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 /*
  53
  54 @deftypefn Replacement int mkstemps (char *@var{template}, int @var{suffix_len})
  55
  56 Generate a unique temporary file name from @var{template}.
  57 @var{template} 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
  64 length).  The last six characters of @var{template} before @var{suffix}
  65 must be @samp{XXXXXX}; they are replaced with a string that makes the
  66 filename unique.  Returns a file descriptor open on the file for
  67 reading and writing.
  68
  69 @end deftypefn
  70
  71 */
  72
  73 int
  74 mkstemps (char *template, 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 (template);
  87
  88   if ((int) len < 6 + suffix_len
  89       || strncmp (&template[len - 6 - suffix_len], "XXXXXX", 6))
  90     {
  91       return -1;
  92     }
  93
  94   XXXXXX = &template[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 (template, 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   template[0] = '\0';
 135   return -1;
 136 }