/* crypto/bn/bn_div.c *//* Copyright (C) 1995-1998 Eric Young (eay@cryptsoft.com) * All rights reserved. * * This package is an SSL implementation written * by Eric Young (eay@cryptsoft.com). * The implementation was written so as to conform with Netscapes SSL. *  * This library is free for commercial and non-commercial use as long as * the following conditions are aheared to.  The following conditions * apply to all code found in this distribution, be it the RC4, RSA, * lhash, DES, etc., code; not just the SSL code.  The SSL documentation * included with this distribution is covered by the same copyright terms * except that the holder is Tim Hudson (tjh@cryptsoft.com). *  * Copyright remains Eric Young's, and as such any Copyright notices in * the code are not to be removed. * If this package is used in a product, Eric Young should be given attribution * as the author of the parts of the library used. * This can be in the form of a textual message at program startup or * in documentation (online or textual) provided with the package. *  * 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 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 cryptographic software written by *     Eric Young (eay@cryptsoft.com)" *    The word 'cryptographic' can be left out if the rouines from the library *    being used are not cryptographic related :-). * 4. If you include any Windows specific code (or a derivative thereof) from  *    the apps directory (application code) you must include an acknowledgement: *    "This product includes software written by Tim Hudson (tjh@cryptsoft.com)" *  * THIS SOFTWARE IS PROVIDED BY ERIC YOUNG ``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 AUTHOR 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. *  * The licence and distribution terms for any publically available version or * derivative of this code cannot be changed.  i.e. this code cannot simply be * copied and put under another distribution licence * [including the GNU Public Licence.] */#include <stdio.h>#include <openssl/bn.h>#include "cryptlib.h"#include "bn_lcl.h"/* The old slow way */#if 0int BN_div(BIGNUM *dv, BIGNUM *rem, const BIGNUM *m, const BIGNUM *d,	   BN_CTX *ctx)	{	int i,nm,nd;	int ret = 0;	BIGNUM *D;	bn_check_top(m);	bn_check_top(d);	if (BN_is_zero(d))		{		BNerr(BN_F_BN_DIV,BN_R_DIV_BY_ZERO);		return(0);		}	if (BN_ucmp(m,d) < 0)		{		if (rem != NULL)			{ if (BN_copy(rem,m) == NULL) return(0); }		if (dv != NULL) BN_zero(dv);		return(1);		}	BN_CTX_start(ctx);	D = BN_CTX_get(ctx);	if (dv == NULL) dv = BN_CTX_get(ctx);	if (rem == NULL) rem = BN_CTX_get(ctx);	if (D == NULL || dv == NULL || rem == NULL)		goto end;	nd=BN_num_bits(d);	nm=BN_num_bits(m);	if (BN_copy(D,d) == NULL) goto end;	if (BN_copy(rem,m) == NULL) goto end;	/* The next 2 are needed so we can do a dv->d[0]|=1 later	 * since BN_lshift1 will only work once there is a value :-) */	BN_zero(dv);	bn_wexpand(dv,1);	dv->top=1;	if (!BN_lshift(D,D,nm-nd)) goto end;	for (i=nm-nd; i>=0; i--)		{		if (!BN_lshift1(dv,dv)) goto end;		if (BN_ucmp(rem,D) >= 0)			{			dv->d[0]|=1;			if (!BN_usub(rem,rem,D)) goto end;			}/* CAN IMPROVE (and have now :=) */		if (!BN_rshift1(D,D)) goto end;		}	rem->neg=BN_is_zero(rem)?0:m->neg;	dv->neg=m->neg^d->neg;	ret = 1; end:	BN_CTX_end(ctx);	return(ret);	}#else#if !defined(OPENSSL_NO_ASM) && !defined(OPENSSL_NO_INLINE_ASM) \    && !defined(PEDANTIC) && !defined(BN_DIV3W)# if defined(__GNUC__) && __GNUC__>=2#  if defined(__i386) || 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#  elif defined(__x86_64) && defined(SIXTY_FOUR_BIT_LONG)   /*    * Same story here, but it's 128-bit by 64-bit division. Wow!    *					<appro@fy.chalmers.se>    */#  define bn_div_words(n0,n1,d0)		\	({  asm volatile (			\		"divq	%4"			\		: "=a"(q), "=d"(rem)		\		: "a"(n1), "d"(n0), "g"(d0)	\		: "cc");			\	    q;					\	})#  define REMAINDER_IS_ALREADY_CALCULATED#  endif /* __<cpu> */# endif /* __GNUC__ */#endif /* OPENSSL_NO_ASM *//* BN_div computes  dv := num / divisor,  rounding towards zero, and sets up * rm  such that  dv*divisor + rm = num  holds. * Thus: *     dv->neg == num->neg ^ divisor->neg  (unless the result is zero) *     rm->neg == num->neg                 (unless the remainder is zero) * If 'dv' or 'rm' is NULL, the respective value is not returned. */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);		}	BN_CTX_start(ctx);	tmp=BN_CTX_get(ctx);	snum=BN_CTX_get(ctx);	sdiv=BN_CTX_get(ctx);	if (dv == NULL)		res=BN_CTX_get(ctx);	else	res=dv;	if (sdiv == NULL || res == NULL) goto err;	tmp->neg=0;	/* First we normalise the numbers */	norm_shift=BN_BITS2-((BN_num_bits(divisor))%BN_BITS2);	if (!(BN_lshift(sdiv,divisor,norm_shift))) goto err;	sdiv->neg=0;	norm_shift+=BN_BITS2;	if (!(BN_lshift(snum,num,norm_shift))) goto err;	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.dmax= snum->dmax+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--;	if (res->top == 0)		res->neg = 0;	resp--;	for (i=0; i<loop-1; i++)		{		BN_ULONG q,l0;#if defined(BN_DIV3W) && !defined(OPENSSL_NO_ASM)		BN_ULONG bn_div_3_words(BN_ULONG*,BN_ULONG,BN_ULONG);		q=bn_div_3_words(wnump,d1,d0);#else		BN_ULONG n0,n1,rem=0;		n0=wnump[0];		n1=wnump[-1];		if (n0 == d0)			q=BN_MASK2;		else 			/* n0 < d0 */			{#ifdef BN_LLONG			BN_ULLONG t2;#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);#ifdef BN_DEBUG_LEVITTE			fprintf(stderr,"DEBUG: bn_div_words(0x%08X,0x%08X,0x%08\X) -> 0x%08X\n",				n0, n1, d0, q);#endif#endif#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_LLONG */			BN_ULONG t2l,t2h,ql,qh;			q=bn_div_words(n0,n1,d0);#ifdef BN_DEBUG_LEVITTE			fprintf(stderr,"DEBUG: bn_div_words(0x%08X,0x%08X,0x%08\X) -> 0x%08X\n",				n0, n1, d0, q);#endif#ifndef REMAINDER_IS_ALREADY_CALCULATED			rem=(n1-q*d0)&BN_MASK2;#endif#if defined(BN_UMULT_LOHI)			BN_UMULT_LOHI(t2l,t2h,d1,q);#elif defined(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 /* !BN_LLONG */			}#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;		if (!BN_sub(&wnum,&wnum,tmp)) goto err;		snum->top=snum->top+wnum.top-j;		if (wnum.neg)			{			q--;			j=wnum.top;			if (!BN_add(&wnum,&wnum,sdiv)) goto err;			snum->top+=wnum.top-j;			}		*(resp--)=q;		wnump--;		}	if (rm != NULL)		{		/* Keep a copy of the neg flag in num because if rm==num		 * BN_rshift() will overwrite it.		 */		int neg = num->neg;		BN_rshift(rm,snum,norm_shift);		if (!BN_is_zero(rm))			rm->neg = neg;		}	BN_CTX_end(ctx);	return(1);err:	BN_CTX_end(ctx);	return(0);	}#endif