/* Copyright (c) 2007-2018 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;

}

static inline void adjust_leap_second(struct tm *tm)

{

  if (tm->tm_sec == 60)

    tm->tm_sec = 59;

}

#ifdef HAVE_TIMEGM

/* Normalization done by timegm is considered a failure here, since it means

 * the timestamp is not valid as-is. Leap second 60 is adjusted to 59 before

 * this though. */

time_t utc_mktime(const struct tm *tm)

{

  struct tm leap_adj_tm = *tm;

  adjust_leap_second(&leap_adj_tm);

  struct tm tmp = leap_adj_tm;

  time_t t;

  t = timegm(&tmp);

  if (tm_cmp(&leap_adj_tm, &tmp) != 0)

    return (time_t)-1;

  return t;

}

#else

time_t utc_mktime(const struct tm *tm)

{

  struct tm leap_adj_tm = *tm;

  adjust_leap_second(&leap_adj_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(&leap_adj_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;

}

#endif