TimeZoneInfo.cs

/*
 * System.TimeZoneInfo
 *
 * Author(s)
 * 	Stephane Delcroix <stephane@delcroix.org>
 *
 * Copyright 2011 Xamarin Inc.
 *
 * 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.
 */

using System;
using System.Runtime.CompilerServices;
using System.Runtime.InteropServices;
using System.Threading;

#if !INSIDE_CORLIB && NET_4_0

[assembly:TypeForwardedTo (typeof(TimeZoneInfo))]

#elif INSIDE_CORLIB || (NET_3_5 && !NET_4_0 && !MOBILE)

using System.Collections.Generic;
using System.Collections.ObjectModel;
using System.Runtime.Serialization;
using System.Text;

#if LIBC || MONODROID
using System.IO;
using Mono;
#endif

using Microsoft.Win32;

namespace System
{
#if MOBILE
	[TypeForwardedFrom (Consts.AssemblySystem_Core)]
#elif NET_4_0
	[TypeForwardedFrom (Consts.AssemblySystemCore_3_5)]
#endif
	[SerializableAttribute]
#if NET_4_0 || !INSIDE_CORLIB
	public
#endif
	sealed partial class TimeZoneInfo : IEquatable<TimeZoneInfo>, ISerializable, IDeserializationCallback
	{
		TimeSpan baseUtcOffset;
		public TimeSpan BaseUtcOffset {
			get { return baseUtcOffset; }
		}

		string daylightDisplayName;
		public string DaylightName {
			get { 
				return supportsDaylightSavingTime
					? daylightDisplayName
					: string.Empty;
			}
		}

		string displayName;
		public string DisplayName {
			get { return displayName; }
		}

		string id;
		public string Id {
			get { return id; }
		}

		static TimeZoneInfo local;
		public static TimeZoneInfo Local {
			get { 
				var l = local;
				if (l == null) {
					l = CreateLocal ();
					if (l == null)
						throw new TimeZoneNotFoundException ();

					if (Interlocked.CompareExchange (ref local, l, null) != null)
						l = local;
				}

				return l;
			}
		}

		/*
			TimeZone transitions are stored when there is a change on the base offset.
		*/
		private List<KeyValuePair<DateTime, TimeType>> transitions;

		[StructLayout(LayoutKind.Sequential)]
		private struct SYSTEMTIME {
			short wYear;
			short wMonth;
			short wDayOfWeek;
			short wDay;
			short wHour;
			short wMinute;
			short wSecond;
			short wMilliseconds;
		}

		[StructLayout(LayoutKind.Sequential, CharSet=CharSet.Unicode)]
		private struct TIME_ZONE_INFORMATION {
			internal int Bias;
			[MarshalAs(UnmanagedType.ByValTStr, SizeConst=32)]
			internal string StandardName;
			internal SYSTEMTIME StandardDate;
			internal int StandardBias;
			[MarshalAs(UnmanagedType.ByValTStr, SizeConst=32)]
			internal string DaylightName;
			internal SYSTEMTIME DaylightDate;
			internal int DaylightBias;
		}

		[DllImport ("kernel32.dll", CallingConvention=CallingConvention.StdCall)]
		private extern static uint GetTimeZoneInformation(out TIME_ZONE_INFORMATION tzi);

		static TimeZoneInfo CreateLocal ()
		{
#if MONODROID
			return AndroidTimeZones.Local;
#elif MONOTOUCH
			using (Stream stream = GetMonoTouchData (null)) {
				return BuildFromStream ("Local", stream);
			}
#else
			if (IsWindows && LocalZoneKey != null) {
				/* Wine Mono hack: Wine doesn't set TimeZoneKeyName, so use
				GetTimeZoneInformation to get the name. This may not quite be
				correct because StandardName isn't the same as TimeZoneKeyName,
				but it is for all builtin Wine timezones at least.

				string name = (string)LocalZoneKey.GetValue ("TimeZoneKeyName");
				name = TrimSpecial (name);
				if (name != null) */
				TIME_ZONE_INFORMATION tzi;
				if (GetTimeZoneInformation(out tzi) <= 2)
					return TimeZoneInfo.FindSystemTimeZoneById (tzi.StandardName);
			}

			var tz = Environment.GetEnvironmentVariable ("TZ");
			if (tz != null) {
				if (tz == String.Empty)
					return Utc;
				try {
					return FindSystemTimeZoneByFileName (tz, Path.Combine (TimeZoneDirectory, tz));
				} catch {
					return Utc;
				}
			}

			try {
				return FindSystemTimeZoneByFileName ("Local", "/etc/localtime");	
			} catch {
				try {
					return FindSystemTimeZoneByFileName ("Local", Path.Combine (TimeZoneDirectory, "localtime"));	
				} catch {
					return null;
				}
			}
#endif
		}

		string standardDisplayName;
		public string StandardName {
			get { return standardDisplayName; }
		}

		bool supportsDaylightSavingTime;
		public bool SupportsDaylightSavingTime {
			get  { return supportsDaylightSavingTime; }
		}

		static TimeZoneInfo utc;
		public static TimeZoneInfo Utc {
			get {
				if (utc == null)
					utc = CreateCustomTimeZone ("UTC", new TimeSpan (0), "UTC", "UTC");
				return utc;
			}
		}
#if LIBC
		static string timeZoneDirectory;
		static string TimeZoneDirectory {
			get {
				if (timeZoneDirectory == null)
					timeZoneDirectory = "/usr/share/zoneinfo";
				return timeZoneDirectory;
			}
			set {
				ClearCachedData ();
				timeZoneDirectory = value;
			}
		}
#endif
		private AdjustmentRule [] adjustmentRules;

#if !NET_2_1
		/// <summary>
		/// Determine whether windows of not (taken Stephane Delcroix's code)
		/// </summary>
		private static bool IsWindows
		{
			get {
				int platform = (int) Environment.OSVersion.Platform;
				return ((platform != 4) && (platform != 6) && (platform != 128));
			}
		}
		
		/// <summary>
		/// Needed to trim misc garbage in MS registry keys
		/// </summary>
		private static string TrimSpecial (string str)
		{
			var Istart = 0;
			while (Istart < str.Length && !char.IsLetterOrDigit(str[Istart])) Istart++;
			var Iend = str.Length - 1;
			while (Iend > Istart && !char.IsLetterOrDigit(str[Iend])) Iend--;
			
			return str.Substring (Istart, Iend-Istart+1);
		}
		
		static RegistryKey timeZoneKey;
		static RegistryKey TimeZoneKey {
			get {
				if (timeZoneKey != null)
					return timeZoneKey;
				if (!IsWindows)
					return null;
				
				return timeZoneKey = Registry.LocalMachine.OpenSubKey (
					"SOFTWARE\\Microsoft\\Windows NT\\CurrentVersion\\Time Zones",
					false);
			}
		}
		
		static RegistryKey localZoneKey;
		static RegistryKey LocalZoneKey {
			get {
				if (localZoneKey != null)
					return localZoneKey;
				
				if (!IsWindows)
					return null;
				
				return localZoneKey = Registry.LocalMachine.OpenSubKey (
					"SYSTEM\\CurrentControlSet\\Control\\TimeZoneInformation", false);
			}
		}
#endif

		public static void ClearCachedData ()
		{
			local = null;
			utc = null;
			systemTimeZones = null;
		}

		public static DateTime ConvertTime (DateTime dateTime, TimeZoneInfo destinationTimeZone)
		{
			return ConvertTime (dateTime, dateTime.Kind == DateTimeKind.Utc ? TimeZoneInfo.Utc : TimeZoneInfo.Local, destinationTimeZone);
		}

		public static DateTime ConvertTime (DateTime dateTime, TimeZoneInfo sourceTimeZone, TimeZoneInfo destinationTimeZone)
		{
			if (sourceTimeZone == null)
				throw new ArgumentNullException ("sourceTimeZone");

			if (destinationTimeZone == null)
				throw new ArgumentNullException ("destinationTimeZone");
			
			if (dateTime.Kind == DateTimeKind.Local && sourceTimeZone != TimeZoneInfo.Local)
				throw new ArgumentException ("Kind property of dateTime is Local but the sourceTimeZone does not equal TimeZoneInfo.Local");

			if (dateTime.Kind == DateTimeKind.Utc && sourceTimeZone != TimeZoneInfo.Utc)
				throw new ArgumentException ("Kind property of dateTime is Utc but the sourceTimeZone does not equal TimeZoneInfo.Utc");
			
			if (sourceTimeZone.IsInvalidTime (dateTime))
				throw new ArgumentException ("dateTime parameter is an invalid time");

			if (dateTime.Kind == DateTimeKind.Local && sourceTimeZone == TimeZoneInfo.Local && destinationTimeZone == TimeZoneInfo.Local)
				return dateTime;

			DateTime utc = ConvertTimeToUtc (dateTime);

			if (destinationTimeZone != TimeZoneInfo.Utc) {
				utc = ConvertTimeFromUtc (utc, destinationTimeZone);
				if (dateTime.Kind == DateTimeKind.Unspecified)
					return DateTime.SpecifyKind (utc, DateTimeKind.Unspecified);
			}
			
			return utc;
		}

		public static DateTimeOffset ConvertTime(DateTimeOffset dateTimeOffset, TimeZoneInfo destinationTimeZone) 
		{
			if (destinationTimeZone == null) 
				throw new ArgumentNullException("destinationTimeZone");
		
			var utcDateTime = dateTimeOffset.UtcDateTime;
			AdjustmentRule rule = destinationTimeZone.GetApplicableRule (utcDateTime);
		
			if (rule != null && destinationTimeZone.IsDaylightSavingTime(utcDateTime)) {
				var offset = destinationTimeZone.BaseUtcOffset + rule.DaylightDelta;
				return new DateTimeOffset(DateTime.SpecifyKind(utcDateTime, DateTimeKind.Unspecified) + offset, offset);
			}
			else {
				return new DateTimeOffset(DateTime.SpecifyKind(utcDateTime, DateTimeKind.Unspecified) + destinationTimeZone.BaseUtcOffset, destinationTimeZone.BaseUtcOffset);
			}
		}

		public static DateTime ConvertTimeBySystemTimeZoneId (DateTime dateTime, string destinationTimeZoneId)
		{
			return ConvertTime (dateTime, FindSystemTimeZoneById (destinationTimeZoneId));
		}

		public static DateTime ConvertTimeBySystemTimeZoneId (DateTime dateTime, string sourceTimeZoneId, string destinationTimeZoneId)
		{
			return ConvertTime (dateTime, FindSystemTimeZoneById (sourceTimeZoneId), FindSystemTimeZoneById (destinationTimeZoneId));
		}

		public static DateTimeOffset ConvertTimeBySystemTimeZoneId (DateTimeOffset dateTimeOffset, string destinationTimeZoneId)
		{
			return ConvertTime (dateTimeOffset, FindSystemTimeZoneById (destinationTimeZoneId));
		}

		private DateTime ConvertTimeFromUtc (DateTime dateTime)
		{
			if (dateTime.Kind == DateTimeKind.Local)
				throw new ArgumentException ("Kind property of dateTime is Local");

			if (this == TimeZoneInfo.Utc)
				return DateTime.SpecifyKind (dateTime, DateTimeKind.Utc);
			
			//FIXME: do not rely on DateTime implementation !
			if (this == TimeZoneInfo.Local) 
			{
#if NET_4_0
				return dateTime.ToLocalTime ();
#else
				return DateTime.SpecifyKind (dateTime.ToLocalTime (), DateTimeKind.Unspecified);
#endif
			}


			AdjustmentRule rule = GetApplicableRule (dateTime);
			if (rule != null && IsDaylightSavingTime (DateTime.SpecifyKind (dateTime, DateTimeKind.Utc)))
				return DateTime.SpecifyKind (dateTime + BaseUtcOffset + rule.DaylightDelta , DateTimeKind.Unspecified);
			else
				return DateTime.SpecifyKind (dateTime + BaseUtcOffset, DateTimeKind.Unspecified);
		}

		public static DateTime ConvertTimeFromUtc (DateTime dateTime, TimeZoneInfo destinationTimeZone)
		{
			if (destinationTimeZone == null)
				throw new ArgumentNullException ("destinationTimeZone");

			return destinationTimeZone.ConvertTimeFromUtc (dateTime);
		}

		public static DateTime ConvertTimeToUtc (DateTime dateTime)
		{
			if (dateTime.Kind == DateTimeKind.Utc)
				return dateTime;

			return ConvertTimeToUtc (dateTime, TimeZoneInfo.Local);
		}

		public static DateTime ConvertTimeToUtc (DateTime dateTime, TimeZoneInfo sourceTimeZone)
		{
			if (sourceTimeZone == null)
				throw new ArgumentNullException ("sourceTimeZone");

			if (dateTime.Kind == DateTimeKind.Utc && sourceTimeZone != TimeZoneInfo.Utc)
				throw new ArgumentException ("Kind property of dateTime is Utc but the sourceTimeZone does not equal TimeZoneInfo.Utc");

			if (dateTime.Kind == DateTimeKind.Local && sourceTimeZone != TimeZoneInfo.Local)
				throw new ArgumentException ("Kind property of dateTime is Local but the sourceTimeZone does not equal TimeZoneInfo.Local");

			if (sourceTimeZone.IsInvalidTime (dateTime))
				throw new ArgumentException ("dateTime parameter is an invalid time");

			if (dateTime.Kind == DateTimeKind.Utc)
				return dateTime;

			if (sourceTimeZone.IsAmbiguousTime (dateTime) || !sourceTimeZone.IsDaylightSavingTime (dateTime))
				return DateTime.SpecifyKind (dateTime - sourceTimeZone.BaseUtcOffset, DateTimeKind.Utc);
			else {
				AdjustmentRule rule = sourceTimeZone.GetApplicableRule (dateTime);
				if (rule != null)
					return DateTime.SpecifyKind (dateTime - sourceTimeZone.BaseUtcOffset - rule.DaylightDelta, DateTimeKind.Utc);
				else
					return DateTime.SpecifyKind (dateTime - sourceTimeZone.BaseUtcOffset, DateTimeKind.Utc);
			}
		}

		public static TimeZoneInfo CreateCustomTimeZone (string id, TimeSpan baseUtcOffset, string displayName, string standardDisplayName) 
		{
			return CreateCustomTimeZone (id, baseUtcOffset, displayName, standardDisplayName, null, null, true);
		}

		public static TimeZoneInfo CreateCustomTimeZone (string id, TimeSpan baseUtcOffset, string displayName, string standardDisplayName, string daylightDisplayName, TimeZoneInfo.AdjustmentRule [] adjustmentRules)
		{
			return CreateCustomTimeZone (id, baseUtcOffset, displayName, standardDisplayName, daylightDisplayName, adjustmentRules, false);
		}

		public static TimeZoneInfo CreateCustomTimeZone ( string id, TimeSpan baseUtcOffset, string displayName, string standardDisplayName, string daylightDisplayName, TimeZoneInfo.AdjustmentRule [] adjustmentRules, bool disableDaylightSavingTime)
		{
			return new TimeZoneInfo (id, baseUtcOffset, displayName, standardDisplayName, daylightDisplayName, adjustmentRules, disableDaylightSavingTime);
		}

#if NET_4_5
		public override bool Equals (object obj)
		{
			return Equals (obj as TimeZoneInfo);
		}
#endif

		public bool Equals (TimeZoneInfo other)
		{
			if (other == null)
				return false;

			return other.Id == this.Id && HasSameRules (other);
		}

		public static TimeZoneInfo FindSystemTimeZoneById (string id)
		{
			//FIXME: this method should check for cached values in systemTimeZones
			if (id == null)
				throw new ArgumentNullException ("id");
#if !NET_2_1
			if (TimeZoneKey != null)
			{
				RegistryKey key = TimeZoneKey.OpenSubKey (id, false);
				if (key == null)
					throw new TimeZoneNotFoundException ();
				return FromRegistryKey(id, key);
			}
#endif
#if MONODROID
			var timeZoneInfo = AndroidTimeZones.GetTimeZone (id, id);
			if (timeZoneInfo == null)
				throw new TimeZoneNotFoundException ();
			return timeZoneInfo;
#else
			// Local requires special logic that already exists in the Local property (bug #326)
			if (id == "Local")
				return Local;
#if MONOTOUCH
			using (Stream stream = GetMonoTouchData (id)) {
				return BuildFromStream (id, stream);
			}
#elif LIBC
			string filepath = Path.Combine (TimeZoneDirectory, id);
			return FindSystemTimeZoneByFileName (id, filepath);
#else
			throw new NotImplementedException ();
#endif
#endif
		}

#if LIBC
		private static TimeZoneInfo FindSystemTimeZoneByFileName (string id, string filepath)
		{
			if (!File.Exists (filepath))
				throw new TimeZoneNotFoundException ();

			using (FileStream stream = File.OpenRead (filepath)) {
				return BuildFromStream (id, stream);
			}
		}
#endif
#if LIBC || MONOTOUCH
		const int BUFFER_SIZE = 16384; //Big enough for any tz file (on Oct 2008, all tz files are under 10k)
		
		private static TimeZoneInfo BuildFromStream (string id, Stream stream) 
		{
			byte [] buffer = new byte [BUFFER_SIZE];
			int length = stream.Read (buffer, 0, BUFFER_SIZE);
			
			if (!ValidTZFile (buffer, length))
				throw new InvalidTimeZoneException ("TZ file too big for the buffer");

			try {
				return ParseTZBuffer (id, buffer, length);
			} catch (Exception e) {
				throw new InvalidTimeZoneException (e.Message);
			}
		}
#endif

#if !NET_2_1
		private static TimeZoneInfo FromRegistryKey (string id, RegistryKey key)
		{
			byte [] reg_tzi = (byte []) key.GetValue ("TZI");

			if (reg_tzi == null)
				throw new InvalidTimeZoneException ();

			int bias = BitConverter.ToInt32 (reg_tzi, 0);
			TimeSpan baseUtcOffset = new TimeSpan (0, -bias, 0);

			string display_name = (string) key.GetValue ("Display");
			string standard_name = (string) key.GetValue ("Std");
			string daylight_name = (string) key.GetValue ("Dlt");

			List<AdjustmentRule> adjustmentRules = new List<AdjustmentRule> ();

			RegistryKey dst_key = key.OpenSubKey ("Dynamic DST", false);
			if (dst_key != null) {
				int first_year = (int) dst_key.GetValue ("FirstEntry");
				int last_year = (int) dst_key.GetValue ("LastEntry");
				int year;

				for (year=first_year; year<=last_year; year++) {
					byte [] dst_tzi = (byte []) dst_key.GetValue (year.ToString ());
					if (dst_tzi != null) {
						int start_year = year == first_year ? 1 : year;
						int end_year = year == last_year ? 9999 : year;
						ParseRegTzi(adjustmentRules, start_year, end_year, dst_tzi);
					}
				}
			}
			else
				ParseRegTzi(adjustmentRules, 1, 9999, reg_tzi);

			return CreateCustomTimeZone (id, baseUtcOffset, display_name, standard_name, daylight_name, ValidateRules (adjustmentRules).ToArray ());
		}

		private static void ParseRegTzi (List<AdjustmentRule> adjustmentRules, int start_year, int end_year, byte [] buffer)
		{
			//int standard_bias = BitConverter.ToInt32 (buffer, 4); /* not sure how to handle this */
			int daylight_bias = BitConverter.ToInt32 (buffer, 8);

			int standard_year = BitConverter.ToInt16 (buffer, 12);
			int standard_month = BitConverter.ToInt16 (buffer, 14);
			int standard_dayofweek = BitConverter.ToInt16 (buffer, 16);
			int standard_day = BitConverter.ToInt16 (buffer, 18);
			int standard_hour = BitConverter.ToInt16 (buffer, 20);
			int standard_minute = BitConverter.ToInt16 (buffer, 22);
			int standard_second = BitConverter.ToInt16 (buffer, 24);
			int standard_millisecond = BitConverter.ToInt16 (buffer, 26);

			int daylight_year = BitConverter.ToInt16 (buffer, 28);
			int daylight_month = BitConverter.ToInt16 (buffer, 30);
			int daylight_dayofweek = BitConverter.ToInt16 (buffer, 32);
			int daylight_day = BitConverter.ToInt16 (buffer, 34);
			int daylight_hour = BitConverter.ToInt16 (buffer, 36);
			int daylight_minute = BitConverter.ToInt16 (buffer, 38);
			int daylight_second = BitConverter.ToInt16 (buffer, 40);
			int daylight_millisecond = BitConverter.ToInt16 (buffer, 42);

			if (standard_month == 0 || daylight_month == 0)
				return;

			DateTime start_date;
			DateTime start_timeofday = new DateTime (1, 1, 1, daylight_hour, daylight_minute, daylight_second, daylight_millisecond);
			TransitionTime start_transition_time;

			if (daylight_year == 0) {
				start_date = new DateTime (start_year, 1, 1);
				start_transition_time = TransitionTime.CreateFloatingDateRule (
					start_timeofday, daylight_month, daylight_day,
					(DayOfWeek) daylight_dayofweek);
			}
			else {
				start_date = new DateTime (daylight_year, daylight_month, daylight_day,
					daylight_hour, daylight_minute, daylight_second, daylight_millisecond);
				start_transition_time = TransitionTime.CreateFixedDateRule (
					start_timeofday, daylight_month, daylight_day);
			}

			DateTime end_date;
			DateTime end_timeofday = new DateTime (1, 1, 1, standard_hour, standard_minute, standard_second, standard_millisecond);
			TransitionTime end_transition_time;

			if (standard_year == 0) {
				end_date = new DateTime (end_year, 12, 31);
				end_transition_time = TransitionTime.CreateFloatingDateRule (
					end_timeofday, standard_month, standard_day,
					(DayOfWeek) standard_dayofweek);
			}
			else {
				end_date = new DateTime (standard_year, standard_month, standard_day,
					standard_hour, standard_minute, standard_second, standard_millisecond);
				end_transition_time = TransitionTime.CreateFixedDateRule (
					end_timeofday, standard_month, standard_day);
			}

			TimeSpan daylight_delta = new TimeSpan(0, -daylight_bias, 0);

			adjustmentRules.Add (AdjustmentRule.CreateAdjustmentRule (
				start_date, end_date, daylight_delta,
				start_transition_time, end_transition_time));
		}
#endif

		public AdjustmentRule [] GetAdjustmentRules ()
		{
			if (!supportsDaylightSavingTime)
				return new AdjustmentRule [0];
			else
				return (AdjustmentRule []) adjustmentRules.Clone ();
		}

		public TimeSpan [] GetAmbiguousTimeOffsets (DateTime dateTime)
		{
			if (!IsAmbiguousTime (dateTime))
				throw new ArgumentException ("dateTime is not an ambiguous time");

			AdjustmentRule rule = GetApplicableRule (dateTime);
			if (rule != null)
				return new TimeSpan[] {baseUtcOffset, baseUtcOffset + rule.DaylightDelta};
			else
				return new TimeSpan[] {baseUtcOffset, baseUtcOffset};
		}

		public TimeSpan [] GetAmbiguousTimeOffsets (DateTimeOffset dateTimeOffset)
		{
			if (!IsAmbiguousTime (dateTimeOffset))
				throw new ArgumentException ("dateTimeOffset is not an ambiguous time");

			throw new NotImplementedException ();
		}

		public override int GetHashCode ()
		{
			int hash_code = Id.GetHashCode ();
			foreach (AdjustmentRule rule in GetAdjustmentRules ())
				hash_code ^= rule.GetHashCode ();
			return hash_code;
		}

#if NET_4_0
		void ISerializable.GetObjectData (SerializationInfo info, StreamingContext context)
#else
		public void GetObjectData (SerializationInfo info, StreamingContext context)
#endif
		{
			if (info == null)
				throw new ArgumentNullException ("info");
			info.AddValue ("Id", id);
			info.AddValue ("DisplayName", displayName);
			info.AddValue ("StandardName", standardDisplayName);
			info.AddValue ("DaylightName", daylightDisplayName);
			info.AddValue ("BaseUtcOffset", baseUtcOffset);
			info.AddValue ("AdjustmentRules", adjustmentRules);
			info.AddValue ("SupportsDaylightSavingTime", SupportsDaylightSavingTime);
		}

		//FIXME: change this to a generic Dictionary and allow caching for FindSystemTimeZoneById
		private static List<TimeZoneInfo> systemTimeZones;
		public static ReadOnlyCollection<TimeZoneInfo> GetSystemTimeZones ()
		{
			if (systemTimeZones == null) {
				systemTimeZones = new List<TimeZoneInfo> ();
#if !NET_2_1
				if (TimeZoneKey != null) {
					foreach (string id in TimeZoneKey.GetSubKeyNames ()) {
						try {
							systemTimeZones.Add (FindSystemTimeZoneById (id));
						} catch {}
					}

					return new ReadOnlyCollection<TimeZoneInfo> (systemTimeZones);
				}
#endif
#if MONODROID
			foreach (string id in AndroidTimeZones.GetAvailableIds ()) {
				var tz = AndroidTimeZones.GetTimeZone (id, id);
				if (tz != null)
					systemTimeZones.Add (tz);
			}
#elif MONOTOUCH
				if (systemTimeZones.Count == 0) {
					foreach (string name in GetMonoTouchNames ()) {
						using (Stream stream = GetMonoTouchData (name, false)) {
							if (stream == null)
								continue;
							systemTimeZones.Add (BuildFromStream (name, stream));
						}
					}
				}
#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 {
						foreach (string zonepath in Directory.GetFiles (Path.Combine (TimeZoneDirectory, continent))) {
							try {
								string id = String.Format ("{0}/{1}", continent, Path.GetFileName (zonepath));
								systemTimeZones.Add (FindSystemTimeZoneById (id));
							} catch (ArgumentNullException) {
							} catch (TimeZoneNotFoundException) {
							} catch (InvalidTimeZoneException) {
							} catch (Exception) {
								throw;
							}
						}
					} catch {}
				}
#else
				throw new NotImplementedException ("This method is not implemented for this platform");
#endif
			}
			return new ReadOnlyCollection<TimeZoneInfo> (systemTimeZones);
		}

		public TimeSpan GetUtcOffset (DateTime dateTime)
		{
			bool isDST;
			return GetUtcOffset (dateTime, out isDST);
		}

		public TimeSpan GetUtcOffset (DateTimeOffset dateTimeOffset)
		{
			throw new NotImplementedException ();
		}

		private TimeSpan GetUtcOffset (DateTime dateTime, out bool isDST)
		{
			isDST = false;

			TimeZoneInfo tz = this;
			if (dateTime.Kind == DateTimeKind.Utc)
				tz = TimeZoneInfo.Utc;

			if (dateTime.Kind == DateTimeKind.Local)
				tz = TimeZoneInfo.Local;

			bool isTzDst;
			var tzOffset = GetUtcOffset (dateTime, tz, out isTzDst);

			if (tz == this) {
				isDST = isTzDst;
				return tzOffset;
			}

			var utcTicks = dateTime.Ticks - tzOffset.Ticks;
			if (utcTicks < 0 || utcTicks > DateTime.MaxValue.Ticks)
				return BaseUtcOffset;

			var utcDateTime = new DateTime (utcTicks, DateTimeKind.Utc);

			return GetUtcOffset (utcDateTime, this, out isDST);
		}

		private static TimeSpan GetUtcOffset (DateTime dateTime, TimeZoneInfo tz, out bool isDST)
		{
			if (dateTime.Kind == DateTimeKind.Local && tz != TimeZoneInfo.Local)
				throw new Exception ();

			isDST = false;

			if (tz == TimeZoneInfo.Utc)
				return TimeSpan.Zero;

			TimeSpan offset;
			if (tz.TryGetTransitionOffset(dateTime, out offset, out isDST))
				return offset;

			if (dateTime.Kind == DateTimeKind.Utc) {
				var utcRule = tz.GetApplicableRule (dateTime);
				if (utcRule != null && tz.IsInDST (utcRule, dateTime)) {
					isDST = true;
					return tz.BaseUtcOffset + utcRule.DaylightDelta;
				}

				return tz.BaseUtcOffset;
			}

			var stdTicks = dateTime.Ticks - tz.BaseUtcOffset.Ticks;
			if (stdTicks < 0 || stdTicks > DateTime.MaxValue.Ticks)
				return tz.BaseUtcOffset;

			var stdUtcDateTime = new DateTime (stdTicks, DateTimeKind.Utc);
			var tzRule = tz.GetApplicableRule (stdUtcDateTime);

			DateTime dstUtcDateTime = DateTime.MinValue;
			if (tzRule != null) {
				var dstTicks = stdUtcDateTime.Ticks - tzRule.DaylightDelta.Ticks;
				if (dstTicks < 0 || dstTicks > DateTime.MaxValue.Ticks)
					return tz.BaseUtcOffset;

				dstUtcDateTime = new DateTime (dstTicks, DateTimeKind.Utc);
			}

			if (tzRule != null && tz.IsInDST (tzRule, stdUtcDateTime) && tz.IsInDST (tzRule, dstUtcDateTime)) {
				isDST = true;
				return tz.BaseUtcOffset + tzRule.DaylightDelta;
			}

			return tz.BaseUtcOffset;
		}

		public bool HasSameRules (TimeZoneInfo other)
		{
			if (other == null)
				throw new ArgumentNullException ("other");

			if ((this.adjustmentRules == null) != (other.adjustmentRules == null))
				return false;

			if (this.adjustmentRules == null)
      				return true;

			if (this.BaseUtcOffset != other.BaseUtcOffset)
				return false;

			if (this.adjustmentRules.Length != other.adjustmentRules.Length)
				return false;

			for (int i = 0; i < adjustmentRules.Length; i++) {
				if (! (this.adjustmentRules [i]).Equals (other.adjustmentRules [i]))
					return false;
			}
			
			return true;
		}

		public bool IsAmbiguousTime (DateTime dateTime)
		{
			if (dateTime.Kind == DateTimeKind.Local && IsInvalidTime (dateTime))
				throw new ArgumentException ("Kind is Local and time is Invalid");

			if (this == TimeZoneInfo.Utc)
				return false;
			
			if (dateTime.Kind == DateTimeKind.Utc)
				dateTime = ConvertTimeFromUtc (dateTime);

			if (dateTime.Kind == DateTimeKind.Local && this != TimeZoneInfo.Local)
				dateTime = ConvertTime (dateTime, TimeZoneInfo.Local, this);

			AdjustmentRule rule = GetApplicableRule (dateTime);
			if (rule != null) {
				DateTime tpoint = TransitionPoint (rule.DaylightTransitionEnd, dateTime.Year);
				if (dateTime > tpoint - rule.DaylightDelta  && dateTime <= tpoint)
					return true;
			}
				
			return false;
		}

		public bool IsAmbiguousTime (DateTimeOffset dateTimeOffset)
		{
			throw new NotImplementedException ();
		}

		private bool IsInDST (AdjustmentRule rule, DateTime dateTime)
		{
			// Check whether we're in the dateTime year's DST period
			if (IsInDSTForYear (rule, dateTime, dateTime.Year))
				return true;

			// We might be in the dateTime previous year's DST period
			return IsInDSTForYear (rule, dateTime, dateTime.Year - 1);
		}

		bool IsInDSTForYear (AdjustmentRule rule, DateTime dateTime, int year)
		{
			DateTime DST_start = TransitionPoint (rule.DaylightTransitionStart, year);
			DateTime DST_end = TransitionPoint (rule.DaylightTransitionEnd, year + ((rule.DaylightTransitionStart.Month < rule.DaylightTransitionEnd.Month) ? 0 : 1));
			if (dateTime.Kind == DateTimeKind.Utc) {
				DST_start -= BaseUtcOffset;
				DST_end -= (BaseUtcOffset + rule.DaylightDelta);
			}

			return (dateTime >= DST_start && dateTime < DST_end);
		}
		
		public bool IsDaylightSavingTime (DateTime dateTime)
		{
			if (dateTime.Kind == DateTimeKind.Local && IsInvalidTime (dateTime))
				throw new ArgumentException ("dateTime is invalid and Kind is Local");

			if (this == TimeZoneInfo.Utc)
				return false;
			
			if (!SupportsDaylightSavingTime)
				return false;

			bool isDst;
			GetUtcOffset (dateTime, out isDst);

			return isDst;
		}

		public bool IsDaylightSavingTime (DateTimeOffset dateTimeOffset)
		{
			throw new NotImplementedException ();
		}

		public bool IsInvalidTime (DateTime dateTime)
		{
			if (dateTime.Kind == DateTimeKind.Utc)
				return false;
			if (dateTime.Kind == DateTimeKind.Local && this != Local)
				return false;

			AdjustmentRule rule = GetApplicableRule (dateTime);
			if (rule != null) {
				DateTime tpoint = TransitionPoint (rule.DaylightTransitionStart, dateTime.Year);
				if (dateTime >= tpoint && dateTime < tpoint + rule.DaylightDelta)
					return true;
			}
				
			return false;
		}

#if NET_4_0
		void IDeserializationCallback.OnDeserialization (object sender)
#else
		public void OnDeserialization (object sender)
#endif
		{
			try {
					TimeZoneInfo.Validate (id, baseUtcOffset, adjustmentRules);
				} catch (ArgumentException ex) {
					throw new SerializationException ("invalid serialization data", ex);
				}
 		}

		private static void Validate (string id, TimeSpan baseUtcOffset, AdjustmentRule [] adjustmentRules)
		{
			if (id == null)
				throw new ArgumentNullException ("id");

			if (id == String.Empty)
				throw new ArgumentException ("id parameter is an empty string");

			if (baseUtcOffset.Ticks % TimeSpan.TicksPerMinute != 0)
				throw new ArgumentException ("baseUtcOffset parameter does not represent a whole number of minutes");

			if (baseUtcOffset > new TimeSpan (14, 0, 0) || baseUtcOffset < new TimeSpan (-14, 0, 0))
				throw new ArgumentOutOfRangeException ("baseUtcOffset parameter is greater than 14 hours or less than -14 hours");

#if STRICT
			if (id.Length > 32)
				throw new ArgumentException ("id parameter shouldn't be longer than 32 characters");
#endif

			if (adjustmentRules != null && adjustmentRules.Length != 0) {
				AdjustmentRule prev = null;
				foreach (AdjustmentRule current in adjustmentRules) {
					if (current == null)
						throw new InvalidTimeZoneException ("one or more elements in adjustmentRules are null");

					if ((baseUtcOffset + current.DaylightDelta < new TimeSpan (-14, 0, 0)) ||
							(baseUtcOffset + current.DaylightDelta > new TimeSpan (14, 0, 0)))
						throw new InvalidTimeZoneException ("Sum of baseUtcOffset and DaylightDelta of one or more object in adjustmentRules array is greater than 14 or less than -14 hours;");

					if (prev != null && prev.DateStart > current.DateStart)
						throw new InvalidTimeZoneException ("adjustment rules specified in adjustmentRules parameter are not in chronological order");
					
					if (prev != null && prev.DateEnd > current.DateStart)
						throw new InvalidTimeZoneException ("some adjustment rules in the adjustmentRules parameter overlap");

					if (prev != null && prev.DateEnd == current.DateStart)
						throw new InvalidTimeZoneException ("a date can have multiple adjustment rules applied to it");

					prev = current;
				}
			}
		}
		
		public override string ToString ()
		{
			return DisplayName;
		}

		private TimeZoneInfo (SerializationInfo info, StreamingContext context)
		{
			if (info == null)
				throw new ArgumentNullException ("info");
			id = (string) info.GetValue ("Id", typeof (string));
			displayName = (string) info.GetValue ("DisplayName", typeof (string));
			standardDisplayName = (string) info.GetValue ("StandardName", typeof (string));
			daylightDisplayName = (string) info.GetValue ("DaylightName", typeof (string));
			baseUtcOffset = (TimeSpan) info.GetValue ("BaseUtcOffset", typeof (TimeSpan));
			adjustmentRules = (TimeZoneInfo.AdjustmentRule []) info.GetValue ("AdjustmentRules", typeof (TimeZoneInfo.AdjustmentRule []));
			supportsDaylightSavingTime = (bool) info.GetValue ("SupportsDaylightSavingTime", typeof (bool));
		}

		private TimeZoneInfo (string id, TimeSpan baseUtcOffset, string displayName, string standardDisplayName, string daylightDisplayName, TimeZoneInfo.AdjustmentRule [] adjustmentRules, bool disableDaylightSavingTime)
		{
			if (id == null)
				throw new ArgumentNullException ("id");

			if (id == String.Empty)
				throw new ArgumentException ("id parameter is an empty string");

			if (baseUtcOffset.Ticks % TimeSpan.TicksPerMinute != 0)
				throw new ArgumentException ("baseUtcOffset parameter does not represent a whole number of minutes");

			if (baseUtcOffset > new TimeSpan (14, 0, 0) || baseUtcOffset < new TimeSpan (-14, 0, 0))
				throw new ArgumentOutOfRangeException ("baseUtcOffset parameter is greater than 14 hours or less than -14 hours");

#if STRICT
			if (id.Length > 32)
				throw new ArgumentException ("id parameter shouldn't be longer than 32 characters");
#endif

			bool supportsDaylightSavingTime = !disableDaylightSavingTime;

			if (adjustmentRules != null && adjustmentRules.Length != 0) {
				AdjustmentRule prev = null;
				foreach (AdjustmentRule current in adjustmentRules) {
					if (current == null)
						throw new InvalidTimeZoneException ("one or more elements in adjustmentRules are null");

					if ((baseUtcOffset + current.DaylightDelta < new TimeSpan (-14, 0, 0)) ||
							(baseUtcOffset + current.DaylightDelta > new TimeSpan (14, 0, 0)))
						throw new InvalidTimeZoneException ("Sum of baseUtcOffset and DaylightDelta of one or more object in adjustmentRules array is greater than 14 or less than -14 hours;");

					if (prev != null && prev.DateStart > current.DateStart)
						throw new InvalidTimeZoneException ("adjustment rules specified in adjustmentRules parameter are not in chronological order");
					
					if (prev != null && prev.DateEnd > current.DateStart)
						throw new InvalidTimeZoneException ("some adjustment rules in the adjustmentRules parameter overlap");

					if (prev != null && prev.DateEnd == current.DateStart)
						throw new InvalidTimeZoneException ("a date can have multiple adjustment rules applied to it");

					prev = current;
				}
			} else {
				supportsDaylightSavingTime = false;
			}
			
			this.id = id;
			this.baseUtcOffset = baseUtcOffset;
			this.displayName = displayName ?? id;
			this.standardDisplayName = standardDisplayName ?? id;
			this.daylightDisplayName = daylightDisplayName;
			this.supportsDaylightSavingTime = supportsDaylightSavingTime;
			this.adjustmentRules = adjustmentRules;
		}

		private AdjustmentRule GetApplicableRule (DateTime dateTime)
		{
			//Transitions are always in standard time
			DateTime date = dateTime;

			if (dateTime.Kind == DateTimeKind.Local && this != TimeZoneInfo.Local)
				date = date.ToUniversalTime () + BaseUtcOffset;

			if (dateTime.Kind == DateTimeKind.Utc && this != TimeZoneInfo.Utc)
				date = date + BaseUtcOffset;

			if (adjustmentRules != null) {
				foreach (AdjustmentRule rule in adjustmentRules) {
					if (rule.DateStart > date.Date)
						return null;
					if (rule.DateEnd < date.Date)
						continue;
					return rule;
				}
			}
			return null;
		}

		private bool TryGetTransitionOffset (DateTime dateTime, out TimeSpan offset,out bool isDst)
		{
			offset = BaseUtcOffset;
			isDst = false;

			if (transitions == null)
				return false;

			//Transitions are always in standard time
			DateTime date = dateTime;

			if (dateTime.Kind == DateTimeKind.Local && this != TimeZoneInfo.Local)
				date = date.ToUniversalTime () + BaseUtcOffset;

			if (dateTime.Kind == DateTimeKind.Utc && this != TimeZoneInfo.Utc)
				date = date + BaseUtcOffset;

			for (var i =  transitions.Count - 1; i >= 0; i--) {
				var pair = transitions [i];
				DateTime ttime = pair.Key;
				TimeType ttype = pair.Value;

				if (ttime > date)
					continue;

				offset =  new TimeSpan (0, 0, ttype.Offset);
				isDst = ttype.IsDst;

				return true;
			}

			return false;
		}

		private static DateTime TransitionPoint (TransitionTime transition, int year)
		{
			if (transition.IsFixedDateRule)
				return new DateTime (year, transition.Month, transition.Day) + transition.TimeOfDay.TimeOfDay;

			DayOfWeek first = (new DateTime (year, transition.Month, 1)).DayOfWeek;
			int day = 1 + (transition.Week - 1) * 7 + (transition.DayOfWeek - first) % 7;
			if (day >  DateTime.DaysInMonth (year, transition.Month))
				day -= 7;
			if (day < 1)
				day += 7;
			return new DateTime (year, transition.Month, day) + transition.TimeOfDay.TimeOfDay;
		}

		static List<AdjustmentRule> ValidateRules (List<AdjustmentRule> adjustmentRules)
		{
			AdjustmentRule prev = null;
			foreach (AdjustmentRule current in adjustmentRules.ToArray ()) {
				if (prev != null && prev.DateEnd > current.DateStart) {
					adjustmentRules.Remove (current);
				}
				prev = current;
			}
			return adjustmentRules;
		}

#if LIBC || MONODROID
		private static bool ValidTZFile (byte [] buffer, int length)
		{
			StringBuilder magic = new StringBuilder ();

			for (int i = 0; i < 4; i++)
				magic.Append ((char)buffer [i]);
			
			if (magic.ToString () != "TZif")
				return false;

			if (length >= BUFFER_SIZE)
				return false;

			return true;
		}

		static int SwapInt32 (int i)
		{
			return (((i >> 24) & 0xff)
				| ((i >> 8) & 0xff00)
				| ((i << 8) & 0xff0000)
				| ((i << 24)));
		}

		static int ReadBigEndianInt32 (byte [] buffer, int start)
		{
			int i = BitConverter.ToInt32 (buffer, start);
			if (!BitConverter.IsLittleEndian)
				return i;

			return SwapInt32 (i);
		}

		private static TimeZoneInfo ParseTZBuffer (string id, byte [] buffer, int length)
		{
			//Reading the header. 4 bytes for magic, 16 are reserved
			int ttisgmtcnt = ReadBigEndianInt32 (buffer, 20);
			int ttisstdcnt = ReadBigEndianInt32 (buffer, 24);
			int leapcnt = ReadBigEndianInt32 (buffer, 28);
			int timecnt = ReadBigEndianInt32 (buffer, 32);
			int typecnt = ReadBigEndianInt32 (buffer, 36);
			int charcnt = ReadBigEndianInt32 (buffer, 40);

			if (length < 44 + timecnt * 5 + typecnt * 6 + charcnt + leapcnt * 8 + ttisstdcnt + ttisgmtcnt)
				throw new InvalidTimeZoneException ();

			Dictionary<int, string> abbreviations = ParseAbbreviations (buffer, 44 + 4 * timecnt + timecnt + 6 * typecnt, charcnt);
			Dictionary<int, TimeType> time_types = ParseTimesTypes (buffer, 44 + 4 * timecnt + timecnt, typecnt, abbreviations);
			List<KeyValuePair<DateTime, TimeType>> transitions = ParseTransitions (buffer, 44, timecnt, time_types);

			if (time_types.Count == 0)
				throw new InvalidTimeZoneException ();

			if (time_types.Count == 1 && ((TimeType)time_types[0]).IsDst)
				throw new InvalidTimeZoneException ();

			TimeSpan baseUtcOffset = new TimeSpan (0);
			TimeSpan dstDelta = new TimeSpan (0);
			string standardDisplayName = null;
			string daylightDisplayName = null;
			bool dst_observed = false;
			DateTime dst_start = DateTime.MinValue;
			List<AdjustmentRule> adjustmentRules = new List<AdjustmentRule> ();
			bool storeTransition = false;

			for (int i = 0; i < transitions.Count; i++) {
				var pair = transitions [i];
				DateTime ttime = pair.Key;
				TimeType ttype = pair.Value;
				if (!ttype.IsDst) {
					if (standardDisplayName != ttype.Name || baseUtcOffset.TotalSeconds != ttype.Offset) {
						standardDisplayName = ttype.Name;
						daylightDisplayName = null;
						baseUtcOffset = new TimeSpan (0, 0, ttype.Offset);
						if (adjustmentRules.Count > 0) // We ignore AdjustmentRules but store transitions.
							storeTransition = true;
						adjustmentRules = new List<AdjustmentRule> ();
						dst_observed = false;
					}
					if (dst_observed) {
						//FIXME: check additional fields for this:
						//most of the transitions are expressed in GMT 
						dst_start += baseUtcOffset;
						DateTime dst_end = ttime + baseUtcOffset + dstDelta;

						//some weird timezone (America/Phoenix) have end dates on Jan 1st
						if (dst_end.Date == new DateTime (dst_end.Year, 1, 1) && dst_end.Year > dst_start.Year)
							dst_end -= new TimeSpan (24, 0, 0);

						DateTime dateStart, dateEnd;
						if (dst_start.Month < 7)
							dateStart = new DateTime (dst_start.Year, 1, 1);
						else
							dateStart = new DateTime (dst_start.Year, 7, 1);

						if (dst_end.Month >= 7)
							dateEnd = new DateTime (dst_end.Year, 12, 31);
						else
							dateEnd = new DateTime (dst_end.Year, 6, 30);

						
						TransitionTime transition_start = TransitionTime.CreateFixedDateRule (new DateTime (1, 1, 1) + dst_start.TimeOfDay, dst_start.Month, dst_start.Day);
						TransitionTime transition_end = TransitionTime.CreateFixedDateRule (new DateTime (1, 1, 1) + dst_end.TimeOfDay, dst_end.Month, dst_end.Day);
						if  (transition_start != transition_end) //y, that happened in Argentina in 1943-1946
							adjustmentRules.Add (AdjustmentRule.CreateAdjustmentRule (dateStart, dateEnd, dstDelta, transition_start, transition_end));
					}
					dst_observed = false;
				} else {
					if (daylightDisplayName != ttype.Name || dstDelta.TotalSeconds != ttype.Offset - baseUtcOffset.TotalSeconds) {
						daylightDisplayName = ttype.Name;
						dstDelta = new TimeSpan(0, 0, ttype.Offset) - baseUtcOffset;
					}
					dst_start = ttime;
					dst_observed = true;
				}
			}

			TimeZoneInfo tz;
			if (adjustmentRules.Count == 0 && !storeTransition) {
				TimeType t = (TimeType)time_types [0];
				if (standardDisplayName == null) {
					standardDisplayName = t.Name;
					baseUtcOffset = new TimeSpan (0, 0, t.Offset);
				}
				tz = CreateCustomTimeZone (id, baseUtcOffset, id, standardDisplayName);
			} else {
				tz = CreateCustomTimeZone (id, baseUtcOffset, id, standardDisplayName, daylightDisplayName, ValidateRules (adjustmentRules).ToArray ());
			}

			if (storeTransition)
				tz.transitions = transitions;

			return tz;
		}

		static Dictionary<int, string> ParseAbbreviations (byte [] buffer, int index, int count)
		{
			var abbrevs = new Dictionary<int, string> ();
			int abbrev_index = 0;
			var sb = new StringBuilder ();
			for (int i = 0; i < count; i++) {
				char c = (char) buffer [index + i];
				if (c != '\0')
					sb.Append (c);
				else {
					abbrevs.Add (abbrev_index, sb.ToString ());
					//Adding all the substrings too, as it seems to be used, at least for Africa/Windhoek
					for (int j = 1; j < sb.Length; j++)
						abbrevs.Add (abbrev_index + j, sb.ToString (j, sb.Length - j));
					abbrev_index = i + 1;
					sb = new StringBuilder ();
				}
			}
			return abbrevs;
		}

		static Dictionary<int, TimeType> ParseTimesTypes (byte [] buffer, int index, int count, Dictionary<int, string> abbreviations)
		{
			var types = new Dictionary<int, TimeType> (count);
			for (int i = 0; i < count; i++) {
				int offset = ReadBigEndianInt32 (buffer, index + 6 * i);
				byte is_dst = buffer [index + 6 * i + 4];
				byte abbrev = buffer [index + 6 * i + 5];
				types.Add (i, new TimeType (offset, (is_dst != 0), abbreviations [(int)abbrev]));
			}
			return types;
		}

		static List<KeyValuePair<DateTime, TimeType>> ParseTransitions (byte [] buffer, int index, int count, Dictionary<int, TimeType> time_types)
		{
			var list = new List<KeyValuePair<DateTime, TimeType>> (count);
			for (int i = 0; i < count; i++) {
				int unixtime = ReadBigEndianInt32 (buffer, index + 4 * i);
				DateTime ttime = DateTimeFromUnixTime (unixtime);
				byte ttype = buffer [index + 4 * count + i];
				list.Add (new KeyValuePair<DateTime, TimeType> (ttime, time_types [(int)ttype]));
			}
			return list;
		}

		static DateTime DateTimeFromUnixTime (long unix_time)
		{
			DateTime date_time = new DateTime (1970, 1, 1);
			return date_time.AddSeconds (unix_time);
		}
	}

	struct TimeType {
		public readonly int Offset;
		public readonly bool IsDst;
		public string Name;

		public TimeType (int offset, bool is_dst, string abbrev)
		{
			this.Offset = offset;
			this.IsDst = is_dst;
			this.Name = abbrev;
		}

		public override string ToString ()
		{
			return "offset: " + Offset + "s, is_dst: " + IsDst + ", zone name: " + Name;
		}
#else
	}
#endif
	}
}

#endif