mcs/class/corlib/System/TimeZone.cs

   1 //
   2 // System.TimeZone.cs
   3 //
   4 // Author: Duncan Mak (duncan@ximian.com)
   5 //         Ajay Kumar Dwivedi (adwiv@yahoo.com)
   6 //         Martin Baulig (martin@gnome.org)
   7 //
   8 // (C) Ximian, Inc.
   9 //
  10
  11 using System.Collections;
  12 using System.Globalization;
  13 using System.Runtime.CompilerServices;
  14
  15 namespace System {
  16
  17         [Serializable]
  18         public abstract class TimeZone
  19         {
  20                 // Fields
  21                 private static TimeZone currentTimeZone;
  22
  23                 // Constructor
  24                 protected TimeZone ()
  25                 {
  26                 }
  27
  28                 // Properties
  29                 public static TimeZone CurrentTimeZone
  30                 {
  31                         get {
  32                                 if (currentTimeZone == null)
  33                                         currentTimeZone = new CurrentTimeZone ();
  34
  35                                 return currentTimeZone;
  36                         }
  37                 }
  38
  39                 public abstract string DaylightName
  40                 {
  41                         get;
  42                 }
  43
  44                 public abstract string StandardName
  45                 {
  46                         get;
  47                 }
  48
  49                 // Methods
  50                 public abstract DaylightTime GetDaylightChanges (int year);
  51
  52                 public abstract TimeSpan GetUtcOffset (DateTime time);
  53
  54                 public virtual bool IsDaylightSavingTime (DateTime time)
  55                 {
  56                         return IsDaylightSavingTime (time, GetDaylightChanges (time.Year));
  57                 }
  58
  59                 public static bool IsDaylightSavingTime (DateTime time, DaylightTime daylightTimes)
  60                 {
  61                         if (daylightTimes == null)
  62                                 throw new ArgumentNullException ("daylightTimes");
  63
  64                         // If Start == End, then DST is off
  65                         if (daylightTimes.Start.Ticks == daylightTimes.End.Ticks)
  66                                 return false;
  67
  68                         //We are in the northern hemisphere.
  69                         if (daylightTimes.Start.Ticks < daylightTimes.End.Ticks) {
  70                                 if (daylightTimes.Start.Ticks < time.Ticks
  71                                     && daylightTimes.End.Ticks > time.Ticks)
  72                                         return true; // time lies between Start and End
  73
  74                         } else {  // We are in the southern hemisphere.
  75                                 if (time.Year == daylightTimes.Start.Year && time.Year == daylightTimes.End.Year)
  76                                         if (time.Ticks < daylightTimes.End.Ticks
  77                                             || time.Ticks > daylightTimes.Start.Ticks)
  78                                                 return true; // time is less than End OR more than Start
  79                         }
  80
  81                         return false;
  82                 }
  83
  84                 public virtual DateTime ToLocalTime (DateTime time)
  85                 {
  86                         return time + GetUtcOffset (time);
  87                 }
  88
  89                 public virtual DateTime ToUniversalTime (DateTime time)
  90                 {
  91                         return time - GetUtcOffset (time);
  92                 }
  93         }
  94
  95         internal class CurrentTimeZone : TimeZone
  96         {
  97                 // Fields
  98                 private static string daylightName;
  99                 private static string standardName;
 100
 101                 // A yearwise cache of DaylightTime.
 102                 private static Hashtable daylightCache = new Hashtable (1);
 103
 104                 // the offset when daylightsaving is not on.
 105                 private static TimeSpan utcOffsetWithOutDLS;
 106
 107                 // the offset when daylightsaving is on.
 108                 private static TimeSpan utcOffsetWithDLS;
 109
 110                 internal enum TimeZoneData {
 111                         DaylightSavingStartIdx,
 112                         DaylightSavingEndIdx,
 113                         UtcOffsetIdx,
 114                         AdditionalDaylightOffsetIdx
 115                 };
 116
 117                 internal enum TimeZoneNames {
 118                         StandardNameIdx,
 119                         DaylightNameIdx
 120                 };
 121
 122                 // Internal method to get timezone data.
 123                 //    data[0]:  start of daylight saving time (in DateTime ticks).
 124                 //    data[1]:  end of daylight saving time (in DateTime ticks).
 125                 //    data[2]:  utcoffset (in TimeSpan ticks).
 126                 //    data[3]:  additional offset when daylight saving (in TimeSpan ticks).
 127                 //    name[0]:  name of this timezone when not daylight saving.
 128                 //    name[1]:  name of this timezone when daylight saving.
 129                 [MethodImplAttribute(MethodImplOptions.InternalCall)]
 130                 private static extern bool GetTimeZoneData (int year,
 131                                                             out Int64[] data,
 132                                                             out string[] names);
 133
 134                 // Constructor
 135                 internal CurrentTimeZone ()
 136                         : base ()
 137                 {
 138                         Int64[] data;
 139                         string[] names;
 140
 141                         DateTime now = new DateTime(DateTime.GetNow ());
 142                         if (!GetTimeZoneData (now.Year, out data, out names))
 143                                 throw new NotSupportedException (Locale.GetText ("Can't get timezone name"));
 144
 145                         standardName = Locale.GetText (names[(int)TimeZoneNames.StandardNameIdx]);
 146                         daylightName = Locale.GetText (names[(int)TimeZoneNames.DaylightNameIdx]);
 147
 148                         utcOffsetWithOutDLS = new TimeSpan (data[(int)TimeZoneData.UtcOffsetIdx]);
 149                         utcOffsetWithDLS = new TimeSpan (data[(int)TimeZoneData.UtcOffsetIdx] + data[(int)TimeZoneData.AdditionalDaylightOffsetIdx]);
 150                 }
 151
 152                 // Properties
 153                 public override string DaylightName
 154                 {
 155                         get { return daylightName; }
 156                 }
 157
 158                 public override string StandardName
 159                 {
 160                         get { return standardName; }
 161                 }
 162
 163                 // Methods
 164                 [MonoTODO]
 165                 public override DaylightTime GetDaylightChanges (int year)
 166                 {
 167                         if (year < 1 || year > 9999)
 168                                 throw new ArgumentOutOfRangeException (year + " is not in a range between 1 and 9999.");
 169
 170                         if (daylightCache [year] == null) {
 171                                 lock (this) {
 172                                         if (daylightCache [year] == null) {
 173                                                 Int64[] data;
 174                                                 string[] names;
 175
 176                                                 if (!GetTimeZoneData (year, out data, out names))
 177                                                         throw new ArgumentException (Locale.GetText ("Can't get timezone data for " + year));
 178
 179                                                 DaylightTime dlt = new DaylightTime (new DateTime (data[(int)TimeZoneData.DaylightSavingStartIdx]),
 180                                                                                      new DateTime (data[(int)TimeZoneData.DaylightSavingEndIdx]),
 181                                                                                      new TimeSpan (data[(int)TimeZoneData.AdditionalDaylightOffsetIdx]));
 182                                                 daylightCache.Add (year, dlt);
 183                                         };
 184                                 };
 185                         }
 186
 187                         return (DaylightTime) daylightCache [year];
 188                 }
 189
 190                 public override TimeSpan GetUtcOffset (DateTime time)
 191                 {
 192                         if (IsDaylightSavingTime (time))
 193                                 return utcOffsetWithDLS;
 194
 195                         return utcOffsetWithOutDLS;
 196                 }
 197         }
 198 }