/*
 * Copyright (c) 1983, 1993
 *	The Regents of the University of California.  All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 * 3. All advertising materials mentioning features or use of this software
 *    must display the following acknowledgement:
 *	This product includes software developed by the University of
 *	California, Berkeley and its contributors.
 * 4. Neither the name of the University nor the names of its contributors
 *    may be used to endorse or promote products derived from this software
 *    without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 */

/* This is a stripped-down version of random.c distributed with
   FreeBSD 2.2 */

#include "bsd_rand.h"

#define	DEG		31
#define	SEP		3

static short fpos, rpos;
static int state[DEG];

int bsd_rand(int n)
{
  int i;
  
  state[fpos] += state[rpos];
  i = (state[fpos] >> 1) & 0x7fffffff; /* chucking least random bit */
  if (++(fpos) >= DEG) {
    fpos = 0;
    rpos++;
  } else if (++(rpos) >= DEG)
    rpos = 0;

  return i % n;
}

void bsd_srand(int x)
{
  register int i;

  state[0] = x & 0x7fffffff;
  for (i = 1; i < DEG; i++) {
    register long hi, lo, v;
  
    v = state[i - 1];
    hi = v / 127773;
    lo = v % 127773;
    v = 16807 * lo - 2836 * hi;
    if (v <= 0)
      v += 0x7fffffff;
    state[i] = v;
  }
  fpos = SEP;
  rpos = 0;
  for (i = 0; i < 10 * DEG; i++) {
    (void)bsd_rand(1);
  }
}