string/strfry.c

   1 /* Copyright (C) 1992, 1996, 1999 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 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 #include <string.h>
  20 #include <stdlib.h>
  21 #include <time.h>
  22
  23 char *
  24 strfry (char *string)
  25 {
  26   static int init;
  27   static struct random_data rdata;
  28   size_t len, i;
  29
  30   if (!init)
  31     {
  32       static char state[32];
  33       rdata.state = NULL;
  34       __initstate_r (time ((time_t *) NULL), state, sizeof (state), &rdata);
  35       init = 1;
  36     }
  37
  38   len = strlen (string);
  39   for (i = 0; i < len; ++i)
  40     {
  41       int32_t j;
  42       char c;
  43
  44       __random_r (&rdata, &j);
  45       j %= len;
  46
  47       c = string[i];
  48       string[i] = string[j];
  49       string[j] = c;
  50     }
  51
  52   return string;
  53 }