libiberty/mkstemps.c

   1 /* Copyright (C) 1991-2021 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 #elif HAVE_TIME_H
  39 #include <time.h>
  40 #endif
  41 #include "ansidecl.h"
  42
  43 /* We need to provide a type for gcc_uint64_t.  */
  44 #ifdef __GNUC__
  45 __extension__ typedef unsigned long long gcc_uint64_t;
  46 #else
  47 typedef unsigned long gcc_uint64_t;
  48 #endif
  49
  50 #ifndef TMP_MAX
  51 #define TMP_MAX 16384
  52 #endif
  53
  54 #ifndef O_BINARY
  55 # define O_BINARY 0
  56 #endif
  57
  58 /*
  59
  60 @deftypefn Replacement int mkstemps (char *@var{pattern}, int @var{suffix_len})
  61
  62 Generate a unique temporary file name from @var{pattern}.
  63 @var{pattern} has the form:
  64
  65 @example
  66    @var{path}/ccXXXXXX@var{suffix}
  67 @end example
  68
  69 @var{suffix_len} tells us how long @var{suffix} is (it can be zero
  70 length).  The last six characters of @var{pattern} before @var{suffix}
  71 must be @samp{XXXXXX}; they are replaced with a string that makes the
  72 filename unique.  Returns a file descriptor open on the file for
  73 reading and writing.
  74
  75 @end deftypefn
  76
  77 */
  78
  79 int
  80 mkstemps (char *pattern, int suffix_len)
  81 {
  82   static const char letters[]
  83     = "abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789";
  84   static gcc_uint64_t value;
  85 #ifdef HAVE_GETTIMEOFDAY
  86   struct timeval tv;
  87 #endif
  88   char *XXXXXX;
  89   size_t len;
  90   int count;
  91
  92   len = strlen (pattern);
  93
  94   if ((int) len < 6 + suffix_len
  95       || strncmp (&pattern[len - 6 - suffix_len], "XXXXXX", 6))
  96     {
  97       return -1;
  98     }
  99
 100   XXXXXX = &pattern[len - 6 - suffix_len];
 101
 102 #ifdef HAVE_GETTIMEOFDAY
 103   /* Get some more or less random data.  */
 104   gettimeofday (&tv, NULL);
 105   value += ((gcc_uint64_t) tv.tv_usec << 16) ^ tv.tv_sec ^ getpid ();
 106 #else
 107   value += getpid ();
 108 #endif
 109
 110   for (count = 0; count < TMP_MAX; ++count)
 111     {
 112       gcc_uint64_t v = value;
 113       int fd;
 114
 115       /* Fill in the random bits.  */
 116       XXXXXX[0] = letters[v % 62];
 117       v /= 62;
 118       XXXXXX[1] = letters[v % 62];
 119       v /= 62;
 120       XXXXXX[2] = letters[v % 62];
 121       v /= 62;
 122       XXXXXX[3] = letters[v % 62];
 123       v /= 62;
 124       XXXXXX[4] = letters[v % 62];
 125       v /= 62;
 126       XXXXXX[5] = letters[v % 62];
 127
 128       fd = open (pattern, O_BINARY|O_RDWR|O_CREAT|O_EXCL, 0600);
 129       if (fd >= 0)
 130         /* The file does not exist.  */
 131         return fd;
 132       if (errno != EEXIST
 133 #ifdef EISDIR
 134           && errno != EISDIR
 135 #endif
 136          )
 137         /* Fatal error (EPERM, ENOSPC etc).  Doesn't make sense to loop.  */
 138         break;
 139
 140       /* This is a random value.  It is only necessary that the next
 141          TMP_MAX values generated by adding 7777 to VALUE are different
 142          with (module 2^32).  */
 143       value += 7777;
 144     }
 145
 146   /* We return the null string if we can't find a unique file name.  */
 147   pattern[0] = '\0';
 148   return -1;
 149 }