mcs/class/corlib/System/TimeZone.cs

   1 //
   2 // System.TimeZone.cs
   3 //
   4 // Authors:
   5 //   Duncan Mak (duncan@ximian.com)
   6 //   Ajay Kumar Dwivedi (adwiv@yahoo.com)
   7 //   Martin Baulig (martin@gnome.org)
   8 //
   9 // (C) Ximian, Inc.
  10 // Copyright (C) 2004-2006 Novell, Inc (http://www.novell.com)
  11 // Copyright 2011 Xamarin Inc.
  12 //
  13 // Permission is hereby granted, free of charge, to any person obtaining
  14 // a copy of this software and associated documentation files (the
  15 // "Software"), to deal in the Software without restriction, including
  16 // without limitation the rights to use, copy, modify, merge, publish,
  17 // distribute, sublicense, and/or sell copies of the Software, and to
  18 // permit persons to whom the Software is furnished to do so, subject to
  19 // the following conditions:
  20 //
  21 // The above copyright notice and this permission notice shall be
  22 // included in all copies or substantial portions of the Software.
  23 //
  24 // THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
  25 // EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
  26 // MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
  27 // NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE
  28 // LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION
  29 // OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
  30 // WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
  31 //
  32 //
  33 // TODO:
  34 //
  35 //    Rewrite ToLocalTime to use GetLocalTimeDiff(DateTime,TimeSpan),
  36 //    this should only leave the validation at the beginning (for MaxValue)
  37 //    and then call the helper function.  This would remove all the
  38 //    ifdefs in that code, and replace it with only one, for the construction
  39 //    of the object.
  40 //
  41 //    Rewrite ToUniversalTime to use a similar setup to that
  42 //
  43 using System.Collections.Generic;
  44 using System.Globalization;
  45 using System.Runtime.CompilerServices;
  46 using System.Runtime.Serialization;
  47 using System.Runtime.InteropServices;
  48
  49 namespace System
  50 {
  51         [Serializable]
  52         [ComVisible (true)]
  53         public abstract class TimeZone
  54         {
  55                 // Fields
  56                 static TimeZone currentTimeZone;
  57
  58                 [NonSerialized]
  59                 static object tz_lock = new object ();
  60                 [NonSerialized]
  61                 static long timezone_check;
  62
  63                 // Constructor
  64                 protected TimeZone ()
  65                 {
  66                 }
  67
  68                 // Properties
  69                 public static TimeZone CurrentTimeZone {
  70                         get {
  71                                 long now = DateTime.GetNow ();
  72                                 TimeZone tz = currentTimeZone;
  73
  74                                 lock (tz_lock) {
  75                                         if (tz == null || Math.Abs (now - timezone_check) > TimeSpan.TicksPerMinute) {
  76                                                 tz = new CurrentSystemTimeZone (now);
  77                                                 timezone_check = now;
  78
  79                                                 currentTimeZone = tz;
  80                                         }
  81                                 }
  82
  83                                 return tz;
  84                         }
  85                 }
  86
  87                 public abstract string DaylightName {
  88                         get;
  89                 }
  90
  91                 public abstract string StandardName {
  92                         get;
  93                 }
  94
  95                 // Methods
  96                 public abstract DaylightTime GetDaylightChanges (int year);
  97
  98                 public abstract TimeSpan GetUtcOffset (DateTime time);
  99
 100                 public virtual bool IsDaylightSavingTime (DateTime time)
 101                 {
 102                         return IsDaylightSavingTime (time, GetDaylightChanges (time.Year));
 103                 }
 104
 105                 public static bool IsDaylightSavingTime (DateTime time, DaylightTime daylightTimes)
 106                 {
 107                         if (daylightTimes == null)
 108                                 throw new ArgumentNullException ("daylightTimes");
 109
 110                         // If Start == End, then DST is off
 111                         if (daylightTimes.Start.Ticks == daylightTimes.End.Ticks)
 112                                 return false;
 113
 114                         //We are in the northern hemisphere.
 115                         if (daylightTimes.Start.Ticks < daylightTimes.End.Ticks) {
 116                                 if (daylightTimes.Start.Ticks < time.Ticks && daylightTimes.End.Ticks > time.Ticks)
 117                                         return true; // time lies between Start and End
 118
 119                         }
 120                         else {  // We are in the southern hemisphere.
 121                                 if (time.Year == daylightTimes.Start.Year && time.Year == daylightTimes.End.Year)
 122                                         if (time.Ticks < daylightTimes.End.Ticks || time.Ticks > daylightTimes.Start.Ticks)
 123                                                 return true; // time is less than End OR more than Start
 124                         }
 125
 126                         return false;
 127                 }
 128
 129                 public virtual DateTime ToLocalTime (DateTime time)
 130                 {
 131                         if (time.Kind == DateTimeKind.Local)
 132                                 return time;
 133
 134                         TimeSpan utcOffset = GetUtcOffset (new DateTime (time.Ticks));
 135                         if (utcOffset.Ticks > 0) {
 136                                 if (DateTime.MaxValue - utcOffset < time)
 137                                         return DateTime.SpecifyKind (DateTime.MaxValue, DateTimeKind.Local);
 138                         } else if (utcOffset.Ticks < 0) {
 139                                 if (time.Ticks + utcOffset.Ticks < DateTime.MinValue.Ticks)
 140                                         return DateTime.SpecifyKind (DateTime.MinValue, DateTimeKind.Local);
 141                         }
 142
 143                         DateTime local = DateTime.SpecifyKind (time.Add (utcOffset), DateTimeKind.Local);
 144                         DaylightTime dlt = GetDaylightChanges (time.Year);
 145                         if (dlt.Delta.Ticks == 0)
 146                                 return DateTime.SpecifyKind (local, DateTimeKind.Local);
 147
 148                         // FIXME: check all of the combination of
 149                         //      - basis: local-based or UTC-based
 150                         //      - hemisphere: Northern or Southern
 151                         //      - offset: positive or negative
 152
 153                         // PST should work fine here.
 154                         if (local < dlt.End && dlt.End.Subtract (dlt.Delta) <= local)
 155                                 return DateTime.SpecifyKind (local, DateTimeKind.Local);
 156
 157                         TimeSpan localOffset = GetUtcOffset (local);
 158                         return DateTime.SpecifyKind (time.Add (localOffset), DateTimeKind.Local);
 159                 }
 160
 161                 public virtual DateTime ToUniversalTime (DateTime time)
 162                 {
 163                         if (time.Kind == DateTimeKind.Utc)
 164                                 return time;
 165
 166                         TimeSpan offset = GetUtcOffset (time);
 167
 168                         if (offset.Ticks < 0) {
 169                                 if (DateTime.MaxValue + offset < time)
 170                                         return DateTime.SpecifyKind (DateTime.MaxValue, DateTimeKind.Utc);
 171                         } else if (offset.Ticks > 0) {
 172                                 if (DateTime.MinValue + offset > time)
 173                                         return DateTime.SpecifyKind (DateTime.MinValue, DateTimeKind.Utc);
 174                         }
 175
 176                         return DateTime.SpecifyKind (new DateTime (time.Ticks - offset.Ticks), DateTimeKind.Utc);
 177                 }
 178
 179                 internal static void ClearCachedData ()
 180                 {
 181                         currentTimeZone = null;
 182                 }
 183
 184                 //
 185                 // This routine returns the TimeDiff that would have to be
 186                 // added to "time" to turn it into a local time.   This would
 187                 // be equivalent to call ToLocalTime.
 188                 //
 189                 // There is one important consideration:
 190                 //
 191                 //    This information is only valid during the minute it
 192                 //    was called.
 193                 //
 194                 //    This only works with a real time, not one of the boundary
 195                 //    cases like DateTime.MaxValue, so validation must be done
 196                 //    before.
 197                 //
 198                 //    This is intended to be used by DateTime.Now
 199                 //
 200                 // We use a minute, just to be conservative and cope with
 201                 // any potential time zones that might be defined in the future
 202                 // that might not nicely fit in hour or half-hour steps.
 203                 //
 204                 internal TimeSpan GetLocalTimeDiff (DateTime time)
 205                 {
 206                         return GetLocalTimeDiff (time, GetUtcOffset (time));
 207                 }
 208
 209                 //
 210                 // This routine is intended to be called by GetLocalTimeDiff(DatetTime)
 211                 // or by ToLocalTime after validation has been performed
 212                 //
 213                 // time is the time to map, utc_offset is the utc_offset that
 214                 // has been computed for calling GetUtcOffset on time.
 215                 //
 216                 // When called by GetLocalTime, utc_offset is assumed to come
 217                 // from a time constructed by new DateTime (DateTime.GetNow ()), that
 218                 // is a valid time.
 219                 //
 220                 // When called by ToLocalTime ranges are checked before this is
 221                 // called.
 222                 //
 223                 internal TimeSpan GetLocalTimeDiff (DateTime time, TimeSpan utc_offset)
 224                 {
 225                         DaylightTime dlt = GetDaylightChanges (time.Year);
 226
 227                         if (dlt.Delta.Ticks == 0)
 228                                 return utc_offset;
 229
 230                         DateTime local = time.Add (utc_offset);
 231                         if (local < dlt.End && dlt.End.Subtract (dlt.Delta) <= local)
 232                                 return utc_offset;
 233
 234                         if (local >= dlt.Start && dlt.Start.Add (dlt.Delta) > local)
 235                                 return utc_offset - dlt.Delta;
 236
 237                         return GetUtcOffset (local);
 238                 }
 239         }
 240
 241         [Serializable]
 242         internal class CurrentSystemTimeZone : TimeZone, IDeserializationCallback {
 243
 244                 // Fields
 245                 private string m_standardName;
 246                 private string m_daylightName;
 247
 248                 // A yearwise cache of DaylightTime.
 249                 private Dictionary<int, DaylightTime> m_CachedDaylightChanges = new Dictionary<int, DaylightTime> (1);
 250
 251                 // the offset when daylightsaving is not on (in ticks)
 252                 private long m_ticksOffset;
 253
 254                 // the offset when daylightsaving is not on.
 255                 [NonSerialized]
 256                 private TimeSpan utcOffsetWithOutDLS;
 257
 258                 // the offset when daylightsaving is on.
 259                 [NonSerialized]
 260                 private TimeSpan utcOffsetWithDLS;
 261
 262                 internal enum TimeZoneData
 263                 {
 264                         DaylightSavingStartIdx,
 265                         DaylightSavingEndIdx,
 266                         UtcOffsetIdx,
 267                         AdditionalDaylightOffsetIdx
 268                 };
 269
 270                 internal enum TimeZoneNames
 271                 {
 272                         StandardNameIdx,
 273                         DaylightNameIdx
 274                 };
 275
 276                 // Internal method to get timezone data.
 277                 //    data[0]:  start of daylight saving time (in DateTime ticks).
 278                 //    data[1]:  end of daylight saving time (in DateTime ticks).
 279                 //    data[2]:  utcoffset (in TimeSpan ticks).
 280                 //    data[3]:  additional offset when daylight saving (in TimeSpan ticks).
 281                 //    name[0]:  name of this timezone when not daylight saving.
 282                 //    name[1]:  name of this timezone when daylight saving.
 283                 [MethodImplAttribute(MethodImplOptions.InternalCall)]
 284                 private static extern bool GetTimeZoneData (int year, out Int64[] data, out string[] names);
 285
 286                 // Constructor
 287                 internal CurrentSystemTimeZone ()
 288                 {
 289                 }
 290
 291                 //
 292                 // Initialized by the constructor
 293                 //
 294                 static int this_year;
 295                 static DaylightTime this_year_dlt;
 296
 297                 //
 298                 // The "lnow" parameter must be the current time, I could have moved
 299                 // the code here, but I do not want to interfere with serialization
 300                 // which is why I kept the other constructor around
 301                 //
 302                 internal CurrentSystemTimeZone (long lnow)
 303                 {
 304                         Int64[] data;
 305                         string[] names;
 306
 307                         DateTime now = new DateTime (lnow);
 308                         if (!GetTimeZoneData (now.Year, out data, out names))
 309                                 throw new NotSupportedException (Locale.GetText ("Can't get timezone name."));
 310
 311                         m_standardName = Locale.GetText (names[(int)TimeZoneNames.StandardNameIdx]);
 312                         m_daylightName = Locale.GetText (names[(int)TimeZoneNames.DaylightNameIdx]);
 313
 314                         m_ticksOffset = data[(int)TimeZoneData.UtcOffsetIdx];
 315
 316                         DaylightTime dlt = GetDaylightTimeFromData (data);
 317                         m_CachedDaylightChanges.Add (now.Year, dlt);
 318                         OnDeserialization (dlt);
 319                 }
 320
 321                 // Properties
 322                 public override string DaylightName {
 323                         get { return m_daylightName; }
 324                 }
 325
 326                 public override string StandardName {
 327                         get { return m_standardName; }
 328                 }
 329
 330                 // Methods
 331                 public override DaylightTime GetDaylightChanges (int year)
 332                 {
 333                         if (year < 1 || year > 9999)
 334                                 throw new ArgumentOutOfRangeException ("year", year +
 335                                         Locale.GetText (" is not in a range between 1 and 9999."));
 336
 337                         //
 338                         // First we try the case for this year, very common, and is used
 339                         // by DateTime.Now (a popular call) indirectly.
 340                         //
 341                         if (year == this_year)
 342                                 return this_year_dlt;
 343
 344                         lock (m_CachedDaylightChanges) {
 345                                 DaylightTime dlt;
 346                                 if (!m_CachedDaylightChanges.TryGetValue (year, out dlt)) {
 347                                         Int64[] data;
 348                                         string[] names;
 349
 350                                         if (!GetTimeZoneData (year, out data, out names))
 351                                                 throw new ArgumentException (Locale.GetText ("Can't get timezone data for " + year));
 352
 353                                         dlt = GetDaylightTimeFromData (data);
 354                                         m_CachedDaylightChanges.Add (year, dlt);
 355                                 }
 356                                 return dlt;
 357                         }
 358                 }
 359
 360                 public override TimeSpan GetUtcOffset (DateTime time)
 361                 {
 362                         if (time.Kind == DateTimeKind.Utc)
 363                                 return TimeSpan.Zero;
 364
 365                         if (IsDaylightSavingTime (time) && !IsAmbiguousTime (time))
 366                                 return utcOffsetWithDLS;
 367
 368                         return utcOffsetWithOutDLS;
 369                 }
 370
 371                 private bool IsAmbiguousTime (DateTime time)
 372                 {
 373                         if (time.Kind == DateTimeKind.Utc)
 374                                 return false;
 375
 376                         DaylightTime changes = GetDaylightChanges (time.Year);
 377
 378                         return time < changes.End && time >= changes.End - changes.Delta;
 379                 }
 380
 381                 void IDeserializationCallback.OnDeserialization (object sender)
 382                 {
 383                         OnDeserialization (null);
 384                 }
 385
 386                 private void OnDeserialization (DaylightTime dlt)
 387                 {
 388                         if (dlt == null) {
 389                                 Int64[] data;
 390                                 string[] names;
 391
 392                                 this_year = DateTime.Now.Year;
 393                                 if (!GetTimeZoneData (this_year, out data, out names))
 394                                         throw new ArgumentException (Locale.GetText ("Can't get timezone data for " + this_year));
 395                                 dlt = GetDaylightTimeFromData (data);
 396                         } else
 397                                 this_year = dlt.Start.Year;
 398
 399                         utcOffsetWithOutDLS = new TimeSpan (m_ticksOffset);
 400                         utcOffsetWithDLS = new TimeSpan (m_ticksOffset + dlt.Delta.Ticks);
 401                         this_year_dlt = dlt;
 402                 }
 403
 404                 private DaylightTime GetDaylightTimeFromData (long[] data)
 405                 {
 406                         return new DaylightTime (new DateTime (data[(int)TimeZoneData.DaylightSavingStartIdx]),
 407                                 new DateTime (data[(int)TimeZoneData.DaylightSavingEndIdx]),
 408                                 new TimeSpan (data[(int)TimeZoneData.AdditionalDaylightOffsetIdx]));
 409                 }
 410
 411         }
 412 }