harvey/sys/src/ape/lib/v/rand.c

/*
 * This file is part of the UCB release of Plan 9. It is subject to the license
 * terms in the LICENSE file found in the top-level directory of this
 * distribution and at http://akaros.cs.berkeley.edu/files/Plan9License. No
 * part of the UCB release of Plan 9, including this file, may be copied,
 * modified, propagated, or distributed except according to the terms contained
 * in the LICENSE file.
 */

#define _RESEARCH_SOURCE
#include <stdlib.h>
#include <libv.h>
/*
	random number generator from cacm 31 10, oct 88
	for 32 bit integers (called long here)
*/

#ifdef	MAIN
#define	A	16807
#define	M	2147483647
#define	Q	127773
#define	R	2836
#else
#define	A	48271
#define	M	2147483647
#define	Q	44488
#define	R	3399
#endif

static int32_t seed = 1;

void
srand(unsigned int newseed)
{
	seed = newseed;
}

int32_t
lrand(void)
{
	int32_t lo, hi, test;

	hi = seed/Q;
	lo = seed%Q;
	test = A*lo - R*hi;
	if(test > 0)
		seed = test;
	else
		seed = test+M;
	return(seed);
}

int
rand(void)
{
	return lrand()%(RAND_MAX+1);
}

#ifdef	MAIN

main()
{
	int i;

	for(i = 0; i < 10000; i++)
		rand();
	if(seed == 1043618065)
		printf("     rand: pass\n");
	else
		printf("*****rand: fail; seed=%u, should be 1043618065\n", seed);
	exit(0);
}
#endif