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 #ifdef HAVE_STDLIB_H
  24 #include <stdlib.h>
  25 #endif
  26 #ifdef HAVE_STRING_H
  27 #include <string.h>
  28 #endif
  29 #include <errno.h>
  30 #include <stdio.h>
  31 #include <fcntl.h>
  32 #ifdef HAVE_UNISTD_H
  33 #include <unistd.h>
  34 #endif
  35 #ifdef HAVE_SYS_TIME_H
  36 #include <sys/time.h>
  37 #endif
  38 #include "ansidecl.h"
  39
  40 /* We need to provide a type for gcc_uint64_t.  */
  41 #ifdef __GNUC__
  42 __extension__ typedef unsigned long long gcc_uint64_t;
  43 #else
  44 typedef unsigned long gcc_uint64_t;
  45 #endif
  46
  47 #ifndef TMP_MAX
  48 #define TMP_MAX 16384
  49 #endif
  50
  51 /* Generate a unique temporary file name from TEMPLATE.
  52
  53    TEMPLATE has the form:
  54
  55    <path>/ccXXXXXX<suffix>
  56
  57    SUFFIX_LEN tells us how long <suffix> is (it can be zero length).
  58
  59    The last six characters of TEMPLATE before <suffix> must be "XXXXXX";
  60    they are replaced with a string that makes the filename unique.
  61
  62    Returns a file descriptor open on the file for reading and writing.  */
  63 int
  64 mkstemps (template, suffix_len)
  65      char *template;
  66      int suffix_len;
  67 {
  68   static const char letters[]
  69     = "abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789";
  70   static gcc_uint64_t value;
  71 #ifdef HAVE_GETTIMEOFDAY
  72   struct timeval tv;
  73 #endif
  74   char *XXXXXX;
  75   size_t len;
  76   int count;
  77
  78   len = strlen (template);
  79
  80   if ((int) len < 6 + suffix_len
  81       || strncmp (&template[len - 6 - suffix_len], "XXXXXX", 6))
  82     {
  83       return -1;
  84     }
  85
  86   XXXXXX = &template[len - 6 - suffix_len];
  87
  88 #ifdef HAVE_GETTIMEOFDAY
  89   /* Get some more or less random data.  */
  90   gettimeofday (&tv, NULL);
  91   value += ((gcc_uint64_t) tv.tv_usec << 16) ^ tv.tv_sec ^ getpid ();
  92 #else
  93   value += getpid ();
  94 #endif
  95
  96   for (count = 0; count < TMP_MAX; ++count)
  97     {
  98       gcc_uint64_t v = value;
  99       int fd;
 100
 101       /* Fill in the random bits.  */
 102       XXXXXX[0] = letters[v % 62];
 103       v /= 62;
 104       XXXXXX[1] = letters[v % 62];
 105       v /= 62;
 106       XXXXXX[2] = letters[v % 62];
 107       v /= 62;
 108       XXXXXX[3] = letters[v % 62];
 109       v /= 62;
 110       XXXXXX[4] = letters[v % 62];
 111       v /= 62;
 112       XXXXXX[5] = letters[v % 62];
 113
 114       fd = open (template, O_RDWR|O_CREAT|O_EXCL, 0600);
 115       if (fd >= 0)
 116         /* The file does not exist.  */
 117         return fd;
 118
 119       /* This is a random value.  It is only necessary that the next
 120          TMP_MAX values generated by adding 7777 to VALUE are different
 121          with (module 2^32).  */
 122       value += 7777;
 123     }
 124
 125   /* We return the null string if we can't find a unique file name.  */
 126   template[0] = '\0';
 127   return -1;
 128 }