pebble/third_party/mktime/mktime.c

/*
 * 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/
 */

#include <stdint.h>

#include "util/time/time.h"
#include <stddef.h>

/*
 * ChkAdd evaluates to TRUE if dest = src1 + src2 has overflowed
 */
#define ChkAdd(dest, src1, src2)   ( ((src1 >= 0L) && (src2 >= 0L) \
    && (dest < 0L)) || ((src1 < 0L) && (src2 < 0L) && (dest >= 0L)) )

/*
 * ChkMul evaluates to TRUE if dest = src1 * src2 has overflowed
 */
#define ChkMul(dest, src1, src2)   ( src1 ? (dest/src1 != src2) : 0 )

#define   _BASE_YEAR   70L
#define   _LEAP_YEAR_ADJUST   17L // leap years between 1900 and 1970
#define   _MAX_YEAR   138L


time_t mktime(struct tm *tb) {
  const int16_t _days[] = {-1, 30, 58, 89, 119, 150, 180, 211, 242, 272, 303, 333, 364};
  time_t tmptm1, tmptm2, tmptm3;
  struct tm *tbtemp;

  /*
   * First, make sure tm_year is reasonably close to being in range.
   */
  if (((tmptm1 = tb->tm_year) < _BASE_YEAR - 1) || (tmptm1 > _MAX_YEAR + 1))
    goto err_mktime;


  /*
   * Adjust month value so it is in the range 0 - 11.  This is because
   * we don't know how many days are in months 12, 13, 14, etc.
   */

  if ((tb->tm_mon < 0) || (tb->tm_mon > 11)) {

    /*
     * no danger of overflow because the range check above.
     */
    tmptm1 += (tb->tm_mon / 12);

    if ((tb->tm_mon %= 12) < 0) {
      tb->tm_mon += 12;
      tmptm1--;
    }

    /*
     * Make sure year count is still in range.
     */
    if ((tmptm1 < _BASE_YEAR - 1) || (tmptm1 > _MAX_YEAR + 1))
      goto err_mktime;
  }

  /***** HERE: tmptm1 holds number of elapsed years *****/

  /*
   * Calculate days elapsed minus one, in the given year, to the given
   * month. Check for leap year and adjust if necessary.
   */
  tmptm2 = _days[tb->tm_mon];
  if (!(tmptm1 & 3) && (tb->tm_mon > 1))
    tmptm2++;

  /*
   * Calculate elapsed days since base date (midnight, 1/1/70, UTC)
   *
   *
   * 365 days for each elapsed year since 1970, plus one more day for
   * each elapsed leap year. no danger of overflow because of the range
   * check (above) on tmptm1.
   */
  tmptm3 = (tmptm1 - _BASE_YEAR) * 365L + ((tmptm1 - 1L) >> 2)
  - _LEAP_YEAR_ADJUST;

  /*
   * elapsed days to current month (still no possible overflow)
   */
  tmptm3 += tmptm2;

  /*
   * elapsed days to current date. overflow is now possible.
   */
  tmptm1 = tmptm3 + (tmptm2 = (int32_t) (tb->tm_mday));
  if (ChkAdd(tmptm1, tmptm3, tmptm2))
    goto err_mktime;

  /***** HERE: tmptm1 holds number of elapsed days *****/

  /*
   * Calculate elapsed hours since base date
   */
  tmptm2 = tmptm1 * 24L;
  if (ChkMul(tmptm2, tmptm1, 24L))
    goto err_mktime;

  tmptm1 = tmptm2 + (tmptm3 = (int32_t) tb->tm_hour);
  if (ChkAdd(tmptm1, tmptm2, tmptm3))
    goto err_mktime;

  /***** HERE: tmptm1 holds number of elapsed hours *****/

  /*
   * Calculate elapsed minutes since base date
   */

  tmptm2 = tmptm1 * 60L;
  if (ChkMul(tmptm2, tmptm1, 60L))
    goto err_mktime;

  tmptm1 = tmptm2 + (tmptm3 = (int32_t) tb->tm_min);
  if (ChkAdd(tmptm1, tmptm2, tmptm3))
    goto err_mktime;

  /***** HERE: tmptm1 holds number of elapsed minutes *****/

  /*
   * Calculate elapsed seconds since base date
   */

  tmptm2 = tmptm1 * 60L;
  if (ChkMul(tmptm2, tmptm1, 60L))
    goto err_mktime;

  tmptm1 = tmptm2 + (tmptm3 = (int32_t) tb->tm_sec);
  if (ChkAdd(tmptm1, tmptm2, tmptm3))
    goto err_mktime;

  /***** HERE: tmptm1 holds number of elapsed seconds *****/

     /*
         * Adjust for timezone. No need to check for overflow since
         * localtime() will check its arg value
         */

  tmptm1 -= tb->tm_gmtoff;
  tmptm1 -= tb->tm_isdst * 60 * 60;

  /*
   * Convert this second count back into a time block structure.
   * If localtime returns NULL, return an error.
   */
  struct tm tm;
  if ((tbtemp = gmtime_r((time_t*)&tmptm1, &tm)) == NULL)
    goto err_mktime;


  /***** HERE: tmptm1 holds number of elapsed seconds, adjusted *****/
  /*****       for local time if requested                      *****/

  *tb = *tbtemp;
  return (time_t) tmptm1;

  err_mktime:
  /*
   * All errors come to here
   */
  return (time_t) (-1);
}