Warning: Attempt to read property "date" on null in /usr/local/www/websvn.planix.org/blame.php on line 247

Warning: Attempt to read property "msg" on null in /usr/local/www/websvn.planix.org/blame.php on line 247
WebSVN – planix.SVN – Blame – /os/branches/feature_posix/sys/src/ape/lib/ap/gen/rand.c – Rev 2

Subversion Repositories planix.SVN

Rev

Go to most recent revision | Details | Last modification | View Log | RSS feed

Rev Author Line No. Line
2 - 1 
#include	<stdlib.h>
2 
 
3 
/*
4 
 *	algorithm by
5 
 *	D. P. Mitchell & J. A. Reeds
6 
 */
7 
#define	LEN	607
8 
#define	TAP	273
9 
#define	MASK	0x7fffffffL
10 
#define	A	48271
11 
#define	M	2147483647
12 
#define	Q	44488
13 
#define	R	3399
14 
 
15 
typedef unsigned long	ulong;
16 
 
17 
static	ulong	rng_vec[LEN];
18 
static	ulong*	rng_tap = rng_vec;
19 
static	ulong*	rng_feed = 0;
20 
 
21 
void
22 
srand(unsigned int seed)
23 
{
24 
	long lo, hi, x;
25 
	int i;
26 
 
27 
	rng_tap = rng_vec;
28 
	rng_feed = rng_vec+LEN-TAP;
29 
	seed = seed%M;
30 
	if(0 && seed < 0)			/* seed is unsigned */
31 
		seed += M;
32 
	if(seed == 0)
33 
		seed = 89482311;
34 
	x = seed;
35 
	/*
36 
	 *	Initialize by x[n+1] = 48271 * x[n] mod (2**31 - 1)
37 
	 */
38 
	for(i = -20; i < LEN; i++) {
39 
		hi = x / Q;
40 
		lo = x % Q;
41 
		x = A*lo - R*hi;
42 
		if(x < 0)
43 
			x += M;
44 
		if(i >= 0)
45 
			rng_vec[i] = x;
46 
	}
47 
}
48 
 
49 
static long
50 
lrand(void)
51 
{
52 
	ulong x;
53 
 
54 
	rng_tap--;
55 
        if(rng_tap < rng_vec) {
56 
                if(rng_feed == 0) {
57 
			srand(1);
58 
			rng_tap--;
59 
		}
60 
                rng_tap += LEN;
61 
        }
62 
	rng_feed--;
63 
        if(rng_feed < rng_vec)
64 
                rng_feed += LEN;
65 
	x = (*rng_feed + *rng_tap) & MASK;
66 
	*rng_feed = x;
67 
        return x;
68 
}
69 
 
70 
int
71 
rand(void)
72 
{
73 
 
74 
	return lrand() & 0x7fff;
75 
}