timegm.c

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/*
 * Copyright (c) 1997 Kungliga Tekniska H鰃skolan
 * (Royal Institute of Technology, Stockholm, Sweden). 
 * 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 Institute nor the names of its contributors 
 *    may be used to endorse or promote products derived from this software 
 *    without specific prior written permission. 
 *
 * THIS SOFTWARE IS PROVIDED BY THE INSTITUTE 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 THE INSTITUTE 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. 
 */

#include "der_locl.h"

RCSID("$Id: timegm.c 21366 2007-06-27 10:06:22Z lha $");

static int
is_leap(unsigned y)
{
    y += 1900;
    return (y % 4) == 0 && ((y % 100) != 0 || (y % 400) == 0);
}

/* 
 * This is a simplifed version of timegm(3) that doesn't accept out of
 * bound values that timegm(3) normally accepts but those are not
 * valid in asn1 encodings.
 */

time_t
_der_timegm (struct tm *tm)
{
  static const unsigned ndays[2][12] ={
    {31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31},
    {31, 29, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31}};
  time_t res = 0;
  unsigned i;

  if (tm->tm_year < 0) 
      return -1;
  if (tm->tm_mon < 0 || tm->tm_mon > 11) 
      return -1;
  if (tm->tm_mday < 1 || tm->tm_mday > ndays[is_leap(tm->tm_year)][tm->tm_mon])
      return -1;
  if (tm->tm_hour < 0 || tm->tm_hour > 23) 
      return -1;
  if (tm->tm_min < 0 || tm->tm_min > 59) 
      return -1;
  if (tm->tm_sec < 0 || tm->tm_sec > 59) 
      return -1;

  for (i = 70; i < tm->tm_year; ++i)
    res += is_leap(i) ? 366 : 365;

  for (i = 0; i < tm->tm_mon; ++i)
    res += ndays[is_leap(tm->tm_year)][i];
  res += tm->tm_mday - 1;
  res *= 24;
  res += tm->tm_hour;
  res *= 60;
  res += tm->tm_min;
  res *= 60;
  res += tm->tm_sec;
  return res;
}