/* Copyright (C) 1991-2024 Free Software Foundation, Inc.
  This file is derived from mkstemp.c from the GNU C Library.

  The GNU C Library is free software; you can redistribute it and/or
  modify it under the terms of the GNU Library General Public License as
  published by the Free Software Foundation; either version 2 of the
  License, or (at your option) any later version.

  The GNU C Library is distributed in the hope that it will be useful,
  but WITHOUT ANY WARRANTY; without even the implied warranty of
  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  Library General Public License for more details.

  You should have received a copy of the GNU Library General Public
  License along with the GNU C Library; see the file COPYING.LIB.  If not,
  write to the Free Software Foundation, Inc., 51 Franklin Street - Fifth Floor,
  Boston, MA 02110-1301, USA.  */

#ifdef HAVE_CONFIG_H
#include "config.h"
#endif

#include <sys/types.h>
#ifdef HAVE_STDLIB_H
#include <stdlib.h>
#endif
#ifdef HAVE_STRING_H
#include <string.h>
#endif
#include <errno.h>
#include <stdio.h>
#include <fcntl.h>
#ifdef HAVE_UNISTD_H
#include <unistd.h>
#endif
#ifdef HAVE_SYS_TIME_H
#include <sys/time.h>
#elif HAVE_TIME_H
#include <time.h>
#endif
#include "ansidecl.h"

/* We need to provide a type for gcc_uint64_t.  */
#ifdef __GNUC__
__extension__ typedef unsigned long long gcc_uint64_t;
#else
typedef unsigned long gcc_uint64_t;
#endif

#ifndef TMP_MAX
#define TMP_MAX 16384
#endif

#ifndef O_BINARY
# define O_BINARY 0
#endif

/*

@deftypefn Replacement int mkstemps (char *@var{pattern}, int @var{suffix_len})

Generate a unique temporary file name from @var{pattern}.
@var{pattern} has the form:

@example
  @var{path}/ccXXXXXX@var{suffix}
@end example

@var{suffix_len} tells us how long @var{suffix} is (it can be zero
length).  The last six characters of @var{pattern} before @var{suffix}
must be @samp{XXXXXX}; they are replaced with a string that makes the
filename unique.  Returns a file descriptor open on the file for
reading and writing.

@end deftypefn

*/

int
mkstemps (char *pattern, int suffix_len)
{
 static const char letters[]
   = "abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789";
 static gcc_uint64_t value;
#ifdef HAVE_GETTIMEOFDAY
 struct timeval tv;
#endif
 char *XXXXXX;
 size_t len;
 int count;

 len = strlen (pattern);

 if ((int) len < 6 + suffix_len
     || strncmp (&pattern[len - 6 - suffix_len], "XXXXXX", 6))
   {
     return -1;
   }

 XXXXXX = &pattern[len - 6 - suffix_len];

#ifdef HAVE_GETTIMEOFDAY
 /* Get some more or less random data.  */
 gettimeofday (&tv, NULL);
 value += ((gcc_uint64_t) tv.tv_usec << 16) ^ tv.tv_sec ^ getpid ();
#else
 value += getpid ();
#endif

 for (count = 0; count < TMP_MAX; ++count)
   {
     gcc_uint64_t v = value;
     int fd;

     /* Fill in the random bits.  */
     XXXXXX[0] = letters[v % 62];
     v /= 62;
     XXXXXX[1] = letters[v % 62];
     v /= 62;
     XXXXXX[2] = letters[v % 62];
     v /= 62;
     XXXXXX[3] = letters[v % 62];
     v /= 62;
     XXXXXX[4] = letters[v % 62];
     v /= 62;
     XXXXXX[5] = letters[v % 62];

     fd = open (pattern, O_BINARY|O_RDWR|O_CREAT|O_EXCL, 0600);
     if (fd >= 0)
       /* The file does not exist.  */
       return fd;
     if (errno != EEXIST
#ifdef EISDIR
         && errno != EISDIR
#endif
        )
       /* Fatal error (EPERM, ENOSPC etc).  Doesn't make sense to loop.  */
       break;

     /* This is a random value.  It is only necessary that the next
        TMP_MAX values generated by adding 7777 to VALUE are different
        with (module 2^32).  */
     value += 7777;
   }

 /* We return the null string if we can't find a unique file name.  */
 pattern[0] = '\0';
 return -1;
}