Obsolete/experimental code.

/* crypto/bn/bn_m.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"

#include <openssl/stack.h>

int limit=16;

typedef struct bn_pool_st

	{

	int used;

	int tos;

	STACK *sk; 

	} BN_POOL;

BIGNUM *BN_POOL_push(BN_POOL *bp)

	{

	BIGNUM *ret;

	if (bp->used >= bp->tos)

		{

		ret=BN_new();

		sk_push(bp->sk,(char *)ret);

		bp->tos++;

		bp->used++;

		}

	else

		{

		ret=(BIGNUM *)sk_value(bp->sk,bp->used);

		bp->used++;

		}

	return(ret);

	}

void BN_POOL_pop(BN_POOL *bp, int num)

	{

	bp->used-=num;

	}

int BN_m(BIGNUM *r, BIGNUM *a, BIGNUM *b)

	{

	static BN_POOL bp;

	static init=1;

	if (init)

		{

		bp.used=0;

		bp.tos=0;

		bp.sk=sk_new_null();

		init=0;

		}

	return(BN_mm(r,a,b,&bp));

	}

/* r must be different to a and b */

int BN_mm(BIGNUM *m, BIGNUM *A, BIGNUM *B, BN_POOL *bp)

	{

	int i,num;

	int an,bn;

	BIGNUM *a,*b,*c,*d,*ac,*bd;

	an=A->top;

	bn=B->top;

	if ((an <= limit) || (bn <= limit))

		{

		return(BN_mul(m,A,B));

		}

	a=BN_POOL_push(bp);

	b=BN_POOL_push(bp);

	c=BN_POOL_push(bp);

	d=BN_POOL_push(bp);

	ac=BN_POOL_push(bp);

	bd=BN_POOL_push(bp);

	num=(an <= bn)?an:bn;

	num=1<<(BN_num_bits_word(num-1)-1);

	/* Are going to now chop things into 'num' word chunks. */

	num*=BN_BITS2;

	BN_copy(a,A);

	BN_mask_bits(a,num);

	BN_rshift(b,A,num);

	BN_copy(c,B);

	BN_mask_bits(c,num);

	BN_rshift(d,B,num);

	BN_sub(ac ,b,a);

	BN_sub(bd,c,d);

	BN_mm(m,ac,bd,bp);

	BN_mm(ac,a,c,bp);

	BN_mm(bd,b,d,bp);

	BN_add(m,m,ac);

	BN_add(m,m,bd);

	BN_lshift(m,m,num);

	BN_lshift(bd,bd,num*2);

	BN_add(m,m,ac);

	BN_add(m,m,bd);

	BN_POOL_pop(bp,6);

	return(1);

	}