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void TimeZone::initDefault ( void   )  [static, private]

Responsible for setting up DEFAULT_ZONE. Uses routines in TPlatformUtilities (i.e., platform-specific calls) to get the current system time zone. Failing that, uses the platform-specific default time zone. Failing that, uses GMT.

Initialize DEFAULT_ZONE from the system default time zone. The caller should confirm that DEFAULT_ZONE is NULL before calling. Upon return, DEFAULT_ZONE will not be NULL, unless operator new() returns NULL.

Must be called OUTSIDE mutex.

Definition at line 531 of file timezone.cpp.

References UnicodeString::append(), clone(), createSystemTimeZone(), getGMT(), getRawOffset(), UnicodeString::length(), NULL, UnicodeString::truncate(), U_MILLIS_PER_SECOND, and US_INV.

Referenced by createDefault().

    // We access system timezone data through TPlatformUtilities,
    // including tzset(), timezone, and tzname[].
    int32_t rawOffset = 0;
    const char *hostID;

    // First, try to create a system timezone, based
    // on the string ID in tzname[0].
        // NOTE: Local mutex here. TimeZone mutex below
        // mutexed to avoid threading issues in the platform functions.
        // Some of the locale/timezone OS functions may not be thread safe,
        // so the intent is that any setting from anywhere within ICU
        // happens while the ICU mutex is held.
        // The operating system might actually use ICU to implement timezones.
        // So we may have ICU calling ICU here, like on AIX.
        // In order to prevent a double lock of a non-reentrant mutex in a
        // different part of ICU, we use TZSET_LOCK to allow only one instance
        // of ICU to query these thread unsafe OS functions at any given time.
        Mutex lock(&TZSET_LOCK);

        ucln_i18n_registerCleanup(UCLN_I18N_TIMEZONE, timeZone_cleanup);
        uprv_tzset(); // Initialize tz... system data
        // Get the timezone ID from the host.  This function should do
        // any required host-specific remapping; e.g., on Windows this
        // function maps the Date and Time control panel setting to an
        // ICU timezone ID.
        hostID = uprv_tzname(0);
        // Invert sign because UNIX semantics are backwards
        rawOffset = uprv_timezone() * -U_MILLIS_PER_SECOND;

    UBool initialized;
    UMTX_CHECK(&LOCK, (DEFAULT_ZONE != NULL), initialized);
    if (initialized) {
        /* Hrmph? Either a race condition happened, or tzset initialized ICU. */

    TimeZone* default_zone = NULL;

    /* Make sure that the string is NULL terminated to prevent BoundsChecker/Purify warnings. */
    UnicodeString hostStrID(hostID, -1, US_INV);
    default_zone = createSystemTimeZone(hostStrID);

#ifdef U_WINDOWS
    // hostID points to a heap-allocated location on Windows.
    uprv_free(const_cast<char *>(hostID));

    int32_t hostIDLen = hostStrID.length();
    if (default_zone != NULL && rawOffset != default_zone->getRawOffset()
        && (3 <= hostIDLen && hostIDLen <= 4))
        // Uh oh. This probably wasn't a good id.
        // It was probably an ambiguous abbreviation
        delete default_zone;
        default_zone = NULL;

    // Construct a fixed standard zone with the host's ID
    // and raw offset.
    if (default_zone == NULL) {
        default_zone = new SimpleTimeZone(rawOffset, hostStrID);

    // If we _still_ don't have a time zone, use GMT.
    if (default_zone == NULL) {
        const TimeZone* temptz = getGMT();
        // If we can't use GMT, get out.
        if (temptz == NULL) {
        default_zone = temptz->clone();

    // If DEFAULT_ZONE is still NULL, set it up.
    if (DEFAULT_ZONE == NULL) {
        DEFAULT_ZONE = default_zone;
        default_zone = NULL;
        ucln_i18n_registerCleanup(UCLN_I18N_TIMEZONE, timeZone_cleanup);
    delete default_zone;

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