Back to index

glibc  2.9
strfry.c
Go to the documentation of this file.
00001 /* Copyright (C) 1992, 1996, 1999, 2002, 2007 Free Software Foundation, Inc.
00002    This file is part of the GNU C Library.
00003 
00004    The GNU C Library is free software; you can redistribute it and/or
00005    modify it under the terms of the GNU Lesser General Public
00006    License as published by the Free Software Foundation; either
00007    version 2.1 of the License, or (at your option) any later version.
00008 
00009    The GNU C Library is distributed in the hope that it will be useful,
00010    but WITHOUT ANY WARRANTY; without even the implied warranty of
00011    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
00012    Lesser General Public License for more details.
00013 
00014    You should have received a copy of the GNU Lesser General Public
00015    License along with the GNU C Library; if not, write to the Free
00016    Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
00017    02111-1307 USA.  */
00018 
00019 #include <string.h>
00020 #include <stdlib.h>
00021 #include <time.h>
00022 #include <unistd.h>
00023 
00024 char *
00025 strfry (char *string)
00026 {
00027   static int init;
00028   static struct random_data rdata;
00029 
00030   if (!init)
00031     {
00032       static char state[32];
00033       rdata.state = NULL;
00034       __initstate_r (time ((time_t *) NULL) ^ getpid (),
00035                    state, sizeof (state), &rdata);
00036       init = 1;
00037     }
00038 
00039   size_t len = strlen (string);
00040   if (len > 0)
00041     for (size_t i = 0; i < len - 1; ++i)
00042       {
00043        int32_t j;
00044        __random_r (&rdata, &j);
00045        j = j % (len - i) + i;
00046 
00047        char c = string[i];
00048        string[i] = string[j];
00049        string[j] = c;
00050       }
00051 
00052   return string;
00053 }