aboutsummaryrefslogtreecommitdiff
path: root/src/stable/randomcmwc.cpp
blob: a4e807e8ecc20525e6e7187b711c665ee2120f0c (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
/*
 * Copyright (C) 2007-2012 Xagasoft, All rights reserved.
 *
 * This file is part of the libbu++ library and is released under the
 * terms of the license contained in the file LICENSE.
 */

#include "bu/randomcmwc.h"

#define PHI 0x9e3779b9

Bu::RandomCmwc::RandomCmwc() :
	q( 0 ),
	c( 362436 )
{
	q = new uint32_t[4096];
}

Bu::RandomCmwc::~RandomCmwc()
{
	delete[] q;
}

void Bu::RandomCmwc::seed( int32_t iSeed )
{
	int i;

	q[0] = iSeed;
	q[1] = iSeed + PHI;
	q[2] = iSeed + PHI + PHI;

	for (i = 3; i < 4096; i++)
		q[i] = q[i - 3] ^ q[i - 2] ^ PHI ^ i;	
}

int32_t Bu::RandomCmwc::rand()
{
	uint64_t t, a = 18782LL;
	static uint32_t i = 4095;
	uint32_t x, r = 0xfffffffe;
	i = (i + 1) & 4095;
	t = a * q[i] + c;
	c = (t >> 32);
	x = t + c;
	if( x < c )
	{
		x++;
		c++;
	}
	return (q[i] = r - x);
}