crypto/bn/bn_div.c - third_party/openssl - Git at Google

 /* 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 "cryptlib.h"
 #include "bn_lcl.h"

 /* The old slow way */
 #if 0
 int BN_div(BIGNUM *dv, BIGNUM *rem, BIGNUM *m, BIGNUM *d, BN_CTX *ctx)
 	{
 	int i,nm,nd;
 	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);
 		}

 	D= &(ctx->bn[ctx->tos]);
 	if (dv == NULL) dv= &(ctx->bn[ctx->tos+1]);
 	if (rem == NULL) rem= &(ctx->bn[ctx->tos+2]);

 	nd=BN_num_bits(d);
 	nm=BN_num_bits(m);
 	if (BN_copy(D,d) == NULL) return(0);
 	if (BN_copy(rem,m) == NULL) return(0);

 	/* 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)) return(0);
 	for (i=nm-nd; i>=0; i--)
 		{
 		if (!BN_lshift1(dv,dv)) return(0);
 		if (BN_ucmp(rem,D) >= 0)
 			{
 			dv->d[0]|=1;
 			if (!BN_usub(rem,rem,D)) return(0);
 			}
 /* CAN IMPROVE (and have now :=) */
 		if (!BN_rshift1(D,D)) return(0);
 		}
 	rem->neg=BN_is_zero(rem)?0:m->neg;
 	dv->neg=m->neg^d->neg;
 	return(1);
 	}

 #else

 int BN_div(BIGNUM *dv, BIGNUM *rm, BIGNUM *num, 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,n0,n1;
 		BN_ULONG l0;

 		wnum.d--; wnum.top++;
 		n0=wnump[0];
 		n1=wnump[-1];
 		if (n0 == d0)
 			q=BN_MASK2;
 		else
 			q=bn_div_words(n0,n1,d0);
 		{
 #ifdef BN_LLONG
 		BN_ULLONG t1,t2,rem;
 		t1=((BN_ULLONG)n0<<BN_BITS2)|n1;
 		for (;;)
 			{
 			t2=(BN_ULLONG)d1*q;
 			rem=t1-(BN_ULLONG)q*d0;
 			if ((rem>>BN_BITS2) ||
 				(t2 <= ((BN_ULLONG)(rem<<BN_BITS2)+wnump[-2])))
 				break;
 			q--;
 			}
 #else
 		BN_ULONG t1l,t1h,t2l,t2h,t3l,t3h,ql,qh,t3t;
 		t1h=n0;
 		t1l=n1;
 		for (;;)
 			{
 			t2l=LBITS(d1); t2h=HBITS(d1);
 			ql =LBITS(q);  qh =HBITS(q);
 			mul64(t2l,t2h,ql,qh); /* t2=(BN_ULLONG)d1*q; */

 			t3t=LBITS(d0); t3h=HBITS(d0);
 			mul64(t3t,t3h,ql,qh); /* t3=t1-(BN_ULLONG)q*d0; */
 			t3l=(t1l-t3t)&BN_MASK2;
 			if (t3l > t1l) t3h++;
 			t3h=(t1h-t3h)&BN_MASK2;

 			/*if ((t3>>BN_BITS2) ||
 				(t2 <= ((t3<<BN_BITS2)+wnump[-2])))
 				break; */
 			if (t3h) break;
 			if (t2h < t3l) break;
 			if ((t2h == t3l) && (t2l <= wnump[-2])) break;

 			q--;
 			}
 #endif
 		}
 		l0=bn_mul_words(tmp->d,sdiv->d,div_n,q);
 		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);
 	}

 #endif

 /* rem != m */
 int BN_mod(BIGNUM *rem, BIGNUM *m, BIGNUM *d, BN_CTX *ctx)
 	{
 #if 0 /* The old slow way */
 	int i,nm,nd;
 	BIGNUM *dv;

 	if (BN_ucmp(m,d) < 0)
 		return((BN_copy(rem,m) == NULL)?0:1);

 	dv= &(ctx->bn[ctx->tos]);

 	if (!BN_copy(rem,m)) return(0);

 	nm=BN_num_bits(rem);
 	nd=BN_num_bits(d);
 	if (!BN_lshift(dv,d,nm-nd)) return(0);
 	for (i=nm-nd; i>=0; i--)
 		{
 		if (BN_cmp(rem,dv) >= 0)
 			{
 			if (!BN_sub(rem,rem,dv)) return(0);
 			}
 		if (!BN_rshift1(dv,dv)) return(0);
 		}
 	return(1);
 #else
 	return(BN_div(NULL,rem,m,d,ctx));
 #endif
 	}
	/* 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 "cryptlib.h"
	#include "bn_lcl.h"

	/* The old slow way */
	#if 0
	int BN_div(BIGNUM dv, BIGNUM rem, BIGNUM m, BIGNUM d, BN_CTX *ctx)
	{
	int i,nm,nd;
	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);
	}

	D= &(ctx->bn[ctx->tos]);
	if (dv == NULL) dv= &(ctx->bn[ctx->tos+1]);
	if (rem == NULL) rem= &(ctx->bn[ctx->tos+2]);

	nd=BN_num_bits(d);
	nm=BN_num_bits(m);
	if (BN_copy(D,d) == NULL) return(0);
	if (BN_copy(rem,m) == NULL) return(0);

	/* 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)) return(0);
	for (i=nm-nd; i>=0; i--)
	{
	if (!BN_lshift1(dv,dv)) return(0);
	if (BN_ucmp(rem,D) >= 0)
	{
	dv->d[0]\|=1;
	if (!BN_usub(rem,rem,D)) return(0);
	}
	/* CAN IMPROVE (and have now :=) */
	if (!BN_rshift1(D,D)) return(0);
	}
	rem->neg=BN_is_zero(rem)?0:m->neg;
	dv->neg=m->neg^d->neg;
	return(1);
	}

	#else

	int BN_div(BIGNUM dv, BIGNUM rm, BIGNUM num, 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,n0,n1;
	BN_ULONG l0;

	wnum.d--; wnum.top++;
	n0=wnump[0];
	n1=wnump[-1];
	if (n0 == d0)
	q=BN_MASK2;
	else
	q=bn_div_words(n0,n1,d0);
	{
	#ifdef BN_LLONG
	BN_ULLONG t1,t2,rem;
	t1=((BN_ULLONG)n0<<BN_BITS2)\|n1;
	for (;;)
	{
	t2=(BN_ULLONG)d1*q;
	rem=t1-(BN_ULLONG)q*d0;
	if ((rem>>BN_BITS2) \|\|
	(t2 <= ((BN_ULLONG)(rem<<BN_BITS2)+wnump[-2])))
	break;
	q--;
	}
	#else
	BN_ULONG t1l,t1h,t2l,t2h,t3l,t3h,ql,qh,t3t;
	t1h=n0;
	t1l=n1;
	for (;;)
	{
	t2l=LBITS(d1); t2h=HBITS(d1);
	ql =LBITS(q); qh =HBITS(q);
	mul64(t2l,t2h,ql,qh); /* t2=(BN_ULLONG)d1q; /

	t3t=LBITS(d0); t3h=HBITS(d0);
	mul64(t3t,t3h,ql,qh); /* t3=t1-(BN_ULLONG)qd0; /
	t3l=(t1l-t3t)&BN_MASK2;
	if (t3l > t1l) t3h++;
	t3h=(t1h-t3h)&BN_MASK2;

	/*if ((t3>>BN_BITS2) \|\|
	(t2 <= ((t3<<BN_BITS2)+wnump[-2])))
	break; */
	if (t3h) break;
	if (t2h < t3l) break;
	if ((t2h == t3l) && (t2l <= wnump[-2])) break;

	q--;
	}
	#endif
	}
	l0=bn_mul_words(tmp->d,sdiv->d,div_n,q);
	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);
	}

	#endif

	/* rem != m */
	int BN_mod(BIGNUM rem, BIGNUM m, BIGNUM d, BN_CTX ctx)
	{
	#if 0 /* The old slow way */
	int i,nm,nd;
	BIGNUM *dv;

	if (BN_ucmp(m,d) < 0)
	return((BN_copy(rem,m) == NULL)?0:1);

	dv= &(ctx->bn[ctx->tos]);

	if (!BN_copy(rem,m)) return(0);

	nm=BN_num_bits(rem);
	nd=BN_num_bits(d);
	if (!BN_lshift(dv,d,nm-nd)) return(0);
	for (i=nm-nd; i>=0; i--)
	{
	if (BN_cmp(rem,dv) >= 0)
	{
	if (!BN_sub(rem,rem,dv)) return(0);
	}
	if (!BN_rshift1(dv,dv)) return(0);
	}
	return(1);
	#else
	return(BN_div(NULL,rem,m,d,ctx));
	#endif
	}