int BN_div(BIGNUM *dv, BIGNUM *rm, const BIGNUM *num, const BIGNUM *divisor,
	   BN_CTX *ctx)
	{
	int norm_shift,i,j,loop;
	BIGNUM *tmp,wnum,*snum,*sdiv,*res;
	BN_ULONG *resp,*wnump;
	BN_ULONG d0,d1;
	int num_n,div_n;

	bn_check_top(num);
	bn_check_top(divisor);

	if (BN_is_zero(divisor))
		{
		BNerr(BN_F_BN_DIV,BN_R_DIV_BY_ZERO);
		return(0);
		}

	if (BN_ucmp(num,divisor) < 0)
		{
		if (rm != NULL)
			{ if (BN_copy(rm,num) == NULL) return(0); }
		if (dv != NULL) BN_zero(dv);
		return(1);
		}

	tmp= &(ctx->bn[ctx->tos]);
	tmp->neg=0;
	snum= &(ctx->bn[ctx->tos+1]);
	sdiv= &(ctx->bn[ctx->tos+2]);
	if (dv == NULL)
		res= &(ctx->bn[ctx->tos+3]);
	else	res=dv;

	/* First we normalise the numbers */
	norm_shift=BN_BITS2-((BN_num_bits(divisor))%BN_BITS2);
	BN_lshift(sdiv,divisor,norm_shift);
	sdiv->neg=0;
	norm_shift+=BN_BITS2;
	BN_lshift(snum,num,norm_shift);
	snum->neg=0;
	div_n=sdiv->top;
	num_n=snum->top;
	loop=num_n-div_n;

	/* Lets setup a 'window' into snum
	 * This is the part that corresponds to the current
	 * 'area' being divided */
	BN_init(&wnum);
	wnum.d=	 &(snum->d[loop]);
	wnum.top= div_n;
	wnum.max= snum->max+1; /* a bit of a lie */

	/* Get the top 2 words of sdiv */
	/* i=sdiv->top; */
	d0=sdiv->d[div_n-1];
	d1=(div_n == 1)?0:sdiv->d[div_n-2];

	/* pointer to the 'top' of snum */
	wnump= &(snum->d[num_n-1]);

	/* Setup to 'res' */
	res->neg= (num->neg^divisor->neg);
	if (!bn_wexpand(res,(loop+1))) goto err;
	res->top=loop;
	resp= &(res->d[loop-1]);

	/* space for temp */
	if (!bn_wexpand(tmp,(div_n+1))) goto err;

	if (BN_ucmp(&wnum,sdiv) >= 0)
		{
		if (!BN_usub(&wnum,&wnum,sdiv)) goto err;
		*resp=1;
		res->d[res->top-1]=1;
		}
	else
		res->top--;
	resp--;

	for (i=0; i<loop-1; i++)
		{
		BN_ULONG q,l0;
#ifdef BN_DIV3W
		q=bn_div_3_words(wnump,d1,d0);
#else

#if !defined(NO_ASM) && !defined(PEDANTIC)
# if defined(__GNUC__) && __GNUC__>=2
#  if defined(__i386)
   /*
    * There were two reasons for implementing this template:
    * - GNU C generates a call to a function (__udivdi3 to be exact)
    *   in reply to ((((BN_ULLONG)n0)<<BN_BITS2)|n1)/d0 (I fail to
    *   understand why...);
    * - divl doesn't only calculate quotient, but also leaves
    *   remainder in %edx which we can definitely use here:-)
    *
    *					<appro@fy.chalmers.se>
    */
#  define bn_div_words(n0,n1,d0)		\
	({  asm volatile (			\
		"divl	%4"			\
		: "=a"(q), "=d"(rem)		\
		: "a"(n1), "d"(n0), "g"(d0)	\
		: "cc");			\
	    q;					\
	})
#  define REMAINDER_IS_ALREADY_CALCULATED
#  endif /* __<cpu> */
# endif /* __GNUC__ */
#endif /* NO_ASM */
		BN_ULONG n0,n1,rem=0;

		n0=wnump[0];
		n1=wnump[-1];
		if (n0 == d0)
			{
			q=BN_MASK2;
#ifdef REMAINDER_IS_ALREADY_CALCULATED /* in this case it isn't */
			rem=(n1-q*d0)&BN_MASK2;
#endif
			}
		else /* n0 < d0 */
#if defined(BN_LLONG) && defined(BN_DIV2W) && !defined(bn_div_words)
			q=(BN_ULONG)(((((BN_ULLONG)n0)<<BN_BITS2)|n1)/d0);
#else
			q=bn_div_words(n0,n1,d0);
#endif
		{
#ifdef BN_LLONG
		BN_ULLONG t2;

#ifndef REMAINDER_IS_ALREADY_CALCULATED
		/*
		 * rem doesn't have to be BN_ULLONG. The least we
		 * know it's less that d0, isn't it?
		 */
		rem=(n1-q*d0)&BN_MASK2;
#endif
		t2=(BN_ULLONG)d1*q;

		for (;;)
			{
                        if (t2 <= ((((BN_ULLONG)rem)<<BN_BITS2)|wnump[-2]))
				break;
			q--;
			rem += d0;
			if (rem < d0) break; /* don't let rem overflow */
			t2 -= d1;
			}
#else
		BN_ULONG t2l,t2h,ql,qh;

#ifndef REMAINDER_IS_ALREADY_CALCULATED
		/*
		 * It's more than enough with the only multiplication.
		 * See the comment above in BN_LLONG section...
		 */
		rem=(n1-q*d0)&BN_MASK2;
#endif
#ifdef BN_UMULT_HIGH
		t2l = d1 * q;
		t2h = BN_UMULT_HIGH(d1,q);
#else
		t2l=LBITS(d1); t2h=HBITS(d1);
		ql =LBITS(q);  qh =HBITS(q);
		mul64(t2l,t2h,ql,qh); /* t2=(BN_ULLONG)d1*q; */
#endif

		for (;;)
			{
			if ((t2h < rem) ||
				((t2h == rem) && (t2l <= wnump[-2])))
				break;
			q--;
			rem += d0;
			if (rem < d0) break; /* don't let rem overflow */
			if (t2l < d1) t2h--; t2l -= d1;
			}
#endif
		}
#endif /* !BN_DIV3W */
		l0=bn_mul_words(tmp->d,sdiv->d,div_n,q);
		wnum.d--; wnum.top++;
		tmp->d[div_n]=l0;
		for (j=div_n+1; j>0; j--)
			if (tmp->d[j-1]) break;
		tmp->top=j;

		j=wnum.top;
		BN_sub(&wnum,&wnum,tmp);

		snum->top=snum->top+wnum.top-j;

		if (wnum.neg)
			{
			q--;
			j=wnum.top;
			BN_add(&wnum,&wnum,sdiv);
			snum->top+=wnum.top-j;
			}
		*(resp--)=q;
		wnump--;
		}
	if (rm != NULL)
		{
		BN_rshift(rm,snum,norm_shift);
		rm->neg=num->neg;
		}
	return(1);
err:
	return(0);
	}