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authorMichael Walle <michael@walle.cc>2012-06-05 11:33:14 +0000
committerAlbert ARIBAUD <albert.u.boot@aribaud.net>2012-07-07 14:07:32 +0200
commit9acf1ca50d8b031511d146f6ffd73201fedce28c (patch)
treea10e3bb54c3a410ea568ce0d69ff9ef42a601145 /lib/rand.c
parentd131ad68c6566749df10154d2a6fa93df5865495 (diff)
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lib: add rand() function
It's a PRNG using the simple and fast xorshift method. Signed-off-by: Michael Walle <michael@walle.cc> Cc: Wolfgang Denk <wd@denx.de>
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+/*
+ * Simple xorshift PRNG
+ * see http://www.jstatsoft.org/v08/i14/paper
+ *
+ * Copyright (c) 2012 Michael Walle
+ * Michael Walle <michael@walle.cc>
+ *
+ * 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 <common.h>
+
+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;
+}
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