mcs/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 namespace System
  47 {
  48 #if NET_4_0 || BOOTSTRAP_NET_4_0
  49         [TypeForwardedFrom (Consts.AssemblySystemCore_3_5)]
  50 #elif MOONLIGHT
  51         [TypeForwardedFrom (Consts.AssemblySystem_Core)]
  52 #endif
  53         [SerializableAttribute]
  54         public sealed partial class TimeZoneInfo : IEquatable<TimeZoneInfo>, ISerializable, IDeserializationCallback
  55         {
  56                 TimeSpan baseUtcOffset;
  57                 public TimeSpan BaseUtcOffset {
  58                         get { return baseUtcOffset; }
  59                 }
  60
  61                 string daylightDisplayName;
  62                 public string DaylightName {
  63                         get {
  64                                 if (disableDaylightSavingTime)
  65                                         return String.Empty;
  66                                 return daylightDisplayName;
  67                         }
  68                 }
  69
  70                 string displayName;
  71                 public string DisplayName {
  72                         get { return displayName; }
  73                 }
  74
  75                 string id;
  76                 public string Id {
  77                         get { return id; }
  78                 }
  79
  80                 static TimeZoneInfo local;
  81                 public static TimeZoneInfo Local {
  82                         get {
  83                                 if (local == null) {
  84 #if LIBC
  85                                         try {
  86                                                 local = FindSystemTimeZoneByFileName ("Local", "/etc/localtime");
  87                                         } catch {
  88                                                 try {
  89                                                         local = FindSystemTimeZoneByFileName ("Local", Path.Combine (TimeZoneDirectory, "localtime"));
  90                                                 } catch {
  91                                                         throw new TimeZoneNotFoundException ();
  92                                                 }
  93                                         }
  94 #else
  95                                         throw new TimeZoneNotFoundException ();
  96 #endif
  97                                 }
  98                                 return local;
  99                         }
 100                 }
 101
 102                 string standardDisplayName;
 103                 public string StandardName {
 104                         get { return standardDisplayName; }
 105                 }
 106
 107                 bool disableDaylightSavingTime;
 108                 public bool SupportsDaylightSavingTime {
 109                         get  { return !disableDaylightSavingTime; }
 110                 }
 111
 112                 static TimeZoneInfo utc;
 113                 public static TimeZoneInfo Utc {
 114                         get {
 115                                 if (utc == null)
 116                                         utc = CreateCustomTimeZone ("UTC", new TimeSpan (0), "UTC", "UTC");
 117                                 return utc;
 118                         }
 119                 }
 120 #if LIBC
 121                 static string timeZoneDirectory = null;
 122                 static string TimeZoneDirectory {
 123                         get {
 124                                 if (timeZoneDirectory == null)
 125                                         timeZoneDirectory = "/usr/share/zoneinfo";
 126                                 return timeZoneDirectory;
 127                         }
 128                         set {
 129                                 ClearCachedData ();
 130                                 timeZoneDirectory = value;
 131                         }
 132                 }
 133 #endif
 134                 private AdjustmentRule [] adjustmentRules;
 135
 136                 public static void ClearCachedData ()
 137                 {
 138                         local = null;
 139                         utc = null;
 140                         systemTimeZones = null;
 141                 }
 142
 143                 public static DateTime ConvertTime (DateTime dateTime, TimeZoneInfo destinationTimeZone)
 144                 {
 145                         return ConvertTime (dateTime, TimeZoneInfo.Local, destinationTimeZone);
 146                 }
 147
 148                 public static DateTime ConvertTime (DateTime dateTime, TimeZoneInfo sourceTimeZone, TimeZoneInfo destinationTimeZone)
 149                 {
 150                         if (dateTime.Kind == DateTimeKind.Local && sourceTimeZone != TimeZoneInfo.Local)
 151                                 throw new ArgumentException ("Kind propery of dateTime is Local but the sourceTimeZone does not equal TimeZoneInfo.Local");
 152
 153                         if (dateTime.Kind == DateTimeKind.Utc && sourceTimeZone != TimeZoneInfo.Utc)
 154                                 throw new ArgumentException ("Kind propery of dateTime is Utc but the sourceTimeZone does not equal TimeZoneInfo.Utc");
 155
 156                         if (sourceTimeZone.IsInvalidTime (dateTime))
 157                                 throw new ArgumentException ("dateTime parameter is an invalid time");
 158
 159                         if (sourceTimeZone == null)
 160                                 throw new ArgumentNullException ("sourceTimeZone");
 161
 162                         if (destinationTimeZone == null)
 163                                 throw new ArgumentNullException ("destinationTimeZone");
 164
 165                         if (dateTime.Kind == DateTimeKind.Local && sourceTimeZone == TimeZoneInfo.Local && destinationTimeZone == TimeZoneInfo.Local)
 166                                 return dateTime;
 167
 168                         DateTime utc = ConvertTimeToUtc (dateTime);
 169
 170                         if (destinationTimeZone == TimeZoneInfo.Utc)
 171                                 return utc;
 172
 173                         return ConvertTimeFromUtc (utc, destinationTimeZone);
 174
 175                 }
 176
 177                 public static DateTimeOffset ConvertTime (DateTimeOffset dateTimeOffset, TimeZoneInfo destinationTimeZone)
 178                 {
 179                         throw new NotImplementedException ();
 180                 }
 181
 182                 public static DateTime ConvertTimeBySystemTimeZoneId (DateTime dateTime, string destinationTimeZoneId)
 183                 {
 184                         return ConvertTime (dateTime, FindSystemTimeZoneById (destinationTimeZoneId));
 185                 }
 186
 187                 public static DateTime ConvertTimeBySystemTimeZoneId (DateTime dateTime, string sourceTimeZoneId, string destinationTimeZoneId)
 188                 {
 189                         return ConvertTime (dateTime, FindSystemTimeZoneById (sourceTimeZoneId), FindSystemTimeZoneById (destinationTimeZoneId));
 190                 }
 191
 192                 public static DateTimeOffset ConvertTimeBySystemTimeZoneId (DateTimeOffset dateTimeOffset, string destinationTimeZoneId)
 193                 {
 194                         return ConvertTime (dateTimeOffset, FindSystemTimeZoneById (destinationTimeZoneId));
 195                 }
 196
 197                 private DateTime ConvertTimeFromUtc (DateTime dateTime)
 198                 {
 199                         if (dateTime.Kind == DateTimeKind.Local)
 200                                 throw new ArgumentException ("Kind property of dateTime is Local");
 201
 202                         if (this == TimeZoneInfo.Utc)
 203                                 return DateTime.SpecifyKind (dateTime, DateTimeKind.Utc);
 204
 205                         //FIXME: do not rely on DateTime implementation !
 206                         if (this == TimeZoneInfo.Local)
 207                                 return DateTime.SpecifyKind (dateTime.ToLocalTime (), DateTimeKind.Unspecified);
 208
 209                         AdjustmentRule rule = GetApplicableRule (dateTime);
 210
 211                         if (IsDaylightSavingTime (DateTime.SpecifyKind (dateTime, DateTimeKind.Utc)))
 212                                 return DateTime.SpecifyKind (dateTime + BaseUtcOffset + rule.DaylightDelta , DateTimeKind.Unspecified);
 213                         else
 214                                 return DateTime.SpecifyKind (dateTime + BaseUtcOffset, DateTimeKind.Unspecified);
 215                 }
 216
 217                 public static DateTime ConvertTimeFromUtc (DateTime dateTime, TimeZoneInfo destinationTimeZone)
 218                 {
 219                         if (destinationTimeZone == null)
 220                                 throw new ArgumentNullException ("destinationTimeZone");
 221
 222                         return destinationTimeZone.ConvertTimeFromUtc (dateTime);
 223                 }
 224
 225                 public static DateTime ConvertTimeToUtc (DateTime dateTime)
 226                 {
 227                         if (dateTime.Kind == DateTimeKind.Utc)
 228                                 return dateTime;
 229
 230                         //FIXME: do not rely on DateTime implementation !
 231                         return DateTime.SpecifyKind (dateTime.ToUniversalTime (), DateTimeKind.Utc);
 232                 }
 233
 234                 public static DateTime ConvertTimeToUtc (DateTime dateTime, TimeZoneInfo sourceTimeZone)
 235                 {
 236                         if (sourceTimeZone == null)
 237                                 throw new ArgumentNullException ("sourceTimeZone");
 238
 239                         if (dateTime.Kind == DateTimeKind.Utc && sourceTimeZone != TimeZoneInfo.Utc)
 240                                 throw new ArgumentException ("Kind propery of dateTime is Utc but the sourceTimeZone does not equal TimeZoneInfo.Utc");
 241
 242                         if (dateTime.Kind == DateTimeKind.Local && sourceTimeZone != TimeZoneInfo.Local)
 243                                 throw new ArgumentException ("Kind propery of dateTime is Local but the sourceTimeZone does not equal TimeZoneInfo.Local");
 244
 245                         if (sourceTimeZone.IsInvalidTime (dateTime))
 246                                 throw new ArgumentException ("dateTime parameter is an invalid time");
 247
 248                         if (dateTime.Kind == DateTimeKind.Utc && sourceTimeZone == TimeZoneInfo.Utc)
 249                                 return dateTime;
 250
 251                         if (dateTime.Kind == DateTimeKind.Utc)
 252                                 return dateTime;
 253
 254                         if (dateTime.Kind == DateTimeKind.Local)
 255                                 return ConvertTimeToUtc (dateTime);
 256
 257                         if (sourceTimeZone.IsAmbiguousTime (dateTime) || !sourceTimeZone.IsDaylightSavingTime (dateTime))
 258                                 return DateTime.SpecifyKind (dateTime - sourceTimeZone.BaseUtcOffset, DateTimeKind.Utc);
 259                         else {
 260                                 AdjustmentRule rule = sourceTimeZone.GetApplicableRule (dateTime);
 261                                 return DateTime.SpecifyKind (dateTime - sourceTimeZone.BaseUtcOffset - rule.DaylightDelta, DateTimeKind.Utc);
 262                         }
 263                 }
 264
 265                 public static TimeZoneInfo CreateCustomTimeZone (string id, TimeSpan baseUtcOffset, string displayName, string standardDisplayName)
 266                 {
 267                         return CreateCustomTimeZone (id, baseUtcOffset, displayName, standardDisplayName, null, null, true);
 268                 }
 269
 270                 public static TimeZoneInfo CreateCustomTimeZone (string id, TimeSpan baseUtcOffset, string displayName, string standardDisplayName, string daylightDisplayName, TimeZoneInfo.AdjustmentRule [] adjustmentRules)
 271                 {
 272                         return CreateCustomTimeZone (id, baseUtcOffset, displayName, standardDisplayName, daylightDisplayName, adjustmentRules, false);
 273                 }
 274
 275                 public static TimeZoneInfo CreateCustomTimeZone ( string id, TimeSpan baseUtcOffset, string displayName, string standardDisplayName, string daylightDisplayName, TimeZoneInfo.AdjustmentRule [] adjustmentRules, bool disableDaylightSavingTime)
 276                 {
 277                         return new TimeZoneInfo (id, baseUtcOffset, displayName, standardDisplayName, daylightDisplayName, adjustmentRules, disableDaylightSavingTime);
 278                 }
 279
 280                 public bool Equals (TimeZoneInfo other)
 281                 {
 282                         if (other == null)
 283                                 return false;
 284
 285                         return other.Id == this.Id && HasSameRules (other);
 286                 }
 287
 288                 public static TimeZoneInfo FindSystemTimeZoneById (string id)
 289                 {
 290                         //FIXME: this method should check for cached values in systemTimeZones
 291                         if (id == null)
 292                                 throw new ArgumentNullException ("id");
 293 #if LIBC
 294                         string filepath = Path.Combine (TimeZoneDirectory, id);
 295                         return FindSystemTimeZoneByFileName (id, filepath);
 296 #else
 297                         throw new NotImplementedException ();
 298 #endif
 299                 }
 300
 301 #if LIBC
 302                 const int BUFFER_SIZE = 16384; //Big enough for any tz file (on Oct 2008, all tz files are under 10k)
 303                 private static TimeZoneInfo FindSystemTimeZoneByFileName (string id, string filepath)
 304                 {
 305                         if (!File.Exists (filepath))
 306                                 throw new TimeZoneNotFoundException ();
 307
 308                         byte [] buffer = new byte [BUFFER_SIZE];
 309                         int length;
 310                         using (FileStream stream = File.OpenRead (filepath)) {
 311                                 length = stream.Read (buffer, 0, BUFFER_SIZE);
 312                         }
 313
 314                         if (!ValidTZFile (buffer, length))
 315                                 throw new InvalidTimeZoneException ("TZ file too big for the buffer");
 316
 317                         try {
 318                                 return ParseTZBuffer (id, buffer, length);
 319                         } catch (Exception e) {
 320                                 throw new InvalidTimeZoneException (e.Message);
 321                         }
 322                 }
 323 #endif
 324
 325                 public static TimeZoneInfo FromSerializedString (string source)
 326                 {
 327                         throw new NotImplementedException ();
 328                 }
 329
 330                 public AdjustmentRule [] GetAdjustmentRules ()
 331                 {
 332                         if (disableDaylightSavingTime)
 333                                 return new AdjustmentRule [0];
 334                         else
 335                                 return (AdjustmentRule []) adjustmentRules.Clone ();
 336                 }
 337
 338                 public TimeSpan [] GetAmbiguousTimeOffsets (DateTime dateTime)
 339                 {
 340                         if (!IsAmbiguousTime (dateTime))
 341                                 throw new ArgumentException ("dateTime is not an ambiguous time");
 342
 343                         AdjustmentRule rule = GetApplicableRule (dateTime);
 344                         return new TimeSpan[] {baseUtcOffset, baseUtcOffset + rule.DaylightDelta};
 345                 }
 346
 347                 public TimeSpan [] GetAmbiguousTimeOffsets (DateTimeOffset dateTimeOffset)
 348                 {
 349                         if (!IsAmbiguousTime (dateTimeOffset))
 350                                 throw new ArgumentException ("dateTimeOffset is not an ambiguous time");
 351
 352                         throw new NotImplementedException ();
 353                 }
 354
 355                 public override int GetHashCode ()
 356                 {
 357                         int hash_code = Id.GetHashCode ();
 358                         foreach (AdjustmentRule rule in GetAdjustmentRules ())
 359                                 hash_code ^= rule.GetHashCode ();
 360                         return hash_code;
 361                 }
 362
 363 #if NET_4_0
 364                 void ISerializable.GetObjectData (SerializationInfo info, StreamingContext context)
 365 #else
 366                 public void GetObjectData (SerializationInfo info, StreamingContext context)
 367 #endif
 368                 {
 369                         throw new NotImplementedException ();
 370                 }
 371
 372                 //FIXME: change this to a generic Dictionary and allow caching for FindSystemTimeZoneById
 373                 private static List<TimeZoneInfo> systemTimeZones = null;
 374                 public static ReadOnlyCollection<TimeZoneInfo> GetSystemTimeZones ()
 375                 {
 376                         if (systemTimeZones == null) {
 377                                 systemTimeZones = new List<TimeZoneInfo> ();
 378 #if LIBC
 379                                 string[] continents = new string [] {"Africa", "America", "Antarctica", "Arctic", "Asia", "Atlantic", "Brazil", "Canada", "Chile", "Europe", "Indian", "Mexico", "Mideast", "Pacific", "US"};
 380                                 foreach (string continent in continents) {
 381                                         try {
 382                                                 foreach (string zonepath in Directory.GetFiles (Path.Combine (TimeZoneDirectory, continent))) {
 383                                                         try {
 384                                                                 string id = String.Format ("{0}/{1}", continent, Path.GetFileName (zonepath));
 385                                                                 systemTimeZones.Add (FindSystemTimeZoneById (id));
 386                                                         } catch (ArgumentNullException) {
 387                                                         } catch (TimeZoneNotFoundException) {
 388                                                         } catch (InvalidTimeZoneException) {
 389                                                         } catch (Exception) {
 390                                                                 throw;
 391                                                         }
 392                                                 }
 393                                         } catch {}
 394                                 }
 395 #else
 396                                 throw new NotImplementedException ("This method is not implemented for this platform");
 397 #endif
 398                         }
 399                         return new ReadOnlyCollection<TimeZoneInfo> (systemTimeZones);
 400                 }
 401
 402                 public TimeSpan GetUtcOffset (DateTime dateTime)
 403                 {
 404                         if (IsDaylightSavingTime (dateTime)) {
 405                                 AdjustmentRule rule = GetApplicableRule (dateTime);
 406                                 return BaseUtcOffset + rule.DaylightDelta;
 407                         }
 408
 409                         return BaseUtcOffset;
 410                 }
 411
 412                 public TimeSpan GetUtcOffset (DateTimeOffset dateTimeOffset)
 413                 {
 414                         throw new NotImplementedException ();
 415                 }
 416
 417                 public bool HasSameRules (TimeZoneInfo other)
 418                 {
 419                         if (other == null)
 420                                 throw new ArgumentNullException ("other");
 421
 422                         if ((this.adjustmentRules == null) != (other.adjustmentRules == null))
 423                                 return false;
 424
 425                         if (this.adjustmentRules == null)
 426                                 return true;
 427
 428                         if (this.BaseUtcOffset != other.BaseUtcOffset)
 429                                 return false;
 430
 431                         if (this.adjustmentRules.Length != other.adjustmentRules.Length)
 432                                 return false;
 433
 434                         for (int i = 0; i < adjustmentRules.Length; i++) {
 435                                 if (! (this.adjustmentRules [i]).Equals (other.adjustmentRules [i]))
 436                                         return false;
 437                         }
 438
 439                         return true;
 440                 }
 441
 442                 public bool IsAmbiguousTime (DateTime dateTime)
 443                 {
 444                         if (dateTime.Kind == DateTimeKind.Local && IsInvalidTime (dateTime))
 445                                 throw new ArgumentException ("Kind is Local and time is Invalid");
 446
 447                         if (this == TimeZoneInfo.Utc)
 448                                 return false;
 449
 450                         if (dateTime.Kind == DateTimeKind.Utc)
 451                                 dateTime = ConvertTimeFromUtc (dateTime);
 452
 453                         if (dateTime.Kind == DateTimeKind.Local && this != TimeZoneInfo.Local)
 454                                 dateTime = ConvertTime (dateTime, TimeZoneInfo.Local, this);
 455
 456                         AdjustmentRule rule = GetApplicableRule (dateTime);
 457                         DateTime tpoint = TransitionPoint (rule.DaylightTransitionEnd, dateTime.Year);
 458                         if (dateTime > tpoint - rule.DaylightDelta  && dateTime <= tpoint)
 459                                 return true;
 460
 461                         return false;
 462                 }
 463
 464                 public bool IsAmbiguousTime (DateTimeOffset dateTimeOffset)
 465                 {
 466                         throw new NotImplementedException ();
 467                 }
 468
 469                 public bool IsDaylightSavingTime (DateTime dateTime)
 470                 {
 471                         if (dateTime.Kind == DateTimeKind.Local && IsInvalidTime (dateTime))
 472                                 throw new ArgumentException ("dateTime is invalid and Kind is Local");
 473
 474                         if (this == TimeZoneInfo.Utc)
 475                                 return false;
 476
 477                         if (!SupportsDaylightSavingTime)
 478                                 return false;
 479                         //FIXME: do not rely on DateTime implementation !
 480                         if ((dateTime.Kind == DateTimeKind.Local || dateTime.Kind == DateTimeKind.Unspecified) && this == TimeZoneInfo.Local)
 481                                 return dateTime.IsDaylightSavingTime ();
 482
 483                         //FIXME: do not rely on DateTime implementation !
 484                         if (dateTime.Kind == DateTimeKind.Local && this != TimeZoneInfo.Utc)
 485                                 return IsDaylightSavingTime (DateTime.SpecifyKind (dateTime.ToUniversalTime (), DateTimeKind.Utc));
 486
 487                         AdjustmentRule rule = GetApplicableRule (dateTime.Date);
 488                         if (rule == null)
 489                                 return false;
 490
 491                         DateTime DST_start = TransitionPoint (rule.DaylightTransitionStart, dateTime.Year);
 492                         DateTime DST_end = TransitionPoint (rule.DaylightTransitionEnd, dateTime.Year + ((rule.DaylightTransitionStart.Month < rule.DaylightTransitionEnd.Month) ? 0 : 1));
 493                         if (dateTime.Kind == DateTimeKind.Utc) {
 494                                 DST_start -= BaseUtcOffset;
 495                                 DST_end -= (BaseUtcOffset + rule.DaylightDelta);
 496                         }
 497
 498                         return (dateTime >= DST_start && dateTime < DST_end);
 499                 }
 500
 501                 public bool IsDaylightSavingTime (DateTimeOffset dateTimeOffset)
 502                 {
 503                         throw new NotImplementedException ();
 504                 }
 505
 506                 public bool IsInvalidTime (DateTime dateTime)
 507                 {
 508                         if (dateTime.Kind == DateTimeKind.Utc)
 509                                 return false;
 510                         if (dateTime.Kind == DateTimeKind.Local && this != Local)
 511                                 return false;
 512
 513                         AdjustmentRule rule = GetApplicableRule (dateTime);
 514                         DateTime tpoint = TransitionPoint (rule.DaylightTransitionStart, dateTime.Year);
 515                         if (dateTime >= tpoint && dateTime < tpoint + rule.DaylightDelta)
 516                                 return true;
 517
 518                         return false;
 519                 }
 520
 521 #if NET_4_0
 522                 void IDeserializationCallback.OnDeserialization (object sender)
 523 #else
 524                 public void OnDeserialization (object sender)
 525 #endif
 526                 {
 527                         throw new NotImplementedException ();
 528                 }
 529
 530                 public string ToSerializedString ()
 531                 {
 532                         throw new NotImplementedException ();
 533                 }
 534
 535                 public override string ToString ()
 536                 {
 537                         return DisplayName;
 538                 }
 539
 540                 private TimeZoneInfo (string id, TimeSpan baseUtcOffset, string displayName, string standardDisplayName, string daylightDisplayName, TimeZoneInfo.AdjustmentRule [] adjustmentRules, bool disableDaylightSavingTime)
 541                 {
 542                         if (id == null)
 543                                 throw new ArgumentNullException ("id");
 544
 545                         if (id == String.Empty)
 546                                 throw new ArgumentException ("id parameter is an empty string");
 547
 548                         if (baseUtcOffset.Ticks % TimeSpan.TicksPerMinute != 0)
 549                                 throw new ArgumentException ("baseUtcOffset parameter does not represent a whole number of minutes");
 550
 551                         if (baseUtcOffset > new TimeSpan (14, 0, 0) || baseUtcOffset < new TimeSpan (-14, 0, 0))
 552                                 throw new ArgumentOutOfRangeException ("baseUtcOffset parameter is greater than 14 hours or less than -14 hours");
 553
 554 #if STRICT
 555                         if (id.Length > 32)
 556                                 throw new ArgumentException ("id parameter shouldn't be longer than 32 characters");
 557 #endif
 558
 559                         if (adjustmentRules != null && adjustmentRules.Length != 0) {
 560                                 AdjustmentRule prev = null;
 561                                 foreach (AdjustmentRule current in adjustmentRules) {
 562                                         if (current == null)
 563                                                 throw new InvalidTimeZoneException ("one or more elements in adjustmentRules are null");
 564
 565                                         if ((baseUtcOffset + current.DaylightDelta < new TimeSpan (-14, 0, 0)) ||
 566                                                         (baseUtcOffset + current.DaylightDelta > new TimeSpan (14, 0, 0)))
 567                                                 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;");
 568
 569                                         if (prev != null && prev.DateStart > current.DateStart)
 570                                                 throw new InvalidTimeZoneException ("adjustment rules specified in adjustmentRules parameter are not in chronological order");
 571
 572                                         if (prev != null && prev.DateEnd > current.DateStart)
 573                                                 throw new InvalidTimeZoneException ("some adjustment rules in the adjustmentRules parameter overlap");
 574
 575                                         if (prev != null && prev.DateEnd == current.DateStart)
 576                                                 throw new InvalidTimeZoneException ("a date can have multiple adjustment rules applied to it");
 577
 578                                         prev = current;
 579                                 }
 580                         }
 581
 582                         this.id = id;
 583                         this.baseUtcOffset = baseUtcOffset;
 584                         this.displayName = displayName ?? id;
 585                         this.standardDisplayName = standardDisplayName ?? id;
 586                         this.daylightDisplayName = daylightDisplayName;
 587                         this.disableDaylightSavingTime = disableDaylightSavingTime;
 588                         this.adjustmentRules = adjustmentRules;
 589                 }
 590
 591                 private AdjustmentRule GetApplicableRule (DateTime dateTime)
 592                 {
 593                         //Transitions are always in standard time
 594                         DateTime date = dateTime;
 595
 596                         if (dateTime.Kind == DateTimeKind.Local && this != TimeZoneInfo.Local)
 597                                 date = date.ToUniversalTime () + BaseUtcOffset;
 598
 599                         if (dateTime.Kind == DateTimeKind.Utc && this != TimeZoneInfo.Utc)
 600                                 date = date + BaseUtcOffset;
 601
 602                         foreach (AdjustmentRule rule in adjustmentRules) {
 603                                 if (rule.DateStart > date.Date)
 604                                         return null;
 605                                 if (rule.DateEnd < date.Date)
 606                                         continue;
 607                                 return rule;
 608                         }
 609                         return null;
 610                 }
 611
 612                 private static DateTime TransitionPoint (TransitionTime transition, int year)
 613                 {
 614                         if (transition.IsFixedDateRule)
 615                                 return new DateTime (year, transition.Month, transition.Day) + transition.TimeOfDay.TimeOfDay;
 616
 617                         DayOfWeek first = (new DateTime (year, transition.Month, 1)).DayOfWeek;
 618                         int day = 1 + (transition.Week - 1) * 7 + (transition.DayOfWeek - first) % 7;
 619                         if (day >  DateTime.DaysInMonth (year, transition.Month))
 620                                 day -= 7;
 621                         return new DateTime (year, transition.Month, day) + transition.TimeOfDay.TimeOfDay;
 622                 }
 623
 624 #if LIBC
 625                 private static bool ValidTZFile (byte [] buffer, int length)
 626                 {
 627                         StringBuilder magic = new StringBuilder ();
 628
 629                         for (int i = 0; i < 4; i++)
 630                                 magic.Append ((char)buffer [i]);
 631
 632                         if (magic.ToString () != "TZif")
 633                                 return false;
 634
 635                         if (length >= BUFFER_SIZE)
 636                                 return false;
 637
 638                         return true;
 639                 }
 640
 641                 struct TimeType
 642                 {
 643                         public readonly int Offset;
 644                         public readonly bool IsDst;
 645                         public string Name;
 646
 647                         public TimeType (int offset, bool is_dst, string abbrev)
 648                         {
 649                                 this.Offset = offset;
 650                                 this.IsDst = is_dst;
 651                                 this.Name = abbrev;
 652                         }
 653
 654                         public override string ToString ()
 655                         {
 656                                 return "offset: " + Offset + "s, is_dst: " + IsDst + ", zone name: " + Name;
 657                         }
 658                 }
 659
 660                 static int SwapInt32 (int i)
 661                 {
 662                         return (((i >> 24) & 0xff)
 663                                 | ((i >> 8) & 0xff00)
 664                                 | ((i << 8) & 0xff0000)
 665                                 | ((i << 24)));
 666                 }
 667
 668                 static int ReadBigEndianInt32 (byte [] buffer, int start)
 669                 {
 670                         int i = BitConverter.ToInt32 (buffer, start);
 671                         if (!BitConverter.IsLittleEndian)
 672                                 return i;
 673
 674                         return SwapInt32 (i);
 675                 }
 676
 677                 private static TimeZoneInfo ParseTZBuffer (string id, byte [] buffer, int length)
 678                 {
 679                         //Reading the header. 4 bytes for magic, 16 are reserved
 680                         int ttisgmtcnt = ReadBigEndianInt32 (buffer, 20);
 681                         int ttisstdcnt = ReadBigEndianInt32 (buffer, 24);
 682                         int leapcnt = ReadBigEndianInt32 (buffer, 28);
 683                         int timecnt = ReadBigEndianInt32 (buffer, 32);
 684                         int typecnt = ReadBigEndianInt32 (buffer, 36);
 685                         int charcnt = ReadBigEndianInt32 (buffer, 40);
 686
 687                         if (length < 44 + timecnt * 5 + typecnt * 6 + charcnt + leapcnt * 8 + ttisstdcnt + ttisgmtcnt)
 688                                 throw new InvalidTimeZoneException ();
 689
 690                         Dictionary<int, string> abbreviations = ParseAbbreviations (buffer, 44 + 4 * timecnt + timecnt + 6 * typecnt, charcnt);
 691                         Dictionary<int, TimeType> time_types = ParseTimesTypes (buffer, 44 + 4 * timecnt + timecnt, typecnt, abbreviations);
 692                         List<KeyValuePair<DateTime, TimeType>> transitions = ParseTransitions (buffer, 44, timecnt, time_types);
 693
 694                         if (time_types.Count == 0)
 695                                 throw new InvalidTimeZoneException ();
 696
 697                         if (time_types.Count == 1 && ((TimeType)time_types[0]).IsDst)
 698                                 throw new InvalidTimeZoneException ();
 699
 700                         TimeSpan baseUtcOffset = new TimeSpan (0);
 701                         TimeSpan dstDelta = new TimeSpan (0);
 702                         string standardDisplayName = null;
 703                         string daylightDisplayName = null;
 704                         bool dst_observed = false;
 705                         DateTime dst_start = DateTime.MinValue;
 706                         List<AdjustmentRule> adjustmentRules = new List<AdjustmentRule> ();
 707
 708                         for (int i = 0; i < transitions.Count; i++) {
 709                                 var pair = transitions [i];
 710                                 DateTime ttime = pair.Key;
 711                                 TimeType ttype = pair.Value;
 712                                 if (!ttype.IsDst) {
 713                                         if (standardDisplayName != ttype.Name || baseUtcOffset.TotalSeconds != ttype.Offset) {
 714                                                 standardDisplayName = ttype.Name;
 715                                                 daylightDisplayName = null;
 716                                                 baseUtcOffset = new TimeSpan (0, 0, ttype.Offset);
 717                                                 adjustmentRules = new List<AdjustmentRule> ();
 718                                                 dst_observed = false;
 719                                         }
 720                                         if (dst_observed) {
 721                                                 //FIXME: check additional fields for this:
 722                                                 //most of the transitions are expressed in GMT
 723                                                 dst_start += baseUtcOffset;
 724                                                 DateTime dst_end = ttime + baseUtcOffset + dstDelta;
 725
 726                                                 //some weird timezone (America/Phoenix) have end dates on Jan 1st
 727                                                 if (dst_end.Date == new DateTime (dst_end.Year, 1, 1) && dst_end.Year > dst_start.Year)
 728                                                         dst_end -= new TimeSpan (24, 0, 0);
 729
 730                                                 DateTime dateStart, dateEnd;
 731                                                 if (dst_start.Month < 7)
 732                                                         dateStart = new DateTime (dst_start.Year, 1, 1);
 733                                                 else
 734                                                         dateStart = new DateTime (dst_start.Year, 7, 1);
 735
 736                                                 if (dst_end.Month >= 7)
 737                                                         dateEnd = new DateTime (dst_end.Year, 12, 31);
 738                                                 else
 739                                                         dateEnd = new DateTime (dst_end.Year, 6, 30);
 740
 741
 742                                                 TransitionTime transition_start = TransitionTime.CreateFixedDateRule (new DateTime (1, 1, 1) + dst_start.TimeOfDay, dst_start.Month, dst_start.Day);
 743                                                 TransitionTime transition_end = TransitionTime.CreateFixedDateRule (new DateTime (1, 1, 1) + dst_end.TimeOfDay, dst_end.Month, dst_end.Day);
 744                                                 if  (transition_start != transition_end) //y, that happened in Argentina in 1943-1946
 745                                                         adjustmentRules.Add (AdjustmentRule.CreateAdjustmentRule (dateStart, dateEnd, dstDelta, transition_start, transition_end));
 746                                         }
 747                                         dst_observed = false;
 748                                 } else {
 749                                         if (daylightDisplayName != ttype.Name || dstDelta.TotalSeconds != ttype.Offset - baseUtcOffset.TotalSeconds) {
 750                                                 daylightDisplayName = ttype.Name;
 751                                                 dstDelta = new TimeSpan(0, 0, ttype.Offset) - baseUtcOffset;
 752                                         }
 753                                         dst_start = ttime;
 754                                         dst_observed = true;
 755                                 }
 756                         }
 757
 758                         if (adjustmentRules.Count == 0) {
 759                                 TimeType t = (TimeType)time_types [0];
 760                                 if (standardDisplayName == null) {
 761                                         standardDisplayName = t.Name;
 762                                         baseUtcOffset = new TimeSpan (0, 0, t.Offset);
 763                                 }
 764                                 return CreateCustomTimeZone (id, baseUtcOffset, id, standardDisplayName);
 765                         } else {
 766                                 return CreateCustomTimeZone (id, baseUtcOffset, id, standardDisplayName, daylightDisplayName, ValidateRules (adjustmentRules).ToArray ());
 767                         }
 768                 }
 769
 770                 static List<AdjustmentRule> ValidateRules (List<AdjustmentRule> adjustmentRules)
 771                 {
 772                         AdjustmentRule prev = null;
 773                         foreach (AdjustmentRule current in adjustmentRules.ToArray ()) {
 774                                 if (prev != null && prev.DateEnd > current.DateStart) {
 775                                         adjustmentRules.Remove (current);
 776                                 }
 777                                 prev = current;
 778                         }
 779                         return adjustmentRules;
 780                 }
 781
 782                 static Dictionary<int, string> ParseAbbreviations (byte [] buffer, int index, int count)
 783                 {
 784                         var abbrevs = new Dictionary<int, string> ();
 785                         int abbrev_index = 0;
 786                         var sb = new StringBuilder ();
 787                         for (int i = 0; i < count; i++) {
 788                                 char c = (char) buffer [index + i];
 789                                 if (c != '\0')
 790                                         sb.Append (c);
 791                                 else {
 792                                         abbrevs.Add (abbrev_index, sb.ToString ());
 793                                         //Adding all the substrings too, as it seems to be used, at least for Africa/Windhoek
 794                                         for (int j = 1; j < sb.Length; j++)
 795                                                 abbrevs.Add (abbrev_index + j, sb.ToString (j, sb.Length - j));
 796                                         abbrev_index = i + 1;
 797                                         sb = new StringBuilder ();
 798                                 }
 799                         }
 800                         return abbrevs;
 801                 }
 802
 803                 static Dictionary<int, TimeType> ParseTimesTypes (byte [] buffer, int index, int count, Dictionary<int, string> abbreviations)
 804                 {
 805                         var types = new Dictionary<int, TimeType> (count);
 806                         for (int i = 0; i < count; i++) {
 807                                 int offset = ReadBigEndianInt32 (buffer, index + 6 * i);
 808                                 byte is_dst = buffer [index + 6 * i + 4];
 809                                 byte abbrev = buffer [index + 6 * i + 5];
 810                                 types.Add (i, new TimeType (offset, (is_dst != 0), abbreviations [(int)abbrev]));
 811                         }
 812                         return types;
 813                 }
 814
 815                 static List<KeyValuePair<DateTime, TimeType>> ParseTransitions (byte [] buffer, int index, int count, Dictionary<int, TimeType> time_types)
 816                 {
 817                         var list = new List<KeyValuePair<DateTime, TimeType>> (count);
 818                         for (int i = 0; i < count; i++) {
 819                                 int unixtime = ReadBigEndianInt32 (buffer, index + 4 * i);
 820                                 DateTime ttime = DateTimeFromUnixTime (unixtime);
 821                                 byte ttype = buffer [index + 4 * count + i];
 822                                 list.Add (new KeyValuePair<DateTime, TimeType> (ttime, time_types [(int)ttype]));
 823                         }
 824                         return list;
 825                 }
 826
 827                 static DateTime DateTimeFromUnixTime (long unix_time)
 828                 {
 829                         DateTime date_time = new DateTime (1970, 1, 1);
 830                         return date_time.AddSeconds (unix_time);
 831                 }
 832 #endif
 833         }
 834 }
 835
 836 #endif