From 9acf1ca50d8b031511d146f6ffd73201fedce28c Mon Sep 17 00:00:00 2001 From: Michael Walle Date: Tue, 5 Jun 2012 11:33:14 +0000 Subject: lib: add rand() function It's a PRNG using the simple and fast xorshift method. Signed-off-by: Michael Walle Cc: Wolfgang Denk --- lib/rand.c | 48 ++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 48 insertions(+) create mode 100644 lib/rand.c (limited to 'lib/rand.c') diff --git a/lib/rand.c b/lib/rand.c new file mode 100644 index 0000000000..c9764f5c1a --- /dev/null +++ b/lib/rand.c @@ -0,0 +1,48 @@ +/* + * Simple xorshift PRNG + * see http://www.jstatsoft.org/v08/i14/paper + * + * Copyright (c) 2012 Michael Walle + * Michael Walle + * + * See file CREDITS for list of people who contributed to this + * project. + * + * This program is free software; you can redistribute it and/or + * modify it under the terms of the GNU General Public License as + * published by the Free Software Foundation; either version 2 of + * the License, or (at your option) any later version. + * + * This program is distributed in the hope that it will be useful, + * but WITHOUT ANY WARRANTY; without even the implied warranty of + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the + * GNU General Public License for more details. + * + * You should have received a copy of the GNU General Public License + * along with this program; if not, write to the Free Software + * Foundation, Inc., 59 Temple Place, Suite 330, Boston, + * MA 02111-1307 USA + */ + +#include + +static unsigned int y = 1U; + +unsigned int rand_r(unsigned int *seedp) +{ + *seedp ^= (*seedp << 13); + *seedp ^= (*seedp >> 17); + *seedp ^= (*seedp << 5); + + return *seedp; +} + +unsigned int rand(void) +{ + return rand_r(&y); +} + +void srand(unsigned int seed) +{ + y = seed; +} -- cgit v1.2.3