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.UtcNow.Ticks;
  72                                 TimeZone tz = currentTimeZone;
  73
  74                                 lock (tz_lock) {
  75                                         if (tz == null || Math.Abs (now - timezone_check) > TimeSpan.TicksPerMinute) {
  76 #if MONODROID
  77                                                 tz = AndroidPlatform.GetCurrentSystemTimeZone ();
  78                                                 if (tz == null)
  79 #endif
  80                                                         tz = new CurrentSystemTimeZone (now);
  81                                                 timezone_check = now;
  82
  83                                                 currentTimeZone = tz;
  84                                         }
  85                                 }
  86
  87                                 return tz;
  88                         }
  89                 }
  90
  91                 public abstract string DaylightName {
  92                         get;
  93                 }
  94
  95                 public abstract string StandardName {
  96                         get;
  97                 }
  98
  99                 // Methods
 100                 public abstract DaylightTime GetDaylightChanges (int year);
 101
 102                 public abstract TimeSpan GetUtcOffset (DateTime time);
 103
 104                 public virtual bool IsDaylightSavingTime (DateTime time)
 105                 {
 106                         return IsDaylightSavingTime (time, GetDaylightChanges (time.Year));
 107                 }
 108
 109                 public static bool IsDaylightSavingTime (DateTime time, DaylightTime daylightTimes)
 110                 {
 111                         if (daylightTimes == null)
 112                                 throw new ArgumentNullException ("daylightTimes");
 113
 114                         // If Start == End, then DST is off
 115                         if (daylightTimes.Start.Ticks == daylightTimes.End.Ticks)
 116                                 return false;
 117
 118                         //We are in the northern hemisphere.
 119                         if (daylightTimes.Start.Ticks < daylightTimes.End.Ticks) {
 120                                 if (daylightTimes.Start.Ticks < time.Ticks && daylightTimes.End.Ticks > time.Ticks)
 121                                         return true; // time lies between Start and End
 122
 123                         }
 124                         else {  // We are in the southern hemisphere.
 125                                 if (time.Year == daylightTimes.Start.Year && time.Year == daylightTimes.End.Year)
 126                                         if (time.Ticks < daylightTimes.End.Ticks || time.Ticks > daylightTimes.Start.Ticks)
 127                                                 return true; // time is less than End OR more than Start
 128                         }
 129
 130                         return false;
 131                 }
 132
 133                 public virtual DateTime ToLocalTime (DateTime time)
 134                 {
 135                         if (time.Kind == DateTimeKind.Local)
 136                                 return time;
 137
 138                         TimeSpan utcOffset = GetUtcOffset (new DateTime (time.Ticks));
 139                         if (utcOffset.Ticks > 0) {
 140                                 if (DateTime.MaxValue - utcOffset < time)
 141                                         return DateTime.SpecifyKind (DateTime.MaxValue, DateTimeKind.Local);
 142                         } else if (utcOffset.Ticks < 0) {
 143                                 if (time.Ticks + utcOffset.Ticks < DateTime.MinValue.Ticks)
 144                                         return DateTime.SpecifyKind (DateTime.MinValue, DateTimeKind.Local);
 145                         }
 146
 147                         return DateTime.SpecifyKind (time.Add (utcOffset), DateTimeKind.Local);
 148                 }
 149
 150                 public virtual DateTime ToUniversalTime (DateTime time)
 151                 {
 152                         if (time.Kind == DateTimeKind.Utc)
 153                                 return time;
 154
 155                         TimeSpan offset = GetUtcOffset (time);
 156
 157                         if (offset.Ticks < 0) {
 158                                 if (DateTime.MaxValue + offset < time)
 159                                         return DateTime.SpecifyKind (DateTime.MaxValue, DateTimeKind.Utc);
 160                         } else if (offset.Ticks > 0) {
 161                                 if (DateTime.MinValue + offset > time)
 162                                         return DateTime.SpecifyKind (DateTime.MinValue, DateTimeKind.Utc);
 163                         }
 164
 165                         return DateTime.SpecifyKind (new DateTime (time.Ticks - offset.Ticks), DateTimeKind.Utc);
 166                 }
 167
 168                 internal static void ClearCachedData ()
 169                 {
 170                         currentTimeZone = null;
 171                 }
 172
 173                 //
 174                 // This routine returns the TimeDiff that would have to be
 175                 // added to "time" to turn it into a local time.   This would
 176                 // be equivalent to call ToLocalTime.
 177                 //
 178                 // There is one important consideration:
 179                 //
 180                 //    This information is only valid during the minute it
 181                 //    was called.
 182                 //
 183                 //    This only works with a real time, not one of the boundary
 184                 //    cases like DateTime.MaxValue, so validation must be done
 185                 //    before.
 186                 //
 187                 //    This is intended to be used by DateTime.Now
 188                 //
 189                 // We use a minute, just to be conservative and cope with
 190                 // any potential time zones that might be defined in the future
 191                 // that might not nicely fit in hour or half-hour steps.
 192                 //
 193                 internal TimeSpan GetLocalTimeDiff (DateTime time)
 194                 {
 195                         return GetLocalTimeDiff (time, GetUtcOffset (time));
 196                 }
 197
 198                 //
 199                 // This routine is intended to be called by GetLocalTimeDiff(DatetTime)
 200                 // or by ToLocalTime after validation has been performed
 201                 //
 202                 // time is the time to map, utc_offset is the utc_offset that
 203                 // has been computed for calling GetUtcOffset on time.
 204                 //
 205                 // When called by GetLocalTime, utc_offset is assumed to come
 206                 // from a time constructed by new DateTime (DateTime.GetNow ()), that
 207                 // is a valid time.
 208                 //
 209                 // When called by ToLocalTime ranges are checked before this is
 210                 // called.
 211                 //
 212                 internal TimeSpan GetLocalTimeDiff (DateTime time, TimeSpan utc_offset)
 213                 {
 214                         DaylightTime dlt = GetDaylightChanges (time.Year);
 215
 216                         if (dlt.Delta.Ticks == 0)
 217                                 return utc_offset;
 218
 219                         DateTime local = time.Add (utc_offset);
 220                         if (local < dlt.End && dlt.End.Subtract (dlt.Delta) <= local)
 221                                 return utc_offset;
 222
 223                         if (local >= dlt.Start && dlt.Start.Add (dlt.Delta) > local)
 224                                 return utc_offset - dlt.Delta;
 225
 226                         return GetUtcOffset (local);
 227                 }
 228         }
 229
 230         [Serializable]
 231         internal class CurrentSystemTimeZone : TimeZone, IDeserializationCallback {
 232
 233                 // Fields
 234                 private string m_standardName;
 235                 private string m_daylightName;
 236
 237                 // A yearwise cache of DaylightTime.
 238                 private Dictionary<int, DaylightTime> m_CachedDaylightChanges = new Dictionary<int, DaylightTime> (1);
 239
 240                 internal enum TimeZoneData
 241                 {
 242                         DaylightSavingStartIdx,
 243                         DaylightSavingEndIdx,
 244                         UtcOffsetIdx,
 245                         AdditionalDaylightOffsetIdx
 246                 };
 247
 248                 internal enum TimeZoneNames
 249                 {
 250                         StandardNameIdx,
 251                         DaylightNameIdx
 252                 };
 253
 254                 // Internal method to get timezone data.
 255                 //    data[0]:  start of daylight saving time (in DateTime ticks).
 256                 //    data[1]:  end of daylight saving time (in DateTime ticks).
 257                 //    data[2]:  utcoffset (in TimeSpan ticks).
 258                 //    data[3]:  additional offset when daylight saving (in TimeSpan ticks).
 259                 //    name[0]:  name of this timezone when not daylight saving.
 260                 //    name[1]:  name of this timezone when daylight saving.
 261                 [MethodImplAttribute(MethodImplOptions.InternalCall)]
 262                 private static extern bool GetTimeZoneData (int year, out Int64[] data, out string[] names);
 263
 264                 // Constructor
 265                 internal CurrentSystemTimeZone ()
 266                 {
 267                 }
 268
 269                 //
 270                 // Initialized by the constructor
 271                 //
 272                 static int this_year;
 273                 static DaylightTime this_year_dlt;
 274
 275                 //
 276                 // The "lnow" parameter must be the current time, I could have moved
 277                 // the code here, but I do not want to interfere with serialization
 278                 // which is why I kept the other constructor around
 279                 //
 280                 internal CurrentSystemTimeZone (long lnow)
 281                 {
 282                         Int64[] data;
 283                         string[] names;
 284
 285                         DateTime now = new DateTime (lnow);
 286                         if (!GetTimeZoneData (now.Year, out data, out names))
 287                                 throw new NotSupportedException (Locale.GetText ("Can't get timezone name."));
 288
 289                         m_standardName = Locale.GetText (names[(int)TimeZoneNames.StandardNameIdx]);
 290                         m_daylightName = Locale.GetText (names[(int)TimeZoneNames.DaylightNameIdx]);
 291
 292                         DaylightTime dlt = GetDaylightTimeFromData (data);
 293                         m_CachedDaylightChanges.Add (now.Year, dlt);
 294                         OnDeserialization (dlt);
 295                 }
 296
 297                 // Properties
 298                 public override string DaylightName {
 299                         get { return m_daylightName; }
 300                 }
 301
 302                 public override string StandardName {
 303                         get { return m_standardName; }
 304                 }
 305
 306                 // Methods
 307                 public override DaylightTime GetDaylightChanges (int year)
 308                 {
 309                         if (year < 1 || year > 9999)
 310                                 throw new ArgumentOutOfRangeException ("year", year +
 311                                         Locale.GetText (" is not in a range between 1 and 9999."));
 312
 313                         //
 314                         // First we try the case for this year, very common, and is used
 315                         // by DateTime.Now (a popular call) indirectly.
 316                         //
 317                         if (year == this_year)
 318                                 return this_year_dlt;
 319
 320                         lock (m_CachedDaylightChanges) {
 321                                 DaylightTime dlt;
 322                                 if (!m_CachedDaylightChanges.TryGetValue (year, out dlt)) {
 323                                         Int64[] data;
 324                                         string[] names;
 325
 326                                         if (!GetTimeZoneData (year, out data, out names))
 327                                                 throw new ArgumentException (Locale.GetText ("Can't get timezone data for " + year));
 328
 329                                         dlt = GetDaylightTimeFromData (data);
 330                                         m_CachedDaylightChanges.Add (year, dlt);
 331                                 }
 332                                 return dlt;
 333                         }
 334                 }
 335
 336                 public override TimeSpan GetUtcOffset (DateTime time)
 337                 {
 338                         if (time.Kind == DateTimeKind.Utc)
 339                                 return TimeSpan.Zero;
 340
 341                         return TimeZoneInfo.Local.GetUtcOffset (time);
 342                 }
 343
 344                 void IDeserializationCallback.OnDeserialization (object sender)
 345                 {
 346                         OnDeserialization (null);
 347                 }
 348
 349                 private void OnDeserialization (DaylightTime dlt)
 350                 {
 351                         if (dlt == null) {
 352                                 Int64[] data;
 353                                 string[] names;
 354
 355                                 this_year = DateTime.Now.Year;
 356                                 if (!GetTimeZoneData (this_year, out data, out names))
 357                                         throw new ArgumentException (Locale.GetText ("Can't get timezone data for " + this_year));
 358                                 dlt = GetDaylightTimeFromData (data);
 359                         } else
 360                                 this_year = dlt.Start.Year;
 361
 362                         this_year_dlt = dlt;
 363                 }
 364
 365                 private DaylightTime GetDaylightTimeFromData (long[] data)
 366                 {
 367                         return new DaylightTime (new DateTime (data[(int)TimeZoneData.DaylightSavingStartIdx]),
 368                                 new DateTime (data[(int)TimeZoneData.DaylightSavingEndIdx]),
 369                                 new TimeSpan (data[(int)TimeZoneData.AdditionalDaylightOffsetIdx]));
 370                 }
 371
 372         }
 373 }