/* Id: compat_mkstemps.c,v 1.1 2021/09/19 15:05:39 schwarze Exp  */
/*
* Copyright (c) 2015, 2021 Ingo Schwarze <[email protected]>
*
* Permission to use, copy, modify, and distribute this software for any
* purpose with or without fee is hereby granted, provided that the above
* copyright notice and this permission notice appear in all copies.
*
* THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
* WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
* MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
* ANY SPECIAL, DIRECT, 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 OUT OF
* OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
*
* Parts of the algorithm of this function are inspired by OpenBSD
* mkdtemp(3) by Theo de Raadt and Todd Miller, but the code differs.
*/
#include "config.h"

#include <sys/stat.h>
#include <errno.h>
#include <fcntl.h>
#include <limits.h>
#include <stdlib.h>
#include <string.h>

int
mkstemps(char *path, int suffixlen)
{
       char    *start, *end, *cp;
       int      fd, tries;
       char     backup;

       end = strchr(path, '\0');
       if (suffixlen < 0 || suffixlen > end - path - 6) {
               errno = EINVAL;
               return -1;
       }
       end -= suffixlen;
       for (start = end; start > path; start--)
               if (start[-1] != 'X')
                       break;

       backup = *end;
       for (tries = INT_MAX; tries; tries--) {
               *end = '\0';
               cp = mktemp(path);
               *end = backup;
               if (cp == NULL)
                       return -1;
               fd = open(path, O_CREAT | O_EXCL | O_RDWR, S_IRUSR | S_IWUSR);
               if (fd != -1)
                       return fd;
               for (cp = start; cp < end; cp++)
                       *cp = 'X';
               if (errno != EEXIST)
                       return -1;
       }
       errno = EEXIST;
       return -1;
}