } catch {
 134                                 try {
 135                                         return FindSystemTimeZoneByFileName ("Local", Path.Combine (TimeZoneDirectory, "localtime"));
 136                                 } catch {
 137                                         return null;
 138                                 }
 139                         }
 140 #else
 141                         if (IsWindows && LocalZoneKey != null) {
 142                                 string name = (string)LocalZoneKey.GetValue ("TimeZoneKeyName");
 143                                 name = TrimSpecial (name);
 144                                 if (name != null)
 145                                         return TimeZoneInfo.FindSystemTimeZoneById (name);
 146                         }
 147
 148                         return null;
 149 #endif
 150                 }
 151
 152                 string standardDisplayName;
 153                 public string StandardName {
 154                         get { return standardDisplayName; }
 155                 }
 156
 157                 bool supportsDaylightSavingTime;
 158                 public bool SupportsDaylightSavingTime {
 159                         get  { return supportsDaylightSavingTime; }
 160                 }
 161
 162                 static TimeZoneInfo utc;
 163                 public static TimeZoneInfo Utc {
 164                         get {
 165                                 if (utc == null)
 166                                         utc = CreateCustomTimeZone ("UTC", new TimeSpan (0), "UTC", "UTC");
 167                                 return utc;
 168                         }
 169                 }
 170 #if LIBC
 171                 static string timeZoneDirectory;
 172                 static string TimeZoneDirectory {
 173                         get {
 174                                 if (timeZoneDirectory == null)
 175                                         timeZoneDirectory = "/usr/share/zoneinfo";
 176                                 return timeZoneDirectory;
 177                         }
 178                         set {
 179                                 ClearCachedData ();
 180                                 timeZoneDirectory = value;
 181                         }
 182                 }
 183 #endif
 184                 private AdjustmentRule [] adjustmentRules;
 185
 186 #if !NET_2_1
 187                 /// <summary>
 188                 /// Determine whether windows of not (taken Stephane Delcroix's code)
 189                 /// </summary>
 190                 private static bool IsWindows
 191                 {
 192                         get {
 193                                 int platform = (int) Environment.OSVersion.Platform;
 194                                 return ((platform != 4) && (platform != 6) && (platform != 128));
 195                         }
 196                 }
 197
 198                 /// <summary>
 199                 /// Needed to trim misc garbage in MS registry keys
 200                 /// </summary>
 201                 private static string TrimSpecial (string str)
 202                 {
 203                         var Istart = 0;
 204                         while (Istart < str.Length && !char.IsLetterOrDigit(str[Istart])) Istart++;
 205                         var Iend = str.Length - 1;
 206                         while (Iend > Istart && !char.IsLetterOrDigit(str[Iend])) Iend--;
 207
 208                         return str.Substring (Istart, Iend-Istart+1);
 209                 }
 210
 211                 static RegistryKey timeZoneKey;
 212                 static RegistryKey TimeZoneKey {
 213                         get {
 214                                 if (timeZoneKey != null)
 215                                         return timeZoneKey;
 216                                 if (!IsWindows)
 217                                         return null;
 218
 219                                 return timeZoneKey = Registry.LocalMachine.OpenSubKey (
 220                                         "SOFTWARE\\Microsoft\\Windows NT\\CurrentVersion\\Time Zones",
 221                                         false);
 222                         }
 223                 }
 224
 225                 static RegistryKey localZoneKey;
 226                 static RegistryKey LocalZoneKey {
 227                         get {
 228                                 if (localZoneKey != null)
 229                                         return localZoneKey;
 230
 231                                 if (!IsWindows)
 232                                         return null;
 233
 234                                 return localZoneKey = Registry.LocalMachine.OpenSubKey (
 235                                         "SYSTEM\\CurrentControlSet\\Control\\TimeZoneInformation", false);
 236                         }
 237                 }
 238 #endif
 239
 240                 public static void ClearCachedData ()
 241                 {
 242                         local = null;
 243                         utc = null;
 244                         systemTimeZones = null;
 245                 }
 246
 247                 public static DateTime ConvertTime (DateTime dateTime, TimeZoneInfo destinationTimeZone)
 248                 {
 249                         return ConvertTime (dateTime, dateTime.Kind == DateTimeKind.Utc ? TimeZoneInfo.Utc : TimeZoneInfo.Local, destinationTimeZone);
 250                 }
 251
 252                 public static DateTime ConvertTime (DateTime dateTime, TimeZoneInfo sourceTimeZone, TimeZoneInfo destinationTimeZone)
 253                 {
 254                         if (sourceTimeZone == null)
 255                                 throw new ArgumentNullException ("sourceTimeZone");
 256
 257                         if (destinationTimeZone == null)
 258                                 throw new ArgumentNullException ("destinationTimeZone");
 259
 260                         if (dateTime.Kind == DateTimeKind.Local && sourceTimeZone != TimeZoneInfo.Local)
 261                                 throw new ArgumentException ("Kind property of dateTime is Local but the sourceTimeZone does not equal TimeZoneInfo.Local");
 262
 263                         if (dateTime.Kind == DateTimeKind.Utc && sourceTimeZone != TimeZoneInfo.Utc)
 264                                 throw new ArgumentException ("Kind property of dateTime is Utc but the sourceTimeZone does not equal TimeZoneInfo.Utc");
 265
 266                         if (sourceTimeZone.IsInvalidTime (dateTime))
 267                                 throw new ArgumentException ("dateTime parameter is an invalid time");
 268
 269                         if (dateTime.Kind == DateTimeKind.Local && sourceTimeZone == TimeZoneInfo.Local && destinationTimeZone == TimeZoneInfo.Local)
 270                                 return dateTime;
 271
 272                         DateTime utc = ConvertTimeToUtc (dateTime);
 273
 274                         if (destinationTimeZone != TimeZoneInfo.Utc) {
 275                                 utc = ConvertTimeFromUtc (utc, destinationTimeZone);
 276                                 if (dateTime.Kind == DateTimeKind.Unspecified)
 277                                         return DateTime.SpecifyKind (utc, DateTimeKind.Unspecified);
 278                         }
 279
 280                         return utc;
 281                 }
 282
 283                 public static DateTimeOffset ConvertTime(DateTimeOffset dateTimeOffset, TimeZoneInfo destinationTimeZone)
 284                 {
 285                         if (destinationTimeZone == null)
 286                                 throw new ArgumentNullException("destinationTimeZone");
 287
 288                         var utcDateTime = dateTimeOffset.UtcDateTime;
 289                         AdjustmentRule rule = destinationTimeZone.GetApplicableRule (utcDateTime);
 290
 291                         if (rule != null && destinationTimeZone.IsDaylightSavingTime(utcDateTime)) {
 292                                 var offset = destinationTimeZone.BaseUtcOffset + rule.DaylightDelta;
 293                                 return new DateTimeOffset(DateTime.SpecifyKind(utcDateTime, DateTimeKind.Unspecified) + offset, offset);
 294                         }
 295                         else {
 296                                 return new DateTimeOffset(DateTime.SpecifyKind(utcDateTime, DateTimeKind.Unspecified) + destinationTimeZone.BaseUtcOffset, destinationTimeZone.BaseUtcOffset);
 297                         }
 298                 }
 299
 300                 public static DateTime ConvertTimeBySystemTimeZoneId (DateTime dateTime, string destinationTimeZoneId)
 301                 {
 302                         return ConvertTime (dateTime, FindSystemTimeZoneById (destinationTimeZoneId));
 303                 }
 304
 305                 public static DateTime ConvertTimeBySystemTimeZoneId (DateTime dateTime, string sourceTimeZoneId, string destinationTimeZoneId)
 306                 {
 307                         return ConvertTime (dateTime, FindSystemTimeZoneById (sourceTimeZoneId), FindSystemTimeZoneById (destinationTimeZoneId));
 308                 }
 309
 310                 public static DateTimeOffset ConvertTimeBySystemTimeZoneId (DateTimeOffset dateTimeOffset, string destinationTimeZoneId)
 311                 {
 312                         return ConvertTime (dateTimeOffset, FindSystemTimeZoneById (destinationTimeZoneId));
 313                 }
 314
 315                 private DateTime ConvertTimeFromUtc (DateTime dateTime)
 316                 {
 317                         if (dateTime.Kind == DateTimeKind.Local)
 318                                 throw new ArgumentException ("Kind property of dateTime is Local");
 319
 320                         if (this == TimeZoneInfo.Utc)
 321                                 return DateTime.SpecifyKind (dateTime, DateTimeKind.Utc);
 322
 323                         //FIXME: do not rely on DateTime implementation !
 324                         if (this == TimeZoneInfo.Local)
 325                         {
 326 #if NET_4_0
 327                                 return dateTime.ToLocalTime ();
 328 #else
 329                                 return DateTime.SpecifyKind (dateTime.ToLocalTime (), DateTimeKind.Unspecified);
 330 #endif
 331                         }
 332
 333
 334                         AdjustmentRule rule = GetApplicableRule (dateTime);
 335                         if (rule != null && IsDaylightSavingTime (DateTime.SpecifyKind (dateTime, DateTimeKind.Utc)))
 336                                 return DateTime.SpecifyKind (dateTime + BaseUtcOffset + rule.DaylightDelta , DateTimeKind.Unspecified);
 337                         else
 338                                 return DateTime.SpecifyKind (dateTime + BaseUtcOffset, DateTimeKind.Unspecified);
 339                 }
 340
 341                 public static DateTime ConvertTimeFromUtc (DateTime dateTime, TimeZoneInfo destinationTimeZone)
 342                 {
 343                         if (destinationTimeZone == null)
 344                                 throw new ArgumentNullException ("destinationTimeZone");
 345
 346                         return destinationTimeZone.ConvertTimeFromUtc (dateTime);
 347                 }
 348
 349                 public static DateTime ConvertTimeToUtc (DateTime dateTime)
 350                 {
 351                         if (dateTime.Kind == DateTimeKind.Utc)
 352                                 return dateTime;
 353
 354                         return ConvertTimeToUtc (dateTime, TimeZoneInfo.Local);
 355                 }
 356
 357                 public static DateTime ConvertTimeToUtc (DateTime dateTime, TimeZoneInfo sourceTimeZone)
 358                 {
 359                         if (sourceTimeZone == null)
 360                                 throw new ArgumentNullException ("sourceTimeZone");
 361
 362                         if (dateTime.Kind == DateTimeKind.Utc && sourceTimeZone != TimeZoneInfo.Utc)
 363                                 throw new ArgumentException ("Kind property of dateTime is Utc but the sourceTimeZone does not equal TimeZoneInfo.Utc");
 364
 365                         if (dateTime.Kind == DateTimeKind.Local && sourceTimeZone != TimeZoneInfo.Local)
 366                                 throw new ArgumentException ("Kind property of dateTime is Local but the sourceTimeZone does not equal TimeZoneInfo.Local");
 367
 368                         if (sourceTimeZone.IsInvalidTime (dateTime))
 369                                 throw new ArgumentException ("dateTime parameter is an invalid time");
 370
 371                         if (dateTime.Kind == DateTimeKind.Utc)
 372                                 return dateTime;
 373
 374                         if (sourceTimeZone.IsAmbiguousTime (dateTime) || !sourceTimeZone.IsDaylightSavingTime (dateTime))
 375                                 return DateTime.SpecifyKind (dateTime - sourceTimeZone.BaseUtcOffset, DateTimeKind.Utc);
 376                         else {
 377                                 AdjustmentRule rule = sourceTimeZone.GetApplicableRule (dateTime);
 378                                 if (rule != null)
 379                                         return DateTime.SpecifyKind (dateTime - sourceTimeZone.BaseUtcOffset - rule.DaylightDelta, DateTimeKind.Utc);
 380                                 else
 381                                         return DateTime.SpecifyKind (dateTime - sourceTimeZone.BaseUtcOffset, DateTimeKind.Utc);
 382                         }
 383                 }
 384
 385                 public static TimeZoneInfo CreateCustomTimeZone (string id, TimeSpan baseUtcOffset, string displayName, string standardDisplayName)
 386                 {
 387                         return CreateCustomTimeZone (id, baseUtcOffset, displayName, standardDisplayName, null, null, true);
 388                 }
 389
 390                 public static TimeZoneInfo CreateCustomTimeZone (string id, TimeSpan baseUtcOffset, string displayName, string standardDisplayName, string daylightDisplayName, TimeZoneInfo.AdjustmentRule [] adjustmentRules)
 391                 {
 392                         return CreateCustomTimeZone (id, baseUtcOffset, displayName, standardDisplayName, daylightDisplayName, adjustmentRules, false);
 393                 }
 394
 395                 public static TimeZoneInfo CreateCustomTimeZone ( string id, TimeSpan baseUtcOffset, string displayName, string standardDisplayName, string daylightDisplayName, TimeZoneInfo.AdjustmentRule [] adjustmentRules, bool disableDaylightSavingTime)
 396                 {
 397                         return new TimeZoneInfo (id, baseUtcOffset, displayName, standardDisplayName, daylightDisplayName, adjustmentRules, disableDaylightSavingTime);
 398                 }
 399
 400 #if NET_4_5
 401                 public override bool Equals (object obj)
 402                 {
 403                         return Equals (obj as TimeZoneInfo);
 404                 }
 405 #endif
 406
 407                 public bool Equals (TimeZoneInfo other)
 408                 {
 409                         if (other == null)
 410                                 return false;
 411
 412                         return other.Id == this.Id && HasSameRules (other);
 413                 }
 414
 415                 public static TimeZoneInfo FindSystemTimeZoneById (string id)
 416                 {
 417                         //FIXME: this method should check for cached values in systemTimeZones
 418                         if (id == null)
 419                                 throw new ArgumentNullException ("id");
 420 #if !NET_2_1
 421                         if (TimeZoneKey != null)
 422                         {
 423                                 RegistryKey key = TimeZoneKey.OpenSubKey (id, false);
 424                                 if (key == null)
 425                                         throw new TimeZoneNotFoundException ();
 426                                 return FromRegistryKey(id, key);
 427                         }
 428 #endif
 429 #if MONODROID
 430                         var timeZoneInfo = AndroidTimeZones.GetTimeZone (id, id);
 431                         if (timeZoneInfo == null)
 432                                 throw new TimeZoneNotFoundException ();
 433                         return timeZoneInfo;
 434 #else
 435                         // Local requires special logic that already exists in the Local property (bug #326)
 436                         if (id == "Local")
 437                                 return Local;
 438 #if MONOTOUCH
 439                         using (Stream stream = GetMonoTouchData (id)) {
 440                                 return BuildFromStream (id, stream);
 441                         }
 442 #elif LIBC
 443                         string filepath = Path.Combine (TimeZoneDirectory, id);
 444                         return FindSystemTimeZoneByFileName (id, filepath);
 445 #else
 446                         throw new NotImplementedException ();
 447 #endif
 448 #endif
 449                 }
 450
 451 #if LIBC
 452                 private static TimeZoneInfo FindSystemTimeZoneByFileName (string id, string filepath)
 453                 {
 454                         if (!File.Exists (filepath))
 455                                 throw new TimeZoneNotFoundException ();
 456
 457                         using (FileStream stream = File.OpenRead (filepath)) {
 458                                 return BuildFromStream (id, stream);
 459                         }
 460                 }
 461 #endif
 462 #if LIBC || MONOTOUCH
 463                 const int BUFFER_SIZE = 16384; //Big enough for any tz file (on Oct 2008, all tz files are under 10k)
 464
 465                 private static TimeZoneInfo BuildFromStream (string id, Stream stream)
 466                 {
 467                         byte [] buffer = new byte [BUFFER_SIZE];
 468                         int length = stream.Read (buffer, 0, BUFFER_SIZE);
 469
 470                         if (!ValidTZFile (buffer, length))
 471                                 throw new InvalidTimeZoneException ("TZ file too big for the buffer");
 472
 473                         try {
 474                                 return ParseTZBuffer (id, buffer, length);
 475                         } catch (Exception e) {
 476                                 throw new InvalidTimeZoneException (e.Message);
 477                         }
 478                 }
 479 #endif
 480
 481 #if !NET_2_1
 482                 private static TimeZoneInfo FromRegistryKey (string id, RegistryKey key)
 483                 {
 484                         byte [] reg_tzi = (byte []) key.GetValue ("TZI");
 485
 486                         if (reg_tzi == null)
 487                                 throw new InvalidTimeZoneException ();
 488
 489                         int bias = BitConverter.ToInt32 (reg_tzi, 0);
 490                         TimeSpan baseUtcOffset = new TimeSpan (0, -bias, 0);
 491
 492                         string display_name = (string) key.GetValue ("Display");
 493                         string standard_name = (string) key.GetValue ("Std");
 494                         string daylight_name = (string) key.GetValue ("Dlt");
 495
 496                         List<AdjustmentRule> adjustmentRules = new List<AdjustmentRule> ();
 497
 498                         RegistryKey dst_key = key.OpenSubKey ("Dynamic DST", false);
 499                         if (dst_key != null) {
 500                                 int first_year = (int) dst_key.GetValue ("FirstEntry");
 501                                 int last_year = (int) dst_key.GetValue ("LastEntry");
 502                                 int year;
 503
 504                                 for (year=first_year; year<=last_year; year++) {
 505                                         byte [] dst_tzi = (byte []) dst_key.GetValue (year.ToString ());
 506                                         if (dst_tzi != null) {
 507                                                 int start_year = year == first_year ? 1 : year;
 508                                                 int end_year = year == last_year ? 9999 : year;
 509                                                 ParseRegTzi(adjustmentRules, start_year, end_year, dst_tzi);
 510                                         }
 511                                 }
 512                         }
 513                         else
 514                                 ParseRegTzi(adjustmentRules, 1, 9999, reg_tzi);
 515
 516                         return CreateCustomTimeZone (id, baseUtcOffset, display_name, standard_name, daylight_name, ValidateRules (adjustmentRules).ToArray ());
 517                 }
 518
 519                 private static void ParseRegTzi (List<AdjustmentRule> adjustmentRules, int start_year, int end_year, byte [] buffer)
 520                 {
 521                         //int standard_bias = BitConverter.ToInt32 (buffer, 4); /* not sure how to handle this */
 522                         int daylight_bias = BitConverter.ToInt32 (buffer, 8);
 523
 524                         int standard_year = BitConverter.ToInt16 (buffer, 12);
 525                         int standard_month = BitConverter.ToInt16 (buffer, 14);
 526                         int standard_dayofweek = BitConverter.ToInt16 (buffer, 16);
 527                         int standard_day = BitConverter.ToInt16 (buffer, 18);
 528                         int standard_hour = BitConverter.ToInt16 (buffer, 20);
 529                         int standard_minute = BitConverter.ToInt16 (buffer, 22);
 530                         int standard_second = BitConverter.ToInt16 (buffer, 24);
 531                         int standard_millisecond = BitConverter.ToInt16 (buffer, 26);
 532
 533                         int daylight_year = BitConverter.ToInt16 (buffer, 28);
 534                         int daylight_month = BitConverter.ToInt16 (buffer, 30);
 535                         int daylight_dayofweek = BitConverter.ToInt16 (buffer, 32);
 536                         int daylight_day = BitConverter.ToInt16 (buffer, 34);
 537                         int daylight_hour = BitConverter.ToInt16 (buffer, 36);
 538                         int daylight_minute = BitConverter.ToInt16 (buffer, 38);
 539                         int daylight_second = BitConverter.ToInt16 (buffer, 40);
 540                         int daylight_millisecond = BitConverter.ToInt16 (buffer, 42);
 541
 542                         if (standard_month == 0 || daylight_month == 0)
 543                                 return;
 544
 545                         DateTime start_date;
 546                         DateTime start_timeofday = new DateTime (1, 1, 1, daylight_hour, daylight_minute, daylight_second, daylight_millisecond);
 547                         TransitionTime start_transition_time;
 548
 549                         if (daylight_year == 0) {
 550                                 start_date = new DateTime (start_year, 1, 1);
 551                                 start_transition_time = TransitionTime.CreateFloatingDateRule (
 552                                         start_timeofday, daylight_month, daylight_day,
 553                                         (DayOfWeek) daylight_dayofweek);
 554                         }
 555                         else {
 556                                 start_date = new DateTime (daylight_year, daylight_month, daylight_day,
 557                                         daylight_hour, daylight_minute, daylight_second, daylight_millisecond);
 558                                 start_transition_time = TransitionTime.CreateFixedDateRule (
 559                                         start_timeofday, daylight_month, daylight_day);
 560                         }
 561
 562                         DateTime end_date;
 563                         DateTime end_timeofday = new DateTime (1, 1, 1, standard_hour, standard_minute, standard_second, standard_millisecond);
 564                         TransitionTime end_transition_time;
 565
 566                         if (standard_year == 0) {
 567                                 end_date = new DateTime (end_year, 12, 31);
 568                                 end_transition_time = TransitionTime.CreateFloatingDateRule (
 569                                         end_timeofday, standard_month, standard_day,
 570                                         (DayOfWeek) standard_dayofweek);
 571                         }
 572                         else {
 573                                 end_date = new DateTime (standard_year, standard_month, standard_day,
 574                                         standard_hour, standard_minute, standard_second, standard_millisecond);
 575                                 end_transition_time = TransitionTime.CreateFixedDateRule (
 576                                         end_timeofday, standard_month, standard_day);
 577                         }
 578
 579                         TimeSpan daylight_delta = new TimeSpan(0, -daylight_bias, 0);
 580
 581                         adjustmentRules.Add (AdjustmentRule.CreateAdjustmentRule (
 582                                 start_date, end_date, daylight_delta,
 583                                 start_transition_time, end_transition_time));
 584                 }
 585 #endif
 586
 587                 public AdjustmentRule [] GetAdjustmentRules ()
 588                 {
 589                         if (!supportsDaylightSavingTime)
 590                                 return new AdjustmentRule [0];
 591                         else
 592                                 return (AdjustmentRule []) adjustmentRules.Clone ();
 593                 }
 594
 595                 public TimeSpan [] GetAmbiguousTimeOffsets (DateTime dateTime)
 596                 {
 597                         if (!IsAmbiguousTime (dateTime))
 598                                 throw new ArgumentException ("dateTime is not an ambiguous time");
 599
 600                         AdjustmentRule rule = GetApplicableRule (dateTime);
 601                         if (rule != null)
 602                                 return new TimeSpan[] {baseUtcOffset, baseUtcOffset + rule.DaylightDelta};
 603                         else
 604                                 return new TimeSpan[] {baseUtcOffset, baseUtcOffset};
 605                 }
 606
 607                 public TimeSpan [] GetAmbiguousTimeOffsets (DateTimeOffset dateTimeOffset)
 608                 {
 609                         if (!IsAmbiguousTime (dateTimeOffset))
 610                                 throw new ArgumentException ("dateTimeOffset is not an ambiguous time");
 611
 612                         throw new NotImplementedException ();
 613                 }
 614
 615                 public override int GetHashCode ()
 616                 {
 617                         int hash_code = Id.GetHashCode ();
 618                         foreach (AdjustmentRule rule in GetAdjustmentRules ())
 619                                 hash_code ^= rule.GetHashCode ();
 620                         return hash_code;
 621                 }
 622
 623 #if NET_4_0
 624                 void ISerializable.GetObjectData (SerializationInfo info, StreamingContext context)
 625 #else
 626                 public void GetObjectData (SerializationInfo info, StreamingContext context)
 627 #endif
 628                 {
 629                         if (info == null)
 630                                 throw new ArgumentNullException ("info");
 631                         info.AddValue ("Id", id);
 632                         info.AddValue ("DisplayName", displayName);
 633                         info.AddValue ("StandardName", standardDisplayName);
 634                         info.AddValue ("DaylightName", daylightDisplayName);
 635                         info.AddValue ("BaseUtcOffset", baseUtcOffset);
 636                         info.AddValue ("AdjustmentRules", adjustmentRules);
 637                         info.AddValue ("SupportsDaylightSavingTime", SupportsDaylightSavingTime);
 638                 }
 639
 640                 //FIXME: change this to a generic Dictionary and allow caching for FindSystemTimeZoneById
 641                 private static List<TimeZoneInfo> systemTimeZones;
 642                 public static ReadOnlyCollection<TimeZoneInfo> GetSystemTimeZones ()
 643                 {
 644                         if (systemTimeZones == null) {
 645                                 systemTimeZones = new List<TimeZoneInfo> ();
 646 #if !NET_2_1
 647                                 if (TimeZoneKey != null) {
 648                                         foreach (string id in TimeZoneKey.GetSubKeyNames ()) {
 649                                                 try {
 650                                                         systemTimeZones.Add (FindSystemTimeZoneById (id));
 651                                                 } catch {}
 652                                         }
 653
 654                                         return new ReadOnlyCollection<TimeZoneInfo> (systemTimeZones);
 655                                 }
 656 #endif
 657 #if MONODROID
 658                         foreach (string id in AndroidTimeZones.GetAvailableIds ()) {
 659                                 var tz = AndroidTimeZones.GetTimeZone (id, id);
 660                                 if (tz != null)
 661                                         systemTimeZones.Add (tz);
 662                         }
 663 #elif MONOTOUCH
 664                                 if (systemTimeZones.Count == 0) {
 665                                         foreach (string name in GetMonoTouchNames ()) {
 666                                                 using (Stream stream = GetMonoTouchData (name, false)) {
 667                                                         if (stream == null)
 668                                                                 continue;
 669                                                         systemTimeZones.Add (BuildFromStream (name, stream));
 670                                                 }
 671                                         }
 672                                 }
 673 #elif LIBC
 674                                 string[] continents = new string [] {"Africa", "America", "Antarctica", "Arctic", "Asia", "Atlantic", "Brazil", "Canada", "Chile", "Europe", "Indian", "Mexico", "Mideast", "Pacific", "US"};
 675                                 foreach (string continent in continents) {
 676                                         try {
 677                                                 foreach (string zonepath in Directory.GetFiles (Path.Combine (TimeZoneDirectory, continent))) {
 678                                                         try {
 679                                                                 string id = String.Format ("{0}/{1}", continent, Path.GetFileName (zonepath));
 680                                                                 systemTimeZones.Add (FindSystemTimeZoneById (id));
 681                                                         } catch (ArgumentNullException) {
 682                                                         } catch (TimeZoneNotFoundException) {
 683                                                         } catch (InvalidTimeZoneException) {
 684                                                         } catch (Exception) {
 685                                                                 throw;
 686                                                         }
 687                                                 }
 688                                         } catch {}
 689                                 }
 690 #else
 691                                 throw new NotImplementedException ("This method is not implemented for this platform");
 692 #endif
 693                         }
 694                         return new ReadOnlyCollection<TimeZoneInfo> (systemTimeZones);
 695                 }
 696
 697                 public TimeSpan GetUtcOffset (DateTime dateTime)
 698                 {
 699                         bool isDST;
 700                         return GetUtcOffset (dateTime, out isDST);
 701                 }
 702
 703                 public TimeSpan GetUtcOffset (DateTimeOffset dateTimeOffset)
 704                 {
 705                         throw new NotImplementedException ();
 706                 }
 707
 708                 private TimeSpan GetUtcOffset (DateTime dateTime, out bool isDST)
 709                 {
 710                         isDST = false;
 711
 712                         TimeZoneInfo tz = this;
 713                         if (dateTime.Kind == DateTimeKind.Utc)
 714                                 tz = TimeZoneInfo.Utc;
 715
 716                         if (dateTime.Kind == DateTimeKind.Local)
 717                                 tz = TimeZoneInfo.Local;
 718
 719                         bool isTzDst;
 720                         var tzOffset = GetUtcOffset (dateTime, tz, out isTzDst);
 721
 722                         if (tz == this) {
 723                                 isDST = isTzDst;
 724                                 return tzOffset;
 725                         }
 726
 727                         var utcTicks = dateTime.Ticks - tzOffset.Ticks;
 728                         if (utcTicks < 0 || utcTicks > DateTime.MaxValue.Ticks)
 729                                 return BaseUtcOffset;
 730
 731                         var utcDateTime = new DateTime (utcTicks, DateTimeKind.Utc);
 732
 733                         return GetUtcOffset (utcDateTime, this, out isDST);
 734                 }
 735
 736                 private static TimeSpan GetUtcOffset (DateTime dateTime, TimeZoneInfo tz, out bool isDST)
 737                 {
 738                         if (dateTime.Kind == DateTimeKind.Local && tz != TimeZoneInfo.Local)
 739                                 throw new Exception ();
 740
 741                         isDST = false;
 742
 743                         if (tz == TimeZoneInfo.Utc)
 744                                 return TimeSpan.Zero;
 745
 746                         TimeSpan offset;
 747                         if (tz.TryGetTransitionOffset(dateTime, out offset, out isDST))
 748                                 return offset;
 749
 750                         if (dateTime.Kind == DateTimeKind.Utc) {
 751                                 var utcRule = tz.GetApplicableRule (dateTime);
 752                                 if (utcRule != null && tz.IsInDST (utcRule, dateTime)) {
 753                                         isDST = true;
 754                                         return tz.BaseUtcOffset + utcRule.DaylightDelta;
 755                                 }
 756
 757                                 return tz.BaseUtcOffset;
 758                         }
 759
 760                         var stdTicks = dateTime.Ticks - tz.BaseUtcOffset.Ticks;
 761                         if (stdTicks < 0 || stdTicks > DateTime.MaxValue.Ticks)
 762                                 return tz.BaseUtcOffset;
 763
 764                         var stdUtcDateTime = new DateTime (stdTicks, DateTimeKind.Utc);
 765                         var tzRule = tz.GetApplicableRule (stdUtcDateTime);
 766
 767                         DateTime dstUtcDateTime = DateTime.MinValue;
 768                         if (tzRule != null) {
 769                                 var dstTicks = stdUtcDateTime.Ticks - tzRule.DaylightDelta.Ticks;
 770                                 if (dstTicks < 0 || dstTicks > DateTime.MaxValue.Ticks)
 771                                         return tz.BaseUtcOffset;
 772
 773                                 dstUtcDateTime = new DateTime (dstTicks, DateTimeKind.Utc);
 774                         }
 775
 776                         if (tzRule != null && tz.IsInDST (tzRule, stdUtcDateTime) && tz.IsInDST (tzRule, dstUtcDateTime)) {
 777                                 isDST = true;
 778                                 return tz.BaseUtcOffset + tzRule.DaylightDelta;
 779                         }
 780
 781                         return tz.BaseUtcOffset;
 782                 }
 783
 784                 public bool HasSameRules (TimeZoneInfo other)
 785                 {
 786                         if (other == null)
 787                                 throw new ArgumentNullException ("other");
 788
 789                         if ((this.adjustmentRules == null) != (other.adjustmentRules == null))
 790                                 return false;
 791
 792                         if (this.adjustmentRules == null)
 793                                 return true;
 794
 795                         if (this.BaseUtcOffset != other.BaseUtcOffset)
 796                                 return false;
 797
 798                         if (this.adjustmentRules.Length != other.adjustmentRules.Length)
 799                                 return false;
 800
 801                         for (int i = 0; i < adjustmentRules.Length; i++) {
 802                                 if (! (this.adjustmentRules [i]).Equals (other.adjustmentRules [i]))
 803                                         return false;
 804                         }
 805
 806                         return true;
 807                 }
 808
 809                 public bool IsAmbiguousTime (DateTime dateTime)
 810                 {
 811                         if (dateTime.Kind == DateTimeKind.Local && IsInvalidTime (dateTime))
 812                                 throw new ArgumentException ("Kind is Local and time is Invalid");
 813
 814                         if (this == TimeZoneInfo.Utc)
 815                                 return false;
 816
 817                         if (dateTime.Kind == DateTimeKind.Utc)
 818                                 dateTime = ConvertTimeFromUtc (dateTime);
 819
 820                         if (dateTime.Kind == DateTimeKind.Local && this != TimeZoneInfo.Local)
 821                                 dateTime = ConvertTime (dateTime, TimeZoneInfo.Local, this);
 822
 823                         AdjustmentRule rule = GetApplicableRule (dateTime);
 824                         if (rule != null) {
 825                                 DateTime tpoint = TransitionPoint (rule.DaylightTransitionEnd, dateTime.Year);
 826                                 if (dateTime > tpoint - rule.DaylightDelta  && dateTime <= tpoint)
 827                                         return true;
 828                         }
 829
 830                         return false;
 831                 }
 832
 833                 public bool IsAmbiguousTime (DateTimeOffset dateTimeOffset)
 834                 {
 835                         throw new NotImplementedException ();
 836                 }
 837
 838                 private bool IsInDST (AdjustmentRule rule, DateTime dateTime)
 839                 {
 840                         // Check whether we're in the dateTime year's DST period
 841                         if (IsInDSTForYear (rule, dateTime, dateTime.Year))
 842                                 return true;
 843
 844                         // We might be in the dateTime previous year's DST period
 845                         return IsInDSTForYear (rule, dateTime, dateTime.Year - 1);
 846                 }
 847
 848                 bool IsInDSTForYear (AdjustmentRule rule, DateTime dateTime, int year)
 849                 {
 850                         DateTime DST_start = TransitionPoint (rule.DaylightTransitionStart, year);
 851                         DateTime DST_end = TransitionPoint (rule.DaylightTransitionEnd, year + ((rule.DaylightTransitionStart.Month < rule.DaylightTransitionEnd.Month) ? 0 : 1));
 852                         if (dateTime.Kind == DateTimeKind.Utc) {
 853                                 DST_start -= BaseUtcOffset;
 854                                 DST_end -= (BaseUtcOffset + rule.DaylightDelta);
 855                         }
 856
 857                         return (dateTime >= DST_start && dateTime < DST_end);
 858                 }
 859
 860                 public bool IsDaylightSavingTime (DateTime dateTime)
 861                 {
 862                         if (dateTime.Kind == DateTimeKind.Local && IsInvalidTime (dateTime))
 863                                 throw new ArgumentException ("dateTime is invalid and Kind is Local");
 864
 865                         if (this == TimeZoneInfo.Utc)
 866                                 return false;
 867
 868                         if (!SupportsDaylightSavingTime)
 869                                 return false;
 870
 871                         bool isDst;
 872                         GetUtcOffset (dateTime, out isDst);
 873
 874                         return isDst;
 875                 }
 876
 877                 public bool IsDaylightSavingTime (DateTimeOffset dateTimeOffset)
 878                 {
 879                         throw new NotImplementedException ();
 880                 }
 881
 882                 public bool IsInvalidTime (DateTime dateTime)
 883                 {
 884                         if (dateTime.Kind == DateTimeKind.Utc)
 885                                 return false;
 886                         if (dateTime.Kind == DateTimeKind.Local && this != Local)
 887                                 return false;
 888
 889                         AdjustmentRule rule = GetApplicableRule (dateTime);
 890                         if (rule != null) {
 891                                 DateTime tpoint = TransitionPoint (rule.DaylightTransitionStart, dateTime.Year);
 892                                 if (dateTime >= tpoint && dateTime < tpoint + rule.DaylightDelta)
 893                                         return true;
 894                         }
 895
 896                         return false;
 897                 }
 898
 899 #if NET_4_0
 900                 void IDeserializationCallback.OnDeserialization (object sender)
 901 #else
 902                 public void OnDeserialization (object sender)
 903 #endif
 904                 {
 905                         try {
 906                                         TimeZoneInfo.Validate (id, baseUtcOffset, adjustmentRules);
 907                                 } catch (ArgumentException ex) {
 908                                         throw new SerializationException ("invalid serialization data", ex);
 909                                 }
 910                 }
 911
 912                 private static void Validate (string id, TimeSpan baseUtcOffset, AdjustmentRule [] adjustmentRules)
 913                 {
 914                         if (id == null)
 915                                 throw new ArgumentNullException ("id");
 916
 917                         if (id == String.Empty)
 918                                 throw new ArgumentException ("id parameter is an empty string");
 919
 920                         if (baseUtcOffset.Ticks % TimeSpan.TicksPerMinute != 0)
 921                                 throw new ArgumentException ("baseUtcOffset parameter does not represent a whole number of minutes");
 922
 923                         if (baseUtcOffset > new TimeSpan (14, 0, 0) || baseUtcOffset < new TimeSpan (-14, 0, 0))
 924                                 throw new ArgumentOutOfRangeException ("baseUtcOffset parameter is greater than 14 hours or less than -14 hours");
 925
 926 #if STRICT
 927                         if (id.Length > 32)
 928                                 throw new ArgumentException ("id parameter shouldn't be longer than 32 characters");
 929 #endif
 930
 931                         if (adjustmentRules != null && adjustmentRules.Length != 0) {
 932                                 AdjustmentRule prev = null;
 933                                 foreach (AdjustmentRule current in adjustmentRules) {
 934                                         if (current == null)
 935                                                 throw new InvalidTimeZoneException ("one or more elements in adjustmentRules are null");
 936
 937                                         if ((baseUtcOffset + current.DaylightDelta < new TimeSpan (-14, 0, 0)) ||
 938                                                         (baseUtcOffset + current.DaylightDelta > new TimeSpan (14, 0, 0)))
 939                                                 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;");
 940
 941                                         if (prev != null && prev.DateStart > current.DateStart)
 942                                                 throw new InvalidTimeZoneException ("adjustment rules specified in adjustmentRules parameter are not in chronological order");
 943
 944                                         if (prev != null && prev.DateEnd > current.DateStart)
 945                                                 throw new InvalidTimeZoneException ("some adjustment rules in the adjustmentRules parameter overlap");
 946
 947                                         if (prev != null && prev.DateEnd == current.DateStart)
 948                                                 throw new InvalidTimeZoneException ("a date can have multiple adjustment rules applied to it");
 949
 950                                         prev = current;
 951                                 }
 952                         }
 953                 }
 954
 955                 public override string ToString ()
 956                 {
 957                         return DisplayName;
 958                 }
 959
 960                 private TimeZoneInfo (SerializationInfo info, StreamingContext context)
 961                 {
 962                         if (info == null)
 963                                 throw new ArgumentNullException ("info");
 964                         id = (string) info.GetValue ("Id", typeof (string));
 965                         displayName = (string) info.GetValue ("DisplayName", typeof (string));
 966                         standardDisplayName = (string) info.GetValue ("StandardName", typeof (string));
 967                         daylightDisplayName = (string) info.GetValue ("DaylightName", typeof (string));
 968                         baseUtcOffset = (TimeSpan) info.GetValue ("BaseUtcOffset", typeof (TimeSpan));
 969                         adjustmentRules = (TimeZoneInfo.AdjustmentRule []) info.GetValue ("AdjustmentRules", typeof (TimeZoneInfo.AdjustmentRule []));
 970                         supportsDaylightSavingTime = (bool) info.GetValue ("SupportsDaylightSavingTime", typeof (bool));
 971                 }
 972
 973                 private TimeZoneInfo (string id, TimeSpan baseUtcOffset, string displayName, string standardDisplayName, string daylightDisplayName, TimeZoneInfo.AdjustmentRule [] adjustmentRules, bool disableDaylightSavingTime)
 974                 {
 975                         if (id == null)
 976                                 throw new ArgumentNullException ("id");
 977
 978                         if (id == String.Empty)
 979                                 throw new ArgumentException ("id parameter is an empty string");
 980
 981                         if (baseUtcOffset.Ticks % TimeSpan.TicksPerMinute != 0)
 982                                 throw new ArgumentException ("baseUtcOffset parameter does not represent a whole number of minutes");
 983
 984                         if (baseUtcOffset > new TimeSpan (14, 0, 0) || baseUtcOffset < new TimeSpan (-14, 0, 0))
 985                                 throw new ArgumentOutOfRangeException ("baseUtcOffset parameter is greater than 14 hours or less than -14 hours");
 986
 987 #if STRICT
 988                         if (id.Length > 32)
 989                                 throw new ArgumentException ("id parameter shouldn't be longer than 32 characters");
 990 #endif
 991
 992                         bool supportsDaylightSavingTime = !disableDaylightSavingTime;
 993
 994                         if (adjustmentRules != null && adjustmentRules.Length != 0) {
 995                                 AdjustmentRule prev = null;
 996                                 foreach (AdjustmentRule current in adjustmentRules) {
 997                                         if (current == null)
 998                                                 throw new InvalidTimeZoneException ("one or more elements in adjustmentRules are null");
 999
1000                                         if ((baseUtcOffset + current.DaylightDelta < new TimeSpan (-14, 0, 0)) ||
1001                                                         (baseUtcOffset + current.DaylightDelta > new TimeSpan (14, 0, 0)))
1002                                                 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;");
1003
1004                                         if (prev != null && prev.DateStart > current.DateStart)
1005                                                 throw new InvalidTimeZoneException ("adjustment rules specified in adjustmentRules parameter are not in chronological order");
1006
1007                                         if (prev != null && prev.DateEnd > current.DateStart)
1008                                                 throw new InvalidTimeZoneException ("some adjustment rules in the adjustmentRules parameter overlap");
1009
1010                                         if (prev != null && prev.DateEnd == current.DateStart)
1011                                                 throw new InvalidTimeZoneException ("a date can have multiple adjustment rules applied to it");
1012
1013                                         prev = current;
1014                                 }
1015                         } else {
1016                                 supportsDaylightSavingTime = false;
1017                         }
1018
1019                         this.id = id;
1020                         this.baseUtcOffset = baseUtcOffset;
1021                         this.displayName = displayName ?? id;
1022                         this.standardDisplayName = standardDisplayName ?? id;
1023                         this.daylightDisplayName = daylightDisplayName;
1024                         this.supportsDaylightSavingTime = supportsDaylightSavingTime;
1025                         this.adjustmentRules = adjustmentRules;
1026                 }
1027
1028                 private AdjustmentRule GetApplicableRule (DateTime dateTime)
1029                 {
1030                         //Transitions are always in standard time
1031                         DateTime date = dateTime;
1032
1033                         if (dateTime.Kind == DateTimeKind.Local && this != TimeZoneInfo.Local)
1034                                 date = date.ToUniversalTime () + BaseUtcOffset;
1035
1036                         if (dateTime.Kind == DateTimeKind.Utc && this != TimeZoneInfo.Utc)
1037                                 date = date + BaseUtcOffset;
1038
1039                         if (adjustmentRules != null) {
1040                                 foreach (AdjustmentRule rule in adjustmentRules) {
1041                                         if (rule.DateStart > date.Date)
1042                                                 return null;
1043                                         if (rule.DateEnd < date.Date)
1044                                                 continue;
1045                                         return rule;
1046                                 }
1047                         }
1048                         return null;
1049                 }
1050
1051                 private bool TryGetTransitionOffset (DateTime dateTime, out TimeSpan offset,out bool isDst)
1052                 {
1053                         offset = BaseUtcOffset;
1054                         isDst = false;
1055
1056                         if (transitions == null)
1057                                 return false;
1058
1059                         //Transitions are always in standard time
1060                         DateTime date = dateTime;
1061
1062                         if (dateTime.Kind == DateTimeKind.Local && this != TimeZoneInfo.Local)
1063                                 date = date.ToUniversalTime () + BaseUtcOffset;
1064
1065                         if (dateTime.Kind == DateTimeKind.Utc && this != TimeZoneInfo.Utc)
1066                                 date = date + BaseUtcOffset;
1067
1068                         for (var i =  transitions.Count - 1; i >= 0; i--) {
1069                                 var pair = transitions [i];
1070                                 DateTime ttime = pair.Key;
1071                                 TimeType ttype = pair.Value;
1072
1073                                 if (ttime > date)
1074                                         continue;
1075
1076                                 offset =  new TimeSpan (0, 0, ttype.Offset);
1077                                 isDst = ttype.IsDst;
1078
1079                                 return true;
1080                         }
1081
1082                         return false;
1083                 }
1084
1085                 private static DateTime TransitionPoint (TransitionTime transition, int year)
1086                 {
1087                         if (transition.IsFixedDateRule)
1088                                 return new DateTime (year, transition.Month, transition.Day) + transition.TimeOfDay.TimeOfDay;
1089
1090                         DayOfWeek first = (new DateTime (year, transition.Month, 1)).DayOfWeek;
1091                         int day = 1 + (transition.Week - 1) * 7 + (transition.DayOfWeek - first) % 7;
1092                         if (day >  DateTime.DaysInMonth (year, transition.Month))
1093                                 day -= 7;
1094                         if (day < 1)
1095                                 day += 7;
1096                         return new DateTime (year, transition.Month, day) + transition.TimeOfDay.TimeOfDay;
1097                 }
1098
1099                 static List<AdjustmentRule> ValidateRules (List<AdjustmentRule> adjustmentRules)
1100                 {
1101                         AdjustmentRule prev = null;
1102                         foreach (AdjustmentRule current in adjustmentRules.ToArray ()) {
1103                                 if (prev != null && prev.DateEnd > current.DateStart) {
1104                                         adjustmentRules.Remove (current);
1105                                 }
1106                                 prev = current;
1107                         }
1108                         return adjustmentRules;
1109                 }
1110
1111 #if LIBC || MONODROID
1112                 private static bool ValidTZFile (byte [] buffer, int length)
1113                 {
1114                         StringBuilder magic = new StringBuilder ();
1115
1116                         for (int i = 0; i < 4; i++)
1117                                 magic.Append ((char)buffer [i]);
1118
1119                         if (magic.ToString () != "TZif")
1120                                 return false;
1121
1122                         if (length >= BUFFER_SIZE)
1123                                 return false;
1124
1125                         return true;
1126                 }
1127
1128                 static int SwapInt32 (int i)
1129                 {
1130                         return (((i >> 24) & 0xff)
1131                                 | ((i >> 8) & 0xff00)
1132                                 | ((i << 8) & 0xff0000)
1133                                 | ((i << 24)));
1134                 }
1135
1136                 static int ReadBigEndianInt32 (byte [] buffer, int start)
1137                 {
1138                         int i = BitConverter.ToInt32 (buffer, start);
1139                         if (!BitConverter.IsLittleEndian)
1140                                 return i;
1141
1142                         return SwapInt32 (i);
1143                 }
1144
1145                 private static TimeZoneInfo ParseTZBuffer (string id, byte [] buffer, int length)
1146                 {
1147                         //Reading the header. 4 bytes for magic, 16 are reserved
1148                         int ttisgmtcnt = ReadBigEndianInt32 (buffer, 20);
1149                         int ttisstdcnt = ReadBigEndianInt32 (buffer, 24);
1150                         int leapcnt = ReadBigEndianInt32 (buffer, 28);
1151                         int timecnt = ReadBigEndianInt32 (buffer, 32);
1152                         int typecnt = ReadBigEndianInt32 (buffer, 36);
1153                         int charcnt = ReadBigEndianInt32 (buffer, 40);
1154
1155                         if (length < 44 + timecnt * 5 + typecnt * 6 + charcnt + leapcnt * 8 + ttisstdcnt + ttisgmtcnt)
1156                                 throw new InvalidTimeZoneException ();
1157
1158                         Dictionary<int, string> abbreviations = ParseAbbreviations (buffer, 44 + 4 * timecnt + timecnt + 6 * typecnt, charcnt);
1159                         Dictionary<int, TimeType> time_types = ParseTimesTypes (buffer, 44 + 4 * timecnt + timecnt, typecnt, abbreviations);
1160                         List<KeyValuePair<DateTime, TimeType>> transitions = ParseTransitions (buffer, 44, timecnt, time_types);
1161
1162                         if (time_types.Count == 0)
1163                                 throw new InvalidTimeZoneException ();
1164
1165                         if (time_types.Count == 1 && ((TimeType)time_types[0]).IsDst)
1166                                 throw new InvalidTimeZoneException ();
1167
1168                         TimeSpan baseUtcOffset = new TimeSpan (0);
1169                         TimeSpan dstDelta = new TimeSpan (0);
1170                         string standardDisplayName = null;
1171                         string daylightDisplayName = null;
1172                         bool dst_observed = false;
1173                         DateTime dst_start = DateTime.MinValue;
1174                         List<AdjustmentRule> adjustmentRules = new List<AdjustmentRule> ();
1175                         bool storeTransition = false;
1176
1177                         for (int i = 0; i < transitions.Count; i++) {
1178                                 var pair = transitions [i];
1179                                 DateTime ttime = pair.Key;
1180                                 TimeType ttype = pair.Value;
1181                                 if (!ttype.IsDst) {
1182                                         if (standardDisplayName != ttype.Name || baseUtcOffset.TotalSeconds != ttype.Offset) {
1183                                                 standardDisplayName = ttype.Name;
1184                                                 daylightDisplayName = null;
1185                                                 baseUtcOffset = new TimeSpan (0, 0, ttype.Offset);
1186                                                 if (adjustmentRules.Count > 0) // We ignore AdjustmentRules but store transitions.
1187                                                         storeTransition = true;
1188                                                 adjustmentRules = new List<AdjustmentRule> ();
1189                                                 dst_observed = false;
1190                                         }
1191                                         if (dst_observed) {
1192                                                 //FIXME: check additional fields for this:
1193                                                 //most of the transitions are expressed in GMT
1194                                                 dst_start += baseUtcOffset;
1195                                                 DateTime dst_end = ttime + baseUtcOffset + dstDelta;
1196
1197                                                 //some weird timezone (America/Phoenix) have end dates on Jan 1st
1198                                                 if (dst_end.Date == new DateTime (dst_end.Year, 1, 1) && dst_end.Year > dst_start.Year)
1199                                                         dst_end -= new TimeSpan (24, 0, 0);
1200
1201                                                 DateTime dateStart, dateEnd;
1202                                                 if (dst_start.Month < 7)
1203                                                         dateStart = new DateTime (dst_start.Year, 1, 1);
1204                                                 else
1205                                                         dateStart = new DateTime (dst_start.Year, 7, 1);
1206
1207                                                 if (dst_end.Month >= 7)
1208                                                         dateEnd = new DateTime (dst_end.Year, 12, 31);
1209                                                 else
1210                                                         dateEnd = new DateTime (dst_end.Year, 6, 30);
1211
1212
1213                                                 TransitionTime transition_start = TransitionTime.CreateFixedDateRule (new DateTime (1, 1, 1) + dst_start.TimeOfDay, dst_start.Month, dst_start.Day);
1214                                                 TransitionTime transition_end = TransitionTime.CreateFixedDateRule (new DateTime (1, 1, 1) + dst_end.TimeOfDay, dst_end.Month, dst_end.Day);
1215                                                 if  (transition_start != transition_end) //y, that happened in Argentina in 1943-1946
1216                                                         adjustmentRules.Add (AdjustmentRule.CreateAdjustmentRule (dateStart, dateEnd, dstDelta, transition_start, transition_end));
1217                                         }
1218                                         dst_observed = false;
1219                                 } else {
1220                                         if (daylightDisplayName != ttype.Name || dstDelta.TotalSeconds != ttype.Offset - baseUtcOffset.TotalSeconds) {
1221                                                 daylightDisplayName = ttype.Name;
1222                                                 dstDelta = new TimeSpan(0, 0, ttype.Offset) - baseUtcOffset;
1223                                         }
1224                                         dst_start = ttime;
1225                                         dst_observed = true;
1226                                 }
1227                         }
1228
1229                         TimeZoneInfo tz;
1230                         if (adjustmentRules.Count == 0 && !storeTransition) {
1231                                 TimeType t = (TimeType)time_types [0];
1232                                 if (standardDisplayName == null) {
1233                                         standardDisplayName = t.Name;
1234                                         baseUtcOffset = new TimeSpan (0, 0, t.Offset);
1235                                 }
1236                                 tz = CreateCustomTimeZone (id, baseUtcOffset, id, standardDisplayName);
1237                         } else {
1238                                 tz = CreateCustomTimeZone (id, baseUtcOffset, id, standardDisplayName, daylightDisplayName, ValidateRules (adjustmentRules).ToArray ());
1239                         }
1240
1241                         if (storeTransition)
1242                                 tz.transitions = transitions;
1243
1244                         return tz;
1245                 }
1246
1247                 static Dictionary<int, string> ParseAbbreviations (byte [] buffer, int index, int count)
1248                 {
1249                         var abbrevs = new Dictionary<int, string> ();
1250                         int abbrev_index = 0;
1251                         var sb = new StringBuilder ();
1252                         for (int i = 0; i < count; i++) {
1253                                 char c = (char) buffer [index + i];
1254                                 if (c != '\0')
1255                                         sb.Append (c);
1256                                 else {
1257                                         abbrevs.Add (abbrev_index, sb.ToString ());
1258                                         //Adding all the substrings too, as it seems to be used, at least for Africa/Windhoek
1259                                         for (int j = 1; j < sb.Length; j++)
1260                                                 abbrevs.Add (abbrev_index + j, sb.ToString (j, sb.Length - j));
1261                                         abbrev_index = i + 1;
1262                                         sb = new StringBuilder ();
1263                                 }
1264                         }
1265                         return abbrevs;
1266                 }
1267
1268                 static Dictionary<int, TimeType> ParseTimesTypes (byte [] buffer, int index, int count, Dictionary<int, string> abbreviations)
1269                 {
1270                         var types = new Dictionary<int, TimeType> (count);
1271                         for (int i = 0; i < count; i++) {
1272                                 int offset = ReadBigEndianInt32 (buffer, index + 6 * i);
1273                                 byte is_dst = buffer [index + 6 * i + 4];
1274                                 byte abbrev = buffer [index + 6 * i + 5];
1275                                 types.Add (i, new TimeType (offset, (is_dst != 0), abbreviations [(int)abbrev]));
1276                         }
1277                         return types;
1278                 }
1279
1280                 static List<KeyValuePair<DateTime, TimeType>> ParseTransitions (byte [] buffer, int index, int count, Dictionary<int, TimeType> time_types)
1281                 {
1282                         var list = new List<KeyValuePair<DateTime, TimeType>> (count);
1283                         for (int i = 0; i < count; i++) {
1284                                 int unixtime = ReadBigEndianInt32 (buffer, index + 4 * i);
1285                                 DateTime ttime = DateTimeFromUnixTime (unixtime);
1286                                 byte ttype = buffer [index + 4 * count + i];
1287                                 list.Add (new KeyValuePair<DateTime, TimeType> (ttime, time_types [(int)ttype]));
1288                         }
1289                         return list;
1290                 }
1291
1292                 static DateTime DateTimeFromUnixTime (long unix_time)
1293                 {
1294                         DateTime date_time = new DateTime (1970, 1, 1);
1295                         return date_time.AddSeconds (unix_time);
1296                 }
1297         }
1298
1299         struct TimeType {
1300                 public readonly int Offset;
1301                 public readonly bool IsDst;
1302                 public string Name;
1303
1304                 public TimeType (int offset, bool is_dst, string abbrev)
1305                 {
1306                         this.Offset = offset;
1307                         this.IsDst = is_dst;
1308                         this.Name = abbrev;
1309                 }
1310
1311                 public override string ToString ()
1312                 {
1313                         return "offset: " + Offset + "s, is_dst: " + IsDst + ", zone name: " + Name;
1314                 }
1315 #else
1316         }
1317 #endif
1318         }
1319 }
1320
1321 #endif