/*  * 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. */ /* * libc pseudo-random number generators, but without locks. */#include	"u.h"#include	"../port/lib.h"#include	"mem.h"#include	"dat.h"#include	"fns.h"#include	"io.h"#include	"ureg.h"#include	"pool.h" /* stubs to emulate random.c */ulongrandomread(void *, ulong){	return 0;} voidrandominit(void){} /* *	algorithm by *	D. P. Mitchell & J. A. Reeds */ #define	LEN	607#define	TAP	273#define	MASK	0x7fffffffL#define	A	48271#define	M	2147483647#define	Q	44488#define	R	3399#define	NORM	(1.0/(1.0+MASK)) static	ulong	rng_vec[LEN];static	ulong*	rng_tap = rng_vec;static	ulong*	rng_feed = 0; static voidisrand(long seed){	long lo, hi, x;	int i; 	rng_tap = rng_vec;	rng_feed = rng_vec+LEN-TAP;	seed = seed%M;	if(seed < 0)		seed += M;	if(seed == 0)		seed = 89482311;	x = seed;	/*	 *	Initialize by x[n+1] = 48271 * x[n] mod (2**31 - 1)	 */	for(i = -20; i < LEN; i++) {		hi = x / Q;		lo = x % Q;		x = A*lo - R*hi;		if(x < 0)			x += M;		if(i >= 0)			rng_vec[i] = x;	}} voidsrand(long seed){	isrand(seed);} longlrand(void){	ulong x; 	rng_tap--;	if(rng_tap < rng_vec) {		if(rng_feed == 0) {			isrand(1);			rng_tap--;		}		rng_tap += LEN;	}	rng_feed--;	if(rng_feed < rng_vec)		rng_feed += LEN;	x = (*rng_feed + *rng_tap) & MASK;	*rng_feed = x;	return x;}