1  /* Copyright (C) 1992-2023 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     <https://www.gnu.org/licenses/>.  */
      17  
      18  #include <string.h>
      19  #include <stdlib.h>
      20  #include <random-bits.h>
      21  #include <unistd.h>
      22  
      23  char *
      24  strfry (char *string)
      25  {
      26    static int init;
      27    static struct random_data rdata;
      28  
      29    if (!init)
      30      {
      31        static char state[32];
      32        rdata.state = NULL;
      33        __initstate_r (random_bits (),
      34  		     state, sizeof (state), &rdata);
      35        init = 1;
      36      }
      37  
      38    size_t len = strlen (string);
      39    if (len > 0)
      40      for (size_t i = 0; i < len - 1; ++i)
      41        {
      42  	int32_t j;
      43  	__random_r (&rdata, &j);
      44  	j = j % (len - i) + i;
      45  
      46  	char c = string[i];
      47  	string[i] = string[j];
      48  	string[j] = c;
      49        }
      50  
      51    return string;
      52  }