class/System.Core/System/TimeZoneInfo.cs

   1 /*
   2  * System.TimeZoneInfo
   3  *
   4  * Author(s)
   5  *      Stephane Delcroix <stephane@delcroix.org>
   6  *
   7  * Permission is hereby granted, free of charge, to any person obtaining
   8  * a copy of this software and associated documentation files (the
   9  * "Software"), to deal in the Software without restriction, including
  10  * without limitation the rights to use, copy, modify, merge, publish,
  11  * distribute, sublicense, and/or sell copies of the Software, and to
  12  * permit persons to whom the Software is furnished to do so, subject to
  13  * the following conditions:
  14  *
  15  * The above copyright notice and this permission notice shall be
  16  * included in all copies or substantial portions of the Software.
  17  *
  18  * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
  19  * EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
  20  * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
  21  * NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE
  22  * LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION
  23  * OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
  24  * WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
  25  */
  26
  27 using System;
  28 using System.Runtime.CompilerServices;
  29
  30 #if !INSIDE_CORLIB && (NET_4_0 || BOOTSTRAP_NET_4_0 || MOONLIGHT)
  31
  32 [assembly:TypeForwardedTo (typeof(TimeZoneInfo))]
  33
  34 #elif NET_3_5 || (MONOTOUCH && !INSIDE_CORLIB) || (MOONLIGHT && INSIDE_CORLIB)
  35
  36 using System.Collections.Generic;
  37 using System.Collections.ObjectModel;
  38 using System.Runtime.Serialization;
  39 using System.Text;
  40
  41 #if LIBC
  42 using System.IO;
  43 using Mono;
  44 #endif
  45
  46 using Microsoft.Win32;
  47
  48 namespace System
  49 {
  50 #if NET_4_0 || BOOTSTRAP_NET_4_0
  51         [TypeForwardedFrom (Consts.AssemblySystemCore_3_5)]
  52 #elif MOONLIGHT
  53         [TypeForwardedFrom (Consts.AssemblySystem_Core)]
  54 #endif
  55         [SerializableAttribute]
  56         public sealed partial class TimeZoneInfo : IEquatable<TimeZoneInfo>, ISerializable, IDeserializationCallback
  57         {
  58                 TimeSpan baseUtcOffset;
  59                 public TimeSpan BaseUtcOffset {
  60                         get { return baseUtcOffset; }
  61                 }
  62
  63                 string daylightDisplayName;
  64                 public string DaylightName {
  65                         get {
  66                                 if (disableDaylightSavingTime)
  67                                         return String.Empty;
  68                                 return daylightDisplayName;
  69                         }
  70                 }
  71
  72                 string displayName;
  73                 public string DisplayName {
  74                         get { return displayName; }
  75                 }
  76
  77                 string id;
  78                 public string Id {
  79                         get { return id; }
  80                 }
  81
  82                 static TimeZoneInfo local;
  83                 public static TimeZoneInfo Local {
  84                         get {
  85                                 if (local == null) {
  86 #if LIBC
  87                                         try {
  88                                                 local = FindSystemTimeZoneByFileName ("Local", "/etc/localtime");
  89                                         } catch {
  90                                                 try {
  91                                                         local = FindSystemTimeZoneByFileName ("Local", Path.Combine (TimeZoneDirectory, "localtime"));
  92                                                 } catch {
  93                                                         throw new TimeZoneNotFoundException ();
  94                                                 }
  95                                         }
  96 #else
  97                                         throw new TimeZoneNotFoundException ();
  98 #endif
  99                                 }
 100                                 return local;
 101                         }
 102                 }
 103
 104                 string standardDisplayName;
 105                 public string StandardName {
 106                         get { return standardDisplayName; }
 107                 }
 108
 109                 bool disableDaylightSavingTime;
 110                 public bool SupportsDaylightSavingTime {
 111                         get  { return !disableDaylightSavingTime; }
 112                 }
 113
 114                 static TimeZoneInfo utc;
 115                 public static TimeZoneInfo Utc {
 116                         get {
 117                                 if (utc == null)
 118                                         utc = CreateCustomTimeZone ("UTC", new TimeSpan (0), "UTC", "UTC");
 119                                 return utc;
 120                         }
 121                 }
 122 #if LIBC
 123                 static string timeZoneDirectory = null;
 124                 static string TimeZoneDirectory {
 125                         get {
 126                                 if (timeZoneDirectory == null)
 127                                         timeZoneDirectory = "/usr/share/zoneinfo";
 128                                 return timeZoneDirectory;
 129                         }
 130                         set {
 131                                 ClearCachedData ();
 132                                 timeZoneDirectory = value;
 133                         }
 134                 }
 135 #endif
 136                 private AdjustmentRule [] adjustmentRules;
 137
 138 #if !NET_2_1
 139                 static RegistryKey timeZoneKey = null;
 140                 static bool timeZoneKeySet = false;
 141                 static RegistryKey TimeZoneKey {
 142                         get {
 143                                 if (!timeZoneKeySet) {
 144                                         int p = (int) Environment.OSVersion.Platform;
 145                                         /* Only use the registry on non-Unix platforms. */
 146                                         if ((p != 4) && (p != 6) && (p != 128))
 147                                                 timeZoneKey = Registry.LocalMachine.OpenSubKey (
 148                                                         "SOFTWARE\\Microsoft\\Windows NT\\CurrentVersion\\Time Zones",
 149                                                         false);
 150                                         timeZoneKeySet = true;
 151                                 }
 152                                 return timeZoneKey;
 153                         }
 154                 }
 155 #endif
 156
 157                 public static void ClearCachedData ()
 158                 {
 159                         local = null;
 160                         utc = null;
 161                         systemTimeZones = null;
 162                 }
 163
 164                 public static DateTime ConvertTime (DateTime dateTime, TimeZoneInfo destinationTimeZone)
 165                 {
 166                         return ConvertTime (dateTime, TimeZoneInfo.Local, destinationTimeZone);
 167                 }
 168
 169                 public static DateTime ConvertTime (DateTime dateTime, TimeZoneInfo sourceTimeZone, TimeZoneInfo destinationTimeZone)
 170                 {
 171                         if (dateTime.Kind == DateTimeKind.Local && sourceTimeZone != TimeZoneInfo.Local)
 172                                 throw new ArgumentException ("Kind propery of dateTime is Local but the sourceTimeZone does not equal TimeZoneInfo.Local");
 173
 174                         if (dateTime.Kind == DateTimeKind.Utc && sourceTimeZone != TimeZoneInfo.Utc)
 175                                 throw new ArgumentException ("Kind propery of dateTime is Utc but the sourceTimeZone does not equal TimeZoneInfo.Utc");
 176
 177                         if (sourceTimeZone.IsInvalidTime (dateTime))
 178                                 throw new ArgumentException ("dateTime parameter is an invalid time");
 179
 180                         if (sourceTimeZone == null)
 181                                 throw new ArgumentNullException ("sourceTimeZone");
 182
 183                         if (destinationTimeZone == null)
 184                                 throw new ArgumentNullException ("destinationTimeZone");
 185
 186                         if (dateTime.Kind == DateTimeKind.Local && sourceTimeZone == TimeZoneInfo.Local && destinationTimeZone == TimeZoneInfo.Local)
 187                                 return dateTime;
 188
 189                         DateTime utc = ConvertTimeToUtc (dateTime);
 190
 191                         if (destinationTimeZone == TimeZoneInfo.Utc)
 192                                 return utc;
 193
 194                         return ConvertTimeFromUtc (utc, destinationTimeZone);
 195
 196                 }
 197
 198                 public static DateTimeOffset ConvertTime (DateTimeOffset dateTimeOffset, TimeZoneInfo destinationTimeZone)
 199                 {
 200                         throw new NotImplementedException ();
 201                 }
 202
 203                 public static DateTime ConvertTimeBySystemTimeZoneId (DateTime dateTime, string destinationTimeZoneId)
 204                 {
 205                         return ConvertTime (dateTime, FindSystemTimeZoneById (destinationTimeZoneId));
 206                 }
 207
 208                 public static DateTime ConvertTimeBySystemTimeZoneId (DateTime dateTime, string sourceTimeZoneId, string destinationTimeZoneId)
 209                 {
 210                         return ConvertTime (dateTime, FindSystemTimeZoneById (sourceTimeZoneId), FindSystemTimeZoneById (destinationTimeZoneId));
 211                 }
 212
 213                 public static DateTimeOffset ConvertTimeBySystemTimeZoneId (DateTimeOffset dateTimeOffset, string destinationTimeZoneId)
 214                 {
 215                         return ConvertTime (dateTimeOffset, FindSystemTimeZoneById (destinationTimeZoneId));
 216                 }
 217
 218                 private DateTime ConvertTimeFromUtc (DateTime dateTime)
 219                 {
 220                         if (dateTime.Kind == DateTimeKind.Local)
 221                                 throw new ArgumentException ("Kind property of dateTime is Local");
 222
 223                         if (this == TimeZoneInfo.Utc)
 224                                 return DateTime.SpecifyKind (dateTime, DateTimeKind.Utc);
 225
 226                         //FIXME: do not rely on DateTime implementation !
 227                         if (this == TimeZoneInfo.Local)
 228                                 return DateTime.SpecifyKind (dateTime.ToLocalTime (), DateTimeKind.Unspecified);
 229
 230                         AdjustmentRule rule = GetApplicableRule (dateTime);
 231
 232                         if (IsDaylightSavingTime (DateTime.SpecifyKind (dateTime, DateTimeKind.Utc)))
 233                                 return DateTime.SpecifyKind (dateTime + BaseUtcOffset + rule.DaylightDelta , DateTimeKind.Unspecified);
 234                         else
 235                                 return DateTime.SpecifyKind (dateTime + BaseUtcOffset, DateTimeKind.Unspecified);
 236                 }
 237
 238                 public static DateTime ConvertTimeFromUtc (DateTime dateTime, TimeZoneInfo destinationTimeZone)
 239                 {
 240                         if (destinationTimeZone == null)
 241                                 throw new ArgumentNullException ("destinationTimeZone");
 242
 243                         return destinationTimeZone.ConvertTimeFromUtc (dateTime);
 244                 }
 245
 246                 public static DateTime ConvertTimeToUtc (DateTime dateTime)
 247                 {
 248                         if (dateTime.Kind == DateTimeKind.Utc)
 249                                 return dateTime;
 250
 251                         //FIXME: do not rely on DateTime implementation !
 252                         return DateTime.SpecifyKind (dateTime.ToUniversalTime (), DateTimeKind.Utc);
 253                 }
 254
 255                 public static DateTime ConvertTimeToUtc (DateTime dateTime, TimeZoneInfo sourceTimeZone)
 256                 {
 257                         if (sourceTimeZone == null)
 258                                 throw new ArgumentNullException ("sourceTimeZone");
 259
 260                         if (dateTime.Kind == DateTimeKind.Utc && sourceTimeZone != TimeZoneInfo.Utc)
 261                                 throw new ArgumentException ("Kind propery of dateTime is Utc but the sourceTimeZone does not equal TimeZoneInfo.Utc");
 262
 263                         if (dateTime.Kind == DateTimeKind.Local && sourceTimeZone != TimeZoneInfo.Local)
 264                                 throw new ArgumentException ("Kind propery of dateTime is Local but the sourceTimeZone does not equal TimeZoneInfo.Local");
 265
 266                         if (sourceTimeZone.IsInvalidTime (dateTime))
 267                                 throw new ArgumentException ("dateTime parameter is an invalid time");
 268
 269                         if (dateTime.Kind == DateTimeKind.Utc && sourceTimeZone == TimeZoneInfo.Utc)
 270                                 return dateTime;
 271
 272                         if (dateTime.Kind == DateTimeKind.Utc)
 273                                 return dateTime;
 274
 275                         if (dateTime.Kind == DateTimeKind.Local)
 276                                 return ConvertTimeToUtc (dateTime);
 277
 278                         if (sourceTimeZone.IsAmbiguousTime (dateTime) || !sourceTimeZone.IsDaylightSavingTime (dateTime))
 279                                 return DateTime.SpecifyKind (dateTime - sourceTimeZone.BaseUtcOffset, DateTimeKind.Utc);
 280                         else {
 281                                 AdjustmentRule rule = sourceTimeZone.GetApplicableRule (dateTime);
 282                                 return DateTime.SpecifyKind (dateTime - sourceTimeZone.BaseUtcOffset - rule.DaylightDelta, DateTimeKind.Utc);
 283                         }
 284                 }
 285
 286                 public static TimeZoneInfo CreateCustomTimeZone (string id, TimeSpan baseUtcOffset, string displayName, string standardDisplayName)
 287                 {
 288                         return CreateCustomTimeZone (id, baseUtcOffset, displayName, standardDisplayName, null, null, true);
 289                 }
 290
 291                 public static TimeZoneInfo CreateCustomTimeZone (string id, TimeSpan baseUtcOffset, string displayName, string standardDisplayName, string daylightDisplayName, TimeZoneInfo.AdjustmentRule [] adjustmentRules)
 292                 {
 293                         return CreateCustomTimeZone (id, baseUtcOffset, displayName, standardDisplayName, daylightDisplayName, adjustmentRules, false);
 294                 }
 295
 296                 public static TimeZoneInfo CreateCustomTimeZone ( string id, TimeSpan baseUtcOffset, string displayName, string standardDisplayName, string daylightDisplayName, TimeZoneInfo.AdjustmentRule [] adjustmentRules, bool disableDaylightSavingTime)
 297                 {
 298                         return new TimeZoneInfo (id, baseUtcOffset, displayName, standardDisplayName, daylightDisplayName, adjustmentRules, disableDaylightSavingTime);
 299                 }
 300
 301                 public bool Equals (TimeZoneInfo other)
 302                 {
 303                         if (other == null)
 304                                 return false;
 305
 306                         return other.Id == this.Id && HasSameRules (other);
 307                 }
 308
 309                 public static TimeZoneInfo FindSystemTimeZoneById (string id)
 310                 {
 311                         //FIXME: this method should check for cached values in systemTimeZones
 312                         if (id == null)
 313                                 throw new ArgumentNullException ("id");
 314 #if !NET_2_1
 315                         if (TimeZoneKey != null)
 316                         {
 317                                 RegistryKey key = TimeZoneKey.OpenSubKey (id, false);
 318                                 if (key == null)
 319                                         throw new TimeZoneNotFoundException ();
 320                                 return FromRegistryKey(id, key);
 321                         }
 322 #endif
 323 #if LIBC
 324                         string filepath = Path.Combine (TimeZoneDirectory, id);
 325                         return FindSystemTimeZoneByFileName (id, filepath);
 326 #else
 327                         throw new NotImplementedException ();
 328 #endif
 329                 }
 330
 331 #if LIBC
 332                 const int BUFFER_SIZE = 16384; //Big enough for any tz file (on Oct 2008, all tz files are under 10k)
 333                 private static TimeZoneInfo FindSystemTimeZoneByFileName (string id, string filepath)
 334                 {
 335                         if (!File.Exists (filepath))
 336                                 throw new TimeZoneNotFoundException ();
 337
 338                         byte [] buffer = new byte [BUFFER_SIZE];
 339                         int length;
 340                         using (FileStream stream = File.OpenRead (filepath)) {
 341                                 length = stream.Read (buffer, 0, BUFFER_SIZE);
 342                         }
 343
 344                         if (!ValidTZFile (buffer, length))
 345                                 throw new InvalidTimeZoneException ("TZ file too big for the buffer");
 346
 347                         try {
 348                                 return ParseTZBuffer (id, buffer, length);
 349                         } catch (Exception e) {
 350                                 throw new InvalidTimeZoneException (e.Message);
 351                         }
 352                 }
 353 #endif
 354
 355 #if !NET_2_1
 356                 private static TimeZoneInfo FromRegistryKey (string id, RegistryKey key)
 357                 {
 358                         byte [] reg_tzi = (byte []) key.GetValue ("TZI");
 359
 360                         if (reg_tzi == null)
 361                                 throw new InvalidTimeZoneException ();
 362
 363                         int bias = BitConverter.ToInt32 (reg_tzi, 0);
 364                         TimeSpan baseUtcOffset = new TimeSpan (0, -bias, 0);
 365
 366                         string display_name = (string) key.GetValue ("Display");
 367                         string standard_name = (string) key.GetValue ("Std");
 368                         string daylight_name = (string) key.GetValue ("Dlt");
 369
 370                         List<AdjustmentRule> adjustmentRules = new List<AdjustmentRule> ();
 371
 372                         RegistryKey dst_key = key.OpenSubKey ("Dynamic DST", false);
 373                         if (dst_key != null) {
 374                                 int first_year = (int) dst_key.GetValue ("FirstEntry");
 375                                 int last_year = (int) dst_key.GetValue ("LastEntry");
 376                                 int year;
 377
 378                                 for (year=first_year; year<=last_year; year++) {
 379                                         byte [] dst_tzi = (byte []) dst_key.GetValue (year.ToString ());
 380                                         if (dst_tzi != null) {
 381                                                 int start_year = year == first_year ? 1 : year;
 382                                                 int end_year = year == last_year ? 9999 : year;
 383                                                 ParseRegTzi(adjustmentRules, start_year, end_year, dst_tzi);
 384                                         }
 385                                 }
 386                         }
 387                         else
 388                                 ParseRegTzi(adjustmentRules, 1, 9999, reg_tzi);
 389
 390                         return CreateCustomTimeZone (id, baseUtcOffset, display_name, standard_name, daylight_name, ValidateRules (adjustmentRules).ToArray ());
 391                 }
 392
 393                 private static void ParseRegTzi (List<AdjustmentRule> adjustmentRules, int start_year, int end_year, byte [] buffer)
 394                 {
 395                         //int standard_bias = BitConverter.ToInt32 (buffer, 4); /* not sure how to handle this */
 396                         int daylight_bias = BitConverter.ToInt32 (buffer, 8);
 397
 398                         int standard_year = BitConverter.ToInt16 (buffer, 12);
 399                         int standard_month = BitConverter.ToInt16 (buffer, 14);
 400                         int standard_dayofweek = BitConverter.ToInt16 (buffer, 16);
 401                         int standard_day = BitConverter.ToInt16 (buffer, 18);
 402                         int standard_hour = BitConverter.ToInt16 (buffer, 20);
 403                         int standard_minute = BitConverter.ToInt16 (buffer, 22);
 404                         int standard_second = BitConverter.ToInt16 (buffer, 24);
 405                         int standard_millisecond = BitConverter.ToInt16 (buffer, 26);
 406
 407                         int daylight_year = BitConverter.ToInt16 (buffer, 28);
 408                         int daylight_month = BitConverter.ToInt16 (buffer, 30);
 409                         int daylight_dayofweek = BitConverter.ToInt16 (buffer, 32);
 410                         int daylight_day = BitConverter.ToInt16 (buffer, 34);
 411                         int daylight_hour = BitConverter.ToInt16 (buffer, 36);
 412                         int daylight_minute = BitConverter.ToInt16 (buffer, 38);
 413                         int daylight_second = BitConverter.ToInt16 (buffer, 40);
 414                         int daylight_millisecond = BitConverter.ToInt16 (buffer, 42);
 415
 416                         if (standard_month == 0 || daylight_month == 0)
 417                                 return;
 418
 419                         DateTime start_date;
 420                         DateTime start_timeofday = new DateTime (1, 1, 1, daylight_hour, daylight_minute, daylight_second, daylight_millisecond);
 421                         TransitionTime start_transition_time;
 422
 423                         if (daylight_year == 0) {
 424                                 start_date = new DateTime (start_year, 1, 1);
 425                                 start_transition_time = TransitionTime.CreateFloatingDateRule (
 426                                         start_timeofday, daylight_month, daylight_day,
 427                                         (DayOfWeek) daylight_dayofweek);
 428                         }
 429                         else {
 430                                 start_date = new DateTime (daylight_year, daylight_month, daylight_day,
 431                                         daylight_hour, daylight_minute, daylight_second, daylight_millisecond);
 432                                 start_transition_time = TransitionTime.CreateFixedDateRule (
 433                                         start_timeofday, daylight_month, daylight_day);
 434                         }
 435
 436                         DateTime end_date;
 437                         DateTime end_timeofday = new DateTime (1, 1, 1, standard_hour, standard_minute, standard_second, standard_millisecond);
 438                         TransitionTime end_transition_time;
 439
 440                         if (standard_year == 0) {
 441                                 end_date = new DateTime (end_year, 12, 31);
 442                                 end_transition_time = TransitionTime.CreateFloatingDateRule (
 443                                         end_timeofday, standard_month, standard_day,
 444                                         (DayOfWeek) standard_dayofweek);
 445                         }
 446                         else {
 447                                 end_date = new DateTime (standard_year, standard_month, standard_day,
 448                                         standard_hour, standard_minute, standard_second, standard_millisecond);
 449                                 end_transition_time = TransitionTime.CreateFixedDateRule (
 450                                         end_timeofday, standard_month, standard_day);
 451                         }
 452
 453                         TimeSpan daylight_delta = new TimeSpan(0, -daylight_bias, 0);
 454
 455                         adjustmentRules.Add (AdjustmentRule.CreateAdjustmentRule (
 456                                 start_date, end_date, daylight_delta,
 457                                 start_transition_time, end_transition_time));
 458                 }
 459 #endif
 460
 461                 public static TimeZoneInfo FromSerializedString (string source)
 462                 {
 463                         throw new NotImplementedException ();
 464                 }
 465
 466                 public AdjustmentRule [] GetAdjustmentRules ()
 467                 {
 468                         if (disableDaylightSavingTime)
 469                                 return new AdjustmentRule [0];
 470                         else
 471                                 return (AdjustmentRule []) adjustmentRules.Clone ();
 472                 }
 473
 474                 public TimeSpan [] GetAmbiguousTimeOffsets (DateTime dateTime)
 475                 {
 476                         if (!IsAmbiguousTime (dateTime))
 477                                 throw new ArgumentException ("dateTime is not an ambiguous time");
 478
 479                         AdjustmentRule rule = GetApplicableRule (dateTime);
 480                         return new TimeSpan[] {baseUtcOffset, baseUtcOffset + rule.DaylightDelta};
 481                 }
 482
 483                 public TimeSpan [] GetAmbiguousTimeOffsets (DateTimeOffset dateTimeOffset)
 484                 {
 485                         if (!IsAmbiguousTime (dateTimeOffset))
 486                                 throw new ArgumentException ("dateTimeOffset is not an ambiguous time");
 487
 488                         throw new NotImplementedException ();
 489                 }
 490
 491                 public override int GetHashCode ()
 492                 {
 493                         int hash_code = Id.GetHashCode ();
 494                         foreach (AdjustmentRule rule in GetAdjustmentRules ())
 495                                 hash_code ^= rule.GetHashCode ();
 496                         return hash_code;
 497                 }
 498
 499 #if NET_4_0
 500                 void ISerializable.GetObjectData (SerializationInfo info, StreamingContext context)
 501 #else
 502                 public void GetObjectData (SerializationInfo info, StreamingContext context)
 503 #endif
 504                 {
 505                         throw new NotImplementedException ();
 506                 }
 507
 508                 //FIXME: change this to a generic Dictionary and allow caching for FindSystemTimeZoneById
 509                 private static List<TimeZoneInfo> systemTimeZones = null;
 510                 public static ReadOnlyCollection<TimeZoneInfo> GetSystemTimeZones ()
 511                 {
 512                         if (systemTimeZones == null) {
 513                                 systemTimeZones = new List<TimeZoneInfo> ();
 514 #if !NET_2_1
 515                                 if (TimeZoneKey != null) {
 516                                         foreach (string id in TimeZoneKey.GetSubKeyNames ()) {
 517                                                 try {
 518                                                         systemTimeZones.Add (FindSystemTimeZoneById (id));
 519                                                 } catch {}
 520                                         }
 521
 522                                         return new ReadOnlyCollection<TimeZoneInfo> (systemTimeZones);
 523                                 }
 524 #endif
 525 #if LIBC
 526                                 string[] continents = new string [] {"Africa", "America", "Antarctica", "Arctic", "Asia", "Atlantic", "Brazil", "Canada", "Chile", "Europe", "Indian", "Mexico", "Mideast", "Pacific", "US"};
 527                                 foreach (string continent in continents) {
 528                                         try {
 529                                                 foreach (string zonepath in Directory.GetFiles (Path.Combine (TimeZoneDirectory, continent))) {
 530                                                         try {
 531                                                                 string id = String.Format ("{0}/{1}", continent, Path.GetFileName (zonepath));
 532                                                                 systemTimeZones.Add (FindSystemTimeZoneById (id));
 533                                                         } catch (ArgumentNullException) {
 534                                                         } catch (TimeZoneNotFoundException) {
 535                                                         } catch (InvalidTimeZoneException) {
 536                                                         } catch (Exception) {
 537                                                                 throw;
 538                                                         }
 539                                                 }
 540                                         } catch {}
 541                                 }
 542 #else
 543                                 throw new NotImplementedException ("This method is not implemented for this platform");
 544 #endif
 545                         }
 546                         return new ReadOnlyCollection<TimeZoneInfo> (systemTimeZones);
 547                 }
 548
 549                 public TimeSpan GetUtcOffset (DateTime dateTime)
 550                 {
 551                         if (IsDaylightSavingTime (dateTime)) {
 552                                 AdjustmentRule rule = GetApplicableRule (dateTime);
 553                                 return BaseUtcOffset + rule.DaylightDelta;
 554                         }
 555
 556                         return BaseUtcOffset;
 557                 }
 558
 559                 public TimeSpan GetUtcOffset (DateTimeOffset dateTimeOffset)
 560                 {
 561                         throw new NotImplementedException ();
 562                 }
 563
 564                 public bool HasSameRules (TimeZoneInfo other)
 565                 {
 566                         if (other == null)
 567                                 throw new ArgumentNullException ("other");
 568
 569                         if ((this.adjustmentRules == null) != (other.adjustmentRules == null))
 570                                 return false;
 571
 572                         if (this.adjustmentRules == null)
 573                                 return true;
 574
 575                         if (this.BaseUtcOffset != other.BaseUtcOffset)
 576                                 return false;
 577
 578                         if (this.adjustmentRules.Length != other.adjustmentRules.Length)
 579                                 return false;
 580
 581                         for (int i = 0; i < adjustmentRules.Length; i++) {
 582                                 if (! (this.adjustmentRules [i]).Equals (other.adjustmentRules [i]))
 583                                         return false;
 584                         }
 585
 586                         return true;
 587                 }
 588
 589                 public bool IsAmbiguousTime (DateTime dateTime)
 590                 {
 591                         if (dateTime.Kind == DateTimeKind.Local && IsInvalidTime (dateTime))
 592                                 throw new ArgumentException ("Kind is Local and time is Invalid");
 593
 594                         if (this == TimeZoneInfo.Utc)
 595                                 return false;
 596
 597                         if (dateTime.Kind == DateTimeKind.Utc)
 598                                 dateTime = ConvertTimeFromUtc (dateTime);
 599
 600                         if (dateTime.Kind == DateTimeKind.Local && this != TimeZoneInfo.Local)
 601                                 dateTime = ConvertTime (dateTime, TimeZoneInfo.Local, this);
 602
 603                         AdjustmentRule rule = GetApplicableRule (dateTime);
 604                         DateTime tpoint = TransitionPoint (rule.DaylightTransitionEnd, dateTime.Year);
 605                         if (dateTime > tpoint - rule.DaylightDelta  && dateTime <= tpoint)
 606                                 return true;
 607
 608                         return false;
 609                 }
 610
 611                 public bool IsAmbiguousTime (DateTimeOffset dateTimeOffset)
 612                 {
 613                         throw new NotImplementedException ();
 614                 }
 615
 616                 public bool IsDaylightSavingTime (DateTime dateTime)
 617                 {
 618                         if (dateTime.Kind == DateTimeKind.Local && IsInvalidTime (dateTime))
 619                                 throw new ArgumentException ("dateTime is invalid and Kind is Local");
 620
 621                         if (this == TimeZoneInfo.Utc)
 622                                 return false;
 623
 624                         if (!SupportsDaylightSavingTime)
 625                                 return false;
 626                         //FIXME: do not rely on DateTime implementation !
 627                         if ((dateTime.Kind == DateTimeKind.Local || dateTime.Kind == DateTimeKind.Unspecified) && this == TimeZoneInfo.Local)
 628                                 return dateTime.IsDaylightSavingTime ();
 629
 630                         //FIXME: do not rely on DateTime implementation !
 631                         if (dateTime.Kind == DateTimeKind.Local && this != TimeZoneInfo.Utc)
 632                                 return IsDaylightSavingTime (DateTime.SpecifyKind (dateTime.ToUniversalTime (), DateTimeKind.Utc));
 633
 634                         AdjustmentRule rule = GetApplicableRule (dateTime.Date);
 635                         if (rule == null)
 636                                 return false;
 637
 638                         DateTime DST_start = TransitionPoint (rule.DaylightTransitionStart, dateTime.Year);
 639                         DateTime DST_end = TransitionPoint (rule.DaylightTransitionEnd, dateTime.Year + ((rule.DaylightTransitionStart.Month < rule.DaylightTransitionEnd.Month) ? 0 : 1));
 640                         if (dateTime.Kind == DateTimeKind.Utc) {
 641                                 DST_start -= BaseUtcOffset;
 642                                 DST_end -= (BaseUtcOffset + rule.DaylightDelta);
 643                         }
 644
 645                         return (dateTime >= DST_start && dateTime < DST_end);
 646                 }
 647
 648                 public bool IsDaylightSavingTime (DateTimeOffset dateTimeOffset)
 649                 {
 650                         throw new NotImplementedException ();
 651                 }
 652
 653                 public bool IsInvalidTime (DateTime dateTime)
 654                 {
 655                         if (dateTime.Kind == DateTimeKind.Utc)
 656                                 return false;
 657                         if (dateTime.Kind == DateTimeKind.Local && this != Local)
 658                                 return false;
 659
 660                         AdjustmentRule rule = GetApplicableRule (dateTime);
 661                         DateTime tpoint = TransitionPoint (rule.DaylightTransitionStart, dateTime.Year);
 662                         if (dateTime >= tpoint && dateTime < tpoint + rule.DaylightDelta)
 663                                 return true;
 664
 665                         return false;
 666                 }
 667
 668 #if NET_4_0
 669                 void IDeserializationCallback.OnDeserialization (object sender)
 670 #else
 671                 public void OnDeserialization (object sender)
 672 #endif
 673                 {
 674                         throw new NotImplementedException ();
 675                 }
 676
 677                 public string ToSerializedString ()
 678                 {
 679                         throw new NotImplementedException ();
 680                 }
 681
 682                 public override string ToString ()
 683                 {
 684                         return DisplayName;
 685                 }
 686
 687                 private TimeZoneInfo (string id, TimeSpan baseUtcOffset, string displayName, string standardDisplayName, string daylightDisplayName, TimeZoneInfo.AdjustmentRule [] adjustmentRules, bool disableDaylightSavingTime)
 688                 {
 689                         if (id == null)
 690                                 throw new ArgumentNullException ("id");
 691
 692                         if (id == String.Empty)
 693                                 throw new ArgumentException ("id parameter is an empty string");
 694
 695                         if (baseUtcOffset.Ticks % TimeSpan.TicksPerMinute != 0)
 696                                 throw new ArgumentException ("baseUtcOffset parameter does not represent a whole number of minutes");
 697
 698                         if (baseUtcOffset > new TimeSpan (14, 0, 0) || baseUtcOffset < new TimeSpan (-14, 0, 0))
 699                                 throw new ArgumentOutOfRangeException ("baseUtcOffset parameter is greater than 14 hours or less than -14 hours");
 700
 701 #if STRICT
 702                         if (id.Length > 32)
 703                                 throw new ArgumentException ("id parameter shouldn't be longer than 32 characters");
 704 #endif
 705
 706                         if (adjustmentRules != null && adjustmentRules.Length != 0) {
 707                                 AdjustmentRule prev = null;
 708                                 foreach (AdjustmentRule current in adjustmentRules) {
 709                                         if (current == null)
 710                                                 throw new InvalidTimeZoneException ("one or more elements in adjustmentRules are null");
 711
 712                                         if ((baseUtcOffset + current.DaylightDelta < new TimeSpan (-14, 0, 0)) ||
 713                                                         (baseUtcOffset + current.DaylightDelta > new TimeSpan (14, 0, 0)))
 714                                                 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;");
 715
 716                                         if (prev != null && prev.DateStart > current.DateStart)
 717                                                 throw new InvalidTimeZoneException ("adjustment rules specified in adjustmentRules parameter are not in chronological order");
 718
 719                                         if (prev != null && prev.DateEnd > current.DateStart)
 720                                                 throw new InvalidTimeZoneException ("some adjustment rules in the adjustmentRules parameter overlap");
 721
 722                                         if (prev != null && prev.DateEnd == current.DateStart)
 723                                                 throw new InvalidTimeZoneException ("a date can have multiple adjustment rules applied to it");
 724
 725                                         prev = current;
 726                                 }
 727                         }
 728
 729                         this.id = id;
 730                         this.baseUtcOffset = baseUtcOffset;
 731                         this.displayName = displayName ?? id;
 732                         this.standardDisplayName = standardDisplayName ?? id;
 733                         this.daylightDisplayName = daylightDisplayName;
 734                         this.disableDaylightSavingTime = disableDaylightSavingTime;
 735                         this.adjustmentRules = adjustmentRules;
 736                 }
 737
 738                 private AdjustmentRule GetApplicableRule (DateTime dateTime)
 739                 {
 740                         //Transitions are always in standard time
 741                         DateTime date = dateTime;
 742
 743                         if (dateTime.Kind == DateTimeKind.Local && this != TimeZoneInfo.Local)
 744                                 date = date.ToUniversalTime () + BaseUtcOffset;
 745
 746                         if (dateTime.Kind == DateTimeKind.Utc && this != TimeZoneInfo.Utc)
 747                                 date = date + BaseUtcOffset;
 748
 749                         foreach (AdjustmentRule rule in adjustmentRules) {
 750                                 if (rule.DateStart > date.Date)
 751                                         return null;
 752                                 if (rule.DateEnd < date.Date)
 753                                         continue;
 754                                 return rule;
 755                         }
 756                         return null;
 757                 }
 758
 759                 private static DateTime TransitionPoint (TransitionTime transition, int year)
 760                 {
 761                         if (transition.IsFixedDateRule)
 762                                 return new DateTime (year, transition.Month, transition.Day) + transition.TimeOfDay.TimeOfDay;
 763
 764                         DayOfWeek first = (new DateTime (year, transition.Month, 1)).DayOfWeek;
 765                         int day = 1 + (transition.Week - 1) * 7 + (transition.DayOfWeek - first) % 7;
 766                         if (day >  DateTime.DaysInMonth (year, transition.Month))
 767                                 day -= 7;
 768                         return new DateTime (year, transition.Month, day) + transition.TimeOfDay.TimeOfDay;
 769                 }
 770
 771 #if LIBC
 772                 private static bool ValidTZFile (byte [] buffer, int length)
 773                 {
 774                         StringBuilder magic = new StringBuilder ();
 775
 776                         for (int i = 0; i < 4; i++)
 777                                 magic.Append ((char)buffer [i]);
 778
 779                         if (magic.ToString () != "TZif")
 780                                 return false;
 781
 782                         if (length >= BUFFER_SIZE)
 783                                 return false;
 784
 785                         return true;
 786                 }
 787
 788                 struct TimeType
 789                 {
 790                         public readonly int Offset;
 791                         public readonly bool IsDst;
 792                         public string Name;
 793
 794                         public TimeType (int offset, bool is_dst, string abbrev)
 795                         {
 796                                 this.Offset = offset;
 797                                 this.IsDst = is_dst;
 798                                 this.Name = abbrev;
 799                         }
 800
 801                         public override string ToString ()
 802                         {
 803                                 return "offset: " + Offset + "s, is_dst: " + IsDst + ", zone name: " + Name;
 804                         }
 805                 }
 806
 807                 static int SwapInt32 (int i)
 808                 {
 809                         return (((i >> 24) & 0xff)
 810                                 | ((i >> 8) & 0xff00)
 811                                 | ((i << 8) & 0xff0000)
 812                                 | ((i << 24)));
 813                 }
 814
 815                 static int ReadBigEndianInt32 (byte [] buffer, int start)
 816                 {
 817                         int i = BitConverter.ToInt32 (buffer, start);
 818                         if (!BitConverter.IsLittleEndian)
 819                                 return i;
 820
 821                         return SwapInt32 (i);
 822                 }
 823
 824                 private static TimeZoneInfo ParseTZBuffer (string id, byte [] buffer, int length)
 825                 {
 826                         //Reading the header. 4 bytes for magic, 16 are reserved
 827                         int ttisgmtcnt = ReadBigEndianInt32 (buffer, 20);
 828                         int ttisstdcnt = ReadBigEndianInt32 (buffer, 24);
 829                         int leapcnt = ReadBigEndianInt32 (buffer, 28);
 830                         int timecnt = ReadBigEndianInt32 (buffer, 32);
 831                         int typecnt = ReadBigEndianInt32 (buffer, 36);
 832                         int charcnt = ReadBigEndianInt32 (buffer, 40);
 833
 834                         if (length < 44 + timecnt * 5 + typecnt * 6 + charcnt + leapcnt * 8 + ttisstdcnt + ttisgmtcnt)
 835                                 throw new InvalidTimeZoneException ();
 836
 837                         Dictionary<int, string> abbreviations = ParseAbbreviations (buffer, 44 + 4 * timecnt + timecnt + 6 * typecnt, charcnt);
 838                         Dictionary<int, TimeType> time_types = ParseTimesTypes (buffer, 44 + 4 * timecnt + timecnt, typecnt, abbreviations);
 839                         List<KeyValuePair<DateTime, TimeType>> transitions = ParseTransitions (buffer, 44, timecnt, time_types);
 840
 841                         if (time_types.Count == 0)
 842                                 throw new InvalidTimeZoneException ();
 843
 844                         if (time_types.Count == 1 && ((TimeType)time_types[0]).IsDst)
 845                                 throw new InvalidTimeZoneException ();
 846
 847                         TimeSpan baseUtcOffset = new TimeSpan (0);
 848                         TimeSpan dstDelta = new TimeSpan (0);
 849                         string standardDisplayName = null;
 850                         string daylightDisplayName = null;
 851                         bool dst_observed = false;
 852                         DateTime dst_start = DateTime.MinValue;
 853                         List<AdjustmentRule> adjustmentRules = new List<AdjustmentRule> ();
 854
 855                         for (int i = 0; i < transitions.Count; i++) {
 856                                 var pair = transitions [i];
 857                                 DateTime ttime = pair.Key;
 858                                 TimeType ttype = pair.Value;
 859                                 if (!ttype.IsDst) {
 860                                         if (standardDisplayName != ttype.Name || baseUtcOffset.TotalSeconds != ttype.Offset) {
 861                                                 standardDisplayName = ttype.Name;
 862                                                 daylightDisplayName = null;
 863                                                 baseUtcOffset = new TimeSpan (0, 0, ttype.Offset);
 864                                                 adjustmentRules = new List<AdjustmentRule> ();
 865                                                 dst_observed = false;
 866                                         }
 867                                         if (dst_observed) {
 868                                                 //FIXME: check additional fields for this:
 869                                                 //most of the transitions are expressed in GMT
 870                                                 dst_start += baseUtcOffset;
 871                                                 DateTime dst_end = ttime + baseUtcOffset + dstDelta;
 872
 873                                                 //some weird timezone (America/Phoenix) have end dates on Jan 1st
 874                                                 if (dst_end.Date == new DateTime (dst_end.Year, 1, 1) && dst_end.Year > dst_start.Year)
 875                                                         dst_end -= new TimeSpan (24, 0, 0);
 876
 877                                                 DateTime dateStart, dateEnd;
 878                                                 if (dst_start.Month < 7)
 879                                                         dateStart = new DateTime (dst_start.Year, 1, 1);
 880                                                 else
 881                                                         dateStart = new DateTime (dst_start.Year, 7, 1);
 882
 883                                                 if (dst_end.Month >= 7)
 884                                                         dateEnd = new DateTime (dst_end.Year, 12, 31);
 885                                                 else
 886                                                         dateEnd = new DateTime (dst_end.Year, 6, 30);
 887
 888
 889                                                 TransitionTime transition_start = TransitionTime.CreateFixedDateRule (new DateTime (1, 1, 1) + dst_start.TimeOfDay, dst_start.Month, dst_start.Day);
 890                                                 TransitionTime transition_end = TransitionTime.CreateFixedDateRule (new DateTime (1, 1, 1) + dst_end.TimeOfDay, dst_end.Month, dst_end.Day);
 891                                                 if  (transition_start != transition_end) //y, that happened in Argentina in 1943-1946
 892                                                         adjustmentRules.Add (AdjustmentRule.CreateAdjustmentRule (dateStart, dateEnd, dstDelta, transition_start, transition_end));
 893                                         }
 894                                         dst_observed = false;
 895                                 } else {
 896                                         if (daylightDisplayName != ttype.Name || dstDelta.TotalSeconds != ttype.Offset - baseUtcOffset.TotalSeconds) {
 897                                                 daylightDisplayName = ttype.Name;
 898                                                 dstDelta = new TimeSpan(0, 0, ttype.Offset) - baseUtcOffset;
 899                                         }
 900                                         dst_start = ttime;
 901                                         dst_observed = true;
 902                                 }
 903                         }
 904
 905                         if (adjustmentRules.Count == 0) {
 906                                 TimeType t = (TimeType)time_types [0];
 907                                 if (standardDisplayName == null) {
 908                                         standardDisplayName = t.Name;
 909                                         baseUtcOffset = new TimeSpan (0, 0, t.Offset);
 910                                 }
 911                                 return CreateCustomTimeZone (id, baseUtcOffset, id, standardDisplayName);
 912                         } else {
 913                                 return CreateCustomTimeZone (id, baseUtcOffset, id, standardDisplayName, daylightDisplayName, ValidateRules (adjustmentRules).ToArray ());
 914                         }
 915                 }
 916
 917                 static List<AdjustmentRule> ValidateRules (List<AdjustmentRule> adjustmentRules)
 918                 {
 919                         AdjustmentRule prev = null;
 920                         foreach (AdjustmentRule current in adjustmentRules.ToArray ()) {
 921                                 if (prev != null && prev.DateEnd > current.DateStart) {
 922                                         adjustmentRules.Remove (current);
 923                                 }
 924                                 prev = current;
 925                         }
 926                         return adjustmentRules;
 927                 }
 928
 929                 static Dictionary<int, string> ParseAbbreviations (byte [] buffer, int index, int count)
 930                 {
 931                         var abbrevs = new Dictionary<int, string> ();
 932                         int abbrev_index = 0;
 933                         var sb = new StringBuilder ();
 934                         for (int i = 0; i < count; i++) {
 935                                 char c = (char) buffer [index + i];
 936                                 if (c != '\0')
 937                                         sb.Append (c);
 938                                 else {
 939                                         abbrevs.Add (abbrev_index, sb.ToString ());
 940                                         //Adding all the substrings too, as it seems to be used, at least for Africa/Windhoek
 941                                         for (int j = 1; j < sb.Length; j++)
 942                                                 abbrevs.Add (abbrev_index + j, sb.ToString (j, sb.Length - j));
 943                                         abbrev_index = i + 1;
 944                                         sb = new StringBuilder ();
 945                                 }
 946                         }
 947                         return abbrevs;
 948                 }
 949
 950                 static Dictionary<int, TimeType> ParseTimesTypes (byte [] buffer, int index, int count, Dictionary<int, string> abbreviations)
 951                 {
 952                         var types = new Dictionary<int, TimeType> (count);
 953                         for (int i = 0; i < count; i++) {
 954                                 int offset = ReadBigEndianInt32 (buffer, index + 6 * i);
 955                                 byte is_dst = buffer [index + 6 * i + 4];
 956                                 byte abbrev = buffer [index + 6 * i + 5];
 957                                 types.Add (i, new TimeType (offset, (is_dst != 0), abbreviations [(int)abbrev]));
 958                         }
 959                         return types;
 960                 }
 961
 962                 static List<KeyValuePair<DateTime, TimeType>> ParseTransitions (byte [] buffer, int index, int count, Dictionary<int, TimeType> time_types)
 963                 {
 964                         var list = new List<KeyValuePair<DateTime, TimeType>> (count);
 965                         for (int i = 0; i < count; i++) {
 966                                 int unixtime = ReadBigEndianInt32 (buffer, index + 4 * i);
 967                                 DateTime ttime = DateTimeFromUnixTime (unixtime);
 968                                 byte ttype = buffer [index + 4 * count + i];
 969                                 list.Add (new KeyValuePair<DateTime, TimeType> (ttime, time_types [(int)ttype]));
 970                         }
 971                         return list;
 972                 }
 973
 974                 static DateTime DateTimeFromUnixTime (long unix_time)
 975                 {
 976                         DateTime date_time = new DateTime (1970, 1, 1);
 977                         return date_time.AddSeconds (unix_time);
 978                 }
 979 #endif
 980         }
 981 }
 982
 983 #endif