/* $Id$ */
/*
 * Copyright (C) 1998-2002 RSA Security Inc. All rights reserved.
 *
 * This work contains proprietary information of RSA Security.
 * Distribution is limited to authorized licensees of RSA
 * Security. Any unauthorized reproduction, distribution or
 * modification of this work is strictly prohibited.
 *
 */

#include "bn_lcl.h"

#ifndef OPT_BN_ASM

#ifndef BN_DIV_WORDS
#define BN_DIV_WORDS
#endif

#endif

#ifdef BN_DIV_WORDS
#if defined(BN_LLONG)
BN_ULONG bn_div_words(h,l,d)
BN_ULONG h,l,d;
	{
	return((BN_ULONG)(((((BN_ULLONG)h)<<BN_BITS2)|l)/(BN_ULLONG)d));
	}

#else

/* Divide h-l by d and return the result. */
/* I need to test this some more */
BN_ULONG bn_div_words(h,l,d)
BN_ULONG h,l,d;
	{
	BN_ULONG dh,dl,q,ret=0,th,tl,t;
	int i,count=2;

	if (d == 0) return(BN_MASK2);

	i=BN_num_bits_word(d);
	if ((i != BN_BITS2) && (h > ((BN_ULONG)1)<<i))
		{
                return(0);
		}
	i=BN_BITS2-i;
	if (h >= d) h-=d;

	if (i)
		{
		d=(d<<i)&BN_MASK2;
		h=((h<<i)|(l>>(BN_BITS2-i)))&BN_MASK2;
		l=(l<<i)&BN_MASK2;
		}
	dh=(d>>BN_BITS4)&BN_MASK2lh;
	dl=(d&BN_MASK2l);
	for (;;)
		{
		if ((h>>BN_BITS4) == dh)
			q=BN_MASK2l;
		else
			q=h/dh;

		for (;;)
			{
			t=(h-q*dh)&BN_MASK2;
			if ((t&BN_MASK2h) ||
				(((dl*q)&BN_MASK2) <= ((
					(t<<BN_BITS4)+
					((l>>BN_BITS4)&BN_MASK2lh))&BN_MASK2)))
				break;
			q--;
			}
		th=(q*dh)&BN_MASK2;
		tl=(q*dl)&BN_MASK2;
		t=(tl>>BN_BITS4);
		tl=(tl&BN_MASK2lh)<<BN_BITS4;
		th=(th+t)&BN_MASK2;

		if (l < tl) th++;
		l=(l-tl)&BN_MASK2;
		if (h < th)
			{
			h=(h+d)&BN_MASK2;
			q--;
			}
		h=(h-th)&BN_MASK2;

		if (--count == 0) break;

		ret=(q&BN_MASK2lh)<<BN_BITS4;
		h=((h<<BN_BITS4)|(l>>BN_BITS4))&BN_MASK2;
		l=(l&BN_MASK2l)<<BN_BITS4;
		}
	ret|=q;
	return(ret);
	}
#endif
#endif /* BN_DIV_WORDS */