gmtime.c

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/*
 * Copyright (C) 2001-2003 by egnite Software GmbH. All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 *
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 * 3. Neither the name of the copyright holders nor the names of
 *    contributors may be used to endorse or promote products derived
 *    from this software without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY EGNITE SOFTWARE GMBH AND CONTRIBUTORS
 * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
 * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL EGNITE
 * SOFTWARE GMBH OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
 * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
 * OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
 * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
 * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF
 * THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 *
 * For additional information see http://www.ethernut.de/
 *
 * Portions of the following functions are derived from material which is 
 * Copyright (c) 1985 by Microsoft Corporation.  All rights are reserved.
 */
/*
 * $Log$
 * Revision 1.8  2008/08/11 06:59:40  haraldkipp
 * BSD types replaced by stdint types (feature request #1282721).
 *
 * Revision 1.7  2005/08/02 17:46:47  haraldkipp
 * Major API documentation update.
 *
 * Revision 1.6  2004/10/14 16:43:00  drsung
 * Fixed compiler warning "comparison between signed and unsigned"
 *
 * Revision 1.5  2003/12/19 22:26:37  drsung
 * Dox written.
 *
 * Revision 1.4  2003/11/27 09:17:18  drsung
 * Wrong comment fixed
 *
 * Revision 1.3  2003/11/26 12:45:20  drsung
 * Portability issues ... again
 *
 * Revision 1.2  2003/11/26 11:13:17  haraldkipp
 * Portability issues
 *
 * Revision 1.1  2003/11/24 18:07:37  drsung
 * first release
 *
 *
 */

#include <stdint.h>

#include <time.h>
#include "ctime.h"

#define __need_NULL
#include <stddef.h>

tm _tb;

/*      static arrays used by gmtime to determine date and time
*       values. Shows days from being of year.
***************************************************************/
int _lpdays[] = {
    -1, 30, 59, 90, 120, 151, 181, 212, 243, 273, 304, 334, 365
};
int _days[] = {
    -1, 30, 58, 89, 119, 150, 180, 211, 242, 272, 303, 333, 364
};

int gmtime_r(CONST time_t * timer, tm * ptm)
{
    time_t ctimer = *timer;     /* var to calculate with */
    uint8_t isleapyear = 0;     /* current year is leap year */
    uint32_t tmptimer;
    int *mdays;                 /* pointer to _numdayslp or _numdays */

    if (ptm == NULL)            /* check pointer */
        return -1;

    /*
       First calculate the number of four-year-interval, so calculation
       of leap year will be simple. Btw, because 2000 IS a leap year and
       2100 is out of range, this formula is so simple.
     */
    tmptimer = (uint32_t) (ctimer / _FOUR_YEAR_SEC);
    ctimer -= ((time_t) tmptimer * _FOUR_YEAR_SEC);

    /* Determine the correct year within the interval */
    tmptimer = (tmptimer * 4) + 70;     /* 1970, 1974, 1978,... */
    if (ctimer >= (time_t)_YEAR_SEC) {
        tmptimer++;             /* 1971, 1975, 1979,... */
        ctimer -= _YEAR_SEC;
        if (ctimer >= (time_t)_YEAR_SEC) {
            tmptimer++;         /* 1972, 1976, 1980,... (all leap years!) */
            ctimer -= _YEAR_SEC;
            /* A leap year has 366 days, so compare to _YEAR_SEC + _DAY_SEC */
            if (ctimer >= (time_t)(_YEAR_SEC + _DAY_SEC)) {
                tmptimer++;     /* 1973, 1977, 1981,... */
                ctimer -= (_YEAR_SEC + _DAY_SEC);
            } else
                isleapyear = 1; /*If leap year, set the flag */
        }
    }

    /*
       tmptimer now has the value for tm_year. ctimer now holds the
       number of elapsed seconds since the beginning of that year.
     */
    ptm->tm_year = tmptimer;

    /*
       Calculate days since January 1st and store it to tm_yday.
       Leave ctimer with number of elapsed seconds in that day.
     */
    ptm->tm_yday = (int) (ctimer / _DAY_SEC);
    ctimer -= (time_t) (ptm->tm_yday) * _DAY_SEC;

    /*
       Determine months since January (Note, range is 0 - 11)
       and day of month (range: 1 - 31)
     */
    if (isleapyear)
        mdays = _lpdays;
    else
        mdays = _days;


    for (tmptimer = 1; mdays[tmptimer] < ptm->tm_yday; tmptimer++);

    ptm->tm_mon = --tmptimer;

    ptm->tm_mday = ptm->tm_yday - mdays[tmptimer];

    /* Calculate day of week. Sunday is 0 */
    ptm->tm_wday = ((int) (*timer / _DAY_SEC) + _BASE_DOW) % 7;

    /* Calculate the time of day from the remaining seconds */
    ptm->tm_hour = (int) (ctimer / 3600);
    ctimer -= (time_t) ptm->tm_hour * 3600L;

    ptm->tm_min = (int) (ctimer / 60);
    ptm->tm_sec = (int) (ctimer - (ptm->tm_min) * 60);

    ptm->tm_isdst = 0;
    return 0;
}

tm *gmtime(CONST time_t * timer)
{
    if (gmtime_r(timer, &_tb))
        return NULL;
    else
        return &_tb;
}