1/* Copyright (C) 2001, 2003, 2004 Free Software Foundation, Inc.
2     Written by Werner Lemberg (wl@gnu.org)
3
4This file is part of groff.
5
6groff is free software; you can redistribute it and/or modify it under
7the terms of the GNU General Public License as published by the Free
8Software Foundation; either version 2, or (at your option) any later
9version.
10
11groff is distributed in the hope that it will be useful, but WITHOUT ANY
12WARRANTY; without even the implied warranty of MERCHANTABILITY or
13FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
14for more details.
15
16You should have received a copy of the GNU General Public License along
17with groff; see the file COPYING.  If not, write to the Free Software
18Foundation, 51 Franklin St - Fifth Floor, Boston, MA 02110-1301, USA. */
19
20
21/* This file is heavily based on the function __gen_tempname() in the
22   file tempname.c which is part of the fileutils package. */
23
24
25#include "lib.h"
26
27#include <stddef.h>
28#include <stdlib.h>
29#include <errno.h>
30#include <time.h>
31
32#include "posix.h"
33#include "nonposix.h"
34
35#ifndef TMP_MAX
36# define TMP_MAX 238328
37#endif
38
39#if HAVE_SYS_TIME_H
40# include <sys/time.h>
41#endif
42
43#ifdef HAVE_GETTIMEOFDAY
44#ifdef NEED_DECLARATION_GETTIMEOFDAY
45extern "C" {
46  int gettimeofday(struct timeval *, void *);
47}
48#endif
49#endif
50
51#if HAVE_CC_INTTYPES_H
52# include <inttypes.h>
53#endif
54
55/* Use the widest available unsigned type if uint64_t is not
56   available.  The algorithm below extracts a number less than 62**6
57   (approximately 2**35.725) from uint64_t, so ancient hosts where
58   uintmax_t is only 32 bits lose about 3.725 bits of randomness,
59   which is better than not having mkstemp at all.  */
60#if !defined UINT64_MAX && !defined uint64_t
61# define uint64_t uintmax_t
62#endif
63
64/* These are the characters used in temporary filenames.  */
65static const char letters[] =
66"abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789";
67
68int gen_tempname(char *tmpl, int dir)
69{
70  static uint64_t value;
71
72  size_t len = strlen(tmpl);
73  if (len < 6 || strcmp(&tmpl[len - 6], "XXXXXX"))
74    return -1; /* EINVAL */
75
76  /* This is where the Xs start.  */
77  char *XXXXXX = &tmpl[len - 6];
78
79  /* Get some more or less random data.  */
80#if HAVE_GETTIMEOFDAY
81  timeval tv;
82  gettimeofday(&tv, NULL);
83  uint64_t random_time_bits = ((uint64_t)tv.tv_usec << 16) ^ tv.tv_sec;
84#else
85  uint64_t random_time_bits = time(NULL);
86#endif
87  value += random_time_bits ^ getpid();
88
89  for (int count = 0; count < TMP_MAX; value += 7777, ++count) {
90    uint64_t v = value;
91
92    /* Fill in the random bits.  */
93    XXXXXX[0] = letters[v % 62];
94    v /= 62;
95    XXXXXX[1] = letters[v % 62];
96    v /= 62;
97    XXXXXX[2] = letters[v % 62];
98    v /= 62;
99    XXXXXX[3] = letters[v % 62];
100    v /= 62;
101    XXXXXX[4] = letters[v % 62];
102    v /= 62;
103    XXXXXX[5] = letters[v % 62];
104
105    int fd = dir ? mkdir(tmpl, S_IRUSR | S_IWUSR | S_IXUSR)
106		 : open(tmpl, O_RDWR | O_CREAT | O_EXCL, S_IRUSR | S_IWUSR);
107
108    if (fd >= 0)
109      return fd;
110    else if (errno != EEXIST)
111      return -1;
112  }
113
114  /* We got out of the loop because we ran out of combinations to try.  */
115  return -1; /* EEXIST */
116}
117