libs-base/Source/NSTimeZone.m

/** Time zone management. -*- Mode: ObjC -*-
   Copyright (C) 1997-2002 Free Software Foundation, Inc.

   Written by: Yoo C. Chung <wacko@laplace.snu.ac.kr>
   Date: June 1997

   Rewrite large chunks by: Richard Frith-Macdonald <rfm@gnu.org>
   Date: September 2002

     This file is part of the GNUstep Base Library.

   This library is free software; you can redistribute it and/or
   modify it under the terms of the GNU Lesser General Public License
   as published by the Free Software Foundation; either
   version 2 of the License, or (at your option) any later version.

   This library is distributed in the hope that it will be useful, but
   WITHOUT ANY WARRANTY; without even the implied warranty of
   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
   Library General Public License for more details.

   You should have received a copy of the GNU Lesser General Public
   License along with this library; if not, write to the Free Software
   Foundation, Inc., 51 Franklin Street, Fifth Floor,
   Boston, MA 02111 USA.

   <title>NSTimeZone class reference</title>
   $Date$ $Revision$
 */

/* Use the system time zones if available. In other cases, use an
   implementation independent of the system, since POSIX functions for
   time zones are woefully inadequate for implementing NSTimeZone.
   Time zone names can be different from system to system, but usually
   the user has already set up his timezone independant of GNUstep, so we
   should respect that information.

   We do not use a dictionary for storing time zones, since such a
   dictionary would be VERY large (~500K).  And we would have to use a
   complicated object determining whether we're using daylight savings
   time and such for every entry in the dictionary.  (Though we will
   eventually have to change the implementation to prevent the year
   2038 problem.)

   The local time zone can be specified with:
    1) the user defaults database
    2) the GNUSTEP_TZ environment variable
    3) the file LOCAL_TIME_FILE in _time_zone_path()
    4) the TZ environment variable
    5) tzset() & tznam[] for platforms which have it
    6) TZDEFAULT defined in tzfile.h on platforms which have it
    7) Windows registry, for Win32 systems
    8) or the fallback time zone (which is UTC)
   with the ones listed first having precedence.

   Any time zone must be a file name in ZONES_DIR.

   Files & File System Heirarchy info:
   ===================================

   Default place for the NSTimeZone directory is _time_zone_path():
     {$(GNUSTEP_SYSTEM_LIBRARY)/Libraries/gnustep-base/Versions/1.14/Resources/TIME_ZONE_DIR)

   LOCAL_TIME_FILE is a text file with the name of the time zone file.

   ZONES_DIR is a sub-directory under TIME_ZONE_DIR

   (dir) ../System/Library/Libraries/gnustep-base/Versions/1.14/Resources/..
   (dir)     NSTimeZone
   (file)      localtime {text; time zone eg Australia/Perth}
   (dir)       zones

   Note that full zone info is required, especially the various "GMT"
   files which are created especially for OPENSTEP compatibility.
   Zone info comes from the Olson time database.

   FIXME?: use leap seconds? */

#import "common.h"
#define	EXPOSE_NSTimeZone_IVARS	1
#import "GNUstepBase/GSLock.h"
#include <stdio.h>
#include <string.h>
#include <time.h>
#import "Foundation/NSArray.h"
#import "Foundation/NSCoder.h"
#import "Foundation/NSData.h"
#import "Foundation/NSDate.h"
#import "Foundation/NSDictionary.h"
#import "Foundation/NSException.h"
#import "Foundation/NSFileManager.h"
#import "Foundation/NSLock.h"
#import "Foundation/NSProcessInfo.h"
#import "Foundation/NSUserDefaults.h"
#import "Foundation/NSBundle.h"
#import "Foundation/NSMapTable.h"
#import "Foundation/NSThread.h"
#import "Foundation/NSNotification.h"
#import "Foundation/NSPortCoder.h"
#import "Foundation/NSTimeZone.h"
#import "Foundation/NSByteOrder.h"
#import "GNUstepBase/GSConfig.h"
#import "GNUstepBase/NSObject+GNUstepBase.h"
#import "GNUstepBase/NSString+GNUstepBase.h"
#import "GSPrivate.h"

#ifdef HAVE_TZHEAD
#include <tzfile.h>
#else
#define NOID
#include "nstzfile.h"
#endif

NSString * const NSSystemTimeZoneDidChangeNotification
  = @"NSSystemTimeZoneDidChangeNotification";

/* Key for local time zone in user defaults. */
#define LOCALDBKEY @"Local Time Zone"

/* Directory that contains the time zone data.
   Expected in Resources directory for library bundle. */
#define TIME_ZONE_DIR @"NSTimeZones"

/* Name of time zone abbreviation (plist) dictionary.  */
#define ABBREV_DICT @"abbreviations"

/* Name of time zone abbreviation map.  It is a text file
   with each line comprised of the abbreviation, a whitespace, and the
   name.  Neither the abbreviation nor the name can contain
   whitespace, and each line must not be longer than 80 characters. */
#define ABBREV_MAP @"abbreviations"

/* File holding regions grouped by latitude.  It is a text file with
   each line comprised of the latitude region, whitespace, and the
   name.  Neither the abbreviation nor the name can contain
   whitespace, and each line must not be longer than 80 characters. */
#define REGIONS_FILE @"regions"

/* Name of the file that contains the name of the local time zone. */
#define LOCAL_TIME_FILE @"localtime"

/* Directory that contains the actual time zones. */
#define ZONES_DIR @"zones/"

/* Many systems have this file */
#define SYSTEM_TIME_FILE @"/etc/localtime"

/* If TZDIR told us where the zoneinfo files are, don't append anything else */
#ifdef TZDIR
#define POSIX_TZONES     @""
#else
#define POSIX_TZONES     @"posix/"
#endif

/* Possible location of system time zone files */
static NSString *tzdir = nil;

@class GSAbsTimeZone;
@class GSTimeZoneDetail;
@class GSAbsTimeZoneDetail;

@class GSPlaceholderTimeZone;

/*
 * Information for abstract placeholder class.
 */
static GSPlaceholderTimeZone	*defaultPlaceholderTimeZone;
static NSMapTable		*placeholderMap;

/*
 * Temporary structure for holding time zone details.
 * This is the format in the data object.
 */
struct ttinfo
{
  char offset[4];         // Seconds east of UTC
  unsigned char isdst;    // Daylight savings time?
  unsigned char abbr_idx; // Index into time zone abbreviations string
} __attribute__((packed));

/*
 * And this is the structure used in the time zone instances.
 */
typedef struct {
  int32_t	offset;
  BOOL		isdst;
  unsigned char	abbr_idx;
  char		pad[2];
  NSString	*abbreviation;
} TypeInfo;

@interface	GSTimeZone : NSTimeZone
{
@public
  NSString	*timeZoneName;
  NSArray	*abbreviations;
  NSData	*timeZoneData;
  unsigned int	n_trans;
  unsigned int	n_types;
  int32_t	*trans;
  TypeInfo	*types;
  unsigned char	*idxs;
}
@end

#if	defined(__MINGW__)
@interface	GSWindowsTimeZone : NSTimeZone
{
@public
  NSString	*timeZoneName;
  NSString	*daylightZoneName;
  NSString	*timeZoneNameAbbr;
  NSString	*daylightZoneNameAbbr;
  LONG		Bias;
  LONG		StandardBias;
  LONG		DaylightBias;
  SYSTEMTIME	StandardDate;
  SYSTEMTIME	DaylightDate;
}
@end
#endif

static NSTimeZone	*defaultTimeZone = nil;
static NSTimeZone	*localTimeZone = nil;
static NSTimeZone	*systemTimeZone = nil;

/* Dictionary for time zones.  Each time zone must have a unique
   name. */
static NSMutableDictionary *zoneDictionary;

/* one-to-one abbreviation to time zone name dictionary. */
static NSMutableDictionary *abbreviationDictionary = nil;
/* one-to-many abbreviation to time zone name dictionary. */
static NSMutableDictionary *abbreviationMap = nil;

/* Lock for creating time zones. */
static NSRecursiveLock *zone_mutex = nil;

static Class	NSTimeZoneClass;
static Class	GSPlaceholderTimeZoneClass;

/* Decode the four bytes at PTR as a signed integer in network byte order.
   Based on code included in the GNU C Library 2.0.3. */
static inline int
decode (const void *ptr)
{
#if defined(WORDS_BIGENDIAN) && SIZEOF_INT == 4
#if NEED_WORD_ALIGNMENT
  int value;
  memcpy(&value, ptr, sizeof(NSInteger));
  return value;
#else
  return *(const NSInteger*) ptr;
#endif
#else /* defined(WORDS_BIGENDIAN) && SIZEOF_INT == 4 */
  const unsigned char *p = ptr;
  int result = *p & (1 << (CHAR_BIT - 1)) ? ~0 : 0;

  result = (result << 8) | *p++;
  result = (result << 8) | *p++;
  result = (result << 8) | *p++;
  result = (result << 8) | *p++;
  return result;
#endif /* defined(WORDS_BIGENDIAN) && SIZEOF_INT == 4 */
}

/* Return path to a TimeZone directory file */
static NSString *_time_zone_path(NSString *subpath, NSString *type)
{
  NSBundle *gbundle;
  if (type == nil)
    type = @"";
  gbundle = [NSBundle bundleForClass: [NSObject class]];
  return [gbundle pathForResource: subpath
		           ofType: type
		      inDirectory: TIME_ZONE_DIR];
}

@interface GSPlaceholderTimeZone : NSTimeZone
@end

@interface GSAbsTimeZone : NSTimeZone
{
@public
  NSString	*name;
  id		detail;
  int		offset; // Offset from UTC in seconds.
}

- (id) initWithOffset: (NSInteger)anOffset name: (NSString*)aName;
@end

@interface NSLocalTimeZone : NSTimeZone
@end

@interface GSTimeZoneDetail : NSTimeZoneDetail
{
  NSTimeZone	*timeZone; // Time zone which created this object.
  NSString	*abbrev; // Abbreviation for time zone detail.
  int		offset; // Offset from UTC in seconds.
  BOOL		is_dst; // Is it daylight savings time?
}

- (id) initWithTimeZone: (NSTimeZone*)aZone
	     withAbbrev: (NSString*)anAbbrev
	     withOffset: (NSInteger)anOffset
		withDST: (BOOL)isDST;
@end

@interface GSAbsTimeZoneDetail : NSTimeZoneDetail
{
  GSAbsTimeZone	*zone; // Time zone which created this object.
}

- (id) initWithTimeZone: (GSAbsTimeZone*)aZone;
@end

/* Private methods for obtaining resource file names. */
@interface NSTimeZone (Private)
+ (NSString*) _getTimeZoneFile: (NSString*)name;
+ (void) _notified: (NSNotification*)n;
@end


@implementation GSPlaceholderTimeZone

- (id) autorelease
{
  NSWarnLog(@"-autorelease sent to uninitialised time zone");
  return self;		// placeholders never get released.
}

- (void) dealloc
{
  GSNOSUPERDEALLOC;	// placeholders never get deallocated.
}

- (id) initWithName: (NSString*)name data: (NSData*)data
{
  NSTimeZone	*zone;
  unsigned	length = [name length];

  if (length == 0)
    {
      NSLog(@"Disallowed null time zone name");
      return nil;
    }
  if (length == 15 && [name isEqual: @"NSLocalTimeZone"])
    {
      zone = RETAIN(localTimeZone);
      DESTROY(self);
      return zone;
    }

  /*
   * Return a cached time zone if possible.
   * NB. if data of cached zone does not match new data ... don't use cache
   */
  if (zone_mutex != nil)
    {
      [zone_mutex lock];
    }
  zone = [zoneDictionary objectForKey: name];
  if (data != nil && [data isEqual: [zone data]] == NO)
    {
      zone = nil;
    }
  IF_NO_GC(RETAIN(zone));
  if (zone_mutex != nil)
    {
      [zone_mutex unlock];
    }

  if (zone == nil)
    {
      unichar	c;
      int	i;

      if ((length == 3
	&& ([name isEqualToString: @"GMT"] == YES
          || [name isEqualToString: @"UTC"] == YES
          || [name isEqualToString: @"UCT"] == YES))
	|| (length == 4
	  && ([name isEqualToString: @"GMT0"] == YES
	    || [name isEqualToString: @"Zulu"] == YES))
	|| (length == 9 && [name isEqualToString: @"Universal"] == YES))
	{
	  // Synonyms for GMT
	  zone = [[GSAbsTimeZone alloc] initWithOffset: 0 name: name];
	}
      else if (length == 5 && [name hasPrefix: @"GMT"] == YES
	&& ((c = [name characterAtIndex: 3]) == '+' || c == '-')
	&& ((c = [name characterAtIndex: 4]) >= '0' && c <= '9'))
	{
	  // GMT-9 to GMT+9
	  i = (c - '0') * 60 * 60;
	  if ([name characterAtIndex: 3] == '-')
	    {
	      i = -i;
	    }
	  zone = [[GSAbsTimeZone alloc] initWithOffset: i name: name];
	}
      else if (length == 6 && [name hasPrefix: @"GMT"] == YES
	&& ((c = [name characterAtIndex: 3]) == '+' || c == '-')
	&& ((c = [name characterAtIndex: 4]) == '0' || c == '1')
	&& ((c = [name characterAtIndex: 5]) >= '0' && c <= '4'))
	{
	  // GMT-14 to GMT-10 and GMT+10 to GMT+14
	  i = (c - '0') * 60 * 60;
	  if ([name characterAtIndex: 4] == '1')
	    {
	      i += 60 * 60 * 10;
	    }
	  if ([name characterAtIndex: 3] == '-')
	    {
	      i = -i;
	    }
	  zone = [[GSAbsTimeZone alloc] initWithOffset: i name: name];
	}
      else if (length == 8 && [name hasPrefix: @"GMT"] == YES
	&& ((c = [name characterAtIndex: 3]) == '+' || c == '-'))
	{
	  // GMT+NNNN and GMT-NNNN
	  c = [name characterAtIndex: 4];
	  if (c >= '0' && c <= '9')
	    {
	      i = c - '0';
	      c = [name characterAtIndex: 5];
	      if (c >= '0' && c <= '9')
		{
		  i = i * 10 + (c - '0');
		  c = [name characterAtIndex: 6];
		  if (c >= '0' && c <= '9')
		    {
		      i = i * 6 + (c - '0');
		      c = [name characterAtIndex: 7];
		      if (c >= '0' && c <= '9')
			{
			  i = i * 10 + (c - '0');
			  i = i * 60;
			  if ([name characterAtIndex: 3] == '-')
			    {
			      i = -i;
			    }
			  zone = [[GSAbsTimeZone alloc] initWithOffset: i
								  name: nil];
			}
		    }
		}
	    }
	}

      if (zone == nil && length > 19
	&& [name hasPrefix: @"NSAbsoluteTimeZone: "] == YES)
	{
	  i = [[name substringFromIndex: 19] intValue];

	  zone = [[GSAbsTimeZone alloc] initWithOffset: i name: nil];
	}

      if (zone == nil)
	{
	  if (data == nil)
	    {
	      NSString	*fileName;
	      BOOL	isDir;

	      fileName = [NSTimeZoneClass _getTimeZoneFile: name];
	      if (fileName == nil
		|| ![[NSFileManager defaultManager] fileExistsAtPath: fileName
		isDirectory: &isDir] || YES == isDir)
		{
		  data = nil;
		}
	      else
		{
	          data = [NSData dataWithContentsOfFile: fileName];
		}
	      if (nil == data)
#if	defined(__MINGW__)
                {
                  zone = [[GSWindowsTimeZone alloc] initWithName: name data: 0];
                  DESTROY(self);
                  return zone;
                }
#else
		{
		  NSLog(@"Unknown time zone name `%@'.", name);
		  return nil;
		}
#endif
	    }
#if	defined(__MINGW__)
	  if (!data)
	    zone = [[GSWindowsTimeZone alloc] initWithName: name data: data];
	  else
#endif
	  zone = [[GSTimeZone alloc] initWithName: name data: data];
	}
    }
  DESTROY(self);
  return zone;
}

- (void) release
{
  return;		// placeholders never get released.
}

- (id) retain
{
  return self;		// placeholders never get retained.
}
@end



@implementation	NSLocalTimeZone

- (NSString*) abbreviation
{
  return [[NSTimeZoneClass defaultTimeZone] abbreviation];
}

- (NSString*) abbreviationForDate: (NSDate*)aDate
{
  return [[NSTimeZoneClass defaultTimeZone] abbreviationForDate: aDate];
}

- (id) autorelease
{
  return self;
}

- (NSData*) data
{
  return [[NSTimeZoneClass defaultTimeZone] data];
}

- (void) encodeWithCoder: (NSCoder*)aCoder
{
  [aCoder encodeObject: @"NSLocalTimeZone"];
}

- (id) init
{
  return self;
}

- (BOOL) isDaylightSavingTime
{
  return [[NSTimeZoneClass defaultTimeZone] isDaylightSavingTime];
}

- (BOOL) isDaylightSavingTimeForDate: (NSDate*)aDate
{
  return [[NSTimeZoneClass defaultTimeZone] isDaylightSavingTimeForDate: aDate];
}

- (NSString*) name
{
  return [[NSTimeZoneClass defaultTimeZone] name];
}

- (void) release
{
}

- (id) retain
{
  return self;
}

- (NSInteger) secondsFromGMT
{
  return [[NSTimeZoneClass defaultTimeZone] secondsFromGMT];
}

- (NSInteger) secondsFromGMTForDate: (NSDate*)aDate
{
  return [[NSTimeZoneClass defaultTimeZone] secondsFromGMTForDate: aDate];
}

- (NSArray*) timeZoneDetailArray
{
  return [[NSTimeZoneClass defaultTimeZone] timeZoneDetailArray];
}

- (NSTimeZoneDetail*) timeZoneDetailForDate: (NSDate*)date
{
  return [[NSTimeZoneClass defaultTimeZone] timeZoneDetailForDate: date];
}

- (NSString*) timeZoneName
{
  return [[NSTimeZoneClass defaultTimeZone] timeZoneName];
}

@end


@implementation GSAbsTimeZone

static int		uninitialisedOffset = 100000;
static NSMapTable	*absolutes = 0;

+ (void) initialize
{
  if (self == [GSAbsTimeZone class])
    {
      absolutes = NSCreateMapTable(NSIntMapKeyCallBacks,
	NSNonOwnedPointerMapValueCallBacks, 0);
    }
}

- (NSString*) abbreviationForDate: (NSDate*)aDate
{
  return name;
}

- (void) dealloc
{
  if (offset != uninitialisedOffset)
    {
      if (zone_mutex != nil)
	[zone_mutex lock];
      NSMapRemove(absolutes, (void*)(uintptr_t)offset);
      if (zone_mutex != nil)
	[zone_mutex unlock];
    }
  RELEASE(name);
  RELEASE(detail);
  [super dealloc];
}

- (void) encodeWithCoder: (NSCoder*)aCoder
{
  [aCoder encodeObject: name];
}

- (id) initWithOffset: (NSInteger)anOffset name: (NSString*)aName
{
  GSAbsTimeZone	*z;
  int		extra;
  int		sign = anOffset >= 0 ? 1 : -1;

  /*
   * Set the uninitialised offset so that dealloc before full
   * initialisation won't remove the timezeone for offset 0 from cache.
   */
  offset = uninitialisedOffset;

  /*
   * Round the offset to the nearest minute, (for MacOS-X compatibility)
   * and ensure it is no more than 18 hours.
   */
  anOffset *= sign;
  extra = anOffset % 60;
  if (extra < 30)
    {
      anOffset -= extra;
    }
  else
    {
      anOffset += 60 - extra;
    }
  if (anOffset > 64800)
    {
      DESTROY(self);
      return nil;
    }
  anOffset *= sign;

  if (zone_mutex != nil)
    {
      [zone_mutex lock];
    }
  z = (GSAbsTimeZone*)NSMapGet(absolutes, (void*)(uintptr_t)anOffset);
  if (z != nil)
    {
      IF_NO_GC(RETAIN(z));
      DESTROY(self);
    }
  else
    {
      if (aName == nil)
	{
	  if (anOffset % 60 == 0)
	    {
	      char	s = (anOffset >= 0) ? '+' : '-';
	      int	i = (anOffset >= 0) ? anOffset / 60 : -anOffset / 60;
	      int	h = i / 60;
	      int	m = i % 60;
	      char	buf[9];

	      sprintf(buf, "GMT%c%02d%02d", s, h, m);
	      name = [[NSString alloc] initWithUTF8String: buf];
	    }
	  else
	    {
	      /*
	       * Should never happen now we round to the minute
	       * for MacOS-X compatibnility.
	       */
	      name = [[NSString alloc] initWithFormat: @"NSAbsoluteTimeZone:%d",
		anOffset];
	    }
	}
      else
	{
	  name = [aName copy];
	}
      detail = [[GSAbsTimeZoneDetail alloc] initWithTimeZone: self];
      offset = anOffset;
      z = self;
      NSMapInsert(absolutes, (void*)(uintptr_t)anOffset, (void*)z);
      [zoneDictionary setObject: self forKey: (NSString*)name];
    }
  if (zone_mutex != nil)
    {
      [zone_mutex unlock];
    }
  return z;
}

- (BOOL) isDaylightSavingTimeZoneForDate: (NSDate*)aDate
{
  return NO;
}

- (NSString*) name
{
  return name;
}

- (NSInteger) secondsFromGMTForDate: (NSDate*)aDate
{
  return offset;
}

- (NSArray*) timeZoneDetailArray
{
  return [NSArray arrayWithObject: detail];
}

- (NSTimeZoneDetail*) timeZoneDetailForDate: (NSDate*)date
{
  return detail;
}

- (NSString*) timeZoneName
{
  return name;
}
@end


@implementation GSTimeZoneDetail

- (void) dealloc
{
  RELEASE(timeZone);
  [super dealloc];
}

- (id) initWithCoder: (NSCoder*)aDecoder
{
  [aDecoder decodeValueOfObjCType: @encode(id) at: &abbrev];
  [aDecoder decodeValueOfObjCType: @encode(int) at: &offset];
  [aDecoder decodeValueOfObjCType: @encode(BOOL) at: &is_dst];
  return self;
}

- (id) initWithTimeZone: (NSTimeZone*)aZone
	     withAbbrev: (NSString*)anAbbrev
	     withOffset: (NSInteger)anOffset
		withDST: (BOOL)isDST
{
  timeZone = RETAIN(aZone);
  abbrev = anAbbrev;		// NB. Depend on this being retained in aZone
  offset = anOffset;
  is_dst = isDST;
  return self;
}

- (BOOL) isDaylightSavingTimeZone
{
  return is_dst;
}

- (NSString*) name
{
  return [timeZone name];
}

- (NSString*) timeZoneAbbreviation
{
  return abbrev;
}

- (NSArray*) timeZoneDetailArray
{
  return [timeZone timeZoneDetailArray];
}

- (NSTimeZoneDetail*) timeZoneDetailForDate: (NSDate*)date
{
  return [timeZone timeZoneDetailForDate: date];
}

- (NSInteger) timeZoneSecondsFromGMT
{
  return offset;
}

- (NSInteger) timeZoneSecondsFromGMTForDate: (NSDate*)aDate
{
  return offset;
}

@end


@implementation GSAbsTimeZoneDetail

- (NSString*) abbreviation
{
  return zone->name;
}

- (NSString*) abbreviationForDate: (NSDate*)aDate
{
  return zone->name;
}

- (void) dealloc
{
  RELEASE(zone);
  [super dealloc];
}

- (id) initWithTimeZone: (GSAbsTimeZone*)aZone
{
  zone = RETAIN(aZone);
  return self;
}

- (BOOL) isDaylightSavingTimeZone
{
  return NO;
}

- (BOOL) isDaylightSavingTimeZoneForDate: (NSDate*)aDate
{
  return NO;
}

- (NSString*) name
{
  return zone->name;
}

- (NSString*) timeZoneAbbreviation
{
  return zone->name;
}

- (NSArray*) timeZoneDetailArray
{
  return [zone timeZoneDetailArray];
}

- (NSTimeZoneDetail*) timeZoneDetailForDate: (NSDate*)date
{
  return self;
}

- (NSInteger) timeZoneSecondsFromGMT
{
  return zone->offset;
}

- (NSInteger) timeZoneSecondsFromGMTForDate: (NSDate*)aDate
{
  return zone->offset;
}

@end


/**
 * <p>
 * The local time zone is obtained from, in order of preference:<br/ >
 *  1) the user defaults database: NSGlobalDomain "Local Time Zone"<br/ >
 *  2) the GNUSTEP_TZ environment variable<br/ >
 *  3) the file "localtime" in System/Library/Libraries/Resources/NSTimeZone<br/ >
 *  4) the TZ environment variable<br/ >
 *  5) tzset and tznam on platforms which have it<br/ >
 *  6) The system zone settings (typically in /etc/localtime)<br/ >
 *  7) Windows registry, on Win32 systems<br/ >
 *  8) or the fallback time zone (which is UTC)<br/ >
 * </p>
 * <p>If the GNUstep time zone datafiles become too out of date, one
 * can download an updated database from <uref
 * url="ftp://elsie.nci.nih.gov/pub/">ftp://elsie.nci.nih.gov/pub/</uref>
 * and compile it as specified in the README file in the
 * NSTimeZones directory.
 * </p>
 * <p>Time zone names in NSDates should be GMT, MET etc. not
 * Europe/Berlin, America/Washington etc.
 * </p>
 * <p>The problem with this is that various time zones may use the
 * same abbreviation (e.g. Australia/Brisbane and
 * America/New_York both use EST), and some time zones
 * may have different rules for daylight saving time even if the
 * abbreviation and offsets from UTC are the same.
 * </p>
 * <p>The problems with depending on the OS for providing time zone
 * info are that time zone names may vary
 * wildly between OSes (this could be a big problem when
 * archiving is used between different systems).
 * </p>
 * <p>Win32:  Time zone names read from the registry are different
 * from other GNUstep installations. Be careful when moving data
 * between platforms in this case.
 * </p>
 */
@implementation NSTimeZone

/**
 * Returns a dictionary containing time zone abbreviations and their
 * corresponding time zone names. More than one time zone may be associated
 * with a single abbreviation. In this case, the dictionary contains only
 * one (usually the most common) time zone name for the abbreviation.
 */
+ (NSDictionary*) abbreviationDictionary
{
  if (abbreviationDictionary != nil)
    {
      return abbreviationDictionary;
    }
  if (zone_mutex != nil)
    {
      [zone_mutex lock];
    }
  if (abbreviationDictionary == nil)
    {
      CREATE_AUTORELEASE_POOL(pool);
      NSString		*path;

      path = _time_zone_path (ABBREV_DICT, @"plist");
      if (path != nil)
	{
	  /*
	   * Fast mechanism ... load prebuilt data from file so we don't
	   * need to load in all time zones.
	   */
	  abbreviationDictionary
	    = RETAIN([[NSString stringWithContentsOfFile: path] propertyList]);
	}
      if (abbreviationDictionary == nil)
	{
	  NSMutableDictionary	*md;
	  NSString		*name;
	  NSEnumerator		*names;

	  /*
	   * Slow fallback ... load all time zones and generate
	   * abbreviation dictionary from them.
	   */
	  md = [[NSMutableDictionary alloc] init];
	  names = [[NSTimeZone knownTimeZoneNames] objectEnumerator];
	  while ((name = [names nextObject]) != nil)
	    {
	      NSTimeZone *zone;

	      if ((zone = [NSTimeZone timeZoneWithName: name]))
		{
		  NSEnumerator		*details;
		  NSTimeZoneDetail	*detail;
	
		  details = [[zone timeZoneDetailArray] objectEnumerator];
		  while ((detail = [details nextObject]) != nil)
		    {
		      [md setObject: name
			     forKey: [detail timeZoneAbbreviation]];
		    }
		}
	    }
	  [md makeImmutableCopyOnFail: NO];
	  abbreviationDictionary = md;
	}
      RELEASE(pool);
    }
  if (zone_mutex != nil)
    {
      [zone_mutex unlock];
    }
  return abbreviationDictionary;
}

/**
 * Returns a dictionary that maps abbreviations to the array
 * containing all the time zone names that use the abbreviation.
 */
+ (NSDictionary*) abbreviationMap
{
  /* Instead of creating the abbreviation dictionary when the class is
     initialized, we create it when we first need it, since the
     dictionary can be potentially very large, considering that it's
     almost never used. */
  if (abbreviationMap != nil)
    {
      return abbreviationMap;
    }
  if (zone_mutex != nil)
    {
      [zone_mutex lock];
    }
  if (abbreviationMap == nil)
    {
      CREATE_AUTORELEASE_POOL(pool);
      NSMutableDictionary	*md;
      NSMutableArray		*ma;
      NSString			*the_name;
      NSString			*the_abbrev;
      FILE			*file;
      char			abbrev[80];
      char			name[80];
      NSString			*path;

      /*
       * Read dictionary from file... fast mechanism because we don't have
       * to create all timezoneas and parse all their data files.
       */
      md = [NSMutableDictionary dictionaryWithCapacity: 100];
      path = _time_zone_path (ABBREV_MAP, nil);
      if (path != nil)
	{
#if	defined(__MINGW__)
	  unichar	mode[3];

	  mode[0] = 'r';
	  mode[1] = 'b';
	  mode[2] = '\0';

	  file = _wfopen((const unichar*)[path fileSystemRepresentation], mode);
#else
	  file = fopen([path fileSystemRepresentation], "r");
#endif
	  if (file == NULL)
	    {
	      if (zone_mutex != nil)
		{
		  [zone_mutex unlock];
		}
	      [NSException
		raise: NSInternalInconsistencyException
		format: @"Failed to open time zone abbreviation map."];
	    }
	  while (fscanf(file, "%79s %79s", abbrev, name) == 2)
	    {
	      the_name = [[NSString alloc] initWithUTF8String: name];
	      the_abbrev = [[NSString alloc] initWithUTF8String: abbrev];
	      ma = [md objectForKey: the_abbrev];
	      if (ma == nil)
		{
		  ma = [[NSMutableArray alloc] initWithCapacity: 1];
		  [md setObject: ma forKey: the_abbrev];
		  RELEASE(ma);
		}
	      RELEASE(the_abbrev);
	      if ([ma containsObject: the_name] == NO)
		{
		  [ma addObject: the_name];
		}
	      RELEASE(the_name);
	    }
	  fclose(file);
	}
      else
	{
	  NSString		*name;
	  NSEnumerator		*names;

	  /*
	   * Slow fallback mechanism ... go through all time names
	   * so we load all the time zone data and generate the info
	   * we need from it.
	   */
	  names = [[NSTimeZone knownTimeZoneNames] objectEnumerator];
	  while ((name = [names nextObject]) != nil)
	    {
	      NSTimeZone *zone;

	      if ((zone = [NSTimeZone timeZoneWithName: name]) != nil)
		{
		  NSEnumerator		*details;
		  NSTimeZoneDetail	*detail;
	
		  details = [[zone timeZoneDetailArray] objectEnumerator];
		  while ((detail = [details nextObject]) != nil)
		    {
		      the_abbrev = [detail timeZoneAbbreviation];
		      ma = [md objectForKey: the_abbrev];
		      if (ma == nil)
			{
			  ma = [[NSMutableArray alloc] initWithCapacity: 1];
			  [md setObject: ma forKey: the_abbrev];
			  RELEASE(ma);
			}
		      if ([ma containsObject: name] == NO)
		        {
		          [ma addObject: name];
			}
		    }
		}
	    }
	}

      /* Special case: Add the system time zone if
       * it doesn't exist in the map */
      the_abbrev = [systemTimeZone abbreviation];
      ma = [md objectForKey: the_abbrev];
      if (ma == nil)
	{
	  ma = [NSMutableArray new];
	  [md setObject: ma forKey: the_abbrev];
	  RELEASE(ma);
	}
      the_name = [systemTimeZone timeZoneName];
      if ([ma containsObject: the_name] == NO)
	{
	  [ma addObject: the_name];
	}

      [md makeImmutableCopyOnFail: NO];
      abbreviationMap = RETAIN(md); 
      RELEASE(pool);
    }
  if (zone_mutex != nil)
    {
      [zone_mutex unlock];
    }

  return abbreviationMap;
}

/**
 * Returns an array of all known time zone names.
 */
+ (NSArray*) knownTimeZoneNames
{
  static NSArray *namesArray = nil;

  /* We create the array only when we need it to reduce overhead. */
  if (namesArray != nil)
    {
      return namesArray;
    }

  if (zone_mutex != nil)
    {
      [zone_mutex lock];
    }
  if (namesArray == nil)
    {
      unsigned		i;
      NSMutableArray	*ma;
      NSArray		*regionsArray;

      ma = [NSMutableArray new];
      regionsArray = [self timeZoneArray];

      for (i = 0; i < [regionsArray count]; i++)
	{
	  NSArray *names = [regionsArray objectAtIndex: i];

	  [ma addObjectsFromArray: names];
	}

      [ma makeImmutableCopyOnFail: NO];
      namesArray = ma;
    }
  if (zone_mutex != nil)
    {
      [zone_mutex unlock];
    }
  return namesArray;
}

+ (id) allocWithZone: (NSZone*)z
{
  if (self == NSTimeZoneClass)
    {
      /*
       * We return a placeholder object that can
       * be converted to a real object when its initialisation method
       * is called.
       */
      if (z == NSDefaultMallocZone() || z == 0)
	{
	  /*
	   * As a special case, we can return a placeholder for a time zone
	   * in the default zone extremely efficiently.
	   */
	  return defaultPlaceholderTimeZone;
	}
      else
	{
	  id	obj;

	  /*
	   * For anything other than the default zone, we need to
	   * locate the correct placeholder in the (lock protected)
	   * table of placeholders.
	   */
	  if (zone_mutex != nil)
	    {
	      [zone_mutex lock];
	    }
	  obj = (id)NSMapGet(placeholderMap, (void*)z);
	  if (obj == nil)
	    {
	      /*
	       * There is no placeholder object for this zone, so we
	       * create a new one and use that.
	       */
	      obj = (id)NSAllocateObject(GSPlaceholderTimeZoneClass, 0, z);
	      NSMapInsert(placeholderMap, (void*)z, (void*)obj);
	    }
	  if (zone_mutex != nil)
	    {
	      [zone_mutex unlock];
	    }
	  return obj;
	}
    }
  else
    {
      return NSAllocateObject(self, 0, z);
    }
}

/**
 * Return the default time zone for this process.
 */
+ (NSTimeZone*) defaultTimeZone
{
  NSTimeZone	*zone;

  if (zone_mutex != nil)
    {
      [zone_mutex lock];
    }
  if (defaultTimeZone == nil)
    {
      zone = [self systemTimeZone];
    }
  else
    {
      if (zone_mutex != nil)
	{
	  zone = AUTORELEASE(RETAIN(defaultTimeZone));
	}
      else
	{
	  zone = defaultTimeZone;
	}
    }
  if (zone_mutex != nil)
    {
      [zone_mutex unlock];
    }
  return zone;
}

+ (void) initialize
{
  if (self == [NSTimeZone class])
    {
      NSTimeZoneClass = self;
      GSPlaceholderTimeZoneClass = [GSPlaceholderTimeZone class];
      zoneDictionary = [[NSMutableDictionary alloc] init];

      /*
       * Set up infrastructure for placeholder timezones.
       */
      defaultPlaceholderTimeZone = (GSPlaceholderTimeZone*)
	NSAllocateObject(GSPlaceholderTimeZoneClass, 0, NSDefaultMallocZone());
      placeholderMap = NSCreateMapTable(NSNonOwnedPointerMapKeyCallBacks,
	NSNonRetainedObjectMapValueCallBacks, 0);

      localTimeZone = [[NSLocalTimeZone alloc] init];

      zone_mutex = [GSLazyRecursiveLock new];

      [[NSNotificationCenter defaultCenter] addObserver: self
        selector: @selector(_notified:)
        name: NSUserDefaultsDidChangeNotification
        object: nil];
    }
}

/**
 * Return a proxy to the default time zone for this process.
 */
+ (NSTimeZone*) localTimeZone
{
  return localTimeZone;
}

/**
 * Destroy the system time zone so that it will be recreated
 * next time it is used.
 */
+ (void) resetSystemTimeZone
{
  if (zone_mutex != nil)
    {
      [zone_mutex lock];
    }
  DESTROY(systemTimeZone);
  if (zone_mutex != nil)
    {
      [zone_mutex unlock];
    }
  [[NSNotificationCenter defaultCenter]
    postNotificationName: NSSystemTimeZoneDidChangeNotification
                  object: nil];
}

/**
 * Set the default time zone to be used for this process.
 */
+ (void) setDefaultTimeZone: (NSTimeZone*)aTimeZone
{
  if (aTimeZone != defaultTimeZone)
    {
      /*
       * We can't make the localTimeZone the default since that would
       * cause recursion ...
       */
      if (aTimeZone == localTimeZone)
	{
	  aTimeZone = [self systemTimeZone];
	}
      if (zone_mutex != nil)
	{
	  [zone_mutex lock];
	}
      ASSIGN(defaultTimeZone, aTimeZone);
      if (zone_mutex != nil)
	{
	  [zone_mutex unlock];
	}
    }
}

/**
 * Returns the current system time zone for the process.
 */
+ (NSTimeZone*) systemTimeZone
{
  NSTimeZone	*zone = nil;

  if (zone_mutex != nil)
    {
      [zone_mutex lock];
    }
  if (systemTimeZone == nil)
    {
      NSString	*localZoneString = nil;
      NSString	*localZoneSource = nil;

      /*
       * setup default value in case something goes wrong.
       */
      systemTimeZone = RETAIN([NSTimeZoneClass timeZoneForSecondsFromGMT: 0]);

      /*
       * Try to get timezone from user defaults database
       */
      localZoneSource = [NSString stringWithFormat:
	@"NSUserDefaults: '%@'", LOCALDBKEY];
      localZoneString = [[NSUserDefaults standardUserDefaults]
	stringForKey: LOCALDBKEY];

      /*
       * Try to get timezone from GNUSTEP_TZ environment variable.
       */
      if (localZoneString == nil)
	{
          localZoneSource = _(@"environment variable: 'GNUSTEP_TZ'");
	  localZoneString = [[[NSProcessInfo processInfo]
	    environment] objectForKey: @"GNUSTEP_TZ"];
	}
      /*
       * Try to get timezone from LOCAL_TIME_FILE.
       */
      if (localZoneString == nil)
	{
	  NSString	*f = _time_zone_path(LOCAL_TIME_FILE, nil);

          localZoneSource = [NSString stringWithFormat: @"file: '%@'", f];
	  if (f != nil)
	    {
	      localZoneString = [NSString stringWithContentsOfFile: f];
	      localZoneString = [localZoneString stringByTrimmingSpaces];
	    }
	}
      /*
       * Try to get timezone from standard unix environment variable.
       */
      if (localZoneString == nil)
	{
          localZoneSource = _(@"environment variable: 'TZ'");
	  localZoneString = [[[NSProcessInfo processInfo]
	    environment] objectForKey: @"TZ"];
	}
#if HAVE_TZSET
      /*
       * Try to get timezone from tzset and tzname
       */
      if (localZoneString == nil)
	{
          localZoneSource = @"function: 'tzset()/tzname'";
	  tzset();
	  if (tzname[0] != NULL && *tzname[0] != '\0')
	    localZoneString = [NSString stringWithUTF8String: tzname[0]];
	}
#endif
      if (localZoneString == nil)
        {
          /* Get the zone name from the localtime file, assuming the file
	     is a symlink to the time zone. Getting the actual data (which
	     is easier) doesn't help, since we won't know the name itself.  */
#if defined(HAVE_TZHEAD) && defined(TZDEFAULT)
	  tzdir = RETAIN([NSString stringWithUTF8String: TZDIR]);
	  localZoneString = [NSString stringWithUTF8String: TZDEFAULT];
          localZoneSource = [NSString stringWithFormat:
	    @"file (TZDEFAULT): '%@'", localZoneString];
	  localZoneString = [localZoneString stringByResolvingSymlinksInPath];
#else
	  NSFileManager *dflt = [NSFileManager defaultManager];

          if ([dflt fileExistsAtPath: SYSTEM_TIME_FILE])
	    {
	      localZoneString = SYSTEM_TIME_FILE;
	      localZoneSource = [NSString stringWithFormat:
		@"file (SYSTEM_TIME_FILE): '%@'", localZoneString];
	      localZoneString
		= [localZoneString stringByResolvingSymlinksInPath];
	      /* Guess what tzdir is */
	      tzdir = [localZoneString stringByDeletingLastPathComponent];
	      while ([tzdir length] > 2
		&& [dflt fileExistsAtPath:
		[tzdir stringByAppendingPathComponent: @"GMT"]] == NO)
		{
		  tzdir = [tzdir stringByDeletingLastPathComponent];
		}
	      if ([tzdir length] <= 2)
	        {
		  localZoneString = tzdir = nil;
		}
#if	!GS_WITH_GC
	      else
		{
		  [tzdir retain];
		}
#endif
	    }
#endif
	  if (localZoneString != nil && [localZoneString hasPrefix: tzdir])
	    {
	      /* This must be the time zone name */
	      localZoneString = AUTORELEASE([localZoneString mutableCopy]);
	      [(NSMutableString*)localZoneString deleteCharactersInRange:
		NSMakeRange(0, [tzdir length])];
	      while ([localZoneString hasPrefix: @"/"])
	        {
		  [(NSMutableString*)localZoneString deleteCharactersInRange:
		    NSMakeRange(0, 1)];
	        }
	    }
	  else
	    {
	      localZoneString = nil;
	    }
        }

#if	defined(__MINGW__)
      /*
       * Try to get timezone from windows system call.
       */
      {
      	TIME_ZONE_INFORMATION tz;
      	DWORD DST = GetTimeZoneInformation(&tz);

        localZoneSource = @"function: 'GetTimeZoneInformation()'";
      	if (DST == TIME_ZONE_ID_DAYLIGHT)
	  {
	    localZoneString = [NSString stringWithCharacters: tz.DaylightName
	      length: wcslen(tz.DaylightName)];
	  }
      	else
	  {
	    localZoneString = [NSString stringWithCharacters: tz.StandardName
	      length: wcslen(tz.StandardName)];
	  }
      }
#endif

      if (localZoneString != nil)
	{
	  NSDebugLLog (@"NSTimeZone", @"Using zone %@", localZoneString);
	  zone = [defaultPlaceholderTimeZone initWithName: localZoneString];
	  if (zone == nil)
	    {
              NSLog(@"Unable to create time zone for name: '%@' (source '%@').",
		localZoneString, localZoneSource);
	      if ([localZoneSource hasPrefix: @"file"]
	        || [localZoneSource hasPrefix: @"function"])
		{
                  NSLog(@"It seems that your operating system does not have a valid timzone names configured ... please correct that or override by setting the '%@' user default to a timezone name (such as 'Europe/London' or 'America/Chicago')", LOCALDBKEY);
		}
	    }
	}
      else
	{
	  NSLog(@"No local time zone specified.");
	}

      /*
       * If local time zone fails to allocate, then allocate something
       * that is sure to succeed (unless we run out of memory, of
       * course).
       */
      if (zone == nil)
        {
          NSLog(@"Using time zone with absolute offset 0.");
          zone = systemTimeZone;
        }
      ASSIGN(systemTimeZone, zone);
    }
  if (zone_mutex != nil)
    {
      zone = AUTORELEASE(RETAIN(systemTimeZone));
      [zone_mutex unlock];
    }
  else
    {
      zone = systemTimeZone;
    }
  return zone;
}

/**
 * Returns an array of all the known regions.<br />
 * There are 24 elements, of course, one for each time zone.
 * Each element contains an array of NSStrings which are
 * the region names.
 */
+ (NSArray*) timeZoneArray
{
  static NSArray *regionsArray = nil;

  /* We create the array only when we need it to reduce overhead. */
  if (regionsArray != nil)
    {
      return regionsArray;
    }
  if (zone_mutex != nil)
    {
      [zone_mutex lock];
    }
  if (regionsArray == nil)
    {
      CREATE_AUTORELEASE_POOL(pool);
      int index, i;
      char name[80];
      FILE		*fp;
      NSMutableArray	*temp_array[24];
      NSString		*path;

      for (i = 0; i < 24; i++)
	{
	  temp_array[i] = [NSMutableArray array];
	}

      path = _time_zone_path (REGIONS_FILE, nil);
      if (path != nil)
	{
#if	defined(__MINGW__)
	  unichar	mode[3];

	  mode[0] = 'r';
	  mode[1] = 'b';
	  mode[2] = '\0';

	  fp = _wfopen((const unichar*)[path fileSystemRepresentation], mode);
#else
	  fp = fopen([path fileSystemRepresentation], "r");
#endif
	  if (fp == NULL)
	    {
	      if (zone_mutex != nil)
		{
		  [zone_mutex unlock];
		}
	      [NSException
		raise: NSInternalInconsistencyException
		format: @"Failed to open time zone regions array file."];
	    }
	  while (fscanf(fp, "%d %s", &index, name) == 2)
	    {
	      [temp_array[index]
		addObject: [NSString stringWithUTF8String: name]];
	    }
	  fclose(fp);
	}
      else
	{
	  NSString	*zonedir = [NSTimeZone _getTimeZoneFile: @"WET"]; 

	  if (tzdir != nil)
	    {
	      NSFileManager		*mgr = [NSFileManager defaultManager];
	      NSDirectoryEnumerator	*enumerator;
	      NSString			*name;

	      zonedir = [zonedir stringByDeletingLastPathComponent];
	      enumerator = [mgr enumeratorAtPath: zonedir];
	      while ((name = [enumerator nextObject]) != nil)
		{
		  NSTimeZone	*zone = nil;
		  BOOL		isDir;
		
		  path = [zonedir stringByAppendingPathComponent: name];
		  if ([mgr fileExistsAtPath: path isDirectory: &isDir]
		      && isDir == NO
		      && [[path pathExtension] isEqual: @"tab"] == NO)
		    {
		      zone = [zoneDictionary objectForKey: name];
		      if (zone == nil)
			{
			  NSData	*data;

			  data = [NSData dataWithContentsOfFile: path];
			  /* We should really make sure this is a real
			     zone file and not something extra that happens
			     to be in this directory, but initWithName:data:
			     will do this anyway and log a message if not. */
			  zone = [[self alloc] initWithName: name data: data];
			  IF_NO_GC([zone autorelease];)
			}
		      if (zone != nil)
			{
			  int			offset;
			  NSArray		*details;
			  NSTimeZoneDetail	*detail;
			  NSEnumerator		*e;

			  details = [zone timeZoneDetailArray];
			  e = [details objectEnumerator];
		
			  while ((detail = [e nextObject]) != nil)
			    {
			      if ([detail isDaylightSavingTime] == NO)
				{
				  break;	// Found a standard time
				}
			    }
			  if (detail == nil && [details count] > 0)
			    {
			      // If no standard time
			      detail = [details objectAtIndex: 0];
			    }

			  offset = [detail secondsFromGMT];
			  if (offset < 0)
			    {
			      offset = -offset;
			      offset %= (60 * 60 * 24);
			      offset = -offset;
			      offset += (60 * 60 * 24);
			    }
			  else
			    {
			      offset %= (60 * 60 * 24);
			    }
			  offset /= (60 * 60);

			  [temp_array[offset] addObject: name];
			}
		    }
		}
	    }
	}
      regionsArray = [[NSArray alloc] initWithObjects: temp_array count: 24];
      RELEASE(pool);
    }
  if (zone_mutex != nil)
    {
      [zone_mutex unlock];
    }
  return regionsArray;
}

/**
 * Return a timezone for the specified offset from GMT.<br />
 * The timezone returned does <em>not</em> use daylight savings time.
 * The actual timezone returned has an offset rounded to the nearest
 * minute.<br />
 * Time zones with an offset of more than +/- 18 hours  are disallowed,
 * and nil is returned.
 */
+ (NSTimeZone*) timeZoneForSecondsFromGMT: (NSInteger)seconds
{
  NSTimeZone	*zone;

  zone = [[GSAbsTimeZone alloc] initWithOffset: seconds name: nil];
  return AUTORELEASE(zone);
}

/**
 * Returns a timezone for the specified abbreviation. The same abbreviations
 * are used in different regions so this isn't particularly useful.<br />
 * Calls NSTimeZone-abbreviation dictionary an so uses a lot of memory.
 */
+ (NSTimeZone*) timeZoneWithAbbreviation: (NSString*)abbreviation
{
  NSTimeZone	*zone;
  NSString	*name;

  name = [[self abbreviationDictionary] objectForKey: abbreviation];
  if (name == nil)
    {
      zone = nil;
    }
  else
    {
      zone = [self timeZoneWithName: name data: nil];
    }
  return zone;
}

/**
 * Returns a timezone for the specified name.
 */
+ (NSTimeZone*) timeZoneWithName: (NSString*)aTimeZoneName
{
  NSTimeZone	*zone;

  zone = [defaultPlaceholderTimeZone initWithName: aTimeZoneName data: nil];
  return AUTORELEASE(zone);
}

/**
 * Returns a timezone for aTimeZoneName, created from the supplied
 * time zone data. Data must be in TZ format as per the Olson database.
 */
+ (NSTimeZone*) timeZoneWithName: (NSString*)name data: (NSData*)data
{
  NSTimeZone	*zone;

  zone = [defaultPlaceholderTimeZone initWithName: name data: data];
  return AUTORELEASE(zone);
}

/**
 * Returns the abbreviation for this timezone now.
 * Invokes -abbreviationForDate:
 */
- (NSString*) abbreviation
{
  return [self abbreviationForDate: [NSDate date]];
}

/**
 * Returns the abbreviation for this timezone at aDate.  This may differ
 * depending on whether daylight savings time is in effect or not.
 */
- (NSString*) abbreviationForDate: (NSDate*)aDate
{
  NSTimeZoneDetail	*detail;
  NSString		*abbr;

  detail = [self timeZoneDetailForDate: aDate];
  abbr = [detail timeZoneAbbreviation];

  return abbr;
}

/**
 * Returns the Class for this object
 */
- (Class) classForCoder
{
  return NSTimeZoneClass;
}

- (id) copyWithZone: (NSZone*)z
{
  return RETAIN(self);
}

/**
 * Returns the data with which the receiver was initialised.
 */
- (NSData*) data
{
  return nil;
}

/**
 * Returns the name of this object.
 */
- (NSString*) description
{
  return [self name];
}

- (void) encodeWithCoder: (NSCoder*)aCoder
{
  [aCoder encodeObject: [self name]];
}

- (id) init
{
  return [self initWithName: @"NSLocalTimeZone" data: nil];
}

- (id) initWithCoder: (NSCoder*)aDecoder
{
  NSString	*name;

  name = [aDecoder decodeObject];
  self = [self initWithName: name data: nil];
  return self;
}

/**
 * Initialise a timezone with the supplied name.  May return a cached
 * timezone object rather than the newly created one.
 */
- (id) initWithName: (NSString*)name
{
  return [self initWithName: name data: nil];
}

/**
 * Initialises a time zone object using the supplied data object.<br />
 * This method is intended for internal use by the NSTimeZone
 * class cluster.
 * Don't use it ... use -initWithName: instead.
 */
- (id) initWithName: (NSString*)name data: (NSData*)data
{
  [self notImplemented: _cmd];
  return nil;
}

/**
 * Returns a boolean indicating whether daylight savings time is in
 * effect now.  Invokes -isDaylightSavingTimeForDate:
 */
- (BOOL) isDaylightSavingTime
{
  return [self isDaylightSavingTimeForDate: [NSDate date]];
}

/**
 * Returns a boolean indicating whether daylight savings time is in
 * effect for this time zone at aDate.
 */
- (BOOL) isDaylightSavingTimeForDate: (NSDate*)aDate
{
  NSTimeZoneDetail	*detail;
  BOOL			isDST;

  detail = [self timeZoneDetailForDate: aDate];
  isDST = [detail isDaylightSavingTimeZone];

  return isDST;
}

- (BOOL) isEqual: (id)other
{
  if (other == self)
    return YES;
  if ([other isKindOfClass: NSTimeZoneClass] == NO)
    return NO;
  return [self isEqualToTimeZone: other];
}

/**
 * Returns TRUE if the time zones have the same name.
 */
- (BOOL) isEqualToTimeZone: (NSTimeZone*)aTimeZone
{
  if (aTimeZone == self)
    return YES;
  if ([[self name] isEqual: [aTimeZone name]] == NO)
    return NO;
  if (([self data] == nil && [aTimeZone data] == nil)
    || [[self name] isEqual: [aTimeZone name]] == YES)
    return YES;
  return NO;
}

/**
 * Returns the name of the timezone
 */
- (NSString*) name
{
  return [self subclassResponsibility: _cmd];
}

- (id) replacementObjectForPortCoder: (NSPortCoder*)aCoder
{
  if ([aCoder isByref] == NO)
    {
      return self;
    }
  return [super replacementObjectForPortCoder: aCoder];
}

/**
 * Returns the number of seconds by which the receiver differs
 * from Greenwich Mean Time at the current date and time.<br />
 * Invokes -secondsFromGMTForDate:
 */
- (NSInteger) secondsFromGMT
{
  return [self secondsFromGMTForDate: [NSDate date]];
}

/**
 * Returns the number of seconds by which the receiver differs
 * from Greenwich Mean Time at the date aDate.<br />
 * If the time zone uses daylight savings time, the returned value
 * will vary at different times of year.
 */
- (NSInteger) secondsFromGMTForDate: (NSDate*)aDate
{
  NSTimeZoneDetail	*detail;
  int			offset;

  detail = [self timeZoneDetailForDate: aDate];
  offset = [detail timeZoneSecondsFromGMT];

  return offset;
}

/**
 * DEPRECATED:  see NSTimeZoneDetail
 */
- (NSArray*) timeZoneDetailArray
{
  return [self subclassResponsibility: _cmd];
}

/**
 * DEPRECATED:  see NSTimeZoneDetail
 */
- (NSTimeZoneDetail*) timeZoneDetailForDate: (NSDate*)date
{
  return [self subclassResponsibility: _cmd];
}

/**
 * Returns the name of this timezone.
 */
- (NSString*) timeZoneName
{
  return [self name];
}

- (NSTimeInterval) daylightSavingTimeOffsetForDate: (NSDate *)aDate
{
  return 0.0;   // FIXME
}

- (NSDate *) nextDaylightSavingTimeTransitionAfterDate: (NSDate *)aDate
{
  return nil;   // FIXME;
}

- (NSTimeInterval) daylightSavingTimeOffset
{
  return 0.0;   // FIXME
}

- (NSDate *) nextDaylightSavingTimeTransition
{
  return nil;   // FIXME;
}

- (NSString *)localizedName: (NSTimeZoneNameStyle)style
                     locale: (NSLocale *)locale
{
  return nil;   // FIXME;
}
                    
@end

/**
 * This class serves no useful purpose in GNUstep other than to provide
 * a backup mechanism for handling abbreviations where the precomputed
 * data files cannot be found. It is provided primarily for backward
 * compatibility with the OpenStep spec.  It is missing entirely from MacOS-X.
 */
@implementation NSTimeZoneDetail

- (NSString*) description
{
  return [NSString stringWithFormat: @"%@(%@, %s%d)", [self name],
    [self timeZoneAbbreviation],
    ([self isDaylightSavingTimeZone]? "IS_DST, ": ""),
    [self timeZoneSecondsFromGMT]];
}

/**
 * DEPRECATED: Class is no longer used.
 */
- (BOOL) isDaylightSavingTimeZone
{
  [self subclassResponsibility: _cmd];
  return NO;
}

/**
 * DEPRECATED: Class is no longer used.
 */
- (NSString*) timeZoneAbbreviation
{
  return [self subclassResponsibility: _cmd];
}

/**
 * DEPRECATED: Class is no longer used.
 */
- (NSInteger) timeZoneSecondsFromGMT
{
  [self subclassResponsibility: _cmd];
  return 0;
}

@end


@implementation NSTimeZone (Private)

/**
 * Common locations for timezone info on unix systems.
 */
static NSString *zoneDirs[] = {
#ifdef TZDIR
  @TZDIR,
#endif
  @"/usr/share/zoneinfo", 
  @"/usr/lib/zoneinfo",
  @"/usr/local/share/zoneinfo",
  @"/usr/local/lib/zoneinfo", 
  @"/etc/zoneinfo",
  @"/usr/local/etc/zoneinfo"
};

/**
 * Returns the path to the named zone info file.
 */
+ (NSString*) _getTimeZoneFile: (NSString *)name
{
  static BOOL	beenHere = NO;
  NSString	*dir = nil;

  if (beenHere == NO && tzdir == nil)
    {
      if (zone_mutex != nil)
	{
	  [zone_mutex lock];
	}
      if (beenHere == NO && tzdir == nil)
	{
	  NSFileManager	*mgr = [NSFileManager defaultManager];
	  NSString	*zonedir = nil;
	  unsigned	i;

	  for (i = 0; i < sizeof(zoneDirs)/sizeof(zoneDirs[0]); i++)
	    {
	      BOOL	isDir;

	      zonedir
		= [zoneDirs[i] stringByAppendingPathComponent: POSIX_TZONES];
	      if ([mgr fileExistsAtPath: zonedir isDirectory: &isDir] && isDir)
		{
		  tzdir = RETAIN(zonedir);
		  break;  // use first one
		}
	    }
	  beenHere = YES;
	}
      if (zone_mutex != nil)
	{
	  [zone_mutex unlock];
	}
    }
  /* Use the system zone info if possible, otherwise, use our installed
     info.  */
  if (tzdir && [[NSFileManager defaultManager] fileExistsAtPath:
    [tzdir stringByAppendingPathComponent: name]] == YES)
    {
      dir = tzdir;
    }
  if (dir == nil)
    {
      dir = _time_zone_path (ZONES_DIR, nil);
    }
  return [dir stringByAppendingPathComponent: name];
}

+ (void) _notified: (NSNotification*)n
{
  NSString      *name;

  /* If the name of the system time zone has changed ...
   * get a new system time zone.
   */
  name = [[NSUserDefaults standardUserDefaults] stringForKey: LOCALDBKEY];
  if ([name length] > 0 && [name isEqual: [[self systemTimeZone] name]] == NO)
    {
      [self resetSystemTimeZone];
      [self systemTimeZone];
    }
}
@end


#if	defined(__MINGW__)
/* Timezone information data as stored in the registry */
typedef struct TZI_format {
	LONG       Bias;
	LONG       StandardBias;
	LONG       DaylightBias;
	SYSTEMTIME StandardDate;
	SYSTEMTIME DaylightDate;
} TZI;

static inline unsigned int
lastDayOfGregorianMonth(int month, int year)
{
  switch (month)
    {
      case 2:
        if ((((year % 4) == 0) && ((year % 100) != 0))
          || ((year % 400) == 0))
          return 29;
        else
          return 28;
      case 4:
      case 6:
      case 9:
      case 11: return 30;
      default: return 31;
    }
}

/* IMPORT from NSCalendar date */
void
GSBreakTime(NSTimeInterval when, NSInteger*year, NSInteger*month, NSInteger*day,
  NSInteger*hour, NSInteger*minute, NSInteger*second, NSInteger*mil);


@implementation GSWindowsTimeZone

- (NSString*) abbreviationForDate: (NSDate*)aDate
{
  if ([self isDaylightSavingTimeForDate: aDate])
    return daylightZoneNameAbbr;
  return timeZoneNameAbbr;
}

- (NSData*) data
{
  return 0;
}

- (void) dealloc
{
  RELEASE(timeZoneName);
  RELEASE(daylightZoneName);
  RELEASE(timeZoneNameAbbr);
  RELEASE(daylightZoneNameAbbr);
  [super dealloc];
}

- (id) initWithName: (NSString*)name data: (NSData*)data
{
  HKEY     regDirKey;
  BOOL     isNT = NO, regFound=NO;

  /* Open the key in the local machine hive where
   * the time zone data is stored. */
  if (ERROR_SUCCESS == RegOpenKeyExW(HKEY_LOCAL_MACHINE,
    L"SOFTWARE\\Microsoft\\Windows NT\\CurrentVersion\\Time Zones",
    0,
    KEY_READ,
    &regDirKey))
    {
      isNT=YES;
      regFound=YES;
    }
  else
    {
      if (ERROR_SUCCESS == RegOpenKeyExW(HKEY_LOCAL_MACHINE,
          L"SOFTWARE\\Microsoft\\Windows NT\\CurrentVersion\\Time Zones",
          0,
          KEY_READ,
          &regDirKey))
        {
          regFound=YES;
        }
    }

  if (regFound)
    {
      /* Iterate over all subKeys in the registry to find the right one.
         Unfortunately name is a localized value. The keys in the registry are
         unlocalized names. */
      wchar_t  achKey[255];              // buffer for subkey name
      DWORD    cbName;                   // size of name string 
      wchar_t  achClass[MAX_PATH] = L""; // buffer for class name 
      DWORD    cchClassName = MAX_PATH;  // size of class string 
      DWORD    cSubKeys=0;               // number of subkeys 
      DWORD    cbMaxSubKey;              // longest subkey size 
      DWORD    cchMaxClass;              // longest class string 
      DWORD    cValues;                  // number of values for key 
      DWORD    cchMaxValue;              // longest value name 
      DWORD    cbMaxValueData;           // longest value data 
      DWORD    cbSecurityDescriptor;     // size of security descriptor 
      FILETIME ftLastWriteTime;          // last write time 
      DWORD     i, retCode;
      BOOL	tzFound = NO;
		
      /* Get the class name and the value count. */
      retCode = RegQueryInfoKeyW(
        regDirKey,               // key handle 
        achClass,                // buffer for class name 
        &cchClassName,           // size of class string 
        NULL,                    // reserved 
        &cSubKeys,               // number of subkeys 
        &cbMaxSubKey,            // longest subkey size 
        &cchMaxClass,            // longest class string 
        &cValues,                // number of values for this key 
        &cchMaxValue,            // longest value name 
        &cbMaxValueData,         // longest value data 
        &cbSecurityDescriptor,   // security descriptor 
        &ftLastWriteTime);       // last write time 

      if (cSubKeys && (retCode == ERROR_SUCCESS))
    	{
          unsigned wLen = [name length];
          wchar_t *wName = malloc((wLen+1) * sizeof(wchar_t));

          if (wName)
            {
              [name getCharacters: wName];
              wName[wLen] = 0;
              for (i = 0; i < cSubKeys && !tzFound; i++) 
                { 
                  cbName = 255;
                   
                  retCode = RegEnumKeyExW(regDirKey, i, achKey, &cbName,
                    NULL, NULL, NULL, &ftLastWriteTime);         
                  if (retCode == ERROR_SUCCESS) 
                    {
                      wchar_t keyBuffer[16384];
                      HKEY regKey;
                       
                      if (isNT)
                        wcscpy(keyBuffer, L"SOFTWARE\\Microsoft\\Windows NT\\CurrentVersion\\Time Zones\\");
                      else
                        wcscpy(keyBuffer, L"SOFTWARE\\Microsoft\\Windows\\CurrentVersion\\Time Zones\\");
                       
                      wcscat(keyBuffer, achKey);
                      if (ERROR_SUCCESS == RegOpenKeyExW(HKEY_LOCAL_MACHINE,
                        keyBuffer, 0, KEY_READ, &regKey))
                        {
                          wchar_t buf[256];
                          wchar_t standardName[256];
                          wchar_t daylightName[256];
                          DWORD bufsize;
                          DWORD type;

                          /* check standardname */
                          standardName[0] = L'\0';
                          bufsize = sizeof(buf);
                          if (ERROR_SUCCESS == RegQueryValueExW(regKey,
                            L"Std", 0, &type, (BYTE *)buf, &bufsize))
                            {
                              wcscpy(standardName, buf);
                              if (wcscmp(standardName, wName) == 0)
                                tzFound = YES;
                            }
        
                          /* check daylightname */
                          daylightName[0] = L'\0';
                          bufsize = sizeof(buf);
                          if (ERROR_SUCCESS == RegQueryValueExW(regKey,
                            L"Dlt", 0, &type, (BYTE *)buf, &bufsize))
                            {
                              wcscpy(daylightName, buf);
                              if (wcscmp(daylightName, wName) == 0)
                                tzFound = YES;
                            }

                          if (tzFound)
                            {
                              /* Read in the time zone data */
                              bufsize = sizeof(buf);
                              if (ERROR_SUCCESS == RegQueryValueExW(regKey,
                                L"TZI", 0, &type, (BYTE *)buf, &bufsize))
                                {
                                  TZI *tzi = (void*)buf;
                                  Bias = tzi->Bias;
                                  StandardBias = tzi->StandardBias;
                                  DaylightBias = tzi->DaylightBias;
                                  StandardDate = tzi->StandardDate;
                                  DaylightDate = tzi->DaylightDate;
                                }
                          
                              /* Set the standard name for the time zone. */
                              if (wcslen(standardName))
                                {
                                  int a, b;

                                  ASSIGN(timeZoneName,
                                    [NSString stringWithCharacters: standardName
                                    length: wcslen(standardName)]);

                                  /* Abbr generated here is IMHO
                                   * a bit suspicous but I kept it */
                                  for (a = 0, b = 0; standardName[a]; a++)
                                    {
                                      if (iswupper(standardName[a]))
                                        standardName[b++] = standardName[a];
                                    }
                                  standardName[b] = L'\0';
                                  ASSIGN(timeZoneNameAbbr,
                                    [NSString stringWithCharacters: standardName
                                    length: wcslen(standardName)]);
                                }

                              /* Set the daylight savings name
                               * for the time zone. */
                              if (wcslen(daylightName))
                                {
                                  int a, b;

                                  ASSIGN(daylightZoneName,
                                    [NSString stringWithCharacters: daylightName
                                    length: wcslen(daylightName)]);

                                  /* Abbr generated here is IMHO
                                   * a bit suspicous but I kept it */
                                  for (a = 0, b = 0; daylightName[a]; a++)
                                    {
                                      if (iswupper(daylightName[a]))
                                        daylightName[b++] = daylightName[a];
                                    }
                                  daylightName[b] = L'\0';
                                  ASSIGN(daylightZoneNameAbbr,
                                    [NSString stringWithCharacters: daylightName
                                    length: wcslen(daylightName)]);
                                }
                            }
                          RegCloseKey(regKey);
                        }			       
                    }
                }
              free(wName);
            }
        }
      RegCloseKey(regDirKey);
    }
    
  return self;
}

- (BOOL) isDaylightSavingTimeForDate: (NSDate*)aDate
{
  int year, month, day, hour, minute, second, mil;
  int	dow;
  int daylightdate, count, maxdate;
  NSTimeInterval when;

  if (DaylightDate.wMonth == 0)
    return NO;

  when = [aDate timeIntervalSinceReferenceDate] - Bias*60;

  GSBreakTime(when, &year, &month, &day, &hour, &minute, &second, &mil);

  // Check north globe
  if (StandardDate.wMonth >= DaylightDate.wMonth)
    {
      // Before April or after October is Std
      if (month < DaylightDate.wMonth || month > StandardDate.wMonth)
        {
	  return NO;
	}
      // After April and before October is DST
      if (month > DaylightDate.wMonth && month < StandardDate.wMonth)
        {
	  return YES;
	}
    }
  else
    {
      /* check south globe 
       * Before April or after October is DST
       */
      if (month < StandardDate.wMonth || month > DaylightDate.wMonth)
        {
	  return YES;
	}
      // After April and before October is Std
      if (month > StandardDate.wMonth && month < DaylightDate.wMonth)
        {
	  return NO;
	}
    }

  dow = ((NSInteger)((when / 86400.0) + GREGORIAN_REFERENCE)) % 7;
  if (dow < 0)
    dow += 7;

  if (month == DaylightDate.wMonth /* April */)
    {
      daylightdate = day - dow + DaylightDate.wDayOfWeek;
      maxdate = lastDayOfGregorianMonth(DaylightDate.wMonth, year)-7;
      while (daylightdate > 7)
        daylightdate -= 7;
      if (daylightdate < 1)
        daylightdate += 7;
      count = DaylightDate.wDay;
      while (count > 1 && daylightdate < maxdate)
        {
          daylightdate += 7;
          count--;
        }
      if (day > daylightdate)
        return YES;
      if (day < daylightdate)
        return NO;
      if (hour > DaylightDate.wHour)
        return YES;
      if (hour < DaylightDate.wHour)
        return NO;
      if (minute > DaylightDate.wMinute)
        return YES;
      if (minute < DaylightDate.wMinute)
        return NO;
      if (second > DaylightDate.wSecond)
        return YES;
      if (second < DaylightDate.wSecond)
        return NO;
      if (mil >= DaylightDate.wMilliseconds)
        return YES;
      return NO;
    }
  if (month == StandardDate.wMonth /* October */)
    {
      daylightdate = day - dow + StandardDate.wDayOfWeek;
      maxdate = lastDayOfGregorianMonth(StandardDate.wMonth, year)-7;
      while (daylightdate > 7)
        daylightdate -= 7;
      if (daylightdate < 1)
        daylightdate += 7;
      count = StandardDate.wDay;
      while (count > 1 && daylightdate < maxdate)
        {
          daylightdate += 7;
          count--;
        }
      if (day > daylightdate)
        return NO;
      if (day < daylightdate)
        return YES;
      if (hour > StandardDate.wHour)
        return NO;
      if (hour < StandardDate.wHour)
        return YES;
      if (minute > StandardDate.wMinute)
        return NO;
      if (minute < StandardDate.wMinute)
        return YES;
      if (second > StandardDate.wSecond)
        return NO;
      if (second < StandardDate.wSecond)
        return YES;
      if (mil >= StandardDate.wMilliseconds)
        return NO;
      return YES;
    }
  return NO; // Never reached
}

- (NSString*) name
{
  TIME_ZONE_INFORMATION tz;
  DWORD DST = GetTimeZoneInformation(&tz);

  if (DST == TIME_ZONE_ID_DAYLIGHT)
    {
      return daylightZoneName;
    }
  else
    {
      return timeZoneName;
    }
}

- (NSInteger) secondsFromGMTForDate: (NSDate*)aDate
{
  if ([self isDaylightSavingTimeForDate: aDate])
    return -Bias*60 - DaylightBias*60;
  return -Bias*60 - StandardBias*60;
}

- (NSArray*) timeZoneDetailArray
{
  return [NSArray arrayWithObjects:
    [[[GSTimeZoneDetail alloc] initWithTimeZone: self
      withAbbrev: timeZoneNameAbbr
      withOffset: -Bias*60 - StandardBias*60
      withDST: NO] autorelease],
    [[[GSTimeZoneDetail alloc] initWithTimeZone: self
      withAbbrev: daylightZoneNameAbbr
      withOffset: -Bias*60 - DaylightBias*60
      withDST: YES] autorelease], 0];
}

- (NSTimeZoneDetail*) timeZoneDetailForDate: (NSDate*)aDate
{
  GSTimeZoneDetail	*detail;
  int offset;
  BOOL isDST = [self isDaylightSavingTimeForDate: aDate];
  NSString *abbr;

  if (isDST)
    {
      offset = -Bias*60 - DaylightBias*60;
      abbr = daylightZoneNameAbbr;
    }
  else
    {
      offset = -Bias*60 - StandardBias*60;
      abbr = timeZoneNameAbbr;
    }
  detail = [GSTimeZoneDetail alloc];
  detail = [detail initWithTimeZone: self
                         withAbbrev: abbr
                         withOffset: offset
                            withDST: isDST];
  return detail;
}

- (NSString*) timeZoneName
{
  return [self name];
}
@end
#endif // __MINGW__


@implementation	GSTimeZone

/**
 * Perform a binary search of a transitions table to locate the index
 * of the transition to use for a particular time interval since 1970.<br />
 * We locate the index of the highest transition before the date, or zero
 * if there is no transition before it.
 */
static TypeInfo*
chop(NSTimeInterval since, GSTimeZone *zone)
{
  int32_t		when = (int32_t)since;
  int32_t		*trans = zone->trans;
  unsigned		hi = zone->n_trans;
  unsigned		lo = 0;
  unsigned int		i;

  if (hi == 0 || trans[0] > when)
    {
      unsigned	n_types = zone->n_types;

      /*
       * If the first transition is greater than our date,
       * we locate the first non-DST transition and use that offset,
       * or just use the first transition.
       */
      for (i = 0; i < n_types; i++)
	{
	  if (zone->types[i].isdst == 0)
	    {
	      return &zone->types[i];
	    }
	}
      return &zone->types[0];
    }
  else
    {
      for (i = hi/2; hi != lo; i = (hi + lo)/2)
	{
	  if (when < trans[i])
	    {
	      hi = i;
	    }
	  else if (when > trans[i])
	    {
	      lo = ++i;
	    }
	  else
	    {
	      break;
	    }
	}
      /*
       * If we went off the top of the table or the closest transition
       * was later than our date, we step back to find the last
       * transition before our date.
       */
      if (i > 0 && (i == zone->n_trans || trans[i] > when))
	{
	  i--;
	}
      return &zone->types[zone->idxs[i]];
    }
}

static NSTimeZoneDetail*
newDetailInZoneForType(GSTimeZone *zone, TypeInfo *type)
{
  GSTimeZoneDetail	*detail;

  detail = [GSTimeZoneDetail alloc];
  detail = [detail initWithTimeZone: zone
			 withAbbrev: type->abbreviation
			 withOffset: type->offset
			    withDST: type->isdst];
  return detail;
}

- (NSString*) abbreviationForDate: (NSDate*)aDate
{
  TypeInfo	*type = chop([aDate timeIntervalSince1970], self);

  return type->abbreviation;
}

- (NSData*) data
{
  return timeZoneData;
}

- (void) dealloc
{
  RELEASE(timeZoneName);
  RELEASE(timeZoneData);
  RELEASE(abbreviations);
  if (types != 0)
    {
      NSZoneFree(NSDefaultMallocZone(), types);
    }
  [super dealloc];
}

- (id) initWithName: (NSString*)name data: (NSData*)data
{
  static NSString	*fileException = @"GSTimeZoneFileException";

  timeZoneName = [name copy];
  timeZoneData = [data copy];
  NS_DURING
    {
      const void	*bytes = [timeZoneData bytes];
      unsigned		length = [timeZoneData length];
      void		*buf;
      unsigned		pos = 0;
      unsigned		i, charcnt;
      unsigned char	*abbr;
      struct tzhead	*header;

      if (length < sizeof(struct tzhead))
	{
	  [NSException raise: fileException
		      format: @"File is too small"];
	}
      header = (struct tzhead *)(bytes + pos);
      pos += sizeof(struct tzhead);
#ifdef TZ_MAGIC
      if (memcmp(header->tzh_magic, TZ_MAGIC, strlen(TZ_MAGIC)) != 0)
	{
	  [NSException raise: fileException
		      format: @"TZ_MAGIC is incorrect"];
	}
#endif
      n_trans = GSSwapBigI32ToHost(*(int32_t*)header->tzh_timecnt);
      n_types = GSSwapBigI32ToHost(*(int32_t*)header->tzh_typecnt);
      charcnt = GSSwapBigI32ToHost(*(int32_t*)header->tzh_charcnt);

      i = pos;
      i += sizeof(int32_t)*n_trans;
      if (i > length)
	{
	  [NSException raise: fileException
		      format: @"Transitions list is truncated"];
	}
      i += n_trans;
      if (i > length)
	{
	  [NSException raise: fileException
		      format: @"Transition indexes are truncated"];
	}
      i += sizeof(struct ttinfo)*n_types;
      if (i > length)
	{
	  [NSException raise: fileException
		      format: @"Types list is truncated"];
	}
      if (i + charcnt > length)
	{
	  [NSException raise: fileException
		      format: @"Abbreviations list is truncated"];
	}

      /*
       * Now calculate size we need to store the information
       * for efficient access ... not the same saze as the data
       * we received.
       */
      i = n_trans * (sizeof(int32_t)+1) + n_types * sizeof(TypeInfo);
      buf = NSZoneMalloc(NSDefaultMallocZone(), i);
      types = (TypeInfo*)buf;
      buf += (n_types * sizeof(TypeInfo));
      trans = (int32_t*)buf;
      buf += (n_trans * sizeof(int32_t));
      idxs = (unsigned char*)buf;

      /* Read in transitions. */
      for (i = 0; i < n_trans; i++)
	{
	  trans[i] = GSSwapBigI32ToHost(*(int32_t*)(bytes + pos));
	  pos += sizeof(int32_t);
	}
      for (i = 0; i < n_trans; i++)
	{
	  idxs[i] = *(unsigned char*)(bytes + pos);
	  pos++;
	}
      for (i = 0; i < n_types; i++)
	{
	  struct ttinfo	*ptr = (struct ttinfo*)(bytes + pos);

	  types[i].isdst = (ptr->isdst != 0 ? YES : NO);
	  types[i].abbr_idx = ptr->abbr_idx;
	  types[i].offset = decode(ptr->offset);
	  pos += sizeof(struct ttinfo);
	}
      abbr = (unsigned char*)(bytes + pos);
      {
	id		abbrevs[charcnt];
	unsigned	count = 0;
	unsigned	used = 0;

	memset(abbrevs, '\0', sizeof(id)*charcnt);
	for (i = 0; i < n_types; i++)
	  {
	    int	loc = types[i].abbr_idx;

	    if (abbrevs[loc] == nil)
	      {
		abbrevs[loc]
		  = [[NSString alloc] initWithUTF8String: (char*)abbr + loc];
		count++;
	      }
	    types[i].abbreviation = abbrevs[loc];
	  }
	/*
	 * Now we have created all the abbreviations, we put them in an
	 * array for easy access later and easy deallocation if/when
	 * the receiver is deallocated.
	 */
	i = charcnt;
	while (i-- > count)
	  {
	    if (abbrevs[i] != nil)
	      {
		while (abbrevs[used] != nil)
		  {
		    used++;
		  }
		abbrevs[used] = abbrevs[i];
		abbrevs[i] = nil;
		if (++used >= count)
		  {
		    break;
		  }
	      }
	  }
	abbreviations = [[NSArray alloc] initWithObjects: abbrevs count: count];
	while (count-- > 0)
	  {
	    RELEASE(abbrevs[count]);
	  }
      }

      if (zone_mutex != nil)
	{
	  [zone_mutex lock];
	}
      [zoneDictionary setObject: self forKey: timeZoneName];
      if (zone_mutex != nil)
	{
	  [zone_mutex unlock];
	}
    }
  NS_HANDLER
    {
      DESTROY(self);
      NSLog(@"Unable to obtain time zone `%@'... %@", name, localException);
      if ([localException name] != fileException)
	{
	  [localException raise];
	}
    }
  NS_ENDHANDLER
  return self;
}

- (BOOL) isDaylightSavingTimeForDate: (NSDate*)aDate
{
  TypeInfo	*type = chop([aDate timeIntervalSince1970], self);

  return type->isdst;
}

- (NSString*) name
{
  return timeZoneName;
}

- (NSInteger) secondsFromGMTForDate: (NSDate*)aDate
{
  TypeInfo	*type = chop([aDate timeIntervalSince1970], self);

  return type->offset;
}

- (NSArray*) timeZoneDetailArray
{
  NSTimeZoneDetail	*details[n_types];
  unsigned		i;
  NSArray		*array;

  for (i = 0; i < n_types; i++)
    {
      details[i] = newDetailInZoneForType(self, &types[i]);
    }
  array = [NSArray arrayWithObjects: details count: n_types];
  for (i = 0; i < n_types; i++)
    {
      RELEASE(details[i]);
    }
  return array;
}

- (NSTimeZoneDetail*) timeZoneDetailForDate: (NSDate*)aDate
{
  TypeInfo		*type;
  NSTimeZoneDetail	*detail;

  type = chop([aDate timeIntervalSince1970], self);
  detail = newDetailInZoneForType(self, type);
  return AUTORELEASE(detail);
}

- (NSString*) timeZoneName
{
  return timeZoneName;
}

@end