/*	CFTimeZone.c
	Copyright (c) 1998-2019, Apple Inc. and the Swift project authors
 
	Portions Copyright (c) 2014-2019, Apple Inc. and the Swift project authors
	Licensed under Apache License v2.0 with Runtime Library Exception
	See http://swift.org/LICENSE.txt for license information
	See http://swift.org/CONTRIBUTORS.txt for the list of Swift project authors
	Responsibility: Itai Ferber
*/


#include "CFTimeZone.h"
#include "CFPropertyList.h"
#include "CFDateFormatter.h"
#include "CFPriv.h"
#include "CFInternal.h"
#include "CFRuntime_Internal.h"
#include <math.h>
#include <limits.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <stdlib.h>
#include <string.h>
#include <_foundation_unicode/ucal.h>
#include <_foundation_unicode/udat.h>
#include <_foundation_unicode/ustring.h>
#include "CFDateFormatter.h"
#if TARGET_OS_MAC || TARGET_OS_LINUX || TARGET_OS_BSD || TARGET_OS_WASI
#include <dirent.h>
#include <unistd.h>
#if !TARGET_OS_ANDROID && !TARGET_OS_WASI
#include <sys/fcntl.h>
#elif TARGET_OS_WASI
#include <fcntl.h>
#else
#include <sys/endian.h>
#endif
#endif
#if TARGET_OS_WIN32
#include <tchar.h>

#include "CFTimeZone_WindowsMapping.h"
#define NOMINMAX
#define WIN32_LEAN_AND_MEAN
#include "Windows.h"
#endif

#if TARGET_OS_MAC
#include <tzfile.h>
#define MACOS_TZDIR1 "/usr/share/zoneinfo/"          // 10.12 and earlier
#define MACOS_TZDIR2 "/var/db/timezone/zoneinfo/"    // 10.13 onwards
#elif TARGET_OS_LINUX || TARGET_OS_BSD || TARGET_OS_WASI
#ifndef TZDIR
#define TZDIR	"/usr/share/zoneinfo/" /* Time zone object file directory */
#endif /* !defined TZDIR */

#ifndef TZDEFAULT
#define TZDEFAULT	"/etc/localtime"
#endif /* !defined TZDEFAULT */
#endif

#if TARGET_OS_LINUX || TARGET_OS_BSD || TARGET_OS_WIN32 || TARGET_OS_WASI
struct tzhead {
    char	tzh_magic[4];		/* TZ_MAGIC */
    char	tzh_reserved[16];	/* reserved for future use */
    char	tzh_ttisgmtcnt[4];	/* coded number of trans. time flags */
    char	tzh_ttisstdcnt[4];	/* coded number of trans. time flags */
    char	tzh_leapcnt[4];		/* coded number of leap seconds */
    char	tzh_timecnt[4];		/* coded number of transition times */
    char	tzh_typecnt[4];		/* coded number of local time types */
    char	tzh_charcnt[4];		/* coded number of abbr. chars */
};
#endif

#include <time.h>

#if !TARGET_OS_WIN32 && !TARGET_OS_ANDROID
static CFStringRef __tzZoneInfo = NULL;
static char *__tzDir = NULL;
static void __InitTZStrings(void);
#endif

CONST_STRING_DECL(kCFTimeZoneSystemTimeZoneDidChangeNotification, "kCFTimeZoneSystemTimeZoneDidChangeNotification")

static CFTimeZoneRef __CFTimeZoneSystem = NULL;
static CFTimeZoneRef __CFTimeZoneDefault = NULL;
static CFDictionaryRef __CFTimeZoneAbbreviationDict = NULL;
static CFLock_t __CFTimeZoneAbbreviationLock = CFLockInit;
static CFMutableDictionaryRef __CFTimeZoneCompatibilityMappingDict = NULL;
static CFLock_t __CFTimeZoneCompatibilityMappingLock = CFLockInit;
static CFArrayRef __CFKnownTimeZoneList = NULL;
static CFMutableDictionaryRef __CFTimeZoneCache = NULL;
static CFLock_t __CFTimeZoneGlobalLock = CFLockInit;

CF_INLINE void __CFTimeZoneLockGlobal(void) {
    __CFLock(&__CFTimeZoneGlobalLock);
}

CF_INLINE void __CFTimeZoneUnlockGlobal(void) {
    __CFUnlock(&__CFTimeZoneGlobalLock);
}

CF_INLINE void __CFTimeZoneLockAbbreviations(void) {
    __CFLock(&__CFTimeZoneAbbreviationLock);
}

CF_INLINE void __CFTimeZoneUnlockAbbreviations(void) {
    __CFUnlock(&__CFTimeZoneAbbreviationLock);
}

CF_INLINE void __CFTimeZoneLockCompatibilityMapping(void) {
    __CFLock(&__CFTimeZoneCompatibilityMappingLock);
}

CF_INLINE void __CFTimeZoneUnlockCompatibilityMapping(void) {
    __CFUnlock(&__CFTimeZoneCompatibilityMappingLock);
}

#define COUNT_OF(array) (sizeof((array)) / sizeof((array)[0]))

#if TARGET_OS_WIN32
#define CF_TIME_ZONES_KEY L"SOFTWARE\\Microsoft\\Windows NT\\CurrentVersion\\Time Zones"

/* This function should be used for WIN32 instead of
 * __CFCopyRecursiveDirectoryList function.
 * It takes TimeZone names from the registry
 * (Aleksey Dukhnyakov)
 */
static CFMutableArrayRef __CFCopyWindowsTimeZoneList() {
    CFMutableArrayRef result = NULL;
    HKEY hkResult;
    WCHAR szName[MAX_PATH + 1];
    DWORD dwIndex, retCode;

    if (RegOpenKeyW(HKEY_LOCAL_MACHINE, CF_TIME_ZONES_KEY, &hkResult) != ERROR_SUCCESS)
        return NULL;

    result = CFArrayCreateMutable(kCFAllocatorSystemDefault, 0, &kCFTypeArrayCallBacks);
    for (dwIndex = 0; (retCode = RegEnumKeyW(hkResult, dwIndex, szName, COUNT_OF(szName) - 1)) != ERROR_NO_MORE_ITEMS; dwIndex++) {
        if (retCode != ERROR_SUCCESS) {
            RegCloseKey(hkResult);
            CFRelease(result);
            return NULL;
        } else {
            CFStringRef string = CFStringCreateWithBytes(kCFAllocatorSystemDefault, (const UInt8 *)szName, (wcslen(szName) * sizeof(WCHAR)), kCFStringEncodingUTF16, false);
            CFArrayAppendValue(result, string);
            CFRelease(string);
        }
    }

    RegCloseKey(hkResult);
    return result;
}

static void __CFTimeZoneGetOffset(CFStringRef timezone, int32_t *offset) {
    typedef struct _REG_TZI_FORMAT {
        LONG Bias;
        LONG StandardBias;
        LONG DaylightBias;
        SYSTEMTIME StandardDate;
        SYSTEMTIME DaylightDate;
    } REG_TZI_FORMAT;

    WCHAR szRegKey[COUNT_OF(CF_TIME_ZONES_KEY) + 1 + COUNT_OF(((TIME_ZONE_INFORMATION *)0)->StandardName) + 1];
    REG_TZI_FORMAT tziInfo;
    Boolean bResult;
    DWORD cbData;
    HKEY hKey;

    *offset = 0;

    memset(szRegKey, 0, sizeof(szRegKey));
    wcscpy(szRegKey, CF_TIME_ZONES_KEY);
    szRegKey[COUNT_OF(CF_TIME_ZONES_KEY) - 1] = L'\\';
    CFStringGetBytes(timezone, CFRangeMake(0, CFStringGetLength(timezone)), kCFStringEncodingUnicode, FALSE, FALSE, (uint8_t *)&szRegKey[wcslen(CF_TIME_ZONES_KEY) + 1], sizeof(((TIME_ZONE_INFORMATION *)0)->StandardName) + sizeof(WCHAR), NULL);

    if (RegOpenKeyW(HKEY_LOCAL_MACHINE, szRegKey, &hKey) != ERROR_SUCCESS)
        return;

    cbData = sizeof(tziInfo);
    if (RegQueryValueExW(hKey, L"TZI", NULL, NULL, (LPBYTE)&tziInfo, &cbData) == ERROR_SUCCESS)
        *offset = tziInfo.Bias * 60; // Bias is in minutes, CF uses seconds for its offset

    RegCloseKey(hKey);
}
#elif TARGET_OS_ANDROID
/*
 * Android does not ship with the standard Unix Olsen files, with the directory
 * structure, and the files with the same name as the time zone.
 * Instead all the information is in one file, where all the time zone
 * information for all the zones is held. Also, to allow upgrades to the time
 * zone database without an update to the system, the database can be overriden
 * by a secondary location.
 * - /data/misc/zoneinfo/current/tzdata overrides for the time zone information
 *   from the system.
 * - /system/usr/share/zoneinfo/tzdata system time zone information.
 * The format of these files is slightly documented in Bionic's source file
 * libc/tzcode/bionic.cpp.
 * The file start with a header which is 24 bytes long.
 * - 6 bytes should be the ASCII string "tzdata"
 * - 6 bytes of the Olson database version in ASCII. For example 2018a. Includes
 *   a final nul character.
 * - 4 bytes MSB of the offset of the index inside the file.
 * - 4 bytes MSB of the offset of the start of the data inside the file.
 * - 4 bytes MSB of the zonetab (unused in this code).
 * The index sits between the offset for the index and the offset for the data.
 * Each index entry is 52 bytes long.
 * - 40 bytes for the name of the zone. Seems to be nul terminated.
 * - 4 bytes MSB of the offset to this time zone data. Notice that this offset
 *   is relative to the data offset from the header.
 * - 4 bytes MSB of the data length.
 * - 4 bytes unused.
 */

#define ANDROID_TZ_HEADER_SIZE 24
#define ANDROID_TZ_HEADER_TAG_SIZE 6
#define ANDROID_TZ_HEADER_INDEX_OFFSET 12
#define ANDROID_TZ_HEADER_DATA_OFFSET 16
#define ANDROID_TZ_ENTRY_SIZE 52
#define ANDROID_TZ_ENTRY_NAME_LENGTH 40
#define ANDROID_TZ_ENTRY_START_OFFSET 40
#define ANDROID_TZ_ENTRY_LENGTH_OFFSET 44

/**
 * Callback invoked for each of the time zones in the timezone file.
 * - name: The name of the time zone.
 * - offset: The final offset inside the file of the data for the time zone.
 * - length: The length of the data for the time zone.
 * - fp: The file pointer to read the data from. The file might not be in the
 *       right offset, so if you want to read the right time zone data, you
 *       probably want to fseek into offset.
 * - context1: The argument passed into __CFAndroidTimeZoneListEnumerate.
 * - context2: The argument passed into __CFAndroidTimeZoneListEnumerate.
 */
typedef Boolean (*__CFAndroidTimeZoneListEnumerateCallback)(const char name[ANDROID_TZ_ENTRY_NAME_LENGTH], int32_t offset, int32_t length, FILE *fp, void *context1, void *context2);

static void __CFAndroidTimeZoneParse(FILE *fp, __CFAndroidTimeZoneListEnumerateCallback callback, void *context1, void *context2) {
    if (!fp) {
        return;
    }

    char header[ANDROID_TZ_HEADER_SIZE];
    if (fread(header, 1, sizeof(header), fp) != sizeof(header)) {
        return;
    }
    if (strncmp(header, "tzdata", ANDROID_TZ_HEADER_TAG_SIZE) != 0) {
        return;
    }

    int32_t indexOffset;
    memcpy(&indexOffset, &header[ANDROID_TZ_HEADER_INDEX_OFFSET], sizeof(int32_t));
    indexOffset = betoh32(indexOffset);

    int32_t dataOffset;
    memcpy(&dataOffset, &header[ANDROID_TZ_HEADER_DATA_OFFSET], sizeof(int32_t));
    dataOffset = betoh32(dataOffset);

    if (indexOffset < 0 || dataOffset < indexOffset) {
        return;
    }
    if (fseek(fp, indexOffset, SEEK_SET) != 0) {
        return;
    }

    char entry[52];
    size_t indexSize = dataOffset - indexOffset;
    size_t zoneCount = indexSize / sizeof(entry);
    if (zoneCount * sizeof(entry) != indexSize) {
        return;
    }
    for (size_t idx = 0; idx < zoneCount; idx++) {
        if (fread(entry, 1, sizeof(entry), fp) != sizeof(entry)) {
            break;
        }

        int32_t start;
        memcpy(&start, &entry[ANDROID_TZ_ENTRY_START_OFFSET], sizeof(int32_t));
        start = betoh32(start);
        start += dataOffset;

        int32_t length;
        memcpy(&length, &entry[ANDROID_TZ_ENTRY_LENGTH_OFFSET], sizeof(int32_t));
        length = betoh32(length);

        if (start < 0 || length < 0) {
            break;
        }

        long pos = ftell(fp);
        Boolean done = callback(entry, start, length, fp, context1, context2);
        if (done || fseek(fp, pos, SEEK_SET) != 0) {
            break;
        }
    }
}

static void __CFAndroidTimeZoneListEnumerate(__CFAndroidTimeZoneListEnumerateCallback callback, void *context1, void *context2) {
    // The best reference should be Android Bionic's libc/tzcode/bionic.cpp
    static const char *tzDataFiles[] = {
        "/data/misc/zoneinfo/current/tzdata",
        "/system/usr/share/zoneinfo/tzdata"
    };

    for (int idx = 0; idx < COUNT_OF(tzDataFiles); idx++) {
        FILE *fp = fopen(tzDataFiles[idx], "rb");
        __CFAndroidTimeZoneParse(fp, callback, context1, context2);
        if (fp) {
            fclose(fp);
        }
    }
}

static Boolean __CFCopyAndroidTimeZoneListCallback(const char name[ANDROID_TZ_ENTRY_NAME_LENGTH], int32_t start, int32_t length, FILE *fp, void *context1, void *context2) {
    CFMutableArrayRef result = (CFMutableArrayRef)context1;
    CFStringRef timeZoneName = CFStringCreateWithCString(kCFAllocatorSystemDefault, name, kCFStringEncodingASCII);
    CFArrayAppendValue(result, timeZoneName);
    CFRelease(timeZoneName);
    return FALSE;
}

static Boolean __CFTimeZoneDataCreateCallback(const char name[ANDROID_TZ_ENTRY_NAME_LENGTH], int32_t start, int32_t length, FILE *fp, void *context1, void *context2) {
    char *tzNameCstr = (char *)context1;
    CFDataRef *dataPtr = (CFDataRef *)context2;

    if (strncmp(tzNameCstr, name, ANDROID_TZ_ENTRY_NAME_LENGTH) == 0) {
        if (fseek(fp, start, SEEK_SET) != 0) {
            return TRUE;
        }
        uint8_t *bytes = malloc(length);
        if (!bytes) {
            return TRUE;
        }
        if (fread(bytes, 1, length, fp) != length) {
            free(bytes);
            return TRUE;
        }
        *dataPtr = CFDataCreate(kCFAllocatorSystemDefault, bytes, length);
        free(bytes);
        return TRUE;
    }

    return FALSE;
}

static CFMutableArrayRef __CFCopyAndroidTimeZoneList() {
    CFMutableArrayRef result = CFArrayCreateMutable(kCFAllocatorSystemDefault, 0, &kCFTypeArrayCallBacks);
    __CFAndroidTimeZoneListEnumerate(__CFCopyAndroidTimeZoneListCallback, result, NULL);
    return result;
}

#elif TARGET_OS_MAC || TARGET_OS_LINUX || TARGET_OS_BSD || TARGET_OS_WASI
static CFMutableArrayRef __CFCopyRecursiveDirectoryList() {
    CFMutableArrayRef result = CFArrayCreateMutable(kCFAllocatorSystemDefault, 0, &kCFTypeArrayCallBacks);
#if !TARGET_OS_ANDROID
    if (!__tzDir) __InitTZStrings();
    if (!__tzDir) return result;
#endif
    int fd = open(__tzDir, O_RDONLY);

    for (; 0 <= fd;) {
        uint8_t buffer[4096];
        ssize_t len = read(fd, buffer, sizeof(buffer));
        if (len <= 0) break;
	if (len < sizeof(buffer)) {
	    // assumes that partial read only occurs at the end of the file
	    buffer[len] = '\n';
	    len++;
	}
        const uint8_t *bytes = buffer;
        for (;;) {
	    const uint8_t *nextl = memchr(bytes, '\n', len);
	    if (!nextl) break;
	    nextl++;
	    if ('#' == *bytes) {
		len -= (nextl - bytes);
		bytes = nextl;
		continue;
	    }
	    const uint8_t *tab1 = memchr(bytes, '\t', (nextl - bytes));
	    if (!tab1) {
		len -= (nextl - bytes);
		bytes = nextl;
		continue;
	    }
	    tab1++;
	    len -= (tab1 - bytes);
	    bytes = tab1; 
	    const uint8_t *tab2 = memchr(bytes, '\t', (nextl - bytes));
	    if (!tab2) {
		len -= (nextl - bytes);
		bytes = nextl;
		continue;
	    }
	    tab2++;
	    len -= (tab2 - bytes);
	    bytes = tab2; 
	    const uint8_t *tab3 = memchr(bytes, '\t', (nextl - bytes));
	    int nmlen = tab3 ? (tab3 - bytes) : (nextl - 1 - bytes);
	    CFStringRef string = CFStringCreateWithBytes(kCFAllocatorSystemDefault, bytes, nmlen, kCFStringEncodingUTF8, false);
	    CFArrayAppendValue(result, string);
	    CFRelease(string);
	    len -= (nextl - bytes);
	    bytes = nextl;
        }
        lseek(fd, -len, SEEK_CUR);
    }
    close(fd);
    return result;
}
#else
#error Unknown or unspecified DEPLOYMENT_TARGET
#endif

typedef struct _CFTZPeriod {
    int32_t startSec;
    CFStringRef abbrev;
    uint32_t info;
} CFTZPeriod;

struct __CFTimeZone {
    CFRuntimeBase _base;
    CFStringRef _name;		/* immutable */
    CFDataRef _data;		/* immutable */
    CFTZPeriod *_periods;	/* immutable */
    int32_t _periodCnt;		/* immutable */
};

/* startSec is the whole integer seconds from a CFAbsoluteTime, giving dates
 * between 1933 and 2069; info outside these years is discarded on read-in */
/* Bits 31-18 of the info are unused */
/* Bit 17 of the info is used for the is-DST state */
/* Bit 16 of the info is used for the sign of the offset (1 == negative) */
/* Bits 15-0 of the info are used for abs(offset) in seconds from GMT */

CF_INLINE void __CFTZPeriodInit(CFTZPeriod *period, int32_t startTime, CFStringRef abbrev, int32_t offset, Boolean isDST) {
    period->startSec = startTime;
    period->abbrev = abbrev ? (CFStringRef)CFRetain(abbrev) : NULL;
    __CFBitfieldSetValue(period->info, 15, 0, abs(offset));
    __CFBitfieldSetValue(period->info, 16, 16, (offset < 0 ? 1 : 0));
    __CFBitfieldSetValue(period->info, 17, 17, (isDST ? 1 : 0));
}

CF_INLINE int32_t __CFTZPeriodStartSeconds(const CFTZPeriod *period) {
    return period->startSec;
}

CF_INLINE CFStringRef __CFTZPeriodAbbreviation(const CFTZPeriod *period) {
    return period->abbrev;
}

CF_INLINE int32_t __CFTZPeriodGMTOffset(const CFTZPeriod *period) {
    int32_t v = __CFBitfieldGetValue(period->info, 15, 0);
    if (__CFBitfieldGetValue(period->info, 16, 16)) v = -v;
    return v;
}

CF_INLINE Boolean __CFTZPeriodIsDST(const CFTZPeriod *period) {
    return (Boolean)__CFBitfieldGetValue(period->info, 17, 17);
}

static CFComparisonResult __CFCompareTZPeriods(const void *val1, const void *val2, void *context) {
    CFTZPeriod *tzp1 = (CFTZPeriod *)val1;
    CFTZPeriod *tzp2 = (CFTZPeriod *)val2;
    // we treat equal as less than, as the code which uses the
    // result of the bsearch doesn't expect exact matches
    // (they're pretty rare, so no point in over-coding for them)
    if (__CFTZPeriodStartSeconds(tzp1) <= __CFTZPeriodStartSeconds(tzp2)) return kCFCompareLessThan;
    return kCFCompareGreaterThan;
}

static CFIndex __CFBSearchTZPeriods(CFTimeZoneRef tz, CFAbsoluteTime at) {
    CFTZPeriod elem;
    __CFTZPeriodInit(&elem, (int32_t)floor(at + 1.0), NULL, 0, false);
    CFIndex idx = CFBSearch(&elem, sizeof(CFTZPeriod), tz->_periods, tz->_periodCnt, __CFCompareTZPeriods, NULL);
    if (tz->_periodCnt <= idx) {
	idx = tz->_periodCnt;
    } else if (0 == idx) {
	idx = 1;
    }
    return idx - 1;
}


CF_INLINE int32_t __CFDetzcode(const unsigned char *bufp) {
     // `result` is uint32_t to avoid undefined behaviour of shifting left negative values
    uint32_t result = (bufp[0] & 0x80) ? ~0L : 0L;
    result = (result << 8) | (bufp[0] & 0xff);
    result = (result << 8) | (bufp[1] & 0xff);
    result = (result << 8) | (bufp[2] & 0xff);
    result = (result << 8) | (bufp[3] & 0xff);
    return (int32_t)result;
}

CF_INLINE void __CFEntzcode(int32_t value, unsigned char *bufp) {
    bufp[0] = (value >> 24) & 0xff;
    bufp[1] = (value >> 16) & 0xff;
    bufp[2] = (value >> 8) & 0xff;
    bufp[3] = (value >> 0) & 0xff;
}

static Boolean __CFParseTimeZoneData(CFAllocatorRef allocator, CFDataRef data, CFTZPeriod **tzpp, CFIndex *cntp) {
    int32_t len, timecnt, typecnt, charcnt, idx, cnt;
    const uint8_t *p, *timep, *typep, *ttisp, *charp;
    CFStringRef *abbrs;
    Boolean result = true;

    p = CFDataGetBytePtr(data);
    len = CFDataGetLength(data);
    if (len < (int32_t)sizeof(struct tzhead)) {
	return false;
    }
    
    if (!(p[0] == 'T' && p[1] == 'Z' && p[2] == 'i' && p[3] == 'f')) return false;  /* Don't parse without TZif at head of file */
   
    p += 20 + 4 + 4 + 4;	/* skip reserved, ttisgmtcnt, ttisstdcnt, leapcnt */
    timecnt = __CFDetzcode(p);
    p += 4;
    typecnt = __CFDetzcode(p);
    p += 4;
    charcnt = __CFDetzcode(p);
    p += 4;
    if (typecnt <= 0 || timecnt < 0 || charcnt < 0) {
	return false;
    }
    if (1024 < timecnt || 32 < typecnt || 128 < charcnt) {
	// reject excessive timezones to avoid arithmetic overflows for
	// security reasons and to reject potentially corrupt files
	return false;
    }
    if (len - (int32_t)sizeof(struct tzhead) < (4 + 1) * timecnt + (4 + 1 + 1) * typecnt + charcnt) {
	return false;
    }
    timep = p;
    typep = timep + 4 * timecnt;
    ttisp = typep + timecnt;
    charp = ttisp + (4 + 1 + 1) * typecnt;
    cnt = (0 < timecnt) ? timecnt : 1;
    *tzpp = CFAllocatorAllocate(allocator, cnt * sizeof(CFTZPeriod), 0);
    if (__CFOASafe) __CFSetLastAllocationEventName(*tzpp, "CFTimeZone (store)");
    memset(*tzpp, 0, cnt * sizeof(CFTZPeriod));
    abbrs = CFAllocatorAllocate(allocator, (charcnt + 1) * sizeof(CFStringRef), 0);
    if (__CFOASafe) __CFSetLastAllocationEventName(abbrs, "CFTimeZone (temp)");
    for (idx = 0; idx < charcnt + 1; idx++) {
	abbrs[idx] = NULL;
    }
    for (idx = 0; idx < cnt; idx++) {
	CFAbsoluteTime at;
	int32_t itime, offset;
	uint8_t type, dst, abbridx;

	at = (CFAbsoluteTime)(__CFDetzcode(timep) + 0.0) - kCFAbsoluteTimeIntervalSince1970;
	if (0 == timecnt) itime = INT_MIN;
	else if (at < (CFAbsoluteTime)INT_MIN) itime = INT_MIN;
	else if ((CFAbsoluteTime)INT_MAX < at) itime = INT_MAX;
	else itime = (int32_t)at;
	timep += 4;	/* harmless if 0 == timecnt */
	type = (0 < timecnt) ? (uint8_t)*typep++ : 0;
	if (typecnt <= type) {
	    result = false;
	    break;
	}
	offset = __CFDetzcode(ttisp + 6 * type);
	dst = (uint8_t)*(ttisp + 6 * type + 4);
	if (0 != dst && 1 != dst) {
	    result = false;
	    break;
	}
	abbridx = (uint8_t)*(ttisp + 6 * type + 5);
	if (charcnt < abbridx) {
	    result = false;
	    break;
	}
	if (NULL == abbrs[abbridx]) {
	    abbrs[abbridx] = CFStringCreateWithCString(allocator, (char *)&charp[abbridx], kCFStringEncodingASCII);
	}
	__CFTZPeriodInit(*tzpp + idx, itime, abbrs[abbridx], offset, (dst ? true : false));
    }
    for (idx = 0; idx < charcnt + 1; idx++) {
	if (NULL != abbrs[idx]) {
	    CFRelease(abbrs[idx]);
	}
    }
    CFAllocatorDeallocate(allocator, abbrs);
    if (result) {
	// dump all but the last INT_MIN and the first INT_MAX
	for (idx = 0; idx < cnt; idx++) {
	    if (((*tzpp + idx)->startSec == INT_MIN) && (idx + 1 < cnt) && (((*tzpp + idx + 1)->startSec == INT_MIN))) {
		if (NULL != (*tzpp + idx)->abbrev) CFRelease((*tzpp + idx)->abbrev);
		cnt--;
		memmove((*tzpp + idx), (*tzpp + idx + 1), sizeof(CFTZPeriod) * (cnt - idx));
		idx--;
	    }
	}
	// Don't combine these loops!  Watch the idx decrementing...
	for (idx = 0; idx < cnt; idx++) {
	    if (((*tzpp + idx)->startSec == INT_MAX) && (0 < idx) && (((*tzpp + idx - 1)->startSec == INT_MAX))) {
		if (NULL != (*tzpp + idx)->abbrev) CFRelease((*tzpp + idx)->abbrev);
		cnt--;
		memmove((*tzpp + idx), (*tzpp + idx + 1), sizeof(CFTZPeriod) * (cnt - idx));
		idx--;
	    }
	}
	CFQSortArray(*tzpp, cnt, sizeof(CFTZPeriod), __CFCompareTZPeriods, NULL);
	// if the first period is in DST and there is more than one period, drop it
	if (1 < cnt && __CFTZPeriodIsDST(*tzpp + 0)) {
	    if (NULL != (*tzpp + 0)->abbrev) CFRelease((*tzpp + 0)->abbrev);
	    cnt--;
	    memmove((*tzpp + 0), (*tzpp + 0 + 1), sizeof(CFTZPeriod) * (cnt - 0));
	}
	*cntp = cnt;
    } else {
	CFAllocatorDeallocate(allocator, *tzpp);
	*tzpp = NULL;
    }
    return result;
}

static Boolean __CFTimeZoneEqual(CFTypeRef cf1, CFTypeRef cf2) {
    CFTimeZoneRef tz1 = (CFTimeZoneRef)cf1;
    CFTimeZoneRef tz2 = (CFTimeZoneRef)cf2;
    if (!CFEqual(CFTimeZoneGetName(tz1), CFTimeZoneGetName(tz2))) return false;
    if (!CFEqual(CFTimeZoneGetData(tz1), CFTimeZoneGetData(tz2))) return false;
    return true;
}

static CFHashCode __CFTimeZoneHash(CFTypeRef cf) {
    CFTimeZoneRef tz = (CFTimeZoneRef)cf;
    return CFHash(CFTimeZoneGetName(tz));
}

static CFStringRef __CFTimeZoneCopyDescription(CFTypeRef cf) {
    CFTimeZoneRef tz = (CFTimeZoneRef)cf;
    CFStringRef result, abbrev;
    CFAbsoluteTime at;
    at = CFAbsoluteTimeGetCurrent();
    abbrev = CFTimeZoneCopyAbbreviation(tz, at);
    result = CFStringCreateWithFormat(kCFAllocatorSystemDefault, NULL, CFSTR("<CFTimeZone %p [%p]>{name = %@; abbreviation = %@; GMT offset = %g; is DST = %s}"), cf, CFGetAllocator(tz), tz->_name, abbrev, CFTimeZoneGetSecondsFromGMT(tz, at), CFTimeZoneIsDaylightSavingTime(tz, at) ? "true" : "false");
    CFRelease(abbrev);
    return result;
}

static void __CFTimeZoneDeallocate(CFTypeRef cf) {
    CFTimeZoneRef tz = (CFTimeZoneRef)cf;
    CFAllocatorRef allocator = CFGetAllocator(tz);
    CFIndex idx;
    if (tz->_name) CFRelease(tz->_name);
    if (tz->_data) CFRelease(tz->_data);
    for (idx = 0; idx < tz->_periodCnt; idx++) {
	if (NULL != tz->_periods[idx].abbrev) CFRelease(tz->_periods[idx].abbrev);
    }
    if (NULL != tz->_periods) CFAllocatorDeallocate(allocator, tz->_periods);
}

const CFRuntimeClass __CFTimeZoneClass = {
    0,
    "CFTimeZone",
    NULL,	// init
    NULL,	// copy
    __CFTimeZoneDeallocate,
    __CFTimeZoneEqual,
    __CFTimeZoneHash,
    NULL,	//
    __CFTimeZoneCopyDescription
};

CFTypeID CFTimeZoneGetTypeID(void) {
    return _kCFRuntimeIDCFTimeZone;
}

#if TARGET_OS_MAC
static void __InitTZStrings(void) {
    static dispatch_once_t initOnce = 0;

    dispatch_once(&initOnce, ^{
        unsigned int major = 0, minor = 0, patch = 0;

        CFDictionaryRef dict = _CFCopySystemVersionDictionary();
        if (dict) {
            CFStringRef version = CFDictionaryGetValue(dict, _kCFSystemVersionProductVersionKey);
            if (version) {
                const char *cStr = CFStringGetCStringPtr(version, kCFStringEncodingASCII);
                if (cStr) {
                    if (sscanf(cStr, "%u.%u.%u", &major, &minor, &patch) != 3) {
                        major = 0;
                        minor = 0;
                        patch = 0;
                    }
                }
            }
            CFRelease(dict);
        }

        // Timezone files moved in High Sierra(10.13)
        if (major == 10 && minor < 13) {
            // older versions
            __tzZoneInfo = CFSTR(MACOS_TZDIR1);
            __tzDir = MACOS_TZDIR1 "zone.tab";
        } else {
            __tzZoneInfo = CFSTR(MACOS_TZDIR2);
            __tzDir = MACOS_TZDIR2 "zone.tab";
        }
    });
}

#elif TARGET_OS_ANDROID || TARGET_OS_WINDOWS
// Nothing
#elif TARGET_OS_LINUX || TARGET_OS_BSD || TARGET_OS_WASI
static void __InitTZStrings(void) {
    __tzZoneInfo = CFSTR(TZDIR);
    __tzDir = TZDIR "zone.tab";
}

#else
#error Unknown or unspecified DEPLOYMENT_TARGET
#endif

static CFTimeZoneRef __CFTimeZoneCreateSystem(void) {
    CFTimeZoneRef result = NULL;
    
    CFStringRef name = NULL;
    
#if TARGET_OS_WIN32
    TIME_ZONE_INFORMATION tzi = { 0 };
    DWORD rval = GetTimeZoneInformation(&tzi);
    if (rval != TIME_ZONE_ID_INVALID) {
        LPWSTR standardName = (LPWSTR)&tzi.StandardName;
        CFStringRef cfStandardName = CFStringCreateWithBytes(kCFAllocatorSystemDefault, (UInt8 *)standardName, wcslen(standardName)*sizeof(WCHAR), kCFStringEncodingUTF16LE, false);
        if (cfStandardName) {
            name = _CFTimeZoneCopyOlsonNameForWindowsName(cfStandardName);
            CFRelease(cfStandardName);
        }
    } else {
        CFLog(kCFLogLevelError, CFSTR("Couldn't get time zone information error %d"), GetLastError());
    }
#else
    const char *tzenv;
    int ret;
    char linkbuf[CFMaxPathSize];
    
    tzenv = __CFgetenv("TZFILE");
    if (NULL != tzenv) {
        CFStringRef name = CFStringCreateWithBytes(kCFAllocatorSystemDefault, (uint8_t *)tzenv, strlen(tzenv), kCFStringEncodingUTF8, false);
        result = CFTimeZoneCreateWithName(kCFAllocatorSystemDefault, name, false);
        CFRelease(name);
        if (result) return result;
    }
    tzenv = __CFgetenv("TZ");
    if (NULL != tzenv) {
        CFStringRef name = CFStringCreateWithBytes(kCFAllocatorSystemDefault, (uint8_t *)tzenv, strlen(tzenv), kCFStringEncodingUTF8, false);
        result = CFTimeZoneCreateWithName(kCFAllocatorSystemDefault, name, true);
        CFRelease(name);
        if (result) return result;
    }

#if !TARGET_OS_ANDROID && !TARGET_OS_WASI
    if (!__tzZoneInfo) __InitTZStrings();
    ret = readlink(TZDEFAULT, linkbuf, sizeof(linkbuf));
    // The link can be relative, we treat this the same as if there was no link
    if (__tzZoneInfo && (0 < ret) && (linkbuf[0] != '.')) {
        linkbuf[ret] = '\0';
        const char *tzZoneInfo = CFStringGetCStringPtr(__tzZoneInfo, kCFStringEncodingASCII);
        size_t zoneInfoDirLen = CFStringGetLength(__tzZoneInfo);
        if (strncmp(linkbuf, tzZoneInfo, zoneInfoDirLen) == 0) {
            name = CFStringCreateWithBytes(kCFAllocatorSystemDefault, (uint8_t *)linkbuf + zoneInfoDirLen,
                                           strlen(linkbuf) - zoneInfoDirLen, kCFStringEncodingUTF8, false);
        } else {
            name = CFStringCreateWithBytes(kCFAllocatorSystemDefault, (uint8_t *)linkbuf, strlen(linkbuf), kCFStringEncodingUTF8, false);
        }
    } else
#endif
    {
        #if !TARGET_OS_WASI
        // TODO: This can still fail on Linux if the time zone is not recognized by ICU later
        // Try localtime
        tzset();
        #endif
        time_t t = time(NULL);
        struct tm lt = {0};
        localtime_r(&t, &lt);
        
        name = CFStringCreateWithCString(kCFAllocatorSystemDefault, lt.tm_zone, kCFStringEncodingUTF8);
    }
#endif
    if (name) {
        result = CFTimeZoneCreateWithName(kCFAllocatorSystemDefault, name, true);
        CFRelease(name);
        if (result) return result;
    }
    return CFTimeZoneCreateWithTimeIntervalFromGMT(kCFAllocatorSystemDefault, 0.0);
}

CFTimeZoneRef CFTimeZoneCopySystem(void) {
    CFTimeZoneRef tz;
    __CFTimeZoneLockGlobal();
    if (NULL == __CFTimeZoneSystem) {
	__CFTimeZoneUnlockGlobal();
	tz = __CFTimeZoneCreateSystem();
	__CFTimeZoneLockGlobal();
	if (NULL == __CFTimeZoneSystem) {
	    __CFTimeZoneSystem = tz;
	} else {
	    if (tz) CFRelease(tz);
	}
    }
    tz = __CFTimeZoneSystem ? (CFTimeZoneRef)CFRetain(__CFTimeZoneSystem) : NULL;
    __CFTimeZoneUnlockGlobal();
    return tz;
}

static CFIndex __noteCount = 0;

void CFTimeZoneResetSystem(void) {
    __CFTimeZoneLockGlobal();
    if (__CFTimeZoneDefault == __CFTimeZoneSystem) {
	if (__CFTimeZoneDefault) CFRelease(__CFTimeZoneDefault);
	__CFTimeZoneDefault = NULL;
    }
    CFTimeZoneRef tz = __CFTimeZoneSystem;
    __CFTimeZoneSystem = NULL;
    __CFTimeZoneUnlockGlobal();
    if (tz) CFRelease(tz);
}

CFIndex _CFTimeZoneGetNoteCount(void) {
    return __noteCount;
}

CFTimeZoneRef CFTimeZoneCopyDefault(void) {
    CFTimeZoneRef tz;
    __CFTimeZoneLockGlobal();
    if (NULL == __CFTimeZoneDefault) {
	__CFTimeZoneUnlockGlobal();
	tz = CFTimeZoneCopySystem();
	__CFTimeZoneLockGlobal();
	if (NULL == __CFTimeZoneDefault) {
	    __CFTimeZoneDefault = tz;
	} else {
	    if (tz) CFRelease(tz);
	}
    }
    tz = __CFTimeZoneDefault ? (CFTimeZoneRef)CFRetain(__CFTimeZoneDefault) : NULL;
    __CFTimeZoneUnlockGlobal();
    return tz;
}

void CFTimeZoneSetDefault(CFTimeZoneRef tz) {
    if (tz) __CFGenericValidateType(tz, CFTimeZoneGetTypeID());
    __CFTimeZoneLockGlobal();
    if (tz != __CFTimeZoneDefault) {
	if (tz) CFRetain(tz);
	if (__CFTimeZoneDefault) CFRelease(__CFTimeZoneDefault);
	__CFTimeZoneDefault = tz;
    }
    __CFTimeZoneUnlockGlobal();
}

static CFDictionaryRef __CFTimeZoneCopyCompatibilityDictionary(void);
static Boolean __nameStringOK(CFStringRef name);

CFArrayRef CFTimeZoneCopyKnownNames(void) {
    CFArrayRef tzs;
    __CFTimeZoneLockGlobal();
    if (NULL == __CFKnownTimeZoneList) {
	CFMutableArrayRef list;
/* TimeZone information locate in the registry for Win32
 * (Aleksey Dukhnyakov)
 */
#if TARGET_OS_WIN32
        list = __CFCopyWindowsTimeZoneList();
#elif TARGET_OS_ANDROID
        list = __CFCopyAndroidTimeZoneList();
#else
        list = __CFCopyRecursiveDirectoryList();
#endif
	// Remove undesirable ancient cruft
	CFDictionaryRef dict = __CFTimeZoneCopyCompatibilityDictionary();
	CFIndex idx;
	for (idx = CFArrayGetCount(list); idx--; ) {
	    CFStringRef item = (CFStringRef)CFArrayGetValueAtIndex(list, idx);
	    if (CFDictionaryContainsKey(dict, item) || !__nameStringOK(item)) {
		CFArrayRemoveValueAtIndex(list, idx);
	    }
	}
	__CFKnownTimeZoneList = CFArrayCreateCopy(kCFAllocatorSystemDefault, list);
	CFRelease(list);
    }
    tzs = __CFKnownTimeZoneList ? (CFArrayRef)CFRetain(__CFKnownTimeZoneList) : NULL;
    __CFTimeZoneUnlockGlobal();
    return tzs;
}

/* The criteria here are sort of: coverage for the U.S. and Europe,
 * large cities, abbreviation uniqueness, and perhaps a few others.
 * But do not make the list too large with obscure information.
 */
static const char *__CFTimeZoneAbbreviationDefaults =
"<?xml version=\"1.0\" encoding=\"UTF-8\"?>"
" <!DOCTYPE plist SYSTEM \"file://localhost/System/Library/DTDs/PropertyList.dtd\">"
" <plist version=\"1.0\">"
" <dict>"
"    <key>ADT</key>  <string>America/Halifax</string>"
"    <key>AKDT</key> <string>America/Juneau</string>"
"    <key>AKST</key> <string>America/Juneau</string>"
"    <key>ART</key>  <string>America/Argentina/Buenos_Aires</string>"
"    <key>AST</key>  <string>America/Halifax</string>"
"    <key>BDT</key>  <string>Asia/Dhaka</string>"
"    <key>BRST</key> <string>America/Sao_Paulo</string>"
"    <key>BRT</key>  <string>America/Sao_Paulo</string>"
"    <key>BST</key>  <string>Europe/London</string>"
"    <key>CAT</key>  <string>Africa/Harare</string>"
"    <key>CDT</key>  <string>America/Chicago</string>"
"    <key>CEST</key> <string>Europe/Paris</string>"
"    <key>CET</key>  <string>Europe/Paris</string>"
"    <key>CLST</key> <string>America/Santiago</string>"
"    <key>CLT</key>  <string>America/Santiago</string>"
"    <key>COT</key>  <string>America/Bogota</string>"
"    <key>CST</key>  <string>America/Chicago</string>"
"    <key>EAT</key>  <string>Africa/Addis_Ababa</string>"
"    <key>EDT</key>  <string>America/New_York</string>"
"    <key>EEST</key> <string>Europe/Istanbul</string>"
"    <key>EET</key>  <string>Europe/Istanbul</string>"
"    <key>EST</key>  <string>America/New_York</string>"
"    <key>GMT</key>  <string>GMT</string>"
"    <key>GST</key>  <string>Asia/Dubai</string>"
"    <key>HKT</key>  <string>Asia/Hong_Kong</string>"
"    <key>HST</key>  <string>Pacific/Honolulu</string>"
"    <key>ICT</key>  <string>Asia/Bangkok</string>"
"    <key>IRST</key> <string>Asia/Tehran</string>"
"    <key>IST</key>  <string>Asia/Calcutta</string>"
"    <key>JST</key>  <string>Asia/Tokyo</string>"
"    <key>KST</key>  <string>Asia/Seoul</string>"
"    <key>MDT</key>  <string>America/Denver</string>"
"    <key>MSD</key>  <string>Europe/Moscow</string>"
"    <key>MSK</key>  <string>Europe/Moscow</string>"
"    <key>MST</key>  <string>America/Denver</string>"
"    <key>NZDT</key> <string>Pacific/Auckland</string>"
"    <key>NZST</key> <string>Pacific/Auckland</string>"
"    <key>PDT</key>  <string>America/Los_Angeles</string>"
"    <key>PET</key>  <string>America/Lima</string>"
"    <key>PHT</key>  <string>Asia/Manila</string>"
"    <key>PKT</key>  <string>Asia/Karachi</string>"
"    <key>PST</key>  <string>America/Los_Angeles</string>"
"    <key>SGT</key>  <string>Asia/Singapore</string>"
"    <key>UTC</key>  <string>UTC</string>"
"    <key>WAT</key>  <string>Africa/Lagos</string>"
"    <key>WEST</key> <string>Europe/Lisbon</string>"
"    <key>WET</key>  <string>Europe/Lisbon</string>"
"    <key>WIT</key>  <string>Asia/Jakarta</string>"
" </dict>"
" </plist>";

CFDictionaryRef CFTimeZoneCopyAbbreviationDictionary(void) {
    CFDictionaryRef dict;
    __CFTimeZoneLockAbbreviations();
    if (NULL == __CFTimeZoneAbbreviationDict) {
	CFDataRef data = CFDataCreate(kCFAllocatorSystemDefault, (uint8_t *)__CFTimeZoneAbbreviationDefaults, strlen(__CFTimeZoneAbbreviationDefaults));
	__CFTimeZoneAbbreviationDict = (CFDictionaryRef)CFPropertyListCreateFromXMLData(kCFAllocatorSystemDefault, data, kCFPropertyListImmutable, NULL);
	CFRelease(data);
    }
    if (NULL == __CFTimeZoneAbbreviationDict) {
	__CFTimeZoneAbbreviationDict = CFDictionaryCreate(kCFAllocatorSystemDefault, NULL, NULL, 0, NULL, NULL);
    }
    dict = __CFTimeZoneAbbreviationDict ? (CFDictionaryRef)CFRetain(__CFTimeZoneAbbreviationDict) : NULL;
    __CFTimeZoneUnlockAbbreviations();
    return dict;
}

void _removeFromCache(const void *key, const void *value, void *context) {
    CFDictionaryRemoveValue(__CFTimeZoneCache, (CFStringRef)key);
}

void CFTimeZoneSetAbbreviationDictionary(CFDictionaryRef dict) {
    __CFGenericValidateType(dict, CFDictionaryGetTypeID());
    __CFTimeZoneLockGlobal();
    if (dict != __CFTimeZoneAbbreviationDict) {
	if (dict) CFRetain(dict);
	if (__CFTimeZoneAbbreviationDict) {
	    CFDictionaryApplyFunction(__CFTimeZoneAbbreviationDict, _removeFromCache, NULL);
	    CFRelease(__CFTimeZoneAbbreviationDict);
	}
	__CFTimeZoneAbbreviationDict = dict;
    }
    __CFTimeZoneUnlockGlobal();
}

CF_INLINE const UChar *STRING_to_UTF16(CFStringRef S) { // UTF16String
    CFIndex length = CFStringGetLength((CFStringRef)S);
    UChar *buffer = (UChar *)malloc((length + 1) * sizeof(UChar));
    CFStringGetBytes((CFStringRef)(S), CFRangeMake(0, CFStringGetLength((CFStringRef)S)), kCFStringEncodingUTF16, 0, false, (UInt8 *)buffer, length * sizeof(UChar), NULL);
    buffer[length] = 0;
    return buffer;
}

CF_INLINE void FREE_STRING_to_UTF16(const UChar *buf) {
    free((void *)buf);
}

static int32_t __tryParseGMTName(CFStringRef name) {
    CFIndex len = CFStringGetLength(name);
    if (len < 3 || 9 < len) return -1;
    UniChar ustr[10];
    CFStringGetCharacters(name, CFRangeMake(0, len), ustr);
    ustr[len] = 0;
    
    // GMT, GMT{+|-}H, GMT{+|-}HH, GMT{+|-}HHMM, GMT{+|-}{H|HH}{:|.}MM
    // UTC, UTC{+|-}H, UTC{+|-}HH, UTC{+|-}HHMM, UTC{+|-}{H|HH}{:|.}MM
    //   where "00" <= HH <= "18", "00" <= MM <= "59", and if HH==18, then MM must == 00

    Boolean isGMT = ('G' == ustr[0] && 'M' == ustr[1] && 'T' == ustr[2]);
    Boolean isUTC = ('U' == ustr[0] && 'T' == ustr[1] && 'C' == ustr[2]);
    if (!isGMT && !isUTC) return -1;
    if (3 == len) return 0;
    
    if (len < 5) return -1;
    if (!('+' == ustr[3] || '-' == ustr[3])) return -1;
    if (!('0' <= ustr[4] && ustr[4] <= '9')) return -1;
    if (5 == len) return (('-' == ustr[3]) ? -1 : 1) * (ustr[4] - '0') * 3600; // GMT{+|-}H
    Boolean twoHourDigits = ('0' <= ustr[5] && ustr[5] <= '9');
    Boolean fiveIsPunct = (':' == ustr[5] || '.' == ustr[5]);
    if (!(twoHourDigits || fiveIsPunct)) return -1;
    
    int32_t hours = twoHourDigits ? (10 * (ustr[4] - '0') + (ustr[5] - '0')) : (ustr[4] - '0');
    if (18 < hours) return -1;
    if (twoHourDigits && 6 == len) return (('-' == ustr[3]) ? -1 : 1) * hours * 3600; // GMT{+|-}HH
    
    if (len < 8) return -1;
    Boolean sixIsDigit = ('0' <= ustr[6] && ustr[6] <= '5');
    Boolean sixIsPunct = (':' == ustr[6] || '.' == ustr[6]);
    if (!(sixIsDigit && 8 == len) && !(sixIsPunct && 9 == len)) return -1;
    
    CFIndex minIdx = len - 2;
    UniChar minDig1 = ustr[minIdx], minDig2 = ustr[minIdx + 1];
    if (!('0' <= minDig1 && minDig1 <= '5' && '0' <= minDig2 && minDig2 <= '9')) return -1;
    int32_t minutes = 10 * (minDig1 - '0') + (minDig2 - '0');
    if (18 == hours && 0 != minutes) return -1;
    
    return (('-' == ustr[3]) ? -1 : 1) * (hours * 3600 + minutes * 60);
}

static Boolean __nameStringOK(CFStringRef name) {
    int32_t offset = __tryParseGMTName(name);
    if (-1 != offset) return true;
    const UChar *ustr = STRING_to_UTF16(name);
    int32_t len = u_strlen(ustr);
    UErrorCode status = U_ZERO_ERROR;
    // In Leopard and beyond, we do not show obsolete zone names in the known
    // zones list, but if you name a zone explicitly, we have always allowed
    // you to create a time zone with that name if we have data for it.
    UBool isSystemID = false;
    UChar ubuffer[1024];
    int32_t res = ucal_getCanonicalTimeZoneID(ustr, len, ubuffer, 1024, &isSystemID, &status);
    FREE_STRING_to_UTF16(ustr);
    if (!U_SUCCESS(status) || !isSystemID || 1000 < res) {
        return false;
    }
    return true;
}

static Boolean __CFTimeZoneInitFixed(CFTimeZoneRef result, int32_t seconds, CFStringRef name, int isDST) {
    CFDataRef data;
    int32_t nameLen = CFStringGetLength(name);
    unsigned char dataBytes[52 + nameLen + 1];
    memset(dataBytes, 0, sizeof(dataBytes));
    
    // Put in correct magic bytes for timezone structures
    dataBytes[0] = 'T';
    dataBytes[1] = 'Z';
    dataBytes[2] = 'i';
    dataBytes[3] = 'f';
    
    __CFEntzcode(1, dataBytes + 20);
    __CFEntzcode(1, dataBytes + 24);
    __CFEntzcode(1, dataBytes + 36);
    __CFEntzcode(nameLen + 1, dataBytes + 40);
    __CFEntzcode(seconds, dataBytes + 44);
    dataBytes[48] = isDST ? 1 : 0;
    CFStringGetCString(name, (char *)dataBytes + 50, nameLen + 1, kCFStringEncodingASCII);
    data = CFDataCreate(kCFAllocatorSystemDefault, dataBytes, 52 + nameLen + 1);
    Boolean success = _CFTimeZoneInit(result, name, data);
    CFRelease(data);
    return success;
}

Boolean _CFTimeZoneInitWithTimeIntervalFromGMT(CFTimeZoneRef result, CFTimeInterval ti) {
    
    CFStringRef name;
    int32_t seconds, minute, hour;
    if (ti < -18.0 * 3600 || 18.0 * 3600 < ti) return false;
    ti = (ti < 0.0) ? ceil((ti / 60.0) - 0.5) * 60.0 : floor((ti / 60.0) + 0.5) * 60.0;
    seconds = (int32_t)ti;
    hour = (ti < 0) ? (-seconds / 3600) : (seconds / 3600);
    seconds -= ((ti < 0) ? -hour : hour) * 3600;
    minute = (ti < 0) ? (-seconds / 60) : (seconds / 60);
    if (fabs(ti) < 1.0) {
        name = (CFStringRef)CFRetain(CFSTR("GMT"));
    } else {
        name = CFStringCreateWithFormat(kCFAllocatorSystemDefault, NULL, CFSTR("GMT%c%02d%02d"), (ti < 0.0 ? '-' : '+'), hour, minute);
    }
    Boolean success = __CFTimeZoneInitFixed(result, (int32_t)ti, name, 0);
    CFRelease(name);
    return success;
}

Boolean _CFTimeZoneInitInternal(CFTimeZoneRef timezone, CFStringRef name, CFDataRef data) {
    CFTZPeriod *tzp = NULL;
    CFIndex cnt = 0;
    Boolean success = false;

    __CFTimeZoneLockGlobal();
    success = __CFParseTimeZoneData(kCFAllocatorSystemDefault, data, &tzp, &cnt);
    __CFTimeZoneUnlockGlobal();

    if (success) {
        ((struct __CFTimeZone *)timezone)->_name = (CFStringRef)CFStringCreateCopy(kCFAllocatorSystemDefault, name);
        ((struct __CFTimeZone *)timezone)->_data = CFDataCreateCopy(kCFAllocatorSystemDefault, data);
        ((struct __CFTimeZone *)timezone)->_periods = tzp;
        ((struct __CFTimeZone *)timezone)->_periodCnt = cnt;
    }

    return success;
}

CFDataRef _CFTimeZoneDataCreate(CFURLRef baseURL, CFStringRef tzName) {
#if TARGET_OS_ANDROID
    CFDataRef data = NULL;
    char *buffer = NULL;
    const char *tzNameCstr = CFStringGetCStringPtr(tzName, kCFStringEncodingASCII);
    if (!tzNameCstr) {
        CFIndex maxSize = CFStringGetMaximumSizeForEncoding(CFStringGetLength(tzName), kCFStringEncodingASCII) + 2;
        if (maxSize == kCFNotFound) {
            return NULL;
        }
        buffer = malloc(maxSize);
        if (!buffer) {
            return NULL;
        }
        if (CFStringGetCString(tzName, buffer, maxSize, kCFStringEncodingASCII)) {
            tzNameCstr = buffer;
        }
    }
    if (!tzNameCstr) {
        free(buffer);
        return NULL;
    }

    __CFAndroidTimeZoneListEnumerate(__CFTimeZoneDataCreateCallback, tzNameCstr, &data);

    free(buffer);
    return data;
#else
    void *bytes;
    CFIndex length;
    CFDataRef data = NULL;
    CFURLRef tempURL = CFURLCreateCopyAppendingPathComponent(kCFAllocatorSystemDefault, baseURL, tzName, false);
    if (NULL != tempURL) {
        if (_CFReadBytesFromFile(kCFAllocatorSystemDefault, tempURL, &bytes, &length, 0, 0)) {
            data = CFDataCreateWithBytesNoCopy(kCFAllocatorSystemDefault, bytes, length, kCFAllocatorSystemDefault);
        }
        CFRelease(tempURL);
    }
    return data;
#endif
}

Boolean _CFTimeZoneInit(CFTimeZoneRef timeZone, CFStringRef name, CFDataRef data) {
    if (!name || !__nameStringOK(name)) {
        return false;
    }

    if (data) {
        return _CFTimeZoneInitInternal(timeZone, name, data);
    }

    CFIndex len = CFStringGetLength(name);
    if (6 == len || 8 == len) {
        UniChar buffer[8];
        CFStringGetCharacters(name, CFRangeMake(0, len), buffer);
        if ('G' == buffer[0] && 'M' == buffer[1] && 'T' == buffer[2] && ('+' == buffer[3] || '-' == buffer[3])) {
            if (('0' <= buffer[4] && buffer[4] <= '9') && ('0' <= buffer[5] && buffer[5] <= '9')) {
                int32_t hours = (buffer[4] - '0') * 10 + (buffer[5] - '0');
                if (-14 <= hours && hours <= 14) {
                    CFTimeInterval ti = hours * 3600.0;
                    if (6 == len) {
                        return _CFTimeZoneInitWithTimeIntervalFromGMT(timeZone, ('-' == buffer[3] ? -1.0 : 1.0) * ti);
                    } else {
                        if (('0' <= buffer[6] && buffer[6] <= '9') && ('0' <= buffer[7] && buffer[7] <= '9')) {
                            int32_t minutes = (buffer[6] - '0') * 10 + (buffer[7] - '0');
                            if ((-14 == hours && 0 == minutes) || (14 == hours && 0 == minutes) || (0 <= minutes && minutes <= 59)) {
                                ti = ti + minutes * 60.0;
                                return _CFTimeZoneInitWithTimeIntervalFromGMT(timeZone, ('-' == buffer[3] ? -1.0 : 1.0) * ti);
                            }
                        }
                    }
                }
            }
        }
    }

    CFStringRef tzName = NULL;
    CFURLRef baseURL = NULL;
    Boolean result = false;

#if TARGET_OS_WIN32
    // Start by checking if we're just given a timezone Windows knows about
    int32_t offset;
    __CFTimeZoneGetOffset(name, &offset);
    if (offset) {
        // TODO: handle DST
        return __CFTimeZoneInitFixed(timeZone, offset, name, 0);
    }

    CFDictionaryRef abbrevs = CFTimeZoneCopyAbbreviationDictionary();

    tzName = CFDictionaryGetValue(abbrevs, name);
    if (tzName == NULL) {
        tzName = _CFTimeZoneCopyWindowsNameForOlsonName(name);
    } else {
        CFRetain(tzName);
    }

    CFRelease(abbrevs);

    if (tzName) {
        __CFTimeZoneGetOffset(tzName, &offset);
        // TODO: handle DST
        CFRelease(tzName);
        return __CFTimeZoneInitFixed(timeZone, offset, name, 0);
    }

    return FALSE;
#else
#if !TARGET_OS_ANDROID && !TARGET_OS_WASI

    if (!__tzZoneInfo) __InitTZStrings();
    if (!__tzZoneInfo) return false;
    baseURL = CFURLCreateWithFileSystemPath(kCFAllocatorSystemDefault, __tzZoneInfo, kCFURLPOSIXPathStyle, true);
#endif

    CFDictionaryRef abbrevs = CFTimeZoneCopyAbbreviationDictionary();
    tzName = CFDictionaryGetValue(abbrevs, name);
    if (NULL != tzName) {
        data = _CFTimeZoneDataCreate(baseURL, tzName);
    }
    CFRelease(abbrevs);

    if (NULL == data) {
        CFDictionaryRef dict = __CFTimeZoneCopyCompatibilityDictionary();
        CFStringRef mapping = CFDictionaryGetValue(dict, name);
        if (mapping) {
            name = mapping;
        }
#if !TARGET_OS_ANDROID && !TARGET_OS_WASI
        else if (CFStringHasPrefix(name, __tzZoneInfo)) {
            CFMutableStringRef unprefixed = CFStringCreateMutableCopy(kCFAllocatorSystemDefault, CFStringGetLength(name), name);
            CFStringDelete(unprefixed, CFRangeMake(0, CFStringGetLength(__tzZoneInfo)));
            mapping = CFDictionaryGetValue(dict, unprefixed);
            if (mapping) {
                name = mapping;
            }
            CFRelease(unprefixed);
        }
#endif
        CFRelease(dict);
        if (CFEqual(CFSTR(""), name)) {
            return false;
        }
    }
    if (NULL == data) {
        tzName = name;
        data = _CFTimeZoneDataCreate(baseURL, tzName);
    }
    if (baseURL) {
        CFRelease(baseURL);
    }
    if (NULL != data) {
        result = _CFTimeZoneInitInternal(timeZone, tzName, data);
        CFRelease(data);
    }
    return result;
#endif
}

CFTimeZoneRef CFTimeZoneCreate(CFAllocatorRef allocator, CFStringRef name, CFDataRef data) {
// assert:    (NULL != name && NULL != data);
    CFTimeZoneRef memory;
    uint32_t size;
    CFTZPeriod *tzp = NULL;
    CFIndex idx, cnt = 0;

    if (allocator == NULL) allocator = __CFGetDefaultAllocator();
    __CFGenericValidateType(allocator, CFAllocatorGetTypeID());
    __CFGenericValidateType(name, CFStringGetTypeID());
    __CFGenericValidateType(data, CFDataGetTypeID());
    __CFTimeZoneLockGlobal();
    if (NULL != __CFTimeZoneCache && CFDictionaryGetValueIfPresent(__CFTimeZoneCache, name, (const void **)&memory)) {
	__CFTimeZoneUnlockGlobal();
	return (CFTimeZoneRef)CFRetain(memory);
    }
    if (!__CFParseTimeZoneData(allocator, data, &tzp, &cnt)) {
	__CFTimeZoneUnlockGlobal();
	return NULL;
    }
    size = sizeof(struct __CFTimeZone) - sizeof(CFRuntimeBase);
    memory = (CFTimeZoneRef)_CFRuntimeCreateInstance(allocator, CFTimeZoneGetTypeID(), size, NULL);
    if (NULL == memory) {
	__CFTimeZoneUnlockGlobal();
	for (idx = 0; idx < cnt; idx++) {
	    if (NULL != tzp[idx].abbrev) CFRelease(tzp[idx].abbrev);
	}
	if (NULL != tzp) CFAllocatorDeallocate(allocator, tzp);
        return NULL;
    }
    ((struct __CFTimeZone *)memory)->_name = (CFStringRef)CFStringCreateCopy(allocator, name);
    ((struct __CFTimeZone *)memory)->_data = CFDataCreateCopy(allocator, data);
    ((struct __CFTimeZone *)memory)->_periods = tzp;
    ((struct __CFTimeZone *)memory)->_periodCnt = cnt;
    if (NULL == __CFTimeZoneCache) {
	__CFTimeZoneCache = CFDictionaryCreateMutable(kCFAllocatorSystemDefault, 0, &kCFTypeDictionaryKeyCallBacks, &kCFTypeDictionaryValueCallBacks);
    }
    CFDictionaryAddValue(__CFTimeZoneCache, ((struct __CFTimeZone *)memory)->_name, memory);
    __CFTimeZoneUnlockGlobal();
    return memory;
}

static CFTimeZoneRef __CFTimeZoneCreateFixed(CFAllocatorRef allocator, int32_t seconds, CFStringRef name, int isDST) {
    CFTimeZoneRef result;
    CFDataRef data;
    int32_t nameLen = CFStringGetLength(name);
    unsigned char dataBytes[52 + nameLen + 1];
    memset(dataBytes, 0, sizeof(dataBytes));
    
    // Put in correct magic bytes for timezone structures
    dataBytes[0] = 'T';
    dataBytes[1] = 'Z';
    dataBytes[2] = 'i';
    dataBytes[3] = 'f';
    
    __CFEntzcode(1, dataBytes + 20);
    __CFEntzcode(1, dataBytes + 24);
    __CFEntzcode(1, dataBytes + 36);
    __CFEntzcode(nameLen + 1, dataBytes + 40);
    __CFEntzcode(seconds, dataBytes + 44);
    dataBytes[48] = isDST ? 1 : 0;
    CFStringGetCString(name, (char *)dataBytes + 50, nameLen + 1, kCFStringEncodingASCII);
    data = CFDataCreate(allocator, dataBytes, 52 + nameLen + 1);
    result = CFTimeZoneCreate(allocator, name, data);
    CFRelease(data);
    return result;
}


// rounds offset to nearest minute
CFTimeZoneRef CFTimeZoneCreateWithTimeIntervalFromGMT(CFAllocatorRef allocator, CFTimeInterval ti) {
    CFTimeZoneRef result;
    CFStringRef name;
    int32_t seconds, minute, hour;
    if (allocator == NULL) allocator = __CFGetDefaultAllocator();
    __CFGenericValidateType(allocator, CFAllocatorGetTypeID());
    if (ti < -18.0 * 3600 || 18.0 * 3600 < ti) return NULL;
    ti = (ti < 0.0) ? ceil((ti / 60.0) - 0.5) * 60.0 : floor((ti / 60.0) + 0.5) * 60.0;
    seconds = (int32_t)ti;
    hour = (ti < 0) ? (-seconds / 3600) : (seconds / 3600);
    seconds -= ((ti < 0) ? -hour : hour) * 3600;
    minute = (ti < 0) ? (-seconds / 60) : (seconds / 60);
    if (fabs(ti) < 1.0) {
	name = (CFStringRef)CFRetain(CFSTR("GMT"));
    } else {
	name = CFStringCreateWithFormat(allocator, NULL, CFSTR("GMT%c%02d%02d"), (ti < 0.0 ? '-' : '+'), hour, minute);
    }
    result = __CFTimeZoneCreateFixed(allocator, (int32_t)ti, name, 0);
    CFRelease(name);
    return result;
}

CFTimeZoneRef CFTimeZoneCreateWithName(CFAllocatorRef allocator, CFStringRef name, Boolean tryAbbrev) {
    CFTimeZoneRef result = NULL;
    CFStringRef tzName = NULL;
    CFDataRef data = NULL;

    if (allocator == NULL) allocator = __CFGetDefaultAllocator();
    __CFGenericValidateType(allocator, CFAllocatorGetTypeID());
    __CFGenericValidateType(name, CFStringGetTypeID());
    if (CFEqual(CFSTR(""), name)) {
	// empty string is not a time zone name, just abort now,
	// following stuff will fail anyway
	return NULL;
    }
    __CFTimeZoneLockGlobal();
    if (NULL != __CFTimeZoneCache && CFDictionaryGetValueIfPresent(__CFTimeZoneCache, name, (const void **)&result)) {
	__CFTimeZoneUnlockGlobal();
	return (CFTimeZoneRef)CFRetain(result);
    }
    __CFTimeZoneUnlockGlobal();
    CFIndex len = CFStringGetLength(name);
    if (6 == len || 8 == len) {
	UniChar buffer[8];
	CFStringGetCharacters(name, CFRangeMake(0, len), buffer);
	if ('G' == buffer[0] && 'M' == buffer[1] && 'T' == buffer[2] && ('+' == buffer[3] || '-' == buffer[3])) {
	    if (('0' <= buffer[4] && buffer[4] <= '9') && ('0' <= buffer[5] && buffer[5] <= '9')) {
		int32_t hours = (buffer[4] - '0') * 10 + (buffer[5] - '0');
		if (-14 <= hours && hours <= 14) {
		    CFTimeInterval ti = hours * 3600.0;
		    if (6 == len) {
			return CFTimeZoneCreateWithTimeIntervalFromGMT(allocator, ('-' == buffer[3] ? -1.0 : 1.0) * ti);
		    } else {
			if (('0' <= buffer[6] && buffer[6] <= '9') && ('0' <= buffer[7] && buffer[7] <= '9')) {
			    int32_t minutes = (buffer[6] - '0') * 10 + (buffer[7] - '0');
			    if ((-14 == hours && 0 == minutes) || (14 == hours && 0 == minutes) || (0 <= minutes && minutes <= 59)) {
				ti = ti + minutes * 60.0;
				return CFTimeZoneCreateWithTimeIntervalFromGMT(allocator, ('-' == buffer[3] ? -1.0 : 1.0) * ti);
			    }
			}
		    }
		}
	    }
	}
    }
    CFURLRef baseURL = NULL;

#if TARGET_OS_WIN32
    // Start by checking if we're just given a timezone Windows knows about
    int32_t offset;
    __CFTimeZoneGetOffset(name, &offset);
    if (offset) {
        // TODO: handle DST
        result = __CFTimeZoneCreateFixed(allocator, offset, name, 0);
    }

    CFDictionaryRef abbrevs = CFTimeZoneCopyAbbreviationDictionary();

    tzName = CFDictionaryGetValue(abbrevs, name);
    if (tzName == NULL) {
        tzName = _CFTimeZoneCopyWindowsNameForOlsonName(name);
    } else {
        tzName = CFRetain(tzName);
    }

    CFRelease(abbrevs);

    if (tzName) {
        __CFTimeZoneGetOffset(tzName, &offset);
        CFRelease(tzName);
        // TODO: handle DST
        result = __CFTimeZoneCreateFixed(allocator, offset, name, 0);
    }

    return result;
#else
#if !TARGET_OS_ANDROID
    if (!__tzZoneInfo) __InitTZStrings();
    if (!__tzZoneInfo) return NULL;
    baseURL = CFURLCreateWithFileSystemPath(kCFAllocatorSystemDefault, __tzZoneInfo, kCFURLPOSIXPathStyle, true);
#endif
    if (tryAbbrev) {
	CFDictionaryRef abbrevs = CFTimeZoneCopyAbbreviationDictionary();
	tzName = CFDictionaryGetValue(abbrevs, name);
	if (NULL != tzName) {
	    data = _CFTimeZoneDataCreate(baseURL, tzName);
	}
	CFRelease(abbrevs);
    }
    if (NULL == data) {
	CFDictionaryRef dict = __CFTimeZoneCopyCompatibilityDictionary();
	CFStringRef mapping = CFDictionaryGetValue(dict, name);
	if (mapping) {
	    name = mapping;
	}
#if !TARGET_OS_ANDROID
	else if (CFStringHasPrefix(name, __tzZoneInfo)) {
	    CFMutableStringRef unprefixed = CFStringCreateMutableCopy(kCFAllocatorSystemDefault, CFStringGetLength(name), name);
	    CFStringDelete(unprefixed, CFRangeMake(0, CFStringGetLength(__tzZoneInfo)));
	    mapping = CFDictionaryGetValue(dict, unprefixed);
	    if (mapping) {
		name = mapping;
	    }
	    CFRelease(unprefixed);
	}
#endif
	CFRelease(dict);
	if (CFEqual(CFSTR(""), name)) {
	    if (baseURL) CFRelease(baseURL);
	    if (data) CFRelease(data);
	    return NULL;
	}
    }
    if (NULL == data) {
        tzName = name;
        data = _CFTimeZoneDataCreate(baseURL, tzName);
    }
    if (baseURL) {
        CFRelease(baseURL);
    }
    if (NULL != data) {
	result = CFTimeZoneCreate(allocator, tzName, data);
	if (name != tzName) {
	    CFStringRef nameCopy = (CFStringRef)CFStringCreateCopy(allocator, name);
	    __CFTimeZoneLockGlobal();
	    CFDictionaryAddValue(__CFTimeZoneCache, nameCopy, result);
	    __CFTimeZoneUnlockGlobal();
	    CFRelease(nameCopy);
	}
	CFRelease(data);
    }
    return result;
#endif
}

CFStringRef CFTimeZoneGetName(CFTimeZoneRef tz) {
    CF_OBJC_FUNCDISPATCHV(CFTimeZoneGetTypeID(), CFStringRef, (NSTimeZone *)tz, name);
    __CFGenericValidateType(tz, CFTimeZoneGetTypeID());
    return tz->_name;
}

CFDataRef CFTimeZoneGetData(CFTimeZoneRef tz) {
    CF_OBJC_FUNCDISPATCHV(CFTimeZoneGetTypeID(), CFDataRef, (NSTimeZone *)tz, data);
    __CFGenericValidateType(tz, CFTimeZoneGetTypeID());
    return tz->_data;
}

/* This function converts CFAbsoluteTime to (Win32) SYSTEMTIME
 * (Aleksey Dukhnyakov)
 */
#if TARGET_OS_WIN32
BOOL __CFTimeZoneGetWin32SystemTime(SYSTEMTIME * sys_time, CFAbsoluteTime time)
{
    LONGLONG l;
    FILETIME * ftime=(FILETIME*)&l;

    /*  seconds between 1601 and 1970 : 11644473600,
     *  seconds between 1970 and 2001 : 978307200,
     *  FILETIME - number of 100-nanosecond intervals since January 1, 1601
     */
    l=(LONGLONG)(time+11644473600LL+978307200)*10000000;
    if (FileTimeToSystemTime(ftime,sys_time))
        return TRUE;
    else
        return FALSE;
}
#endif

CFTimeInterval CFTimeZoneGetSecondsFromGMT(CFTimeZoneRef tz, CFAbsoluteTime at) {
    CFIndex idx;
    __CFGenericValidateType(tz, CFTimeZoneGetTypeID());
    idx = __CFBSearchTZPeriods(tz, at);
    return __CFTZPeriodGMTOffset(&(tz->_periods[idx]));
}

extern UCalendar *__CFCalendarCreateUCalendar(CFStringRef calendarID, CFStringRef localeID, CFTimeZoneRef tz);

CFStringRef CFTimeZoneCopyAbbreviation(CFTimeZoneRef tz, CFAbsoluteTime at) {
    CFStringRef result;
    CFIndex idx;
    __CFGenericValidateType(tz, CFTimeZoneGetTypeID());
#if TARGET_OS_WIN32
    UErrorCode status = U_ZERO_ERROR;
    UCalendar *ucal = __CFCalendarCreateUCalendar(NULL, CFSTR("C"), tz);
    if (ucal == NULL) {
      return NULL;
    }
    ucal_setMillis(ucal, (at + kCFAbsoluteTimeIntervalSince1970) * 1000.0, &status);

    UCalendarDisplayNameType nameType = ucal_inDaylightTime(ucal, &status) ? UCAL_SHORT_DST : UCAL_SHORT_STANDARD;
    UChar buffer[64];
    int32_t length;
    length = ucal_getTimeZoneDisplayName(ucal, nameType, "C", buffer, sizeof(buffer), &status);

    ucal_close(ucal);

    return length <= sizeof(buffer) ? CFStringCreateWithCharacters(kCFAllocatorSystemDefault, buffer, length) : NULL;
#else
    idx = __CFBSearchTZPeriods(tz, at);
    result = __CFTZPeriodAbbreviation(&(tz->_periods[idx]));
    return result ? (CFStringRef)CFRetain(result) : NULL;
#endif
}

Boolean CFTimeZoneIsDaylightSavingTime(CFTimeZoneRef tz, CFAbsoluteTime at) {
    __CFGenericValidateType(tz, CFTimeZoneGetTypeID());
#if TARGET_OS_WIN32
    UErrorCode status = U_ZERO_ERROR;
    UCalendar *ucal = __CFCalendarCreateUCalendar(NULL, CFSTR("C"), tz);
    if (ucal == NULL) {
      return FALSE;
    }
    ucal_setMillis(ucal, (at + kCFAbsoluteTimeIntervalSince1970) * 1000.0, &status);

    UBool isDaylightTime = ucal_inDaylightTime(ucal, &status);
    return isDaylightTime ? TRUE : FALSE;
#else
    CFIndex idx;
    idx = __CFBSearchTZPeriods(tz, at);
    return __CFTZPeriodIsDST(&(tz->_periods[idx]));
#endif
}

CFTimeInterval CFTimeZoneGetDaylightSavingTimeOffset(CFTimeZoneRef tz, CFAbsoluteTime at) {
    CF_OBJC_FUNCDISPATCHV(CFTimeZoneGetTypeID(), CFTimeInterval, (NSTimeZone *)tz, _daylightSavingTimeOffsetForAbsoluteTime:at);
    __CFGenericValidateType(tz, CFTimeZoneGetTypeID());
    CFIndex idx = __CFBSearchTZPeriods(tz, at);
    if (__CFTZPeriodIsDST(&(tz->_periods[idx]))) {
	CFTimeInterval offset = __CFTZPeriodGMTOffset(&(tz->_periods[idx]));
	if (idx + 1 < tz->_periodCnt) {
	    return offset - __CFTZPeriodGMTOffset(&(tz->_periods[idx + 1]));
	} else if (0 < idx) {
            return offset - __CFTZPeriodGMTOffset(&(tz->_periods[idx - 1]));
	}
    }
    return 0.0;
}

CFAbsoluteTime CFTimeZoneGetNextDaylightSavingTimeTransition(CFTimeZoneRef tz, CFAbsoluteTime at) {
    CF_OBJC_FUNCDISPATCHV(CFTimeZoneGetTypeID(), CFTimeInterval, (NSTimeZone *)tz, _nextDaylightSavingTimeTransitionAfterAbsoluteTime:at);
    __CFGenericValidateType(tz, CFTimeZoneGetTypeID());
#if TARGET_OS_WIN32
    UErrorCode status = U_ZERO_ERROR;
    UCalendar *ucal = __CFCalendarCreateUCalendar(NULL, CFSTR("C"), tz);
    if (ucal == NULL) {
      return 0.0;
    }
    ucal_setMillis(ucal, (at + kCFAbsoluteTimeIntervalSince1970) * 1000.0, &status);

    UDate date;
    ucal_getTimeZoneTransitionDate(ucal, UCAL_TZ_TRANSITION_NEXT, &date, &status);

    ucal_close(ucal);

    return (date / 1000.0) - kCFAbsoluteTimeIntervalSince1970;
#else
    CFIndex idx = __CFBSearchTZPeriods(tz, at);
    if (tz->_periodCnt <= idx + 1) {
        return 0.0;
    }
    return (CFAbsoluteTime)__CFTZPeriodStartSeconds(&(tz->_periods[idx + 1]));
#endif
}

#define BUFFER_SIZE 768

CFStringRef CFTimeZoneCopyLocalizedName(CFTimeZoneRef tz, CFTimeZoneNameStyle style, CFLocaleRef locale) {
    CF_OBJC_FUNCDISPATCHV(CFTimeZoneGetTypeID(), CFStringRef, (NSTimeZone *)tz, localizedName:(NSTimeZoneNameStyle)style locale:(NSLocale *)locale);
    __CFGenericValidateType(tz, CFTimeZoneGetTypeID());
    __CFGenericValidateType(locale, CFLocaleGetTypeID());

    if (style == kCFTimeZoneNameStyleGeneric || style == kCFTimeZoneNameStyleShortGeneric) {
	CFDateFormatterRef df = CFDateFormatterCreate(kCFAllocatorSystemDefault, locale, kCFDateFormatterNoStyle, kCFDateFormatterNoStyle);
	CFDateFormatterSetProperty(df, kCFDateFormatterTimeZone, tz);
	CFDateFormatterSetFormat(df, (style == kCFTimeZoneNameStyleGeneric) ? CFSTR("vvvv") : CFSTR("v"));
	CFStringRef str = CFDateFormatterCreateStringWithAbsoluteTime(CFGetAllocator(tz), df, 0.0);
	CFRelease(df);
	return str;
    }

    CFStringRef localeID = CFLocaleGetIdentifier(locale);
    UCalendar *cal = __CFCalendarCreateUCalendar(NULL, localeID, tz);
    if (NULL == cal) {
        return NULL;
    }

    char buffer[BUFFER_SIZE];
    const char *cstr = CFStringGetCStringPtr(localeID, kCFStringEncodingASCII);
    if (NULL == cstr) {
        if (CFStringGetCString(localeID, buffer, BUFFER_SIZE, kCFStringEncodingASCII)) cstr = buffer;
    }
    if (NULL == cstr) {
	ucal_close(cal);
        return NULL;
    }

    UChar ubuffer[BUFFER_SIZE];
    UErrorCode status = U_ZERO_ERROR;
    int32_t cnt = ucal_getTimeZoneDisplayName(cal, (UCalendarDisplayNameType)style, cstr, ubuffer, BUFFER_SIZE, &status);
    ucal_close(cal);
    if (U_SUCCESS(status) && cnt <= BUFFER_SIZE) {
        return CFStringCreateWithCharacters(CFGetAllocator(tz), (const UniChar *)ubuffer, cnt);
    }
    return NULL;
}

static CFDictionaryRef __CFTimeZoneCopyCompatibilityDictionary(void) {
    CFDictionaryRef dict;
    __CFTimeZoneLockCompatibilityMapping();
    if (NULL == __CFTimeZoneCompatibilityMappingDict) {
	__CFTimeZoneCompatibilityMappingDict = CFDictionaryCreateMutable(kCFAllocatorSystemDefault, 112, &kCFTypeDictionaryKeyCallBacks, &kCFTypeDictionaryValueCallBacks);

	// Empty string means delete/ignore these 
    }
    dict = __CFTimeZoneCompatibilityMappingDict ? (CFDictionaryRef)CFRetain(__CFTimeZoneCompatibilityMappingDict) : NULL;
    __CFTimeZoneUnlockCompatibilityMapping();
    return dict;
}

CF_CROSS_PLATFORM_EXPORT CFStringRef __CFTimeZoneCopyDataVersionString(void) {
    UErrorCode err = U_ZERO_ERROR;
    const char *cstr = ucal_getTZDataVersion(&err);
    return (U_SUCCESS(err)) ? CFStringCreateWithCString(kCFAllocatorSystemDefault, cstr, kCFStringEncodingUTF8) : CFRetain(CFSTR(""));
}