lib/rand.c

   1 /*
   2  * Simple xorshift PRNG
   3  *   see http://www.jstatsoft.org/v08/i14/paper
   4  *
   5  * Copyright (c) 2012 Michael Walle
   6  * Michael Walle <michael@walle.cc>
   7  *
   8  * See file CREDITS for list of people who contributed to this
   9  * project.
  10  *
  11  * This program is free software; you can redistribute it and/or
  12  * modify it under the terms of the GNU General Public License as
  13  * published by the Free Software Foundation; either version 2 of
  14  * the License, or (at your option) any later version.
  15  *
  16  * This program is distributed in the hope that it will be useful,
  17  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  18  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  19  * GNU General Public License for more details.
  20  *
  21  * You should have received a copy of the GNU General Public License
  22  * along with this program; if not, write to the Free Software
  23  * Foundation, Inc., 59 Temple Place, Suite 330, Boston,
  24  * MA 02111-1307 USA
  25  */
  26
  27 #include <common.h>
  28
  29 static unsigned int y = 1U;
  30
  31 unsigned int rand_r(unsigned int *seedp)
  32 {
  33         *seedp ^= (*seedp << 13);
  34         *seedp ^= (*seedp >> 17);
  35         *seedp ^= (*seedp << 5);
  36
  37         return *seedp;
  38 }
  39
  40 unsigned int rand(void)
  41 {
  42         return rand_r(&y);
  43 }
  44
  45 void srand(unsigned int seed)
  46 {
  47         y = seed;
  48 }