mkstemps.c

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/* Copyright (C) 1991, 1992, 1996, 1998 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 Lesser General Public
   License as published by the Free Software Foundation; either
   version 2.1 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
   Lesser General Public License for more details.
 
   You should have received a copy of the GNU Lesser General Public
   License along with the GNU C Library; if not, write to the Free
   Software Foundation, Inc., 51 Franklin Street, Fifth Floor,
   Boston, MA 02110-1301, USA.
*/
 
#include <sys/types.h>
#include <stdlib.h>
#include <string.h>
#include <errno.h>
#include <stdio.h>
#include <fcntl.h>
 
#ifdef _WIN32
    #include <io.h>
    #include <process.h>
#else
    #include <unistd.h>
    #include <sys/time.h>
#endif
 
/* 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
 
/* if O_BINARY is not defined, the system is probably not expecting any such flag */
#ifndef O_BINARY
#define O_BINARY 0
#endif
 
/*
 
@deftypefn Replacement int mkstemps (char *@var{template}, int @var{suffix_len})
 
Generate a unique temporary file name from @var{template}.
@var{template} 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{template} 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 *template,
     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 (template);
 
  if ((int) len < 6 + suffix_len
      || strncmp (&template[len - 6 - suffix_len], "XXXXXX", 6))
    {
      printf("wrong parameter\n");
      return -1;
    }
 
  XXXXXX = &template[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];
 
#ifdef VMS
      fd = open (template, O_RDWR|O_CREAT|O_EXCL, 0600, "fop=tmd");
#else
      fd = open (template, O_RDWR|O_CREAT|O_EXCL|O_BINARY, 0600);
#endif
      if (fd >= 0)
    /* The file does not exist.  */
    return fd;
 
      /* 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.  */
  template[0] = '\0';
  return -1;
}