1/* Copyright (C) 1991, 1992, 1996, 1998, 2004 Free Software Foundation, Inc.
2   This file is derived from mkstemp.c from the GNU C Library.
3
4   The GNU C Library is free software; you can redistribute it and/or
5   modify it under the terms of the GNU Library General Public License as
6   published by the Free Software Foundation; either version 2 of the
7   License, or (at your option) any later version.
8
9   The GNU C Library is distributed in the hope that it will be useful,
10   but WITHOUT ANY WARRANTY; without even the implied warranty of
11   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
12   Library General Public License for more details.
13
14   You should have received a copy of the GNU Library General Public
15   License along with the GNU C Library; see the file COPYING.LIB.  If not,
16   write to the Free Software Foundation, Inc., 51 Franklin Street - Fifth Floor,
17   Boston, MA 02110-1301, USA.  */
18
19#ifdef HAVE_CONFIG_H
20#include "config.h"
21#endif
22
23#include <sys/types.h>
24#ifdef HAVE_STDLIB_H
25#include <stdlib.h>
26#endif
27#ifdef HAVE_STRING_H
28#include <string.h>
29#endif
30#include <errno.h>
31#include <stdio.h>
32#include <fcntl.h>
33#ifdef HAVE_UNISTD_H
34#include <unistd.h>
35#endif
36#ifdef HAVE_SYS_TIME_H
37#include <sys/time.h>
38#endif
39#include "ansidecl.h"
40
41/* We need to provide a type for gcc_uint64_t.  */
42#ifdef __GNUC__
43__extension__ typedef unsigned long long gcc_uint64_t;
44#else
45typedef unsigned long gcc_uint64_t;
46#endif
47
48#ifndef TMP_MAX
49#define TMP_MAX 16384
50#endif
51
52/*
53
54@deftypefn Replacement int mkstemps (char *@var{pattern}, int @var{suffix_len})
55
56Generate a unique temporary file name from @var{pattern}.
57@var{pattern} has the form:
58
59@example
60   @var{path}/ccXXXXXX@var{suffix}
61@end example
62
63@var{suffix_len} tells us how long @var{suffix} is (it can be zero
64length).  The last six characters of @var{pattern} before @var{suffix}
65must be @samp{XXXXXX}; they are replaced with a string that makes the
66filename unique.  Returns a file descriptor open on the file for
67reading and writing.
68
69@end deftypefn
70
71*/
72
73int
74mkstemps (char *pattern, int suffix_len)
75{
76  static const char letters[]
77    = "abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789";
78  static gcc_uint64_t value;
79#ifdef HAVE_GETTIMEOFDAY
80  struct timeval tv;
81#endif
82  char *XXXXXX;
83  size_t len;
84  int count;
85
86  len = strlen (pattern);
87
88  if ((int) len < 6 + suffix_len
89      || strncmp (&pattern[len - 6 - suffix_len], "XXXXXX", 6))
90    {
91      return -1;
92    }
93
94  XXXXXX = &pattern[len - 6 - suffix_len];
95
96#ifdef HAVE_GETTIMEOFDAY
97  /* Get some more or less random data.  */
98  gettimeofday (&tv, NULL);
99  value += ((gcc_uint64_t) tv.tv_usec << 16) ^ tv.tv_sec ^ getpid ();
100#else
101  value += getpid ();
102#endif
103
104  for (count = 0; count < TMP_MAX; ++count)
105    {
106      gcc_uint64_t v = value;
107      int fd;
108
109      /* Fill in the random bits.  */
110      XXXXXX[0] = letters[v % 62];
111      v /= 62;
112      XXXXXX[1] = letters[v % 62];
113      v /= 62;
114      XXXXXX[2] = letters[v % 62];
115      v /= 62;
116      XXXXXX[3] = letters[v % 62];
117      v /= 62;
118      XXXXXX[4] = letters[v % 62];
119      v /= 62;
120      XXXXXX[5] = letters[v % 62];
121
122      fd = open (pattern, O_RDWR|O_CREAT|O_EXCL, 0600);
123      if (fd >= 0)
124	/* The file does not exist.  */
125	return fd;
126
127      /* This is a random value.  It is only necessary that the next
128	 TMP_MAX values generated by adding 7777 to VALUE are different
129	 with (module 2^32).  */
130      value += 7777;
131    }
132
133  /* We return the null string if we can't find a unique file name.  */
134  pattern[0] = '\0';
135  return -1;
136}
137