/*

 * Copyright (c) 1997 Kungliga Tekniska Högskolan

 * (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"

#define ASN1_MAX_YEAR 2000

static int

is_leap(unsigned y)

{

    y += 1900;

    return (y % 4) == 0 && ((y % 100) != 0 || (y % 400) == 0);

}

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}};

/*

 * 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)

{

  time_t res = 0;

  int i;

  /*

   * See comment in _der_gmtime

   */

  if (tm->tm_year > ASN1_MAX_YEAR)

      return 0;

  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 > (int)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;

}

struct tm *

_der_gmtime(time_t t, struct tm *tm)

{

    time_t secday = t % (3600 * 24);

    time_t days = t / (3600 * 24);

    memset(tm, 0, sizeof(*tm));

    tm->tm_sec = secday % 60;

    tm->tm_min = (secday % 3600) / 60;

    tm->tm_hour = (int)(secday / 3600);

    /*

     * Refuse to calculate time ~ 2000 years into the future, this is

     * not possible for systems where time_t is a int32_t, however,

     * when time_t is a int64_t, that can happen, and this becomes a

     * denial of sevice.

     */

    if (days > (ASN1_MAX_YEAR * 365))

  return NULL;

    tm->tm_year = 70;

    while(1) {

  unsigned dayinyear = (is_leap(tm->tm_year) ? 366 : 365);

  if (days < dayinyear)

      break;

  tm->tm_year += 1;

  days -= dayinyear;

    }

    tm->tm_mon = 0;

    while (1) {

  unsigned daysinmonth = ndays[is_leap(tm->tm_year)][tm->tm_mon];

  if (days < daysinmonth)

      break;

  days -= daysinmonth;

  tm->tm_mon++;

    }

    tm->tm_mday = (int)(days + 1);

    return tm;

}