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 //
  11
  12 //
  13 // Copyright (C) 2004 Novell, Inc (http://www.novell.com)
  14 //
  15 // Permission is hereby granted, free of charge, to any person obtaining
  16 // a copy of this software and associated documentation files (the
  17 // "Software"), to deal in the Software without restriction, including
  18 // without limitation the rights to use, copy, modify, merge, publish,
  19 // distribute, sublicense, and/or sell copies of the Software, and to
  20 // permit persons to whom the Software is furnished to do so, subject to
  21 // the following conditions:
  22 //
  23 // The above copyright notice and this permission notice shall be
  24 // included in all copies or substantial portions of the Software.
  25 //
  26 // THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
  27 // EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
  28 // MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
  29 // NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE
  30 // LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION
  31 // OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
  32 // WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
  33 //
  34
  35 using System.Collections;
  36 using System.Globalization;
  37 using System.Runtime.CompilerServices;
  38
  39 namespace System
  40 {
  41         [Serializable]
  42         public abstract class TimeZone
  43         {
  44                 // Fields
  45                 private static TimeZone currentTimeZone;
  46
  47                 // Constructor
  48                 protected TimeZone ()
  49                 {
  50                 }
  51
  52                 // Properties
  53                 public static TimeZone CurrentTimeZone {
  54                         get {
  55                                 if (currentTimeZone == null)
  56                                         currentTimeZone = new CurrentTimeZone ();
  57
  58                                 return currentTimeZone;
  59                         }
  60                 }
  61
  62                 public abstract string DaylightName {
  63                         get;
  64                 }
  65
  66                 public abstract string StandardName {
  67                         get;
  68                 }
  69
  70                 // Methods
  71                 public abstract DaylightTime GetDaylightChanges (int year);
  72
  73                 public abstract TimeSpan GetUtcOffset (DateTime time);
  74
  75                 public virtual bool IsDaylightSavingTime (DateTime time)
  76                 {
  77                         return IsDaylightSavingTime (time, GetDaylightChanges (time.Year));
  78                 }
  79
  80                 public static bool IsDaylightSavingTime (DateTime time, DaylightTime daylightTimes)
  81                 {
  82                         if (daylightTimes == null)
  83                                 throw new ArgumentNullException ("daylightTimes");
  84
  85                         // If Start == End, then DST is off
  86                         if (daylightTimes.Start.Ticks == daylightTimes.End.Ticks)
  87                                 return false;
  88
  89                         //We are in the northern hemisphere.
  90                         if (daylightTimes.Start.Ticks < daylightTimes.End.Ticks) {
  91                                 if (daylightTimes.Start.Ticks < time.Ticks && daylightTimes.End.Ticks > time.Ticks)
  92                                         return true; // time lies between Start and End
  93
  94                         }
  95                         else {  // We are in the southern hemisphere.
  96                                 if (time.Year == daylightTimes.Start.Year && time.Year == daylightTimes.End.Year)
  97                                         if (time.Ticks < daylightTimes.End.Ticks || time.Ticks > daylightTimes.Start.Ticks)
  98                                                 return true; // time is less than End OR more than Start
  99                         }
 100
 101                         return false;
 102                 }
 103
 104                 public virtual DateTime ToLocalTime (DateTime time)
 105                 {
 106                         return time + GetUtcOffset (time);
 107                 }
 108
 109                 public virtual DateTime ToUniversalTime (DateTime time)
 110                 {
 111                         return time - GetUtcOffset (time);
 112                 }
 113         }
 114
 115         internal class CurrentTimeZone : TimeZone
 116         {
 117                 // Fields
 118                 private static string daylightName;
 119                 private static string standardName;
 120
 121                 // A yearwise cache of DaylightTime.
 122                 private static Hashtable daylightCache = new Hashtable (1);
 123
 124                 // the offset when daylightsaving is not on.
 125                 private static TimeSpan utcOffsetWithOutDLS;
 126
 127                 // the offset when daylightsaving is on.
 128                 private static TimeSpan utcOffsetWithDLS;
 129
 130                 internal enum TimeZoneData
 131                 {
 132                         DaylightSavingStartIdx,
 133                         DaylightSavingEndIdx,
 134                         UtcOffsetIdx,
 135                         AdditionalDaylightOffsetIdx
 136                 };
 137
 138                 internal enum TimeZoneNames
 139                 {
 140                         StandardNameIdx,
 141                         DaylightNameIdx
 142                 };
 143
 144                 // Internal method to get timezone data.
 145                 //    data[0]:  start of daylight saving time (in DateTime ticks).
 146                 //    data[1]:  end of daylight saving time (in DateTime ticks).
 147                 //    data[2]:  utcoffset (in TimeSpan ticks).
 148                 //    data[3]:  additional offset when daylight saving (in TimeSpan ticks).
 149                 //    name[0]:  name of this timezone when not daylight saving.
 150                 //    name[1]:  name of this timezone when daylight saving.
 151                 [MethodImplAttribute(MethodImplOptions.InternalCall)]
 152                 private static extern bool GetTimeZoneData (int year, out Int64[] data, out string[] names);
 153
 154                 // Constructor
 155                 internal CurrentTimeZone ()
 156                         : base ()
 157                 {
 158                         Int64[] data;
 159                         string[] names;
 160
 161                         DateTime now = new DateTime(DateTime.GetNow ());
 162                         if (!GetTimeZoneData (now.Year, out data, out names))
 163                                 throw new NotSupportedException (Locale.GetText ("Can't get timezone name."));
 164
 165                         standardName = Locale.GetText (names[(int)TimeZoneNames.StandardNameIdx]);
 166                         daylightName = Locale.GetText (names[(int)TimeZoneNames.DaylightNameIdx]);
 167
 168                         utcOffsetWithOutDLS = new TimeSpan (data[(int)TimeZoneData.UtcOffsetIdx]);
 169                         utcOffsetWithDLS = new TimeSpan (data[(int)TimeZoneData.UtcOffsetIdx]
 170                                 + data[(int)TimeZoneData.AdditionalDaylightOffsetIdx]);
 171                 }
 172
 173                 // Properties
 174                 public override string DaylightName {
 175                         get { return daylightName; }
 176                 }
 177
 178                 public override string StandardName {
 179                         get { return standardName; }
 180                 }
 181
 182                 // Methods
 183                 [MonoTODO]
 184                 public override DaylightTime GetDaylightChanges (int year)
 185                 {
 186                         if (year < 1 || year > 9999)
 187                                 throw new ArgumentOutOfRangeException ("year", year +
 188                                         Locale.GetText (" is not in a range between 1 and 9999."));
 189
 190                         if (daylightCache [year] == null) {
 191                                 lock (this) {
 192                                         if (daylightCache [year] == null) {
 193                                                 Int64[] data;
 194                                                 string[] names;
 195
 196                                                 if (!GetTimeZoneData (year, out data, out names))
 197                                                         throw new ArgumentException (Locale.GetText ("Can't get timezone data for " + year));
 198
 199                                                 DaylightTime dlt = new DaylightTime (new DateTime (data[(int)TimeZoneData.DaylightSavingStartIdx]),
 200                                                                                      new DateTime (data[(int)TimeZoneData.DaylightSavingEndIdx]),
 201                                                                                      new TimeSpan (data[(int)TimeZoneData.AdditionalDaylightOffsetIdx]));
 202                                                 daylightCache.Add (year, dlt);
 203                                         };
 204                                 };
 205                         }
 206
 207                         return (DaylightTime) daylightCache [year];
 208                 }
 209
 210                 public override TimeSpan GetUtcOffset (DateTime time)
 211                 {
 212                         if (IsDaylightSavingTime (time))
 213                                 return utcOffsetWithDLS;
 214
 215                         return utcOffsetWithOutDLS;
 216                 }
 217         }
 218 }