#include "timeutils.h"

/* mkgmtime.c - make time corresponding to a GMT timeval struct
 $Id: timeutils.c,v 1.2 2006/12/29 10:35:25 hoa Exp $
 
 * Copyright (c) 1998-2000 Carnegie Mellon University.  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. The name "Carnegie Mellon University" must not be used to
 *    endorse or promote products derived from this software without
 *    prior written permission. For permission or any other legal
 *    details, please contact  
 *      Office of Technology Transfer
 *      Carnegie Mellon University
 *      5000 Forbes Avenue
 *      Pittsburgh, PA  15213-3890
 *      (412) 268-4387, fax: (412) 268-7395
 *      tech-transfer@andrew.cmu.edu
 *
 * 4. Redistributions of any form whatsoever must retain the following
 *    acknowledgment:
 *    "This product includes software developed by Computing Services
 *     at Carnegie Mellon University (http://www.cmu.edu/computing/)."
 *
 * CARNEGIE MELLON UNIVERSITY DISCLAIMS ALL WARRANTIES WITH REGARD TO
 * THIS SOFTWARE, INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY
 * AND FITNESS, IN NO EVENT SHALL CARNEGIE MELLON UNIVERSITY BE LIABLE
 * FOR ANY SPECIAL, INDIRECT OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
 * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN
 * AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING
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/*
 * Copyright (c) 1987, 1989, 1993
 *	The Regents of the University of California.  All rights reserved.
 *
 * This code is derived from software contributed to Berkeley by
 * Arthur David Olson of the National Cancer Institute.
 *
 * 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. All advertising materials mentioning features or use of this software
 *    must display the following acknowledgement:
 *	This product includes software developed by the University of
 *	California, Berkeley and its contributors.
 * 4. Neither the name of the University 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 REGENTS 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 REGENTS 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.
 */

/*
** Adapted from code provided by Robert Elz, who writes:
**	The "best" way to do mktime I think is based on an idea of Bob
**	Kridle's (so its said...) from a long time ago. (mtxinu!kridle now).
**	It does a binary search of the time_t space.  Since time_t's are
**	just 32 bits, its a max of 32 iterations (even at 64 bits it
**	would still be very reasonable).
*/

/*
  adapted for libEtPan! by DINH V. Hoa
*/

#ifndef WRONG
#define WRONG	(-1)
#endif /* !defined WRONG */

static int tmcomp(struct tm * atmp, struct tm * btmp)
{
  register int	result;
  
  if ((result = (atmp->tm_year - btmp->tm_year)) == 0 &&
      (result = (atmp->tm_mon - btmp->tm_mon)) == 0 &&
      (result = (atmp->tm_mday - btmp->tm_mday)) == 0 &&
      (result = (atmp->tm_hour - btmp->tm_hour)) == 0 &&
      (result = (atmp->tm_min - btmp->tm_min)) == 0)
    result = atmp->tm_sec - btmp->tm_sec;
  return result;
}

time_t mail_mkgmtime(struct tm * tmp)
{
  register int			dir;
  register int			bits;
  register int			saved_seconds;
  time_t				t;
  struct tm			yourtm, *mytm;
  
  yourtm = *tmp;
  saved_seconds = yourtm.tm_sec;
  yourtm.tm_sec = 0;
  /*
  ** Calculate the number of magnitude bits in a time_t
  ** (this works regardless of whether time_t is
  ** signed or unsigned, though lint complains if unsigned).
  */
  for (bits = 0, t = 1; t > 0; ++bits, t <<= 1)
    ;
  /*
  ** If time_t is signed, then 0 is the median value,
  ** if time_t is unsigned, then 1 << bits is median.
  */
  t = (t < 0) ? 0 : ((time_t) 1 << bits);
  
  /* Some gmtime() implementations are broken and will return
   * NULL for time_ts larger than 40 bits even on 64-bit platforms
   * so we'll just cap it at 40 bits */
  if(bits > 40) bits = 40;
  
  for ( ; ; ) {
    mytm = gmtime(&t);
    
    if(!mytm) return WRONG;
    
    dir = tmcomp(mytm, &yourtm);
    if (dir != 0) {
      if (bits-- < 0)
	return WRONG;
      if (bits < 0)
	--t;
      else if (dir > 0)
	t -= (time_t) 1 << bits;
      else
	t += (time_t) 1 << bits;
      continue;
    }
    break;
  }
  t += saved_seconds;
  return t;
}
