tzset.c

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/***
*tzset.c - set timezone information and see if we're in daylight time
*
*       Copyright (c) 1985-1998, Microsoft Corporation. All rights reserved.
*
*Purpose:
*       defines _tzset() - set timezone and daylight saving time vars
*
*******************************************************************************/

#ifdef _WIN32


#include <cruntime.h>
#include <ctype.h>
#include <ctime.h>
#include <time.h>
#include <stdlib.h>
#include <internal.h>
#include <mtdll.h>
#include <windows.h>
#include <setlocal.h>
#include <string.h>
#include <dbgint.h>


/*
 * Number of milliseconds in one day
 */
#define DAY_MILLISEC    (24L * 60L * 60L * 1000L)

/*
 * The macro below is valid for years between 1901 and 2099, which easily
 * includes all years representable by the current implementation of time_t.
 */
#define IS_LEAP_YEAR(year)  ( (year & 3) == 0 )

/*
 * Pointer to a saved copy of the TZ value obtained in the previous call
 * to tzset() set (if any).
 */
static char * lastTZ = NULL;

/*
 * Flag indicating that time zone information came from GetTimeZoneInformation
 * API call.
 */
static int tzapiused;

static TIME_ZONE_INFORMATION tzinfo;

/*
 * Structure used to represent DST transition date/times.
 */
typedef struct {
        int  yr;        /* year of interest */
        int  yd;        /* day of year */
        long ms;        /* milli-seconds in the day */
        } transitiondate;

/*
 * DST start and end structs.
 */
static transitiondate dststart = { -1, 0, 0L };
static transitiondate dstend   = { -1, 0, 0L };

static int __cdecl _isindst_lk(struct tm *);



/***
*void tzset() - sets timezone information and calc if in daylight time
*
*Purpose:
*       Sets the timezone information from the TZ environment variable
*       and then sets _timezone, _daylight, and _tzname. If we're in daylight
*       time is automatically calculated.
*
*Entry:
*       None, reads TZ environment variable.
*
*Exit:
*       sets _daylight, _timezone, and _tzname global vars, no return value
*
*Exceptions:
*
*******************************************************************************/


#ifdef _MT
static void __cdecl _tzset_lk(void);
#else  /* _MT */
#define _tzset_lk _tzset
#endif  /* _MT */

void __cdecl __tzset(void)
{
        static int first_time = 0;

        if ( !first_time ) {

            _mlock( _TIME_LOCK );

            if ( !first_time ) {
                _tzset_lk();
                first_time++;
            }

            _munlock(_TIME_LOCK );

        }
}


#ifdef _MT
void __cdecl _tzset (
        void
        )
{
        _mlock( _TIME_LOCK );

        _tzset_lk();

        _munlock( _TIME_LOCK );
}


static void __cdecl _tzset_lk (

#else  /* _MT */

void __cdecl _tzset (

#endif  /* _MT */

        void
        )
{
        char *TZ;
        int defused;
        int negdiff = 0;

        _mlock(_ENV_LOCK);

        /*
         * Clear the flag indicated whether GetTimeZoneInformation was used.
         */
        tzapiused = 0;

        /*
         * Set year fields of dststart and dstend structures to -1 to ensure
         * they are recomputed as after this
         */
        dststart.yr = dstend.yr = -1;

        /*
         * Fetch the value of the TZ environment variable.
         */
        if ( (TZ = _getenv_lk("TZ")) == NULL ) {

            /*
             * There is no TZ environment variable, try to use the time zone
             * information from the system.
             */

            _munlock(_ENV_LOCK);

            if ( GetTimeZoneInformation( &tzinfo ) != 0xFFFFFFFF ) {
                /*
                 * Note that the API was used.
                 */
                tzapiused = 1;

                /*
                 * Derive _timezone value from Bias and StandardBias fields.
                 */
                _timezone = tzinfo.Bias * 60L;

                if ( tzinfo.StandardDate.wMonth != 0 )
                    _timezone += (tzinfo.StandardBias * 60L);

                /*
                 * Check to see if there is a daylight time bias. Since the
                 * StandardBias has been added into _timezone, it must be
                 * compensated for in the value computed for _dstbias.
                 */
                if ( (tzinfo.DaylightDate.wMonth != 0) &&
                     (tzinfo.DaylightBias != 0) )
                {
                    _daylight = 1;
                    _dstbias = (tzinfo.DaylightBias - tzinfo.StandardBias) *
                               60L;
                }
                else {
                        _daylight = 0;

                    /*
                     * Set daylight bias to 0 because GetTimeZoneInformation
                     * may return TIME_ZONE_ID_DAYLIGHT even though there is
                     * no DST (in NT 3.51, just turn off the automatic DST
                     * adjust in the control panel)!
                     */
                    _dstbias = 0;
                }

                /*
                 * Try to grab the name strings for both the time zone and the
                 * daylight zone. Note the wide character strings in tzinfo
                 * must be converted to multibyte characters strings. The
                 * locale codepage, __lc_codepage, is used for this. Note that
                 * if setlocale() with LC_ALL or LC_CTYPE has not been called,
                 * then __lc_codepage will be 0 (_CLOCALECP), which is CP_ACP
                 * (which means use the host's default ANSI codepage).
                 */
                if ( (WideCharToMultiByte( __lc_codepage,
                                           WC_COMPOSITECHECK |
                                            WC_SEPCHARS,
                                           tzinfo.StandardName,
                                           -1,
                                           _tzname[0],
                                           63,
                                           NULL,
                                           &defused ) != 0) &&
                     (!defused) )
                    _tzname[0][63] = '\0';
                else
                    _tzname[0][0] = '\0';

                if ( (WideCharToMultiByte( __lc_codepage,
                                           WC_COMPOSITECHECK |
                                            WC_SEPCHARS,
                                           tzinfo.DaylightName,
                                           -1,
                                           _tzname[1],
                                           63,
                                           NULL,
                                           &defused ) != 0) &&
                     (!defused) )
                    _tzname[1][63] = '\0';
                else
                    _tzname[1][0] = '\0';

            }

            /*
             * Time zone information is unavailable, just return.
             */
            return;
        }


        if ( (*TZ == '\0') || ((lastTZ != NULL) && (strcmp(TZ, lastTZ) == 0)) )
        {
            /*
             * Either TZ is NULL, pointing to '\0', or is the unchanged
             * from a earlier call (to this function). In any case, there
             * is no work to do, so just return
             */
            _munlock(_ENV_LOCK);
            return;
        }

        /*
         * Update lastTZ
         */
        _free_crt(lastTZ);

        if ((lastTZ = _malloc_crt(strlen(TZ)+1)) == NULL)
        {
            _munlock(_ENV_LOCK);
            return;
        }
        strcpy(lastTZ, TZ);

        _munlock(_ENV_LOCK);

        /*
         * Process TZ value and update _tzname, _timezone and _daylight.
         */

        strncpy(_tzname[0], TZ, 3);
        _tzname[0][3] = '\0';

        /*
         * time difference is of the form:
         *
         *      [+|-]hh[:mm[:ss]]
         *
         * check minus sign first.
         */
        if ( *(TZ += 3) == '-' ) {
            negdiff++;
            TZ++;
        }

        /*
         * process, then skip over, the hours
         */
        _timezone = atol(TZ) * 3600L;

        while ( (*TZ == '+') || ((*TZ >= '0') && (*TZ <= '9')) ) TZ++;

        /*
         * check if minutes were specified
         */
        if ( *TZ == ':' ) {
            /*
             * process, then skip over, the minutes
             */
            _timezone += atol(++TZ) * 60L;
            while ( (*TZ >= '0') && (*TZ <= '9') ) TZ++;

            /*
             * check if seconds were specified
             */
            if ( *TZ == ':' ) {
                /*
                 * process, then skip over, the seconds
                 */
                _timezone += atol(++TZ);
                while ( (*TZ >= '0') && (*TZ <= '9') ) TZ++;
            }
        }

        if ( negdiff )
            _timezone = -_timezone;

        /*
         * finally, check for a DST zone suffix
         */
        if ( _daylight = *TZ ) {
            strncpy(_tzname[1], TZ, 3);
            _tzname[1][3] = '\0';
        }
        else
            *_tzname[1] = '\0';

}

/***
*static void cvtdate( trantype, datetype, year, month, week, dayofweek,
*                     date, hour, min, second, millisec ) - convert
*       transition date format
*
*Purpose:
*       Convert the format of a transition date specification to a value of
*       a transitiondate structure.
*
*Entry:
*       int trantype    - 1, if it is the start of DST
*                         0, if is the end of DST (in which case the date is
*                            is a DST date)
*       int datetype    - 1, if a day-in-month format is specified.
*                         0, if an absolute date is specified.
*       int year        - year for which the date is being converted (70 ==
*                         1970)
*       int month       - month (0 == January)
*       int week        - week of month, if datetype == 1 (note that 5== last
*                         week of month),
*                         0, otherwise.
*       int dayofweek   - day of week (0 == Sunday), if datetype == 1.
*                         0, otherwise.
*       int date        - date of month (1 - 31)
*       int hour        - hours (0 - 23)
*       int min         - minutes (0 - 59)
*       int sec         - seconds (0 - 59)
*       int msec        - milliseconds (0 - 999)
*
*Exit:
*       dststart or dstend is filled in with the converted date.
*
*******************************************************************************/

static void __cdecl cvtdate (
        int trantype,
        int datetype,
        int year,
        int month,
        int week,
        int dayofweek,
        int date,
        int hour,
        int min,
        int sec,
        int msec
        )
{
        int yearday;
        int monthdow;

        if ( datetype == 1 ) {

            /*
             * Transition day specified in day-in-month format.
             */

            /*
             * Figure the year-day of the start of the month.
             */
            yearday = 1 + (IS_LEAP_YEAR(year) ? _lpdays[month - 1] :
                      _days[month - 1]);

            /*
             * Figure the day of the week of the start of the month.
             */
            monthdow = (yearday + ((year - 70) * 365) + ((year - 1) >> 2) -
                        _LEAP_YEAR_ADJUST + _BASE_DOW) % 7;

            /*
             * Figure the year-day of the transition date
             */
            if ( monthdow <= dayofweek )
                yearday += (dayofweek - monthdow) + (week - 1) * 7;
            else
                yearday += (dayofweek - monthdow) + week * 7;

            /*
             * May have to adjust the calculation above if week == 5 (meaning
             * the last instance of the day in the month). Check if year falls
             * beyond after month and adjust accordingly.
             */
            if ( (week == 5) &&
                 (yearday > (IS_LEAP_YEAR(year) ? _lpdays[month] :
                             _days[month])) )
            {
                yearday -= 7;
            }
        }
        else {
            /*
             * Transition day specified as an absolute day
             */
            yearday = IS_LEAP_YEAR(year) ? _lpdays[month - 1] :
                      _days[month - 1];

            yearday += date;
        }

        if ( trantype == 1 ) {
            /*
             * Converted date was for the start of DST
             */
            dststart.yd = yearday;
            dststart.ms = (long)msec +
                          (1000L * (sec + 60L * (min + 60L * hour)));
            /*
             * Set year field of dststart so that unnecessary calls to
             * cvtdate() may be avoided.
             */
            dststart.yr = year;
        }
        else {
            /*
             * Converted date was for the end of DST
             */
            dstend.yd = yearday;
            dstend.ms = (long)msec +
                              (1000L * (sec + 60L * (min + 60L * hour)));
            /*
             * The converted date is still a DST date. Must convert to a
             * standard (local) date while being careful the millisecond field
             * does not overflow or underflow.
             */
            if ( (dstend.ms += (_dstbias * 1000L)) < 0 ) {
                dstend.ms += DAY_MILLISEC;
                dstend.yd--;
            }