[monodroid] Add support for the Android TimeZone file format.

Fixes #657609.

Android uses "ye standard" timezone file format, but instead of using
a directory + file structure as libc uses, they throw everything into
two files, a "zoneinfo.dat" and a "zoneinfo.idx", where "zoneinfo.dat"
is the concatenation of all the TZIF files and "zoneinfo.idx" contains
the timezone names and offsets into "zoneinfo.dat".  From the
ZoneInfoDB documentation:

	However, to conserve disk space the data for all time zones
	are concatenated into a single file, and a second file is
	used to indicate the starting position of each time zone
	record.  A third file indicates the version of the zoneinfo
	databse used to generate the data.

TimeZoneInfo.Android.cs is a C# port of the corresponding Android
ZoneInfoDB type so that Mono can use Android's timezone DB.

4 files changed, 320 insertions, 5 deletions

diff --git a/LICENSE b/LICENSE
index d78a60a8525..0cb310e1126 100644
--- a/LICENSE
+++ b/LICENSE
@@ -98,6 +98,13 @@ For comments, corrections and updates, please contact mono@novell.com
             ICSharpCode.SharpZipLib, GPL with exceptions.
 		See: mcs/class/ICSharpCode.SharpZipLib/README
 
+** mcs/class/System.Core/System/TimeZoneInfo.Android.cs
+
+	This is a port of Apache 2.0-licensed Android code, and thus is
+	licensed under the Apache 2.0 license:
+
+	    http://www.apache.org/licenses/LICENSE-2.0
+
 	     
 ** mcs/tools
 
diff --git a/mcs/class/System.Core/System/TimeZoneInfo.Android.cs b/mcs/class/System.Core/System/TimeZoneInfo.Android.cs
new file mode 100644
index 00000000000..c95bb1ef15c
--- /dev/null
+++ b/mcs/class/System.Core/System/TimeZoneInfo.Android.cs
@@ -0,0 +1,299 @@
+/*
+ * System.TimeZoneInfo Android Support
+ *
+ * Author(s)
+ * 	Jonathan Pryor  <jpryor@novell.com>
+ * 	The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#if MONODROID
+
+using System;
+using System.Collections.Generic;
+using System.IO;
+using System.Runtime.CompilerServices;
+using System.Runtime.InteropServices;
+using System.Text;
+
+namespace System {
+
+	partial class TimeZoneInfo {
+
+		/*
+		 * Android Timezone support infrastructure.
+		 *
+		 * This is a C# port of org.apache.harmony.luni.internal.util.ZoneInfoDB:
+		 *
+		 *    http://android.git.kernel.org/?p=platform/libcore.git;a=blob;f=luni/src/main/java/org/apache/harmony/luni/internal/util/ZoneInfoDB.java;h=3e7bdc3a952b24da535806d434a3a27690feae26;hb=HEAD
+		 *
+		 * From the ZoneInfoDB source:
+		 *
+		 *    However, to conserve disk space the data for all time zones are 
+		 *    concatenated into a single file, and a second file is used to indicate 
+		 *    the starting position of each time zone record.  A third file indicates
+		 *    the version of the zoneinfo databse used to generate the data.
+		 *
+		 * which succinctly describes why we can't just use the LIBC implementation in
+		 * TimeZoneInfo.cs -- the "standard Unixy" directory structure is NOT used.
+		 */
+		static class ZoneInfoDB {
+			const int TimeZoneNameLength  = 40;
+			const int TimeZoneIntSize     = 4;
+
+			static readonly string ZoneDirectoryName  = Environment.GetEnvironmentVariable ("ANDROID_ROOT") + "/usr/share/zoneinfo/";
+			static readonly string ZoneFileName       = ZoneDirectoryName + "zoneinfo.dat";
+			static readonly string IndexFileName      = ZoneDirectoryName + "zoneinfo.idx";
+			const           string DefaultVersion     = "2007h";
+			static readonly string VersionFileName    = ZoneDirectoryName + "zoneinfo.version";
+
+			static readonly object _lock = new object ();
+
+			static readonly string    version;
+			static readonly string[]  names;
+			static readonly int[]     starts;
+			static readonly int[]     lengths;
+			static readonly int[]     offsets;
+
+			static ZoneInfoDB ()
+			{
+				try {
+					version = ReadVersion ();
+				} catch {
+					version = DefaultVersion;
+				}
+
+				try {
+					ReadDatabase (out names, out starts, out lengths, out offsets);
+				} catch {
+					names   = new string [0];
+					starts  = new int [0];
+					lengths = new int [0];
+					offsets = new int [0];
+				}
+			}
+
+			static string ReadVersion ()
+			{
+				using (var file = new StreamReader (VersionFileName, Encoding.GetEncoding ("iso-8859-1"))) {
+					return file.ReadToEnd ().Trim ();
+				}
+			}
+
+			static void ReadDatabase (out string[] names, out int[] starts, out int[] lengths, out int[] offsets)
+			{
+				using (var file = File.OpenRead (IndexFileName)) {
+					var nbuf = new byte [TimeZoneNameLength];
+
+					int numEntries = (int) (file.Length / (TimeZoneNameLength + 3*TimeZoneIntSize));
+
+					char[]  namebuf = new char [TimeZoneNameLength];
+
+					names   = new string [numEntries];
+					starts  = new int [numEntries];
+					lengths = new int [numEntries];
+					offsets = new int [numEntries];
+
+					for (int i = 0; i < numEntries; ++i) {
+						Fill (file, nbuf, nbuf.Length);
+						int namelen;
+						for (namelen = 0; namelen < nbuf.Length; ++namelen) {
+							if (nbuf [namelen] == '\0')
+								break;
+							namebuf [namelen] = (char) (nbuf [namelen] & 0xFF);
+						}
+
+						names   [i] = new string (namebuf, 0, namelen);
+						starts  [i] = ReadInt32 (file, nbuf);
+						lengths [i] = ReadInt32 (file, nbuf);
+						offsets [i] = ReadInt32 (file, nbuf);
+					}
+				}
+			}
+
+			static void Fill (Stream stream, byte[] nbuf, int required)
+			{
+				int read, offset = 0;
+				while (offset < required && (read = stream.Read (nbuf, offset, required - offset)) > 0)
+					offset += read;
+				if (read != required)
+					throw new EndOfStreamException ("Needed to read " + required + " bytes; read " + read + " bytes");
+			}
+
+			// From java.io.RandomAccessFioe.readInt(), as we need to use the same
+			// byte ordering as Java uses.
+			static int ReadInt32 (Stream stream, byte[] nbuf)
+			{
+				Fill (stream, nbuf, 4);
+				return ((nbuf [0] & 0xff) << 24) + ((nbuf [1] & 0xff) << 16) +
+					((nbuf [2] & 0xff) << 8) + (nbuf [3] & 0xff);
+			}
+
+			internal static string Version {
+				get {return version;}
+			}
+
+			internal static IEnumerable<string> GetAvailableIds ()
+			{
+				return GetAvailableIds (0, false);
+			}
+
+			internal static IEnumerable<string> GetAvailableIds (int rawOffset)
+			{
+				return GetAvailableIds (rawOffset, true);
+			}
+
+			static IEnumerable<string> GetAvailableIds (int rawOffset, bool checkOffset)
+			{
+				for (int i = 0; i < offsets.Length; ++i) {
+					if (!checkOffset || offsets [i] == rawOffset)
+						yield return names [i];
+				}
+			}
+
+			static TimeZoneInfo _GetTimeZone (string name)
+			{
+				int start, length;
+				using (var stream = GetTimeZoneData (name, out start, out length)) {
+					if (stream == null)
+						return null;
+					byte[] buf = new byte [length];
+					Fill (stream, buf, buf.Length);
+					return TimeZoneInfo.ParseTZBuffer (name, buf, length);
+				}
+			}
+
+			static FileStream GetTimeZoneData (string name, out int start, out int length)
+			{
+				var f = new FileInfo (Path.Combine (ZoneDirectoryName, name));
+				if (f.Exists) {
+					start   = 0;
+					length  = (int) f.Length;
+					return f.OpenRead ();
+				}
+
+				start = length = 0;
+
+				int i = Array.BinarySearch (names, name);
+				if (i < 0)
+					return null;
+
+				start   = starts [i];
+				length  = lengths [i];
+
+				var stream = File.OpenRead (ZoneFileName);
+				stream.Seek (start, SeekOrigin.Begin);
+
+				return stream;
+			}
+
+			internal static TimeZoneInfo GetTimeZone (string id)
+			{
+				if (id != null) {
+					if (id == "GMT" || id == "UTC")
+						return new TimeZoneInfo (id, TimeSpan.FromSeconds (0), id, id, id, null, true);
+					if (id.StartsWith ("GMT"))
+						return new TimeZoneInfo (id,
+								TimeSpan.FromSeconds (ParseNumericZone (id)),
+								id, id, id, null, true);
+				}
+
+				try {
+					return _GetTimeZone (id);
+				} catch (Exception e) {
+					return null;
+				}
+			}
+
+			static int ParseNumericZone (string name)
+			{
+				if (name == null || !name.StartsWith ("GMT") || name.Length <= 3)
+					return 0;
+
+				int sign;
+				if (name [3] == '+')
+					sign = 1;
+				else if (name [3] == '-')
+					sign = -1;
+				else
+					return 0;
+
+				int where;
+				int hour = 0;
+				bool colon = false;
+				for (where = 4; where < name.Length; where++) {
+					char c = name [where];
+
+					if (c == ':') {
+						where++;
+						colon = true;
+						break;
+					}
+
+					if (c >= '0' && c <= '9')
+						hour = hour * 10 + c - '0';
+					else
+						return 0;
+				}
+
+				int min = 0;
+				for (; where < name.Length; where++) {
+					char c = name [where];
+
+					if (c >= '0' && c <= '9')
+						min = min * 10 + c - '0';
+					else
+						return 0;
+				}
+
+				if (colon)
+					return sign * (hour * 60 + min) * 60;
+				else if (hour >= 100)
+					return sign * ((hour / 100) * 60 + (hour % 100)) * 60;
+				else
+					return sign * (hour * 60) * 60;
+			}
+
+			static TimeZoneInfo defaultZone;
+			internal static TimeZoneInfo Default {
+				get {
+					lock (_lock) {
+						if (defaultZone != null)
+							return defaultZone;
+						return defaultZone = GetTimeZone (GetDefaultTimeZoneName ());
+					}
+				}
+			}
+
+			// <sys/system_properties.h>
+			[DllImport ("/system/lib/libc.so")]
+			static extern int __system_property_get (string name, StringBuilder value);
+
+			const int MaxPropertyNameLength   = 32; // <sys/system_properties.h>
+			const int MaxPropertyValueLength  = 92; // <sys/system_properties.h>
+
+			static string GetDefaultTimeZoneName ()
+			{
+				var buf = new StringBuilder (MaxPropertyValueLength + 1);
+				int n = __system_property_get ("persist.sys.timezone", buf);
+				if (n > 0)
+					return buf.ToString ();
+				return null;
+			}
+		}
+	}
+}
+
+#endif // MONODROID
+
diff --git a/mcs/class/System.Core/System/TimeZoneInfo.cs b/mcs/class/System.Core/System/TimeZoneInfo.cs
index 67cafd775da..cb464b54ad9 100644
--- a/mcs/class/System.Core/System/TimeZoneInfo.cs
+++ b/mcs/class/System.Core/System/TimeZoneInfo.cs
@@ -35,10 +35,11 @@ using System.Runtime.CompilerServices;
 
 using System.Collections.Generic;
 using System.Collections.ObjectModel;
+using System.Linq;
 using System.Runtime.Serialization;
 using System.Text;
 
-#if LIBC
+#if LIBC || MONODROID
 using System.IO;
 using Mono;
 #endif
@@ -83,7 +84,9 @@ namespace System
 		public static TimeZoneInfo Local {
 			get { 
 				if (local == null) {
-#if LIBC
+#if MONODROID
+					local = ZoneInfoDB.Default;
+#elif LIBC
 					try {
 						local = FindSystemTimeZoneByFileName ("Local", "/etc/localtime");	
 					} catch {
@@ -320,7 +323,9 @@ namespace System
 				return FromRegistryKey(id, key);
 			}
 #endif
-#if LIBC	
+#if MONODROID
+			return ZoneInfoDB.GetTimeZone (id);
+#elif LIBC
 			string filepath = Path.Combine (TimeZoneDirectory, id);
 			return FindSystemTimeZoneByFileName (id, filepath);
 #else
@@ -522,7 +527,10 @@ namespace System
 					return new ReadOnlyCollection<TimeZoneInfo> (systemTimeZones);
 				}
 #endif
-#if LIBC
+#if MONODROID
+			systemTimeZones.AddRange (ZoneInfoDB.GetAvailableIds ()
+					.Select (id => ZoneInfoDB.GetTimeZone (id)));
+#elif LIBC
 				string[] continents = new string [] {"Africa", "America", "Antarctica", "Arctic", "Asia", "Atlantic", "Brazil", "Canada", "Chile", "Europe", "Indian", "Mexico", "Mideast", "Pacific", "US"};
 				foreach (string continent in continents) {
 					try {
@@ -782,7 +790,7 @@ namespace System
 			return adjustmentRules;
 		}
 
-#if LIBC
+#if LIBC || MONODROID
 		private static bool ValidTZFile (byte [] buffer, int length)
 		{
 			StringBuilder magic = new StringBuilder ();
diff --git a/mcs/class/System.Core/monodroid_System.Core.dll.sources b/mcs/class/System.Core/monodroid_System.Core.dll.sources
index 0129121538c..a1b6e09476d 100644
--- a/mcs/class/System.Core/monodroid_System.Core.dll.sources
+++ b/mcs/class/System.Core/monodroid_System.Core.dll.sources
@@ -1 +1,2 @@
 #include monodroid_bootstrap_System.Core.dll.sources
+System/TimeZoneInfo.Android.cs