libiberty/mkstemps.c

   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
  45 typedef unsigned long gcc_uint64_t;
  46 #endif
  47
  48 #ifndef TMP_MAX
  49 #define TMP_MAX 16384
  50 #endif
  51
  52 #ifndef O_BINARY
  53 # define O_BINARY 0
  54 #endif
  55
  56 /*
  57
  58 @deftypefn Replacement int mkstemps (char *@var{pattern}, int @var{suffix_len})
  59
  60 Generate a unique temporary file name from @var{pattern}.
  61 @var{pattern} has the form:
  62
  63 @example
  64    @var{path}/ccXXXXXX@var{suffix}
  65 @end example
  66
  67 @var{suffix_len} tells us how long @var{suffix} is (it can be zero
  68 length).  The last six characters of @var{pattern} before @var{suffix}
  69 must be @samp{XXXXXX}; they are replaced with a string that makes the
  70 filename unique.  Returns a file descriptor open on the file for
  71 reading and writing.
  72
  73 @end deftypefn
  74
  75 */
  76
  77 int
  78 mkstemps (char *pattern, int suffix_len)
  79 {
  80   static const char letters[]
  81     = "abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789";
  82   static gcc_uint64_t value;
  83 #ifdef HAVE_GETTIMEOFDAY
  84   struct timeval tv;
  85 #endif
  86   char *XXXXXX;
  87   size_t len;
  88   int count;
  89
  90   len = strlen (pattern);
  91
  92   if ((int) len < 6 + suffix_len
  93       || strncmp (&pattern[len - 6 - suffix_len], "XXXXXX", 6))
  94     {
  95       return -1;
  96     }
  97
  98   XXXXXX = &pattern[len - 6 - suffix_len];
  99
 100 #ifdef HAVE_GETTIMEOFDAY
 101   /* Get some more or less random data.  */
 102   gettimeofday (&tv, NULL);
 103   value += ((gcc_uint64_t) tv.tv_usec << 16) ^ tv.tv_sec ^ getpid ();
 104 #else
 105   value += getpid ();
 106 #endif
 107
 108   for (count = 0; count < TMP_MAX; ++count)
 109     {
 110       gcc_uint64_t v = value;
 111       int fd;
 112
 113       /* Fill in the random bits.  */
 114       XXXXXX[0] = letters[v % 62];
 115       v /= 62;
 116       XXXXXX[1] = letters[v % 62];
 117       v /= 62;
 118       XXXXXX[2] = letters[v % 62];
 119       v /= 62;
 120       XXXXXX[3] = letters[v % 62];
 121       v /= 62;
 122       XXXXXX[4] = letters[v % 62];
 123       v /= 62;
 124       XXXXXX[5] = letters[v % 62];
 125
 126       fd = open (pattern, O_BINARY|O_RDWR|O_CREAT|O_EXCL, 0600);
 127       if (fd >= 0)
 128         /* The file does not exist.  */
 129         return fd;
 130
 131       /* This is a random value.  It is only necessary that the next
 132          TMP_MAX values generated by adding 7777 to VALUE are different
 133          with (module 2^32).  */
 134       value += 7777;
 135     }
 136
 137   /* We return the null string if we can't find a unique file name.  */
 138   pattern[0] = '\0';
 139   return -1;
 140 }