libiberty/mkstemp.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 #ifndef IN_GCC
  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 #else
  41 #include "system.h"
  42 #endif
  43
  44 /* We need to provide a type for gcc_uint64_t.  */
  45 #ifdef __GNUC__
  46 typedef unsigned long long gcc_uint64_t;
  47 #else
  48 typedef unsigned long gcc_uint64_t;
  49 #endif
  50
  51 #ifndef TMP_MAX
  52 #define TMP_MAX 16384
  53 #endif
  54
  55 /* Generate a unique temporary file name from TEMPLATE.
  56
  57    TEMPLATE has the form:
  58
  59    <path>/ccXXXXXX<suffix>
  60
  61    SUFFIX_LEN tells us how long <suffix> is (it can be zero length).
  62
  63    The last six characters of TEMPLATE before <suffix> must be "XXXXXX";
  64    they are replaced with a string that makes the filename unique.
  65
  66    Returns a file descriptor open on the file for reading and writing.  */
  67 int
  68 mkstemps (template, suffix_len)
  69      char *template;
  70      int suffix_len;
  71 {
  72   static const char letters[]
  73     = "abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789";
  74   static gcc_uint64_t value;
  75 #ifdef HAVE_GETTIMEOFDAY
  76   struct timeval tv;
  77 #endif
  78   char *XXXXXX;
  79   size_t len;
  80   int count;
  81
  82   len = strlen (template);
  83
  84   if ((int) len < 6 + suffix_len
  85       || strncmp (&template[len - 6 - suffix_len], "XXXXXX", 6))
  86     {
  87       return -1;
  88     }
  89
  90   XXXXXX = &template[len - 6 - suffix_len];
  91
  92 #ifdef HAVE_GETTIMEOFDAY
  93   /* Get some more or less random data.  */
  94   gettimeofday (&tv, NULL);
  95   value += ((gcc_uint64_t) tv.tv_usec << 16) ^ tv.tv_sec ^ getpid ();
  96 #else
  97   value += getpid ();
  98 #endif
  99
 100   for (count = 0; count < TMP_MAX; ++count)
 101     {
 102       gcc_uint64_t v = value;
 103       int fd;
 104
 105       /* Fill in the random bits.  */
 106       XXXXXX[0] = letters[v % 62];
 107       v /= 62;
 108       XXXXXX[1] = letters[v % 62];
 109       v /= 62;
 110       XXXXXX[2] = letters[v % 62];
 111       v /= 62;
 112       XXXXXX[3] = letters[v % 62];
 113       v /= 62;
 114       XXXXXX[4] = letters[v % 62];
 115       v /= 62;
 116       XXXXXX[5] = letters[v % 62];
 117
 118       fd = open (template, O_RDWR|O_CREAT|O_EXCL, 0600);
 119       if (fd >= 0)
 120         /* The file does not exist.  */
 121         return fd;
 122
 123       /* This is a random value.  It is only necessary that the next
 124          TMP_MAX values generated by adding 7777 to VALUE are different
 125          with (module 2^32).  */
 126       value += 7777;
 127     }
 128
 129   /* We return the null string if we can't find a unique file name.  */
 130   template[0] = '\0';
 131   return -1;
 132 }