libiberty/mkstemps.c

   1 /* Copyright (C) 1991, 1992, 1996, 1998 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., 59 Temple Place - Suite 330,
  17    Boston, MA 02111-1307, 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
  45 typedef unsigned long gcc_uint64_t;
  46 #endif
  47
  48 #ifndef TMP_MAX
  49 #define TMP_MAX 16384
  50 #endif
  51
  52 /* Generate a unique temporary file name from TEMPLATE.
  53
  54    TEMPLATE has the form:
  55
  56    <path>/ccXXXXXX<suffix>
  57
  58    SUFFIX_LEN tells us how long <suffix> is (it can be zero length).
  59
  60    The last six characters of TEMPLATE before <suffix> must be "XXXXXX";
  61    they are replaced with a string that makes the filename unique.
  62
  63    Returns a file descriptor open on the file for reading and writing.  */
  64 int
  65 mkstemps (template, suffix_len)
  66      char *template;
  67      int suffix_len;
  68 {
  69   static const char letters[]
  70     = "abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789";
  71   static gcc_uint64_t value;
  72 #ifdef HAVE_GETTIMEOFDAY
  73   struct timeval tv;
  74 #endif
  75   char *XXXXXX;
  76   size_t len;
  77   int count;
  78
  79   len = strlen (template);
  80
  81   if ((int) len < 6 + suffix_len
  82       || strncmp (&template[len - 6 - suffix_len], "XXXXXX", 6))
  83     {
  84       return -1;
  85     }
  86
  87   XXXXXX = &template[len - 6 - suffix_len];
  88
  89 #ifdef HAVE_GETTIMEOFDAY
  90   /* Get some more or less random data.  */
  91   gettimeofday (&tv, NULL);
  92   value += ((gcc_uint64_t) tv.tv_usec << 16) ^ tv.tv_sec ^ getpid ();
  93 #else
  94   value += getpid ();
  95 #endif
  96
  97   for (count = 0; count < TMP_MAX; ++count)
  98     {
  99       gcc_uint64_t v = value;
 100       int fd;
 101
 102       /* Fill in the random bits.  */
 103       XXXXXX[0] = letters[v % 62];
 104       v /= 62;
 105       XXXXXX[1] = letters[v % 62];
 106       v /= 62;
 107       XXXXXX[2] = letters[v % 62];
 108       v /= 62;
 109       XXXXXX[3] = letters[v % 62];
 110       v /= 62;
 111       XXXXXX[4] = letters[v % 62];
 112       v /= 62;
 113       XXXXXX[5] = letters[v % 62];
 114
 115       fd = open (template, O_RDWR|O_CREAT|O_EXCL, 0600);
 116       if (fd >= 0)
 117         /* The file does not exist.  */
 118         return fd;
 119
 120       /* This is a random value.  It is only necessary that the next
 121          TMP_MAX values generated by adding 7777 to VALUE are different
 122          with (module 2^32).  */
 123       value += 7777;
 124     }
 125
 126   /* We return the null string if we can't find a unique file name.  */
 127   template[0] = '\0';
 128   return -1;
 129 }