[U-Boot] [PATCH v4 1/3] lib: add rand() function

[Michael Walle]

It's a PRNG using the simple and fast xorshift method.

Signed-off-by: Michael Walle <michael at walle.cc>
---
 include/common.h |    4 ++++
 lib/Makefile     |    1 +
 lib/rand.c       |   43 +++++++++++++++++++++++++++++++++++++++++++
 3 files changed, 48 insertions(+), 0 deletions(-)
 create mode 100644 lib/rand.c

diff --git a/include/common.h b/include/common.h
index 4b5841e..fbea264 100644
--- a/include/common.h
+++ b/include/common.h
@@ -733,6 +733,10 @@ char *	strmhz(char *buf, unsigned long hz);
 /* lib/crc32.c */
 #include <u-boot/crc.h>
 
+/* lib/rand.c */
+void srand(unsigned int seed);
+unsigned int rand(void);
+
 /* common/console.c */
 int	console_init_f(void);	/* Before relocation; uses the serial  stuff	*/
 int	console_init_r(void);	/* After  relocation; uses the console stuff	*/
diff --git a/lib/Makefile b/lib/Makefile
index a0fec60..290bf6a 100644
--- a/lib/Makefile
+++ b/lib/Makefile
@@ -65,6 +65,7 @@ COBJS-y += string.o
 COBJS-y += time.o
 COBJS-$(CONFIG_BOOTP_PXE) += uuid.o
 COBJS-y += vsprintf.o
+COBJS-y += rand.o
 
 COBJS	:= $(COBJS-y)
 SRCS	:= $(COBJS:.o=.c)
diff --git a/lib/rand.c b/lib/rand.c
new file mode 100644
index 0000000..9923f67
--- /dev/null
+++ b/lib/rand.c
@@ -0,0 +1,43 @@
+/*
+ * Simple xorshift PRNG
+ *   see http://www.jstatsoft.org/v08/i14/paper
+ *
+ * Copyright (c) 2012 Michael Walle
+ * Michael Walle <michael at 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 = 2463534242U;
+
+void srand(unsigned int seed)
+{
+	y = seed;
+}
+
+unsigned int rand(void)
+{
+	y ^= (y << 13);
+	y ^= (y >> 17);
+	y ^= (y << 5);
+
+	return y;
+}
-- 
1.7.2.5