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