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