/* Copyright (c) 2002-2018 Dovecot authors, see the included COPYING file */

#include "lib.h"

#include "utc-offset.h"

#include <sys/time.h>

int utc_offset(struct tm *tm, time_t t ATTR_UNUSED)

{

#ifdef HAVE_TM_GMTOFF

  return (int) (tm->tm_gmtoff/60);

#else

  struct tm ltm, gtm;

  int offset;

  /* gmtime() overwrites tm, so we need to copy it elsewhere */

  ltm = *tm;

  tm = gmtime(&t);

  gtm = *tm;

  /* max offset of 24 hours */

  if ((ltm.tm_yday < gtm.tm_yday && ltm.tm_year == gtm.tm_year) ||

      ltm.tm_year < gtm.tm_year)

    offset = -24 * 60;

  else if ((ltm.tm_yday > gtm.tm_yday && ltm.tm_year == gtm.tm_year) ||

     ltm.tm_year > gtm.tm_year)

    offset = 24 * 60;

  else

    offset = 0;

  offset += (ltm.tm_hour - gtm.tm_hour) * 60;

  offset += (ltm.tm_min - gtm.tm_min);

  /* restore overwritten tm */

  *tm = ltm;

  return offset;

#endif

}