Merge pull request #801 from Unity-Technologies/unity-master-tz-fix-build (case 988428) (case 943047)

Support timezones without daylight savings time

Author: mderoy

mcs/class/corlib/System/TimeZoneInfo.Unity.cs

@@ -1,36 +1,13 @@
 //
-// System.TimeZoneInfo helper for MonoTouch
-// 	because the devices cannot access the file system to read the data
+// System.TimeZoneInfo helper for Unity
+//	because the devices cannot access the file system to read the data
 //
 // Authors:
-//	Sebastien Pouliot  <[email protected]>
-//
-// Copyright 2011-2013 Xamarin Inc.
-//
-// The class can be either constructed from a string (from user code)
-// or from a handle (from iphone-sharp.dll internal calls).  This
-// delays the creation of the actual managed string until actually
-// required
-//
-// Permission is hereby granted, free of charge, to any person obtaining
-// a copy of this software and associated documentation files (the
-// "Software"), to deal in the Software without restriction, including
-// without limitation the rights to use, copy, modify, merge, publish,
-// distribute, sublicense, and/or sell copies of the Software, and to
-// permit persons to whom the Software is furnished to do so, subject to
-// the following conditions:
-// 
-// The above copyright notice and this permission notice shall be
-// included in all copies or substantial portions of the Software.
-// 
-// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
-// EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
-// MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
-// NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE
-// LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION
-// OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
-// WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
+//	Michael DeRoy <[email protected]>
+//	Jonathan Chambers <[email protected]>
 //
+// Copyright 2018 Unity Technologies, Inc.
+// Licensed under the MIT license. See LICENSE file in the project root for full license information.
 
 #if UNITY
 
@@ -45,90 +22,100 @@ namespace System {
 	public partial class TimeZoneInfo {
 		enum TimeZoneData
 		{
-		    DaylightSavingStartIdx,
-		    DaylightSavingEndIdx,
-		    UtcOffsetIdx,
-		    AdditionalDaylightOffsetIdx
+			DaylightSavingStartIdx,
+			DaylightSavingEndIdx,
+			UtcOffsetIdx,
+			AdditionalDaylightOffsetIdx
 		};
 
 		enum TimeZoneNames
 		{
-		    StandardNameIdx,
-		    DaylightNameIdx
+			StandardNameIdx,
+			DaylightNameIdx
 		};
+
+		static AdjustmentRule CreateAdjustmentRule(int year, out Int64[] data, out string[] names, string standardNameCurrentYear, string daylightNameCurrentYear)
+		{
+			if(!System.CurrentSystemTimeZone.GetTimeZoneData(year, out data, out names))
+				return null;
+			var startTime = new DateTime (data[(int)TimeZoneData.DaylightSavingStartIdx]);
+			var endTime = new DateTime (data[(int)TimeZoneData.DaylightSavingEndIdx]);
+			var daylightOffset = new TimeSpan (data[(int)TimeZoneData.AdditionalDaylightOffsetIdx]);
+
+			/* C# TimeZoneInfo does not support timezones the same way as unix. In unix, timezone files are specified by region such as
+			 * America/New_York or Asia/Singapore. If a region like Asia/Singapore changes it's timezone from +0730 to +08, the UTC offset
+			 * has changed, but there is no support in the C# code to transition to this new UTC offset except for the case of daylight
+			 * savings time. As such we'll only generate timezone rules for a region at the times associated with the timezone of the current year.
+			 */
+			if(standardNameCurrentYear != names[(int)TimeZoneNames.StandardNameIdx])
+				return null;
+			if(daylightNameCurrentYear != names[(int)TimeZoneNames.DaylightNameIdx])
+				return null;
+
+			var dlsTransitionStart = TransitionTime.CreateFixedDateRule(new DateTime(1,1,1).Add(startTime.TimeOfDay),
+																				startTime.Month, startTime.Day);
+			var dlsTransitionEnd = TransitionTime.CreateFixedDateRule(new DateTime(1,1,1).Add(endTime.TimeOfDay),
+																				endTime.Month, endTime.Day);
+
+			var rule = TimeZoneInfo.AdjustmentRule.CreateAdjustmentRule(new DateTime(year, 1, 1),
+																				new DateTime(year, 12, DateTime.DaysInMonth(year, 12)),
+																				daylightOffset,
+																				dlsTransitionStart,
+																				dlsTransitionEnd);
+			return rule;
+		}
+
 		static TimeZoneInfo CreateLocalUnity ()
 		{
 			Int64[] data;
-		    string[] names;
-		    if (!System.CurrentSystemTimeZone.GetTimeZoneData (1973, out data, out names))
+			string[] names;
+			int currentYear = DateTime.UtcNow.Year;
+			if (!System.CurrentSystemTimeZone.GetTimeZoneData (currentYear, out data, out names))
 				throw new NotSupportedException ("Can't get timezone name.");
 
-		    TimeSpan utcOffsetTS = TimeSpan.FromTicks(data[(int)TimeZoneData.UtcOffsetIdx]);
-		    char utcOffsetSign = (utcOffsetTS >= TimeSpan.Zero) ? '+' : '-';
-		    string displayName = "(GMT" + utcOffsetSign + utcOffsetTS.ToString(@"hh\:mm") + ") Local Time";
-		    string standardDisplayName = names[(int)TimeZoneNames.StandardNameIdx];
-		    string daylightDisplayName = names[(int)TimeZoneNames.DaylightNameIdx];
-		    
-		    //Create The Adjustment Rules For This TimeZoneInfo.
-		    var adjustmentList = new List<TimeZoneInfo.AdjustmentRule>();
-		    for(int year = 1973; year <= 2037; year++)
-		    {	    
-				if (!System.CurrentSystemTimeZone.GetTimeZoneData (year, out data, out names))
-					continue;
-				
-				DaylightTime dlt = new DaylightTime (new DateTime (data[(int)TimeZoneData.DaylightSavingStartIdx]),
-								     new DateTime (data[(int)TimeZoneData.DaylightSavingEndIdx]),
-								     new TimeSpan (data[(int)TimeZoneData.AdditionalDaylightOffsetIdx]));
-				
-				DateTime dltStartTime = new DateTime(1, 1, 1).Add(dlt.Start.TimeOfDay);
-				DateTime dltEndTime = new DateTime(1, 1, 1).Add(dlt.End.TimeOfDay);
+			var utcOffsetTS = TimeSpan.FromTicks(data[(int)TimeZoneData.UtcOffsetIdx]);
+			char utcOffsetSign = (utcOffsetTS >= TimeSpan.Zero) ? '+' : '-';
+			string displayName = "(GMT" + utcOffsetSign + utcOffsetTS.ToString(@"hh\:mm") + ") Local Time";
+			string standardDisplayName = names[(int)TimeZoneNames.StandardNameIdx];
+			string daylightDisplayName = names[(int)TimeZoneNames.DaylightNameIdx];
 
-				if (dlt.Start == dlt.End)
-					continue;
+			var adjustmentList = new List<AdjustmentRule>();
+			bool disableDaylightSavings = data[(int)TimeZoneData.AdditionalDaylightOffsetIdx] <= 0;
+			//If the timezone supports daylight savings time, generate adjustment rules for the timezone
+			if(!disableDaylightSavings)
+			{
+				//the icall only supports years from 1970 through 2037.
+				int firstSupportedDate = 1970;
+				int lastSupportedDate = 2037;
 
-				TimeZoneInfo.TransitionTime startTime = TimeZoneInfo.TransitionTime.CreateFixedDateRule(dltStartTime, dlt.Start.Month, dlt.Start.Day);
-				TimeZoneInfo.TransitionTime endTime = TimeZoneInfo.TransitionTime.CreateFixedDateRule(dltEndTime, dlt.End.Month, dlt.End.Day);
-				
-
-				//mktime only supports dates starting in 1973, so create an adjustment rule for years before 1973 following 1973s rules 
-				if (year == 1973)
+				//first, generate rules from the current year until the last year mktime is guaranteed to supports
+				for(int year = currentYear; year <= lastSupportedDate; year++)
 				{
-				    TimeZoneInfo.AdjustmentRule firstRule = TimeZoneInfo.AdjustmentRule.CreateAdjustmentRule(DateTime.MinValue,
-															     new DateTime(1969, 12, 31),
-															     dlt.Delta,
-															     startTime,
-															     endTime);
-				    adjustmentList.Add(firstRule);
+					var rule = CreateAdjustmentRule(year, out data, out names, standardDisplayName, daylightDisplayName);
+					//breakout if timezone changes, or fails
+					if(rule == null)
+						break;
+					adjustmentList.Add(rule);
 				}
-				
-				TimeZoneInfo.AdjustmentRule rule = TimeZoneInfo.AdjustmentRule.CreateAdjustmentRule(new DateTime(year, 1, 1),
-														    new DateTime(year, 12, 31),
-														    dlt.Delta,
-														    startTime,
-														    endTime);
-				adjustmentList.Add(rule);
-				
-				//mktime only supports dates up to 2037, so create an adjustment rule for years after 2037 following 2037s rules 
-				if (year == 2037)
+
+				for(int year = currentYear - 1; year >= firstSupportedDate; year--)
 				{
-					// create a max date that does not include any time of day offset to make CreateAdjustmentRule happy
-					var maxDate = new DateTime(DateTime.MaxValue.Year, DateTime.MaxValue.Month, DateTime.MaxValue.Day);
-				    TimeZoneInfo.AdjustmentRule lastRule = TimeZoneInfo.AdjustmentRule.CreateAdjustmentRule(new DateTime(2038, 1, 1),
-				    											maxDate,
-															    dlt.Delta,
-															    startTime,
-															    endTime);
-				    adjustmentList.Add(lastRule);
+					var rule = CreateAdjustmentRule(year, out data, out names, standardDisplayName, daylightDisplayName);
+					//breakout if timezone changes, or fails
+					if(rule == null)
+						break;
+					adjustmentList.Add(rule);
 				}
-		    }
-		    
-		    return TimeZoneInfo.CreateCustomTimeZone("local",
-									   utcOffsetTS,
-									   displayName,
-									   standardDisplayName,
-									   daylightDisplayName,
-									   adjustmentList.ToArray(),
-									   false);
+
+				adjustmentList.Sort( (rule1, rule2) => rule1.DateStart.CompareTo(rule2.DateStart) );
+			}
+			return TimeZoneInfo.CreateCustomTimeZone("Local",
+								utcOffsetTS,
+								displayName,
+								standardDisplayName,
+								daylightDisplayName,
+								adjustmentList.ToArray(),
+								disableDaylightSavings);
 		}
 	}
 }