/*      $NetBSD: _rand48.c,v 1.10 2020/02/23 09:53:42 kamil Exp $       */

/*
* Copyright (c) 1993 Martin Birgmeier
* All rights reserved.
*
* You may redistribute unmodified or modified versions of this source
* code provided that the above copyright notice and this and the
* following conditions are retained.
*
* This software is provided ``as is'', and comes with no warranties
* of any kind. I shall in no event be liable for anything that happens
* to anyone/anything when using this software.
*/

#include <sys/cdefs.h>
#if defined(LIBC_SCCS) && !defined(lint)
__RCSID("$NetBSD: _rand48.c,v 1.10 2020/02/23 09:53:42 kamil Exp $");
#endif /* LIBC_SCCS and not lint */

#include <assert.h>

#include "rand48.h"

unsigned short __rand48_seed[3] = {
       RAND48_SEED_0,
       RAND48_SEED_1,
       RAND48_SEED_2
};
unsigned short __rand48_mult[3] = {
       RAND48_MULT_0,
       RAND48_MULT_1,
       RAND48_MULT_2
};
unsigned short __rand48_add = RAND48_ADD;

void
__dorand48(unsigned short xseed[3])
{
       unsigned long accu;
       unsigned short temp[2];

       _DIAGASSERT(xseed != NULL);

       accu = (unsigned long) __rand48_mult[0] * (unsigned long) xseed[0];
       accu += (unsigned long) __rand48_add;
       temp[0] = (unsigned short) accu;        /* lower 16 bits */
       accu >>= sizeof(unsigned short) * 8;
       accu += (unsigned long) __rand48_mult[0] * (unsigned long) xseed[1];
       accu += (unsigned long) __rand48_mult[1] * (unsigned long) xseed[0];
       temp[1] = (unsigned short) accu;        /* middle 16 bits */
       accu >>= sizeof(unsigned short) * 8;
       accu += (unsigned long) __rand48_mult[0] * (unsigned long) xseed[2];
       accu += (unsigned long) __rand48_mult[1] * (unsigned long) xseed[1];
       accu += (unsigned long) __rand48_mult[2] * (unsigned long) xseed[0];
       xseed[0] = temp[0];
       xseed[1] = temp[1];
       xseed[2] = (unsigned short) accu;
}