1/*	$NetBSD: _rand48.c,v 1.7 2005/06/12 05:21:27 lukem Exp $	*/
2
3/*
4 * Copyright (c) 1993 Martin Birgmeier
5 * All rights reserved.
6 *
7 * You may redistribute unmodified or modified versions of this source
8 * code provided that the above copyright notice and this and the
9 * following conditions are retained.
10 *
11 * This software is provided ``as is'', and comes with no warranties
12 * of any kind. I shall in no event be liable for anything that happens
13 * to anyone/anything when using this software.
14 */
15
16#include <sys/cdefs.h>
17#if defined(LIBC_SCCS) && !defined(lint)
18__RCSID("$NetBSD: _rand48.c,v 1.7 2005/06/12 05:21:27 lukem Exp $");
19#endif /* LIBC_SCCS and not lint */
20
21#include <assert.h>
22
23#include "rand48.h"
24
25unsigned short __rand48_seed[3] = {
26	RAND48_SEED_0,
27	RAND48_SEED_1,
28	RAND48_SEED_2
29};
30unsigned short __rand48_mult[3] = {
31	RAND48_MULT_0,
32	RAND48_MULT_1,
33	RAND48_MULT_2
34};
35unsigned short __rand48_add = RAND48_ADD;
36
37void
38__dorand48(unsigned short xseed[3])
39{
40	unsigned long accu;
41	unsigned short temp[2];
42
43	_DIAGASSERT(xseed != NULL);
44
45	accu = (unsigned long) __rand48_mult[0] * (unsigned long) xseed[0] +
46	 (unsigned long) __rand48_add;
47	temp[0] = (unsigned short) accu;	/* lower 16 bits */
48	accu >>= sizeof(unsigned short) * 8;
49	accu += (unsigned long) __rand48_mult[0] * (unsigned long) xseed[1] +
50	 (unsigned long) __rand48_mult[1] * (unsigned long) xseed[0];
51	temp[1] = (unsigned short) accu;	/* middle 16 bits */
52	accu >>= sizeof(unsigned short) * 8;
53	accu += __rand48_mult[0] * xseed[2] + __rand48_mult[1] * xseed[1] + __rand48_mult[2] * xseed[0];
54	xseed[0] = temp[0];
55	xseed[1] = temp[1];
56	xseed[2] = (unsigned short) accu;
57}
58