Subject: Re: Trying to use AUTHOR_DATE

From: Juliusz Chroboczek <[email-masked]>
Date: Sat, 30 Apr 2005 23:59:44 +0200

Hi,

Here's the code I'm using in darcs-git (copied from Polipo, another
project of mine).  You're welcome to use it in any way you see fit.

sprintf_a is defined as strdup of sprintf.

                                        Juliusz
#if defined __GLIBC__
#define HAVE_TM_GMTOFF
#define HAVE_SETENV
#ifndef __UCLIBC__
#define HAVE_TIMEGM
#endif
#endif

#if defined(__linux__) && (__GNU_LIBRARY__ == 1)
/* Linux libc 5 */
#define HAVE_TIMEGM
#define HAVE_SETENV
#endif

#ifdef BSD
#define HAVE_TM_GMTOFF
#define HAVE_SETENV
#endif

#ifdef __CYGWIN__
#define HAVE_SETENV
#endif

#if _POSIX_VERSION >= 200112L
#define HAVE_SETENV
#endif

#define HAVE_TZSET

/* Like mktime(3), but UTC rather than local time */
#if defined(HAVE_TIMEGM)
time_t
mktime_gmt(struct tm *tm)
{
    return timegm(tm);
}
#elif defined(HAVE_TM_GMTOFF)
time_t
mktime_gmt(struct tm *tm)
{
    time_t t;
    struct tm *ltm;

    t = mktime(tm);
    if(t < 0)
        return -1;
    ltm = localtime(&t);
    if(ltm == NULL)
        return -1;
    return t + ltm->tm_gmtoff;
}
#elif defined(HAVE_TZSET)
#ifdef HAVE_SETENV
/* Taken from the Linux timegm(3) man page. */
time_t
mktime_gmt(struct tm *tm)
{
    time_t t;
    char *tz;

    tz = getenv("TZ");
    setenv("TZ", "", 1);
    tzset();
    t = mktime(tm);
    if(tz)
        setenv("TZ", tz, 1);
    else
        unsetenv("TZ");
    tzset();
    return t;
}
#else
time_t
mktime_gmt(struct tm *tm)
{
    time_t t;
    char *tz;
    static char *old_tz = NULL;

    tz = getenv("TZ");
    putenv("TZ=");
    tzset();
    t = mktime(tm);
    if(old_tz)
        free(old_tz);
    if(tz)
        old_tz = sprintf_a("TZ=%s", tz);
    else
        old_tz = strdup("TZ");  /* XXX - non-portable? */
    if(old_tz)
        putenv(old_tz);
    tzset();
    return t;
}
#endif
#else
#error no mktime_gmt implementation on this platform
#endif