u-boot/lib/rand.c

// SPDX-License-Identifier: GPL-2.0+
/*
 * Simple xorshift PRNG
 *   see http://www.jstatsoft.org/v08/i14/paper
 *
 * Copyright (c) 2012 Michael Walle
 * Michael Walle <michael@walle.cc>
 */

#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;
}
SPDX: Convert all of our single license tags to Linux Kernel style When U-Boot started using SPDX tags we were among the early adopters and there weren't a lot of other examples to borrow from. So we picked the area of the file that usually had a full license text and replaced it with an appropriate SPDX-License-Identifier: entry. Since then, the Linux Kernel has adopted SPDX tags and they place it as the very first line in a file (except where shebangs are used, then it's second line) and with slightly different comment styles than us. In part due to community overlap, in part due to better tag visibility and in part for other minor reasons, switch over to that style. This commit changes all instances where we have a single declared license in the tag as both the before and after are identical in tag contents. There's also a few places where I found we did not have a tag and have introduced one. Signed-off-by: Tom Rini <trini@konsulko.com> 2018-05-06 17:58:06 -04:00			`// SPDX-License-Identifier: GPL-2.0+`
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> 2012-06-05 11:33:14 +00:00			`/*`
			`* Simple xorshift PRNG`
			`* see http://www.jstatsoft.org/v08/i14/paper`
			`*`
			`* Copyright (c) 2012 Michael Walle`
			`* Michael Walle <michael@walle.cc>`
			`*/`

			`#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;`
			`}`