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.Collections.Generic;
  29 using System.Collections.ObjectModel;
  30 using System.Runtime.Serialization;
  31 using System.Text;
  32
  33 #if LIBC
  34 using System.IO;
  35 using Mono;
  36 #endif
  37
  38 namespace System
  39 {
  40         [SerializableAttribute]
  41         public sealed partial class TimeZoneInfo : IEquatable<TimeZoneInfo>, ISerializable, IDeserializationCallback
  42         {
  43                 TimeSpan baseUtcOffset;
  44                 public TimeSpan BaseUtcOffset {
  45                         get { return baseUtcOffset; }
  46                 }
  47
  48                 string daylightDisplayName;
  49                 public string DaylightName {
  50                         get {
  51                                 if (disableDaylightSavingTime)
  52                                         return String.Empty;
  53                                 return daylightDisplayName;
  54                         }
  55                 }
  56
  57                 string displayName;
  58                 public string DisplayName {
  59                         get { return displayName; }
  60                 }
  61
  62                 string id;
  63                 public string Id {
  64                         get { return id; }
  65                 }
  66
  67                 static TimeZoneInfo local;
  68                 public static TimeZoneInfo Local {
  69                         get {
  70                                 if (local == null) {
  71 #if LIBC
  72                                         try {
  73                                                 local = FindSystemTimeZoneByFileName ("Local", "/etc/localtime");
  74                                         } catch {
  75                                                 try {
  76                                                         local = FindSystemTimeZoneByFileName ("Local", Path.Combine (TimeZoneDirectory, "localtime"));
  77                                                 } catch {
  78                                                         throw new TimeZoneNotFoundException ();
  79                                                 }
  80                                         }
  81 #else
  82                                         throw new TimeZoneNotFoundException ();
  83 #endif
  84                                 }
  85                                 return local;
  86                         }
  87                 }
  88
  89                 string standardDisplayName;
  90                 public string StandardName {
  91                         get { return standardDisplayName; }
  92                 }
  93
  94                 bool disableDaylightSavingTime;
  95                 public bool SupportsDaylightSavingTime {
  96                         get  { return !disableDaylightSavingTime; }
  97                 }
  98
  99                 static TimeZoneInfo utc;
 100                 public static TimeZoneInfo Utc {
 101                         get {
 102                                 if (utc == null)
 103                                         utc = CreateCustomTimeZone ("UTC", new TimeSpan (0), "UTC", "UTC");
 104                                 return utc;
 105                         }
 106                 }
 107 #if LIBC
 108                 static string timeZoneDirectory = null;
 109                 public static string TimeZoneDirectory {
 110                         get {
 111                                 if (timeZoneDirectory == null)
 112                                         timeZoneDirectory = "/usr/share/zoneinfo";
 113                                 return timeZoneDirectory;
 114                         }
 115                         set {
 116                                 ClearCachedData ();
 117                                 timeZoneDirectory = value;
 118                         }
 119                 }
 120 #endif
 121                 private AdjustmentRule [] adjustmentRules;
 122
 123                 public static void ClearCachedData ()
 124                 {
 125                         local = null;
 126                         utc = null;
 127                         systemTimeZones = null;
 128                 }
 129
 130                 public static DateTime ConvertTime (DateTime dateTime, TimeZoneInfo destinationTimeZone)
 131                 {
 132                         return ConvertTime (dateTime, TimeZoneInfo.Local, destinationTimeZone);
 133                 }
 134
 135                 public static DateTime ConvertTime (DateTime dateTime, TimeZoneInfo sourceTimeZone, TimeZoneInfo destinationTimeZone)
 136                 {
 137                         if (dateTime.Kind == DateTimeKind.Local && sourceTimeZone != TimeZoneInfo.Local)
 138                                 throw new ArgumentException ("Kind propery of dateTime is Local but the sourceTimeZone does not equal TimeZoneInfo.Local");
 139
 140                         if (dateTime.Kind == DateTimeKind.Utc && sourceTimeZone != TimeZoneInfo.Utc)
 141                                 throw new ArgumentException ("Kind propery of dateTime is Utc but the sourceTimeZone does not equal TimeZoneInfo.Utc");
 142
 143                         if (sourceTimeZone.IsInvalidTime (dateTime))
 144                                 throw new ArgumentException ("dateTime parameter is an invalid time");
 145
 146                         if (sourceTimeZone == null)
 147                                 throw new ArgumentNullException ("sourceTimeZone");
 148
 149                         if (destinationTimeZone == null)
 150                                 throw new ArgumentNullException ("destinationTimeZone");
 151
 152                         if (dateTime.Kind == DateTimeKind.Local && sourceTimeZone == TimeZoneInfo.Local && destinationTimeZone == TimeZoneInfo.Local)
 153                                 return dateTime;
 154
 155                         DateTime utc = ConvertTimeToUtc (dateTime);
 156
 157                         if (destinationTimeZone == TimeZoneInfo.Utc)
 158                                 return utc;
 159
 160                         return ConvertTimeFromUtc (utc, destinationTimeZone);
 161
 162                 }
 163
 164                 public static DateTimeOffset ConvertTime (DateTimeOffset dateTimeOffset, TimeZoneInfo destinationTimeZone)
 165                 {
 166                         throw new NotImplementedException ();
 167                 }
 168
 169                 public static DateTime ConvertTimeBySystemTimeZoneId (DateTime dateTime, string destinationTimeZoneId)
 170                 {
 171                         return ConvertTime (dateTime, FindSystemTimeZoneById (destinationTimeZoneId));
 172                 }
 173
 174                 public static DateTime ConvertTimeBySystemTimeZoneId (DateTime dateTime, string sourceTimeZoneId, string destinationTimeZoneId)
 175                 {
 176                         return ConvertTime (dateTime, FindSystemTimeZoneById (sourceTimeZoneId), FindSystemTimeZoneById (destinationTimeZoneId));
 177                 }
 178
 179                 public static DateTimeOffset ConvertTimeBySystemTimeZoneId (DateTimeOffset dateTimeOffset, string destinationTimeZoneId)
 180                 {
 181                         return ConvertTime (dateTimeOffset, FindSystemTimeZoneById (destinationTimeZoneId));
 182                 }
 183
 184                 private DateTime ConvertTimeFromUtc (DateTime dateTime)
 185                 {
 186                         if (dateTime.Kind == DateTimeKind.Local)
 187                                 throw new ArgumentException ("Kind property of dateTime is Local");
 188
 189                         if (this == TimeZoneInfo.Utc)
 190                                 return DateTime.SpecifyKind (dateTime, DateTimeKind.Utc);
 191
 192                         //FIXME: do not rely on DateTime implementation !
 193                         if (this == TimeZoneInfo.Local)
 194                                 return DateTime.SpecifyKind (dateTime.ToLocalTime (), DateTimeKind.Unspecified);
 195
 196                         AdjustmentRule rule = GetApplicableRule (dateTime);
 197
 198                         if (IsDaylightSavingTime (DateTime.SpecifyKind (dateTime, DateTimeKind.Utc)))
 199                                 return DateTime.SpecifyKind (dateTime + BaseUtcOffset + rule.DaylightDelta , DateTimeKind.Unspecified);
 200                         else
 201                                 return DateTime.SpecifyKind (dateTime + BaseUtcOffset, DateTimeKind.Unspecified);
 202                 }
 203
 204                 public static DateTime ConvertTimeFromUtc (DateTime dateTime, TimeZoneInfo destinationTimeZone)
 205                 {
 206                         if (destinationTimeZone == null)
 207                                 throw new ArgumentNullException ("destinationTimeZone");
 208
 209                         return destinationTimeZone.ConvertTimeFromUtc (dateTime);
 210                 }
 211
 212                 public static DateTime ConvertTimeToUtc (DateTime dateTime)
 213                 {
 214                         if (dateTime.Kind == DateTimeKind.Utc)
 215                                 return dateTime;
 216
 217                         //FIXME: do not rely on DateTime implementation !
 218                         return DateTime.SpecifyKind (dateTime.ToUniversalTime (), DateTimeKind.Utc);
 219                 }
 220
 221                 public static DateTime ConvertTimeToUtc (DateTime dateTime, TimeZoneInfo sourceTimeZone)
 222                 {
 223                         if (sourceTimeZone == null)
 224                                 throw new ArgumentNullException ("sourceTimeZone");
 225
 226                         if (dateTime.Kind == DateTimeKind.Utc && sourceTimeZone != TimeZoneInfo.Utc)
 227                                 throw new ArgumentException ("Kind propery of dateTime is Utc but the sourceTimeZone does not equal TimeZoneInfo.Utc");
 228
 229                         if (dateTime.Kind == DateTimeKind.Local && sourceTimeZone != TimeZoneInfo.Local)
 230                                 throw new ArgumentException ("Kind propery of dateTime is Local but the sourceTimeZone does not equal TimeZoneInfo.Local");
 231
 232                         if (sourceTimeZone.IsInvalidTime (dateTime))
 233                                 throw new ArgumentException ("dateTime parameter is an invalid time");
 234
 235                         if (dateTime.Kind == DateTimeKind.Utc && sourceTimeZone == TimeZoneInfo.Utc)
 236                                 return dateTime;
 237
 238                         if (dateTime.Kind == DateTimeKind.Utc)
 239                                 return dateTime;
 240
 241                         if (dateTime.Kind == DateTimeKind.Local)
 242                                 return ConvertTimeToUtc (dateTime);
 243
 244                         if (sourceTimeZone.IsAmbiguousTime (dateTime) || !sourceTimeZone.IsDaylightSavingTime (dateTime))
 245                                 return DateTime.SpecifyKind (dateTime - sourceTimeZone.BaseUtcOffset, DateTimeKind.Utc);
 246                         else {
 247                                 AdjustmentRule rule = sourceTimeZone.GetApplicableRule (dateTime);
 248                                 return DateTime.SpecifyKind (dateTime - sourceTimeZone.BaseUtcOffset - rule.DaylightDelta, DateTimeKind.Utc);
 249                         }
 250                 }
 251
 252                 public static TimeZoneInfo CreateCustomTimeZone (string id, TimeSpan baseUtcOffset, string displayName, string standardDisplayName)
 253                 {
 254                         return CreateCustomTimeZone (id, baseUtcOffset, displayName, standardDisplayName, null, null, true);
 255                 }
 256
 257                 public static TimeZoneInfo CreateCustomTimeZone (string id, TimeSpan baseUtcOffset, string displayName, string standardDisplayName, string daylightDisplayName, TimeZoneInfo.AdjustmentRule [] adjustmentRules)
 258                 {
 259                         return CreateCustomTimeZone (id, baseUtcOffset, displayName, standardDisplayName, daylightDisplayName, adjustmentRules, false);
 260                 }
 261
 262                 public static TimeZoneInfo CreateCustomTimeZone ( string id, TimeSpan baseUtcOffset, string displayName, string standardDisplayName, string daylightDisplayName, TimeZoneInfo.AdjustmentRule [] adjustmentRules, bool disableDaylightSavingTime)
 263                 {
 264                         return new TimeZoneInfo (id, baseUtcOffset, displayName, standardDisplayName, daylightDisplayName, adjustmentRules, disableDaylightSavingTime);
 265                 }
 266
 267                 public bool Equals (TimeZoneInfo other)
 268                 {
 269                         if (other == null)
 270                                 return false;
 271
 272                         return other.Id == this.Id && HasSameRules (other);
 273                 }
 274
 275                 public static TimeZoneInfo FindSystemTimeZoneById (string id)
 276                 {
 277                         //FIXME: this method should check for cached values in systemTimeZones
 278                         if (id == null)
 279                                 throw new ArgumentNullException ("id");
 280 #if LIBC
 281                         string filepath = Path.Combine (TimeZoneDirectory, id);
 282                         return FindSystemTimeZoneByFileName (id, filepath);
 283 #else
 284                         throw new NotImplementedException ();
 285 #endif
 286                 }
 287
 288 #if LIBC
 289                 const int BUFFER_SIZE = 16384; //Big enough for any tz file (on Oct 2008, all tz files are under 10k)
 290                 private static TimeZoneInfo FindSystemTimeZoneByFileName (string id, string filepath)
 291                 {
 292                         if (!File.Exists (filepath))
 293                                 throw new TimeZoneNotFoundException ();
 294
 295                         byte [] buffer = new byte [BUFFER_SIZE];
 296                         int length;
 297                         using (FileStream stream = File.OpenRead (filepath)) {
 298                                 length = stream.Read (buffer, 0, BUFFER_SIZE);
 299                         }
 300
 301                         if (!ValidTZFile (buffer, length))
 302                                 throw new InvalidTimeZoneException ("TZ file too big for the buffer");
 303
 304                         try {
 305                                 return ParseTZBuffer (id, buffer, length);
 306                         } catch (Exception e) {
 307                                 throw new InvalidTimeZoneException (e.Message);
 308                         }
 309                 }
 310 #endif
 311
 312                 public static TimeZoneInfo FromSerializedString (string source)
 313                 {
 314                         throw new NotImplementedException ();
 315                 }
 316
 317                 public AdjustmentRule [] GetAdjustmentRules ()
 318                 {
 319                         if (disableDaylightSavingTime)
 320                                 return new AdjustmentRule [0];
 321                         else
 322                                 return (AdjustmentRule []) adjustmentRules.Clone ();
 323                 }
 324
 325                 public TimeSpan [] GetAmbiguousTimeOffsets (DateTime dateTime)
 326                 {
 327                         if (!IsAmbiguousTime (dateTime))
 328                                 throw new ArgumentException ("dateTime is not an ambiguous time");
 329
 330                         AdjustmentRule rule = GetApplicableRule (dateTime);
 331                         return new TimeSpan[] {baseUtcOffset, baseUtcOffset + rule.DaylightDelta};
 332                 }
 333
 334                 public TimeSpan [] GetAmbiguousTimeOffsets (DateTimeOffset dateTimeOffset)
 335                 {
 336                         if (!IsAmbiguousTime (dateTimeOffset))
 337                                 throw new ArgumentException ("dateTimeOffset is not an ambiguous time");
 338
 339                         throw new NotImplementedException ();
 340                 }
 341
 342                 public override int GetHashCode ()
 343                 {
 344                         int hash_code = Id.GetHashCode ();
 345                         foreach (AdjustmentRule rule in GetAdjustmentRules ())
 346                                 hash_code ^= rule.GetHashCode ();
 347                         return hash_code;
 348                 }
 349
 350                 public void GetObjectData (SerializationInfo info, StreamingContext context)
 351                 {
 352                         throw new NotImplementedException ();
 353                 }
 354
 355                 //FIXME: change this to a generic Dictionary and allow caching for FindSystemTimeZoneById
 356                 private static List<TimeZoneInfo> systemTimeZones = null;
 357                 public static ReadOnlyCollection<TimeZoneInfo> GetSystemTimeZones ()
 358                 {
 359                         if (systemTimeZones == null) {
 360                                 systemTimeZones = new List<TimeZoneInfo> ();
 361 #if LIBC
 362                                 string[] continents = new string [] {"Africa", "America", "Antarctica", "Arctic", "Asia", "Atlantic", "Brazil", "Canada", "Chile", "Europe", "Indian", "Mexico", "Mideast", "Pacific", "US"};
 363                                 foreach (string continent in continents) {
 364                                         try {
 365                                                 foreach (string zonepath in Directory.GetFiles (Path.Combine (TimeZoneDirectory, continent))) {
 366                                                         try {
 367                                                                 string id = String.Format ("{0}/{1}", continent, Path.GetFileName (zonepath));
 368                                                                 systemTimeZones.Add (FindSystemTimeZoneById (id));
 369                                                         } catch (ArgumentNullException) {
 370                                                         } catch (TimeZoneNotFoundException) {
 371                                                         } catch (InvalidTimeZoneException) {
 372                                                         } catch (Exception) {
 373                                                                 throw;
 374                                                         }
 375                                                 }
 376                                         } catch {}
 377                                 }
 378 #else
 379                                 throw new NotImplementedException ("This method is not implemented for this platform");
 380 #endif
 381                         }
 382                         return new ReadOnlyCollection<TimeZoneInfo> (systemTimeZones);
 383                 }
 384
 385                 public TimeSpan GetUtcOffset (DateTime dateTime)
 386                 {
 387                         if (IsDaylightSavingTime (dateTime)) {
 388                                 AdjustmentRule rule = GetApplicableRule (dateTime);
 389                                 return BaseUtcOffset + rule.DaylightDelta;
 390                         }
 391
 392                         return BaseUtcOffset;
 393                 }
 394
 395                 public TimeSpan GetUtcOffset (DateTimeOffset dateTimeOffset)
 396                 {
 397                         throw new NotImplementedException ();
 398                 }
 399
 400                 public bool HasSameRules (TimeZoneInfo other)
 401                 {
 402                         if (other == null)
 403                                 throw new ArgumentNullException ("other");
 404
 405                         if ((this.adjustmentRules == null) != (other.adjustmentRules == null))
 406                                 return false;
 407
 408                         if (this.adjustmentRules == null)
 409                                 return true;
 410
 411                         if (this.BaseUtcOffset != other.BaseUtcOffset)
 412                                 return false;
 413
 414                         if (this.adjustmentRules.Length != other.adjustmentRules.Length)
 415                                 return false;
 416
 417                         for (int i = 0; i < adjustmentRules.Length; i++) {
 418                                 if (! (this.adjustmentRules [i]).Equals (other.adjustmentRules [i]))
 419                                         return false;
 420                         }
 421
 422                         return true;
 423                 }
 424
 425                 public bool IsAmbiguousTime (DateTime dateTime)
 426                 {
 427                         if (dateTime.Kind == DateTimeKind.Local && IsInvalidTime (dateTime))
 428                                 throw new ArgumentException ("Kind is Local and time is Invalid");
 429
 430                         if (this == TimeZoneInfo.Utc)
 431                                 return false;
 432
 433                         if (dateTime.Kind == DateTimeKind.Utc)
 434                                 dateTime = ConvertTimeFromUtc (dateTime);
 435
 436                         if (dateTime.Kind == DateTimeKind.Local && this != TimeZoneInfo.Local)
 437                                 dateTime = ConvertTime (dateTime, TimeZoneInfo.Local, this);
 438
 439                         AdjustmentRule rule = GetApplicableRule (dateTime);
 440                         DateTime tpoint = TransitionPoint (rule.DaylightTransitionEnd, dateTime.Year);
 441                         if (dateTime > tpoint - rule.DaylightDelta  && dateTime <= tpoint)
 442                                 return true;
 443
 444                         return false;
 445                 }
 446
 447                 public bool IsAmbiguousTime (DateTimeOffset dateTimeOffset)
 448                 {
 449                         throw new NotImplementedException ();
 450                 }
 451
 452                 public bool IsDaylightSavingTime (DateTime dateTime)
 453                 {
 454                         if (dateTime.Kind == DateTimeKind.Local && IsInvalidTime (dateTime))
 455                                 throw new ArgumentException ("dateTime is invalid and Kind is Local");
 456
 457                         if (this == TimeZoneInfo.Utc)
 458                                 return false;
 459
 460                         if (!SupportsDaylightSavingTime)
 461                                 return false;
 462                         //FIXME: do not rely on DateTime implementation !
 463                         if ((dateTime.Kind == DateTimeKind.Local || dateTime.Kind == DateTimeKind.Unspecified) && this == TimeZoneInfo.Local)
 464                                 return dateTime.IsDaylightSavingTime ();
 465
 466                         //FIXME: do not rely on DateTime implementation !
 467                         if (dateTime.Kind == DateTimeKind.Local && this != TimeZoneInfo.Utc)
 468                                 return IsDaylightSavingTime (DateTime.SpecifyKind (dateTime.ToUniversalTime (), DateTimeKind.Utc));
 469
 470                         AdjustmentRule rule = GetApplicableRule (dateTime.Date);
 471                         if (rule == null)
 472                                 return false;
 473
 474                         DateTime DST_start = TransitionPoint (rule.DaylightTransitionStart, dateTime.Year);
 475                         DateTime DST_end = TransitionPoint (rule.DaylightTransitionEnd, dateTime.Year + ((rule.DaylightTransitionStart.Month < rule.DaylightTransitionEnd.Month) ? 0 : 1));
 476                         if (dateTime.Kind == DateTimeKind.Utc) {
 477                                 DST_start -= BaseUtcOffset;
 478                                 DST_end -= (BaseUtcOffset + rule.DaylightDelta);
 479                         }
 480
 481                         return (dateTime >= DST_start && dateTime < DST_end);
 482                 }
 483
 484                 public bool IsDaylightSavingTime (DateTimeOffset dateTimeOffset)
 485                 {
 486                         throw new NotImplementedException ();
 487                 }
 488
 489                 public bool IsInvalidTime (DateTime dateTime)
 490                 {
 491                         if (dateTime.Kind == DateTimeKind.Utc)
 492                                 return false;
 493                         if (dateTime.Kind == DateTimeKind.Local && this != Local)
 494                                 return false;
 495
 496                         AdjustmentRule rule = GetApplicableRule (dateTime);
 497                         DateTime tpoint = TransitionPoint (rule.DaylightTransitionStart, dateTime.Year);
 498                         if (dateTime >= tpoint && dateTime < tpoint + rule.DaylightDelta)
 499                                 return true;
 500
 501                         return false;
 502                 }
 503
 504                 public void OnDeserialization (object sender)
 505                 {
 506                         throw new NotImplementedException ();
 507                 }
 508
 509                 public string ToSerializedString ()
 510                 {
 511                         throw new NotImplementedException ();
 512                 }
 513
 514                 public override string ToString ()
 515                 {
 516                         return DisplayName;
 517                 }
 518
 519                 private TimeZoneInfo (string id, TimeSpan baseUtcOffset, string displayName, string standardDisplayName, string daylightDisplayName, TimeZoneInfo.AdjustmentRule [] adjustmentRules, bool disableDaylightSavingTime)
 520                 {
 521                         if (id == null)
 522                                 throw new ArgumentNullException ("id");
 523
 524                         if (id == String.Empty)
 525                                 throw new ArgumentException ("id parameter is an empty string");
 526
 527                         if (baseUtcOffset.Ticks % TimeSpan.TicksPerMinute != 0)
 528                                 throw new ArgumentException ("baseUtcOffset parameter does not represent a whole number of minutes");
 529
 530                         if (baseUtcOffset > new TimeSpan (14, 0, 0) || baseUtcOffset < new TimeSpan (-14, 0, 0))
 531                                 throw new ArgumentOutOfRangeException ("baseUtcOffset parameter is greater than 14 hours or less than -14 hours");
 532
 533 #if STRICT
 534                         if (id.Length > 32)
 535                                 throw new ArgumentException ("id parameter shouldn't be longer than 32 characters");
 536 #endif
 537
 538                         if (adjustmentRules != null && adjustmentRules.Length != 0) {
 539                                 AdjustmentRule prev = null;
 540                                 foreach (AdjustmentRule current in adjustmentRules) {
 541                                         if (current == null)
 542                                                 throw new InvalidTimeZoneException ("one or more elements in adjustmentRules are null");
 543
 544                                         if ((baseUtcOffset + current.DaylightDelta < new TimeSpan (-14, 0, 0)) ||
 545                                                         (baseUtcOffset + current.DaylightDelta > new TimeSpan (14, 0, 0)))
 546                                                 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;");
 547
 548                                         if (prev != null && prev.DateStart > current.DateStart)
 549                                                 throw new InvalidTimeZoneException ("adjustment rules specified in adjustmentRules parameter are not in chronological order");
 550
 551                                         if (prev != null && prev.DateEnd > current.DateStart)
 552                                                 throw new InvalidTimeZoneException ("some adjustment rules in the adjustmentRules parameter overlap");
 553
 554                                         if (prev != null && prev.DateEnd == current.DateStart)
 555                                                 throw new InvalidTimeZoneException ("a date can have multiple adjustment rules applied to it");
 556
 557                                         prev = current;
 558                                 }
 559                         }
 560
 561                         this.id = id;
 562                         this.baseUtcOffset = baseUtcOffset;
 563                         this.displayName = displayName ?? id;
 564                         this.standardDisplayName = standardDisplayName ?? id;
 565                         this.daylightDisplayName = daylightDisplayName;
 566                         this.disableDaylightSavingTime = disableDaylightSavingTime;
 567                         this.adjustmentRules = adjustmentRules;
 568                 }
 569
 570                 private AdjustmentRule GetApplicableRule (DateTime dateTime)
 571                 {
 572                         //Transitions are always in standard time
 573                         DateTime date = dateTime;
 574
 575                         if (dateTime.Kind == DateTimeKind.Local && this != TimeZoneInfo.Local)
 576                                 date = date.ToUniversalTime () + BaseUtcOffset;
 577
 578                         if (dateTime.Kind == DateTimeKind.Utc && this != TimeZoneInfo.Utc)
 579                                 date = date + BaseUtcOffset;
 580
 581                         foreach (AdjustmentRule rule in adjustmentRules) {
 582                                 if (rule.DateStart > date.Date)
 583                                         return null;
 584                                 if (rule.DateEnd < date.Date)
 585                                         continue;
 586                                 return rule;
 587                         }
 588                         return null;
 589                 }
 590
 591                 private static DateTime TransitionPoint (TransitionTime transition, int year)
 592                 {
 593                         if (transition.IsFixedDateRule)
 594                                 return new DateTime (year, transition.Month, transition.Day) + transition.TimeOfDay.TimeOfDay;
 595
 596                         DayOfWeek first = (new DateTime (year, transition.Month, 1)).DayOfWeek;
 597                         int day = 1 + (transition.Week - 1) * 7 + (transition.DayOfWeek - first) % 7;
 598                         if (day >  DateTime.DaysInMonth (year, transition.Month))
 599                                 day -= 7;
 600                         return new DateTime (year, transition.Month, day) + transition.TimeOfDay.TimeOfDay;
 601                 }
 602
 603 #if LIBC
 604                 private static bool ValidTZFile (byte [] buffer, int length)
 605                 {
 606                         StringBuilder magic = new StringBuilder ();
 607
 608                         for (int i = 0; i < 4; i++)
 609                                 magic.Append ((char)buffer [i]);
 610
 611                         if (magic.ToString () != "TZif")
 612                                 return false;
 613
 614                         if (length >= BUFFER_SIZE)
 615                                 return false;
 616
 617                         return true;
 618                 }
 619
 620                 struct TimeType
 621                 {
 622                         public readonly int Offset;
 623                         public readonly bool IsDst;
 624                         public string Name;
 625
 626                         public TimeType (int offset, bool is_dst, string abbrev)
 627                         {
 628                                 this.Offset = offset;
 629                                 this.IsDst = is_dst;
 630                                 this.Name = abbrev;
 631                         }
 632
 633                         public override string ToString ()
 634                         {
 635                                 return "offset: " + Offset + "s, is_dst: " + IsDst + ", zone name: " + Name;
 636                         }
 637                 }
 638
 639                 static int SwapInt32 (int i)
 640                 {
 641                         return (((i >> 24) & 0xff)
 642                                 | ((i >> 8) & 0xff00)
 643                                 | ((i << 8) & 0xff0000)
 644                                 | ((i << 24)));
 645                 }
 646
 647                 static int ReadBigEndianInt32 (byte [] buffer, int start)
 648                 {
 649                         int i = BitConverter.ToInt32 (buffer, start);
 650                         if (!BitConverter.IsLittleEndian)
 651                                 return i;
 652
 653                         return SwapInt32 (i);
 654                 }
 655
 656                 private static TimeZoneInfo ParseTZBuffer (string id, byte [] buffer, int length)
 657                 {
 658                         //Reading the header. 4 bytes for magic, 16 are reserved
 659                         int ttisgmtcnt = ReadBigEndianInt32 (buffer, 20);
 660                         int ttisstdcnt = ReadBigEndianInt32 (buffer, 24);
 661                         int leapcnt = ReadBigEndianInt32 (buffer, 28);
 662                         int timecnt = ReadBigEndianInt32 (buffer, 32);
 663                         int typecnt = ReadBigEndianInt32 (buffer, 36);
 664                         int charcnt = ReadBigEndianInt32 (buffer, 40);
 665
 666                         if (length < 44 + timecnt * 5 + typecnt * 6 + charcnt + leapcnt * 8 + ttisstdcnt + ttisgmtcnt)
 667                                 throw new InvalidTimeZoneException ();
 668
 669                         Dictionary<int, string> abbreviations = ParseAbbreviations (buffer, 44 + 4 * timecnt + timecnt + 6 * typecnt, charcnt);
 670                         Dictionary<int, TimeType> time_types = ParseTimesTypes (buffer, 44 + 4 * timecnt + timecnt, typecnt, abbreviations);
 671                         List<KeyValuePair<DateTime, TimeType>> transitions = ParseTransitions (buffer, 44, timecnt, time_types);
 672
 673                         if (time_types.Count == 0)
 674                                 throw new InvalidTimeZoneException ();
 675
 676                         if (time_types.Count == 1 && ((TimeType)time_types[0]).IsDst)
 677                                 throw new InvalidTimeZoneException ();
 678
 679                         TimeSpan baseUtcOffset = new TimeSpan (0);
 680                         TimeSpan dstDelta = new TimeSpan (0);
 681                         string standardDisplayName = null;
 682                         string daylightDisplayName = null;
 683                         bool dst_observed = false;
 684                         DateTime dst_start = DateTime.MinValue;
 685                         List<AdjustmentRule> adjustmentRules = new List<AdjustmentRule> ();
 686
 687                         for (int i = 0; i < transitions.Count; i++) {
 688                                 var pair = transitions [i];
 689                                 DateTime ttime = pair.Key;
 690                                 TimeType ttype = pair.Value;
 691                                 if (!ttype.IsDst) {
 692                                         if (standardDisplayName != ttype.Name || baseUtcOffset.TotalSeconds != ttype.Offset) {
 693                                                 standardDisplayName = ttype.Name;
 694                                                 daylightDisplayName = null;
 695                                                 baseUtcOffset = new TimeSpan (0, 0, ttype.Offset);
 696                                                 adjustmentRules = new List<AdjustmentRule> ();
 697                                                 dst_observed = false;
 698                                         }
 699                                         if (dst_observed) {
 700                                                 //FIXME: check additional fields for this:
 701                                                 //most of the transitions are expressed in GMT
 702                                                 dst_start += baseUtcOffset;
 703                                                 DateTime dst_end = ttime + baseUtcOffset + dstDelta;
 704
 705                                                 //some weird timezone (America/Phoenix) have end dates on Jan 1st
 706                                                 if (dst_end.Date == new DateTime (dst_end.Year, 1, 1) && dst_end.Year > dst_start.Year)
 707                                                         dst_end -= new TimeSpan (24, 0, 0);
 708
 709                                                 DateTime dateStart, dateEnd;
 710                                                 if (dst_start.Month < 7)
 711                                                         dateStart = new DateTime (dst_start.Year, 1, 1);
 712                                                 else
 713                                                         dateStart = new DateTime (dst_start.Year, 7, 1);
 714
 715                                                 if (dst_end.Month >= 7)
 716                                                         dateEnd = new DateTime (dst_end.Year, 12, 31);
 717                                                 else
 718                                                         dateEnd = new DateTime (dst_end.Year, 6, 30);
 719
 720
 721                                                 TransitionTime transition_start = TransitionTime.CreateFixedDateRule (new DateTime (1, 1, 1) + dst_start.TimeOfDay, dst_start.Month, dst_start.Day);
 722                                                 TransitionTime transition_end = TransitionTime.CreateFixedDateRule (new DateTime (1, 1, 1) + dst_end.TimeOfDay, dst_end.Month, dst_end.Day);
 723                                                 if  (transition_start != transition_end) //y, that happened in Argentina in 1943-1946
 724                                                         adjustmentRules.Add (AdjustmentRule.CreateAdjustmentRule (dateStart, dateEnd, dstDelta, transition_start, transition_end));
 725                                         }
 726                                         dst_observed = false;
 727                                 } else {
 728                                         if (daylightDisplayName != ttype.Name || dstDelta.TotalSeconds != ttype.Offset - baseUtcOffset.TotalSeconds) {
 729                                                 daylightDisplayName = ttype.Name;
 730                                                 dstDelta = new TimeSpan(0, 0, ttype.Offset) - baseUtcOffset;
 731                                         }
 732                                         dst_start = ttime;
 733                                         dst_observed = true;
 734                                 }
 735                         }
 736
 737                         if (adjustmentRules.Count == 0) {
 738                                 TimeType t = (TimeType)time_types [0];
 739                                 if (standardDisplayName == null) {
 740                                         standardDisplayName = t.Name;
 741                                         baseUtcOffset = new TimeSpan (0, 0, t.Offset);
 742                                 }
 743                                 return CreateCustomTimeZone (id, baseUtcOffset, id, standardDisplayName);
 744                         } else {
 745                                 return CreateCustomTimeZone (id, baseUtcOffset, id, standardDisplayName, daylightDisplayName, ValidateRules (adjustmentRules).ToArray ());
 746                         }
 747                 }
 748
 749                 static List<AdjustmentRule> ValidateRules (List<AdjustmentRule> adjustmentRules)
 750                 {
 751                         AdjustmentRule prev = null;
 752                         foreach (AdjustmentRule current in adjustmentRules.ToArray ()) {
 753                                 if (prev != null && prev.DateEnd > current.DateStart) {
 754                                         adjustmentRules.Remove (current);
 755                                 }
 756                                 prev = current;
 757                         }
 758                         return adjustmentRules;
 759                 }
 760
 761                 static Dictionary<int, string> ParseAbbreviations (byte [] buffer, int index, int count)
 762                 {
 763                         var abbrevs = new Dictionary<int, string> ();
 764                         int abbrev_index = 0;
 765                         var sb = new StringBuilder ();
 766                         for (int i = 0; i < count; i++) {
 767                                 char c = (char) buffer [index + i];
 768                                 if (c != '\0')
 769                                         sb.Append (c);
 770                                 else {
 771                                         abbrevs.Add (abbrev_index, sb.ToString ());
 772                                         //Adding all the substrings too, as it seems to be used, at least for Africa/Windhoek
 773                                         for (int j = 1; j < sb.Length; j++)
 774                                                 abbrevs.Add (abbrev_index + j, sb.ToString (j, sb.Length - j));
 775                                         abbrev_index = i + 1;
 776                                         sb = new StringBuilder ();
 777                                 }
 778                         }
 779                         return abbrevs;
 780                 }
 781
 782                 static Dictionary<int, TimeType> ParseTimesTypes (byte [] buffer, int index, int count, Dictionary<int, string> abbreviations)
 783                 {
 784                         var types = new Dictionary<int, TimeType> (count);
 785                         for (int i = 0; i < count; i++) {
 786                                 int offset = ReadBigEndianInt32 (buffer, index + 6 * i);
 787                                 byte is_dst = buffer [index + 6 * i + 4];
 788                                 byte abbrev = buffer [index + 6 * i + 5];
 789                                 types.Add (i, new TimeType (offset, (is_dst != 0), abbreviations [(int)abbrev]));
 790                         }
 791                         return types;
 792                 }
 793
 794                 static List<KeyValuePair<DateTime, TimeType>> ParseTransitions (byte [] buffer, int index, int count, Dictionary<int, TimeType> time_types)
 795                 {
 796                         var list = new List<KeyValuePair<DateTime, TimeType>> (count);
 797                         for (int i = 0; i < count; i++) {
 798                                 int unixtime = ReadBigEndianInt32 (buffer, index + 4 * i);
 799                                 DateTime ttime = DateTimeFromUnixTime (unixtime);
 800                                 byte ttype = buffer [index + 4 * count + i];
 801                                 list.Add (new KeyValuePair<DateTime, TimeType> (ttime, time_types [(int)ttype]));
 802                         }
 803                         return list;
 804                 }
 805
 806                 static DateTime DateTimeFromUnixTime (long unix_time)
 807                 {
 808                         DateTime date_time = new DateTime (1970, 1, 1);
 809                         return date_time.AddSeconds (unix_time);
 810                 }
 811 #endif
 812         }
 813 }