// © 2016 and later: Unicode, Inc. and others.

// License & terms of use: http://www.unicode.org/copyright.html

/*

*******************************************************************************

* Copyright (C) 1997-2016, International Business Machines Corporation and

* others. All Rights Reserved.

*******************************************************************************

*

* File TIMEZONE.CPP

*

* Modification History:

*

*   Date        Name        Description

*   12/05/96    clhuang     Creation.

*   04/21/97    aliu        General clean-up and bug fixing.

*   05/08/97    aliu        Fixed Hashtable code per code review.

*   07/09/97    helena      Changed createInstance to createDefault.

*   07/29/97    aliu        Updated with all-new list of 96 UNIX-derived

*                           TimeZones.  Changed mechanism to load from static

*                           array rather than resource bundle.

*   07/07/1998  srl         Bugfixes from the Java side: UTC GMT CAT NST

*                           Added getDisplayName API

*                           going to add custom parsing.

*

*                           ISSUES:

*                               - should getDisplayName cache something?

*                               - should custom time zones be cached? [probably]

*  08/10/98     stephen     Brought getDisplayName() API in-line w/ conventions

*  08/19/98     stephen     Changed createTimeZone() to never return 0

*  09/02/98     stephen     Added getOffset(monthLen) and hasSameRules()

*  09/15/98     stephen     Added getStaticClassID()

*  02/22/99     stephen     Removed character literals for EBCDIC safety

*  05/04/99     stephen     Changed initDefault() for Mutex issues

*  07/12/99     helena      HPUX 11 CC Port.

*  12/03/99     aliu        Moved data out of static table into icudata.dll.

*                           Substantial rewrite of zone lookup, default zone, and

*                           available IDs code.  Misc. cleanup.

*********************************************************************************/

#include "utypeinfo.h"  // for 'typeid' to work

#include "unicode/utypes.h"

#include "unicode/ustring.h"

#include "uassert.h"

#include "uinvchar.h"

#include "ustr_imp.h"

#include "util.h"

#ifdef U_DEBUG_TZ

# include <stdio.h>

# include "uresimp.h" // for debugging

static void debug_tz_loc(const char *f, int32_t l)

{

  fprintf(stderr, "%s:%d: ", f, l);

}

static void debug_tz_msg(const char *pat, ...)

{

  va_list ap;

  va_start(ap, pat);

  vfprintf(stderr, pat, ap);

  fflush(stderr);

}

static char gStrBuf[256];

#define U_DEBUG_TZ_STR(x) u_austrncpy(gStrBuf,x,sizeof(gStrBuf)-1)

// must use double parens, i.e.:  U_DEBUG_TZ_MSG(("four is: %d",4));

#define U_DEBUG_TZ_MSG(x) {debug_tz_loc(__FILE__,__LINE__);debug_tz_msg x;}

#else

#define U_DEBUG_TZ_MSG(x)

#endif

#if !UCONFIG_NO_FORMATTING

#include "unicode/simpletz.h"

#include "unicode/calendar.h"

#include "unicode/gregocal.h"

#include "unicode/ures.h"

#include "unicode/tzfmt.h"

#include "gregoimp.h"

#include "uresimp.h" // struct UResourceBundle

#include "olsontz.h"

#include "mutex.h"

#include "unicode/udata.h"

#include "ucln_in.h"

#include "cstring.h"

#include "cmemory.h"

#include "unicode/strenum.h"

#include "uassert.h"

#include "zonemeta.h"

#define kZONEINFO "zoneinfo64"

#define kREGIONS  "Regions"

#define kZONES    "Zones"

#define kRULES    "Rules"

#define kNAMES    "Names"

#define kTZVERSION  "TZVersion"

#define kLINKS    "links"

#define kMAX_CUSTOM_HOUR    23

#define kMAX_CUSTOM_MIN     59

#define kMAX_CUSTOM_SEC     59

#define MINUS 0x002D

#define PLUS 0x002B

#define ZERO_DIGIT 0x0030

#define COLON 0x003A

// Static data and constants

static const char16_t      WORLD[] = {0x30, 0x30, 0x31, 0x00}; /* "001" */

static const char16_t      GMT_ID[] = {0x47, 0x4D, 0x54, 0x00}; /* "GMT" */

static const char16_t      UNKNOWN_ZONE_ID[] = {0x45, 0x74, 0x63, 0x2F, 0x55, 0x6E, 0x6B, 0x6E, 0x6F, 0x77, 0x6E, 0x00}; /* "Etc/Unknown" */

static const int32_t       GMT_ID_LENGTH = 3;

static const int32_t       UNKNOWN_ZONE_ID_LENGTH = 11;

static icu::TimeZone* DEFAULT_ZONE = nullptr;

static icu::UInitOnce gDefaultZoneInitOnce {};

alignas(icu::SimpleTimeZone)

static char gRawGMT[sizeof(icu::SimpleTimeZone)];

alignas(icu::SimpleTimeZone)

static char gRawUNKNOWN[sizeof(icu::SimpleTimeZone)];

static icu::UInitOnce gStaticZonesInitOnce {};

static UBool gStaticZonesInitialized = false; // Whether the static zones are initialized and ready to use.

static char TZDATA_VERSION[16];

static icu::UInitOnce gTZDataVersionInitOnce {};

static int32_t* MAP_SYSTEM_ZONES = nullptr;

static int32_t* MAP_CANONICAL_SYSTEM_ZONES = nullptr;

static int32_t* MAP_CANONICAL_SYSTEM_LOCATION_ZONES = nullptr;

static int32_t LEN_SYSTEM_ZONES = 0;

static int32_t LEN_CANONICAL_SYSTEM_ZONES = 0;

static int32_t LEN_CANONICAL_SYSTEM_LOCATION_ZONES = 0;

static icu::UInitOnce gSystemZonesInitOnce {};

static icu::UInitOnce gCanonicalZonesInitOnce {};

static icu::UInitOnce gCanonicalLocationZonesInitOnce {};

U_CDECL_BEGIN

static UBool U_CALLCONV timeZone_cleanup()

{

    U_NAMESPACE_USE

    delete DEFAULT_ZONE;

    DEFAULT_ZONE = nullptr;

    gDefaultZoneInitOnce.reset();

    if (gStaticZonesInitialized) {

        reinterpret_cast<SimpleTimeZone*>(gRawGMT)->~SimpleTimeZone();

        reinterpret_cast<SimpleTimeZone*>(gRawUNKNOWN)->~SimpleTimeZone();

        gStaticZonesInitialized = false;

        gStaticZonesInitOnce.reset();

    }

    uprv_memset(TZDATA_VERSION, 0, sizeof(TZDATA_VERSION));

    gTZDataVersionInitOnce.reset();

    LEN_SYSTEM_ZONES = 0;

    uprv_free(MAP_SYSTEM_ZONES);

    MAP_SYSTEM_ZONES = nullptr;

    gSystemZonesInitOnce.reset();

    LEN_CANONICAL_SYSTEM_ZONES = 0;

    uprv_free(MAP_CANONICAL_SYSTEM_ZONES);

    MAP_CANONICAL_SYSTEM_ZONES = nullptr;

    gCanonicalZonesInitOnce.reset();

    LEN_CANONICAL_SYSTEM_LOCATION_ZONES = 0;

    uprv_free(MAP_CANONICAL_SYSTEM_LOCATION_ZONES);

    MAP_CANONICAL_SYSTEM_LOCATION_ZONES = nullptr;

    gCanonicalLocationZonesInitOnce.reset();

    return true;

}

U_CDECL_END

U_NAMESPACE_BEGIN

static int32_t findInStringArray(UResourceBundle* array, const UnicodeString& id, UErrorCode &status)

{

    UnicodeString copy;

    const char16_t *u;

    int32_t len;

    int32_t start = 0;

    int32_t limit = ures_getSize(array);

    int32_t mid;

    int32_t lastMid = INT32_MAX;

    if(U_FAILURE(status) || (limit < 1)) {

        return -1;

    }

    U_DEBUG_TZ_MSG(("fisa: Looking for %s, between %d and %d\n", U_DEBUG_TZ_STR(UnicodeString(id).getTerminatedBuffer()), start, limit));

    for (;;) {

        mid = static_cast<int32_t>((start + limit) / 2);

        if (lastMid == mid) {   /* Have we moved? */

            break;  /* We haven't moved, and it wasn't found. */

        }

        lastMid = mid;

        u = ures_getStringByIndex(array, mid, &len, &status);

        if (U_FAILURE(status)) {

            break;

        }

        U_DEBUG_TZ_MSG(("tz: compare to %s, %d .. [%d] .. %d\n", U_DEBUG_TZ_STR(u), start, mid, limit));

        copy.setTo(true, u, len);

        int r = id.compare(copy);

        if(r==0) {

            U_DEBUG_TZ_MSG(("fisa: found at %d\n", mid));

            return mid;

        } else if(r<0) {

            limit = mid;

        } else {

            start = mid;

        }

    }

    U_DEBUG_TZ_MSG(("fisa: not found\n"));

    return -1;

}

/**

 * Fetch a specific zone by name.  Replaces the getByKey call.

 * @param top Top timezone resource

 * @param id Time zone ID

 * @param oldbundle Bundle for reuse (or nullptr).   see 'ures_open()'

 * @return the zone's bundle if found, or undefined if error.  Reuses oldbundle.

 */

static UResourceBundle* getZoneByName(const UResourceBundle* top, const UnicodeString& id, UResourceBundle *oldbundle, UErrorCode& status) {

    // load the Rules object

    UResourceBundle *tmp = ures_getByKey(top, kNAMES, nullptr, &status);

    // search for the string

    int32_t idx = findInStringArray(tmp, id, status);

    if((idx == -1) && U_SUCCESS(status)) {

        // not found

        status = U_MISSING_RESOURCE_ERROR;

        //ures_close(oldbundle);

        //oldbundle = nullptr;

    } else {

        U_DEBUG_TZ_MSG(("gzbn: oldbundle= size %d, type %d, %s\n", ures_getSize(tmp), ures_getType(tmp), u_errorName(status)));

        tmp = ures_getByKey(top, kZONES, tmp, &status); // get Zones object from top

        U_DEBUG_TZ_MSG(("gzbn: loaded ZONES, size %d, type %d, path %s %s\n", ures_getSize(tmp), ures_getType(tmp), ures_getPath(tmp), u_errorName(status)));

        oldbundle = ures_getByIndex(tmp, idx, oldbundle, &status); // get nth Zone object

        U_DEBUG_TZ_MSG(("gzbn: loaded z#%d, size %d, type %d, path %s, %s\n", idx, ures_getSize(oldbundle), ures_getType(oldbundle), ures_getPath(oldbundle),  u_errorName(status)));

    }

    ures_close(tmp);

    if(U_FAILURE(status)) {

        //ures_close(oldbundle);

        return nullptr;

    } else {

        return oldbundle;

    }

}

UResourceBundle* TimeZone::loadRule(const UResourceBundle* top, const UnicodeString& ruleid, UResourceBundle* oldbundle, UErrorCode& status) {

    char key[64];

    ruleid.extract(0, sizeof(key) - 1, key, static_cast<int32_t>(sizeof(key)) - 1, US_INV);

    U_DEBUG_TZ_MSG(("loadRule(%s)\n", key));

    UResourceBundle *r = ures_getByKey(top, kRULES, oldbundle, &status);

    U_DEBUG_TZ_MSG(("loadRule(%s) -> kRULES [%s]\n", key, u_errorName(status)));

    r = ures_getByKey(r, key, r, &status);

    U_DEBUG_TZ_MSG(("loadRule(%s) -> item [%s]\n", key, u_errorName(status)));

    return r;

}

/**

 * Given an ID, open the appropriate resource for the given time zone.

 * Dereference aliases if necessary.

 * @param id zone id

 * @param res resource, which must be ready for use (initialized but not open)

 * @param ec input-output error code

 * @return top-level resource bundle

 */

static UResourceBundle* openOlsonResource(const UnicodeString& id,

                                          UResourceBundle& res,

                                          UErrorCode& ec)

{

#ifdef U_DEBUG_TZ

    char buf[128];

    id.extract(0, sizeof(buf)-1, buf, sizeof(buf), "");

#endif

    UResourceBundle *top = ures_openDirect(nullptr, kZONEINFO, &ec);

    U_DEBUG_TZ_MSG(("pre: res sz=%d\n", ures_getSize(&res)));

    /* &res = */ getZoneByName(top, id, &res, ec);

    // Dereference if this is an alias.  Docs say result should be 1

    // but it is 0 in 2.8 (?).

    U_DEBUG_TZ_MSG(("Loading zone '%s' (%s, size %d) - %s\n", buf, ures_getKey((UResourceBundle*)&res), ures_getSize(&res), u_errorName(ec)));

    if (ures_getType(&res) == URES_INT) {

        int32_t deref = ures_getInt(&res, &ec) + 0;

        U_DEBUG_TZ_MSG(("getInt: %s - type is %d\n", u_errorName(ec), ures_getType(&res)));

        UResourceBundle *ares = ures_getByKey(top, kZONES, nullptr, &ec); // dereference Zones section

        ures_getByIndex(ares, deref, &res, &ec);

        ures_close(ares);

        U_DEBUG_TZ_MSG(("alias to #%d (%s) - %s\n", deref, "??", u_errorName(ec)));

    } else {

        U_DEBUG_TZ_MSG(("not an alias - size %d\n", ures_getSize(&res)));

    }

    U_DEBUG_TZ_MSG(("%s - final status is %s\n", buf, u_errorName(ec)));

    return top;

}

// -------------------------------------

namespace {

void U_CALLCONV initStaticTimeZones() {

    // Initialize _GMT independently of other static data; it should

    // be valid even if we can't load the time zone UDataMemory.

    ucln_i18n_registerCleanup(UCLN_I18N_TIMEZONE, timeZone_cleanup);

    // new can't fail below, as we use placement new into statically allocated space.

    new(gRawGMT) SimpleTimeZone(0, UnicodeString(true, GMT_ID, GMT_ID_LENGTH));

    new(gRawUNKNOWN) SimpleTimeZone(0, UnicodeString(true, UNKNOWN_ZONE_ID, UNKNOWN_ZONE_ID_LENGTH));

    gStaticZonesInitialized = true;

}

}  // anonymous namespace

const TimeZone& U_EXPORT2

TimeZone::getUnknown()

{

    umtx_initOnce(gStaticZonesInitOnce, &initStaticTimeZones);

    return *reinterpret_cast<SimpleTimeZone*>(gRawUNKNOWN);

}

const TimeZone* U_EXPORT2

TimeZone::getGMT()

{

    umtx_initOnce(gStaticZonesInitOnce, &initStaticTimeZones);

    return reinterpret_cast<SimpleTimeZone*>(gRawGMT);

}

// *****************************************************************************

// class TimeZone

// *****************************************************************************

UOBJECT_DEFINE_ABSTRACT_RTTI_IMPLEMENTATION(TimeZone)

TimeZone::TimeZone()

    :   UObject(), fID()

{

}

// -------------------------------------

TimeZone::TimeZone(const UnicodeString &id)

    :   UObject(), fID(id)

{

}

// -------------------------------------

TimeZone::~TimeZone()

{

}

// -------------------------------------

TimeZone::TimeZone(const TimeZone &source)

    :   UObject(source), fID(source.fID)

{

}

// -------------------------------------

TimeZone &

TimeZone::operator=(const TimeZone &right)

{

    if (this != &right) fID = right.fID;

    return *this;

}

// -------------------------------------

bool

TimeZone::operator==(const TimeZone& that) const

{

    return typeid(*this) == typeid(that) &&

        fID == that.fID;

}

// -------------------------------------

namespace {

TimeZone*

createSystemTimeZone(const UnicodeString& id, UErrorCode& ec) {

    if (U_FAILURE(ec)) {

        return nullptr;

    }

    TimeZone* z = nullptr;

    StackUResourceBundle res;

    U_DEBUG_TZ_MSG(("pre-err=%s\n", u_errorName(ec)));

    UResourceBundle *top = openOlsonResource(id, res.ref(), ec);

    U_DEBUG_TZ_MSG(("post-err=%s\n", u_errorName(ec)));

    if (U_SUCCESS(ec)) {

        z = new OlsonTimeZone(top, res.getAlias(), id, ec);

        if (z == nullptr) {

            ec = U_MEMORY_ALLOCATION_ERROR;

            U_DEBUG_TZ_MSG(("cstz: olson time zone failed to initialize - err %s\n", u_errorName(ec)));

        }

    }

    ures_close(top);

    if (U_FAILURE(ec)) {

        U_DEBUG_TZ_MSG(("cstz: failed to create, err %s\n", u_errorName(ec)));

        delete z;

        z = nullptr;

    }

    return z;

}

/**

 * Lookup the given name in our system zone table.  If found,

 * instantiate a new zone of that name and return it.  If not

 * found, return 0.

 */

TimeZone*

createSystemTimeZone(const UnicodeString& id) {

    UErrorCode ec = U_ZERO_ERROR;

    return createSystemTimeZone(id, ec);

}

}

TimeZone* U_EXPORT2

TimeZone::createTimeZone(const UnicodeString& ID)

{

    /* We first try to lookup the zone ID in our system list.  If this

     * fails, we try to parse it as a custom string GMT[+-]hh:mm.  If

     * all else fails, we return GMT, which is probably not what the

     * user wants, but at least is a functioning TimeZone object.

     *

     * We cannot return nullptr, because that would break compatibility

     * with the JDK.

     */

    TimeZone* result = createSystemTimeZone(ID);

    if (result == nullptr) {

        U_DEBUG_TZ_MSG(("failed to load system time zone with id - falling to custom"));

        result = createCustomTimeZone(ID);

    }

    if (result == nullptr) {

        U_DEBUG_TZ_MSG(("failed to load time zone with id - falling to Etc/Unknown(GMT)"));

        const TimeZone& unknown = getUnknown();

        // Unknown zone uses statically allocated memory, so creation of it can never fail due to OOM.

        result = unknown.clone();

    }

    return result;

}

// -------------------------------------

TimeZone* U_EXPORT2

TimeZone::detectHostTimeZone()

{

    // We access system timezone data through uprv_tzset(), uprv_tzname(), and others,

    // which have platform specific implementations in putil.cpp

    int32_t rawOffset = 0;

    const char *hostID;

    UBool hostDetectionSucceeded = true;

    // First, try to create a system timezone, based

    // on the string ID in tzname[0].

    uprv_tzset(); // Initialize tz... system data

    uprv_tzname_clear_cache();

    // Get the timezone ID from the host.  This function should do

    // any required host-specific remapping; e.g., on Windows this

    // function maps the Windows Time Zone name to an ICU timezone ID.

    hostID = uprv_tzname(0);

    // Invert sign because UNIX semantics are backwards

    rawOffset = uprv_timezone() * -U_MILLIS_PER_SECOND;

    TimeZone* hostZone = nullptr;

    UnicodeString hostStrID(hostID, -1, US_INV);

    if (hostStrID.length() == 0) {

        // The host time zone detection (or remapping) above has failed and

        // we have no name at all. Fallback to using the Unknown zone.

        hostStrID = UnicodeString(true, UNKNOWN_ZONE_ID, UNKNOWN_ZONE_ID_LENGTH);

        hostDetectionSucceeded = false;

    }

    hostZone = createSystemTimeZone(hostStrID);

#if U_PLATFORM_USES_ONLY_WIN32_API

    // hostID points to a heap-allocated location on Windows.

    uprv_free(const_cast<char *>(hostID));

#endif

    int32_t hostIDLen = hostStrID.length();

    if (hostZone != nullptr && rawOffset != hostZone->getRawOffset()

        && (3 <= hostIDLen && hostIDLen <= 4))

    {

        // Uh oh. This probably wasn't a good id.

        // It was probably an ambiguous abbreviation

        delete hostZone;

        hostZone = nullptr;

    }

    // Construct a fixed standard zone with the host's ID

    // and raw offset.

    if (hostZone == nullptr && hostDetectionSucceeded) {

        hostZone = new SimpleTimeZone(rawOffset, hostStrID);

    }

    // If we _still_ don't have a time zone, use the Unknown zone.

    //

    // Note: This is extremely unlikely situation. If

    // new SimpleTimeZone(...) above fails, the following

    // code may also fail.

    if (hostZone == nullptr) {

        // Unknown zone uses static allocated memory, so it must always exist.

        // However, clone() allocates memory and can fail.

        hostZone = TimeZone::getUnknown().clone();

    }

    return hostZone;

}

// -------------------------------------

static UMutex gDefaultZoneMutex;

/**

 * Initialize DEFAULT_ZONE from the system default time zone.  

 * Upon return, DEFAULT_ZONE will not be nullptr, unless operator new()

 * returns nullptr.

 */

static void U_CALLCONV initDefault()

{

    ucln_i18n_registerCleanup(UCLN_I18N_TIMEZONE, timeZone_cleanup);

    Mutex lock(&gDefaultZoneMutex);

    // If setDefault() has already been called we can skip getting the

    // default zone information from the system.

    if (DEFAULT_ZONE != nullptr) {

        return;

    }

    // NOTE:  this code is safely single threaded, being only

    // run via umtx_initOnce().

    //

    // Some of the locale/timezone OS functions may not be thread safe,

    //

    // The operating system might actually use ICU to implement timezones.

    // So we may have ICU calling ICU here, like on AIX.

    // There shouldn't be a problem with this; initOnce does not hold a mutex

    // while the init function is being run.

    // The code detecting the host time zone was separated from this

    // and implemented as TimeZone::detectHostTimeZone()

    TimeZone *default_zone = TimeZone::detectHostTimeZone();

    U_ASSERT(DEFAULT_ZONE == nullptr);

    DEFAULT_ZONE = default_zone;

}

// -------------------------------------

TimeZone* U_EXPORT2

TimeZone::createDefault()

{

    umtx_initOnce(gDefaultZoneInitOnce, initDefault);

    {

        Mutex lock(&gDefaultZoneMutex);

        return (DEFAULT_ZONE != nullptr) ? DEFAULT_ZONE->clone() : nullptr;

    }

}

// -------------------------------------

TimeZone* U_EXPORT2

TimeZone::forLocaleOrDefault(const Locale& locale)

{

    char buffer[ULOC_KEYWORDS_CAPACITY] = "";

    UErrorCode localStatus = U_ZERO_ERROR;

    int32_t count = locale.getKeywordValue("timezone", buffer, sizeof(buffer), localStatus);

    if (U_FAILURE(localStatus) || localStatus == U_STRING_NOT_TERMINATED_WARNING) {

        // the "timezone" keyword exceeds ULOC_KEYWORDS_CAPACITY; ignore and use default.

        count = 0;

    }

    if (count > 0) {

        return TimeZone::createTimeZone(UnicodeString(buffer, count, US_INV));

    }

    return TimeZone::createDefault();

}

// -------------------------------------

void U_EXPORT2

TimeZone::adoptDefault(TimeZone* zone)

{

    if (zone != nullptr)

    {

        {

            Mutex lock(&gDefaultZoneMutex);

            TimeZone *old = DEFAULT_ZONE;

            DEFAULT_ZONE = zone;

            delete old;

        }

        ucln_i18n_registerCleanup(UCLN_I18N_TIMEZONE, timeZone_cleanup);

    }

}

// -------------------------------------

void U_EXPORT2

TimeZone::setDefault(const TimeZone& zone)

{

    adoptDefault(zone.clone());

}

//----------------------------------------------------------------------

static void U_CALLCONV initMap(USystemTimeZoneType type, UErrorCode& ec) {

    ucln_i18n_registerCleanup(UCLN_I18N_TIMEZONE, timeZone_cleanup);

    UResourceBundle *res = ures_openDirect(nullptr, kZONEINFO, &ec);

    res = ures_getByKey(res, kNAMES, res, &ec); // dereference Zones section

    if (U_SUCCESS(ec)) {

        int32_t size = ures_getSize(res);

        int32_t* m = static_cast<int32_t*>(uprv_malloc(size * sizeof(int32_t)));

        if (m == nullptr) {

            ec = U_MEMORY_ALLOCATION_ERROR;

        } else {

            int32_t numEntries = 0;

            for (int32_t i = 0; i < size; i++) {

                UnicodeString id = ures_getUnicodeStringByIndex(res, i, &ec);

                if (U_FAILURE(ec)) {

                    break;

                }

                if (0 == id.compare(UNKNOWN_ZONE_ID, UNKNOWN_ZONE_ID_LENGTH)) {

                    // exclude Etc/Unknown

                    continue;

                }

                if (type == UCAL_ZONE_TYPE_CANONICAL || type == UCAL_ZONE_TYPE_CANONICAL_LOCATION) {

                    UnicodeString canonicalID;

                    ZoneMeta::getCanonicalCLDRID(id, canonicalID, ec);

                    if (U_FAILURE(ec)) {

                        break;

                    }

                    if (canonicalID != id) {

                        // exclude aliases

                        continue;

                    }

                }

                if (type == UCAL_ZONE_TYPE_CANONICAL_LOCATION) {

                    const char16_t *region = TimeZone::getRegion(id, ec);

                    if (U_FAILURE(ec)) {

                        break;

                    }

                    if (u_strcmp(region, WORLD) == 0) {

                       // exclude non-location ("001")

                        continue;

                    }

                }

                m[numEntries++] = i;

            }

            if (U_SUCCESS(ec)) {

                int32_t *tmp = m;

                m = static_cast<int32_t*>(uprv_realloc(tmp, numEntries * sizeof(int32_t)));

                if (m == nullptr) {

                    // realloc failed.. use the original one even it has unused

                    // area at the end

                    m = tmp;

                }

                switch(type) {

                case UCAL_ZONE_TYPE_ANY:

                    U_ASSERT(MAP_SYSTEM_ZONES == nullptr);

                    MAP_SYSTEM_ZONES = m;

                    LEN_SYSTEM_ZONES = numEntries;

                    break;

                case UCAL_ZONE_TYPE_CANONICAL:

                    U_ASSERT(MAP_CANONICAL_SYSTEM_ZONES == nullptr);

                    MAP_CANONICAL_SYSTEM_ZONES = m;

                    LEN_CANONICAL_SYSTEM_ZONES = numEntries;

                    break;

                case UCAL_ZONE_TYPE_CANONICAL_LOCATION:

                    U_ASSERT(MAP_CANONICAL_SYSTEM_LOCATION_ZONES == nullptr);

                    MAP_CANONICAL_SYSTEM_LOCATION_ZONES = m;

                    LEN_CANONICAL_SYSTEM_LOCATION_ZONES = numEntries;

                    break;

                }

            }

        }

    }

    ures_close(res);

}

/**

 * This is the default implementation for subclasses that do not

 * override this method.  This implementation calls through to the

 * 8-argument getOffset() method after suitable computations, and

 * correctly adjusts GMT millis to local millis when necessary.

 */

void TimeZone::getOffset(UDate date, UBool local, int32_t& rawOffset,

                         int32_t& dstOffset, UErrorCode& ec) const {

    if (U_FAILURE(ec)) {

        return;

    }

    rawOffset = getRawOffset();

    if (!local) {

        date += rawOffset; // now in local standard millis

    }

    // When local == true, date might not be in local standard

    // millis.  getOffset taking 7 parameters used here assume

    // the given time in day is local standard time.

    // At STD->DST transition, there is a range of time which

    // does not exist.  When 'date' is in this time range

    // (and local == true), this method interprets the specified

    // local time as DST.  At DST->STD transition, there is a

    // range of time which occurs twice.  In this case, this

    // method interprets the specified local time as STD.

    // To support the behavior above, we need to call getOffset

    // (with 7 args) twice when local == true and DST is

    // detected in the initial call.

    for (int32_t pass=0; ; ++pass) {

        int32_t year, millis;

        int8_t month, dom, dow;

        Grego::timeToFields(date, year, month, dom, dow, millis, ec);

        if (U_FAILURE(ec)) return;

        dstOffset = getOffset(GregorianCalendar::AD, year, month, dom,

                              static_cast<uint8_t>(dow), millis,

                              Grego::monthLength(year, month),

                              ec) - rawOffset;

        // Recompute if local==true, dstOffset!=0.

        if (pass!=0 || !local || dstOffset == 0) {

            break;

        }

        // adjust to local standard millis

        date -= dstOffset;

    }

}

// -------------------------------------

// New available IDs API as of ICU 2.4.  Uses StringEnumeration API.

class TZEnumeration : public StringEnumeration {

private:

    // Map into to zones.  Our results are zone[map[i]] for

    // i=0..len-1, where zone[i] is the i-th Olson zone.  If map==nullptr

    // then our results are zone[i] for i=0..len-1.  Len will be zero

    // if the zone data could not be loaded.

    int32_t* map;

    int32_t* localMap;

    int32_t  len;

    int32_t  pos;

    TZEnumeration(int32_t* mapData, int32_t mapLen, UBool adoptMapData) : pos(0) {

        map = mapData;

        localMap = adoptMapData ? mapData : nullptr;

        len = mapLen;

    }

    UBool getID(int32_t i, UErrorCode& ec) {

        int32_t idLen = 0;

        const char16_t* id = nullptr;

        UResourceBundle *top = ures_openDirect(nullptr, kZONEINFO, &ec);

        top = ures_getByKey(top, kNAMES, top, &ec); // dereference Zones section

        id = ures_getStringByIndex(top, i, &idLen, &ec);

        if(U_FAILURE(ec)) {

            unistr.truncate(0);

        }

        else {

            unistr.fastCopyFrom(UnicodeString(true, id, idLen));

        }

        ures_close(top);

        return U_SUCCESS(ec);

    }

    static int32_t* getMap(USystemTimeZoneType type, int32_t& len, UErrorCode& ec) {

        len = 0;

        if (U_FAILURE(ec)) {

            return nullptr;

        }

        int32_t* m = nullptr;

        switch (type) {

        case UCAL_ZONE_TYPE_ANY:

            umtx_initOnce(gSystemZonesInitOnce, &initMap, type, ec);

            m = MAP_SYSTEM_ZONES;

            len = LEN_SYSTEM_ZONES;

            break;

        case UCAL_ZONE_TYPE_CANONICAL:

            umtx_initOnce(gCanonicalZonesInitOnce, &initMap, type, ec);

            m = MAP_CANONICAL_SYSTEM_ZONES;

            len = LEN_CANONICAL_SYSTEM_ZONES;

            break;

        case UCAL_ZONE_TYPE_CANONICAL_LOCATION:

            umtx_initOnce(gCanonicalLocationZonesInitOnce, &initMap, type, ec);

            m = MAP_CANONICAL_SYSTEM_LOCATION_ZONES;

            len = LEN_CANONICAL_SYSTEM_LOCATION_ZONES;

            break;

        default:

            ec = U_ILLEGAL_ARGUMENT_ERROR;

            m = nullptr;

            len = 0;

            break;

        }

        return m;

    }

public:

#define DEFAULT_FILTERED_MAP_SIZE 8

#define MAP_INCREMENT_SIZE 8

    static TZEnumeration* create(USystemTimeZoneType type, const char* region, const int32_t* rawOffset, UErrorCode& ec) {

        if (U_FAILURE(ec)) {

            return nullptr;

        }

        int32_t baseLen;

        int32_t *baseMap = getMap(type, baseLen, ec);

        if (U_FAILURE(ec)) {

            return nullptr;

        }

        // If any additional conditions are available,

        // create instance local map filtered by the conditions.

        int32_t *filteredMap = nullptr;

        int32_t numEntries = 0;

        if (region != nullptr || rawOffset != nullptr) {

            int32_t filteredMapSize = DEFAULT_FILTERED_MAP_SIZE;

            filteredMap = static_cast<int32_t*>(uprv_malloc(filteredMapSize * sizeof(int32_t)));

            if (filteredMap == nullptr) {

                ec = U_MEMORY_ALLOCATION_ERROR;

                return nullptr;

            }

            // Walk through the base map

            UResourceBundle *res = ures_openDirect(nullptr, kZONEINFO, &ec);

            res = ures_getByKey(res, kNAMES, res, &ec); // dereference Zones section

            for (int32_t i = 0; i < baseLen; i++) {

                int32_t zidx = baseMap[i];

                UnicodeString id = ures_getUnicodeStringByIndex(res, zidx, &ec);

                if (U_FAILURE(ec)) {

                    break;

                }

                if (region != nullptr) {

                    // Filter by region

                    char tzregion[4]; // max 3 letters + null term

                    TimeZone::getRegion(id, tzregion, sizeof(tzregion), ec);

                    if (U_FAILURE(ec)) {

                        break;

                    }

                    if (uprv_stricmp(tzregion, region) != 0) {

                        // region does not match

                        continue;

                    }

                }

                if (rawOffset != nullptr) {

                    // Filter by raw offset

                    // Note: This is VERY inefficient

                    TimeZone *z = createSystemTimeZone(id, ec);

                    if (U_FAILURE(ec)) {

                        break;

                    }

                    int32_t tzoffset = z->getRawOffset();

                    delete z;

                    if (tzoffset != *rawOffset) {

                        continue;

                    }

                }

                if (filteredMapSize <= numEntries) {

                    filteredMapSize += MAP_INCREMENT_SIZE;

                    int32_t* tmp = static_cast<int32_t*>(uprv_realloc(filteredMap, filteredMapSize * sizeof(int32_t)));

                    if (tmp == nullptr) {

                        ec = U_MEMORY_ALLOCATION_ERROR;

                        break;

                    } else {

                        filteredMap = tmp;

                    }

                }

                filteredMap[numEntries++] = zidx;

            }

            if (U_FAILURE(ec)) {

                uprv_free(filteredMap);

                filteredMap = nullptr;

            }

            ures_close(res);

        }

        TZEnumeration *result = nullptr;

        if (U_SUCCESS(ec)) {

            // Finally, create a new enumeration instance

            if (filteredMap == nullptr) {

                result = new TZEnumeration(baseMap, baseLen, false);

            } else {

                result = new TZEnumeration(filteredMap, numEntries, true);

                filteredMap = nullptr;

            }

            if (result == nullptr) {

                ec = U_MEMORY_ALLOCATION_ERROR;

            }

        }

        if (filteredMap != nullptr) {

            uprv_free(filteredMap);

        }

        return result;

    }

    TZEnumeration(const TZEnumeration &other) : StringEnumeration(), map(nullptr), localMap(nullptr), len(0), pos(0) {

        if (other.localMap != nullptr) {

            localMap = static_cast<int32_t*>(uprv_malloc(other.len * sizeof(int32_t)));

            if (localMap != nullptr) {

                len = other.len;

                uprv_memcpy(localMap, other.localMap, len * sizeof(int32_t));

                pos = other.pos;

                map = localMap;

            } else {

                len = 0;

                pos = 0;

                map = nullptr;

            }

        } else {

            map = other.map;

            localMap = nullptr;

            len = other.len;

            pos = other.pos;

        }

    }

    virtual ~TZEnumeration();

    virtual StringEnumeration *clone() const override {

        return new TZEnumeration(*this);

    }

    virtual int32_t count(UErrorCode& status) const override {

        return U_FAILURE(status) ? 0 : len;

    }

    virtual const UnicodeString* snext(UErrorCode& status) override {

        if (U_SUCCESS(status) && map != nullptr && pos < len) {

            getID(map[pos], status);

            ++pos;

            return &unistr;

        }

        return nullptr;

    }

    virtual void reset(UErrorCode& /*status*/) override {

        pos = 0;

    }

public:

    static UClassID U_EXPORT2 getStaticClassID();

    virtual UClassID getDynamicClassID() const override;

};

TZEnumeration::~TZEnumeration() {

    if (localMap != nullptr) {

        uprv_free(localMap);

    }

}

UOBJECT_DEFINE_RTTI_IMPLEMENTATION(TZEnumeration)

StringEnumeration* U_EXPORT2

TimeZone::createTimeZoneIDEnumeration(

            USystemTimeZoneType zoneType,

            const char* region,

            const int32_t* rawOffset,

            UErrorCode& ec) {

    return TZEnumeration::create(zoneType, region, rawOffset, ec);