libc/stdio/tmpnam.c

   1 /* Copyright (C) 1991,1993,1996-1999,2000 Free Software Foundation, Inc.
   2    This file is part of 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 Lesser General Public
   6    License as published by the Free Software Foundation; either
   7    version 2.1 of the 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    Lesser General Public License for more details.
  13
  14    You should have received a copy of the GNU Lesser General Public
  15    License along with the GNU C Library; if not, see
  16    <http://www.gnu.org/licenses/>.  */
  17
  18 #include <stdio.h>
  19 #include <string.h>
  20 #include "../misc/internals/tempname.h"
  21
  22
  23 static char tmpnam_buffer[L_tmpnam];
  24
  25 /* Generate a unique filename in P_tmpdir.
  26
  27    This function is *not* thread safe!  */
  28 char *
  29 tmpnam (char *s)
  30 {
  31   /* By using two buffers we manage to be thread safe in the case
  32      where S != NULL.  */
  33   char tmpbufmem[L_tmpnam];
  34   char *tmpbuf = s ?: tmpbufmem;
  35
  36   /* In the following call we use the buffer pointed to by S if
  37      non-NULL although we don't know the size.  But we limit the size
  38      to L_tmpnam characters in any case.  */
  39   if (__builtin_expect (__path_search (tmpbuf, L_tmpnam, NULL, NULL, 0),
  40                         0))
  41     return NULL;
  42
  43   if (__builtin_expect (__gen_tempname (tmpbuf, __GT_NOCREATE, 0, 0, 0), 0))
  44     return NULL;
  45
  46   if (s == NULL)
  47     return (char *) memcpy (tmpnam_buffer, tmpbuf, L_tmpnam);
  48
  49   return s;
  50 }