src/lib/utc-mktime.c

	utc-mktime.c revision cca4ba2a504d70a9fe9fee37f8433997359de52c
* Copyright (c) 2007-2013 Dovecot authors, see the included COPYING file */

#include "lib.h"
#include "utc-mktime.h"

static int tm_cmp(const struct tm *tm1, const struct tm *tm2)
{
    int diff;

    if ((diff = tm1->tm_year - tm2->tm_year) != 0)
        return diff;
    if ((diff = tm1->tm_mon - tm2->tm_mon) != 0)
        return diff;
    if ((diff = tm1->tm_mday - tm2->tm_mday) != 0)
        return diff;
    if ((diff = tm1->tm_hour - tm2->tm_hour) != 0)
        return diff;
    if ((diff = tm1->tm_min - tm2->tm_min) != 0)
        return diff;
    return tm1->tm_sec - tm2->tm_sec;
}

time_t utc_mktime(const struct tm *tm)
{
    const struct tm *try_tm;
    time_t t;
    int bits, dir;

    /* we'll do a binary search across the entire valid time_t range.
       when gmtime()'s output matches the tm parameter, we've found the
       correct time_t value. this also means that if tm contains invalid
       values, -1 is returned. */
#ifdef TIME_T_SIGNED
    t = 0;
#else
    t = (time_t)1 << (TIME_T_MAX_BITS - 1);
#endif
    for (bits = TIME_T_MAX_BITS - 2;; bits--) {
        try_tm = gmtime(&t);
        dir = tm_cmp(tm, try_tm);
        if (dir == 0)
            return t;
        if (bits < 0)
            break;

        if (dir < 0)
            t -= (time_t)1 << bits;
        else
            t += (time_t)1 << bits;
    }

    return (time_t)-1;
}