sl@0: /* crypto/bn/bn_add.c */
sl@0: /* Copyright (C) 1995-1998 Eric Young (eay@cryptsoft.com)
sl@0:  * All rights reserved.
sl@0:  *
sl@0:  * This package is an SSL implementation written
sl@0:  * by Eric Young (eay@cryptsoft.com).
sl@0:  * The implementation was written so as to conform with Netscapes SSL.
sl@0:  * 
sl@0:  * This library is free for commercial and non-commercial use as long as
sl@0:  * the following conditions are aheared to.  The following conditions
sl@0:  * apply to all code found in this distribution, be it the RC4, RSA,
sl@0:  * lhash, DES, etc., code; not just the SSL code.  The SSL documentation
sl@0:  * included with this distribution is covered by the same copyright terms
sl@0:  * except that the holder is Tim Hudson (tjh@cryptsoft.com).
sl@0:  * 
sl@0:  * Copyright remains Eric Young's, and as such any Copyright notices in
sl@0:  * the code are not to be removed.
sl@0:  * If this package is used in a product, Eric Young should be given attribution
sl@0:  * as the author of the parts of the library used.
sl@0:  * This can be in the form of a textual message at program startup or
sl@0:  * in documentation (online or textual) provided with the package.
sl@0:  * 
sl@0:  * Redistribution and use in source and binary forms, with or without
sl@0:  * modification, are permitted provided that the following conditions
sl@0:  * are met:
sl@0:  * 1. Redistributions of source code must retain the copyright
sl@0:  *    notice, this list of conditions and the following disclaimer.
sl@0:  * 2. Redistributions in binary form must reproduce the above copyright
sl@0:  *    notice, this list of conditions and the following disclaimer in the
sl@0:  *    documentation and/or other materials provided with the distribution.
sl@0:  * 3. All advertising materials mentioning features or use of this software
sl@0:  *    must display the following acknowledgement:
sl@0:  *    "This product includes cryptographic software written by
sl@0:  *     Eric Young (eay@cryptsoft.com)"
sl@0:  *    The word 'cryptographic' can be left out if the rouines from the library
sl@0:  *    being used are not cryptographic related :-).
sl@0:  * 4. If you include any Windows specific code (or a derivative thereof) from 
sl@0:  *    the apps directory (application code) you must include an acknowledgement:
sl@0:  *    "This product includes software written by Tim Hudson (tjh@cryptsoft.com)"
sl@0:  * 
sl@0:  * THIS SOFTWARE IS PROVIDED BY ERIC YOUNG ``AS IS'' AND
sl@0:  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
sl@0:  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
sl@0:  * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
sl@0:  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
sl@0:  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
sl@0:  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
sl@0:  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
sl@0:  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
sl@0:  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
sl@0:  * SUCH DAMAGE.
sl@0:  * 
sl@0:  * The licence and distribution terms for any publically available version or
sl@0:  * derivative of this code cannot be changed.  i.e. this code cannot simply be
sl@0:  * copied and put under another distribution licence
sl@0:  * [including the GNU Public Licence.]
sl@0:  */
sl@0: 
sl@0: #include <stdio.h>
sl@0: #include "cryptlib.h"
sl@0: #include "bn_lcl.h"
sl@0: 
sl@0: /* r can == a or b */
sl@0: EXPORT_C int BN_add(BIGNUM *r, const BIGNUM *a, const BIGNUM *b)
sl@0: 	{
sl@0: 	const BIGNUM *tmp;
sl@0: 	int a_neg = a->neg, ret;
sl@0: 
sl@0: 	bn_check_top(a);
sl@0: 	bn_check_top(b);
sl@0: 
sl@0: 	/*  a +  b	a+b
sl@0: 	 *  a + -b	a-b
sl@0: 	 * -a +  b	b-a
sl@0: 	 * -a + -b	-(a+b)
sl@0: 	 */
sl@0: 	if (a_neg ^ b->neg)
sl@0: 		{
sl@0: 		/* only one is negative */
sl@0: 		if (a_neg)
sl@0: 			{ tmp=a; a=b; b=tmp; }
sl@0: 
sl@0: 		/* we are now a - b */
sl@0: 
sl@0: 		if (BN_ucmp(a,b) < 0)
sl@0: 			{
sl@0: 			if (!BN_usub(r,b,a)) return(0);
sl@0: 			r->neg=1;
sl@0: 			}
sl@0: 		else
sl@0: 			{
sl@0: 			if (!BN_usub(r,a,b)) return(0);
sl@0: 			r->neg=0;
sl@0: 			}
sl@0: 		return(1);
sl@0: 		}
sl@0: 
sl@0: 	ret = BN_uadd(r,a,b);
sl@0: 	r->neg = a_neg;
sl@0: 	bn_check_top(r);
sl@0: 	return ret;
sl@0: 	}
sl@0: 
sl@0: /* unsigned add of b to a */
sl@0: EXPORT_C int BN_uadd(BIGNUM *r, const BIGNUM *a, const BIGNUM *b)
sl@0: 	{
sl@0: 	int max,min,dif;
sl@0: 	BN_ULONG *ap,*bp,*rp,carry,t1,t2;
sl@0: 	const BIGNUM *tmp;
sl@0: 
sl@0: 	bn_check_top(a);
sl@0: 	bn_check_top(b);
sl@0: 
sl@0: 	if (a->top < b->top)
sl@0: 		{ tmp=a; a=b; b=tmp; }
sl@0: 	max = a->top;
sl@0: 	min = b->top;
sl@0: 	dif = max - min;
sl@0: 
sl@0: 	if (bn_wexpand(r,max+1) == NULL)
sl@0: 		return 0;
sl@0: 
sl@0: 	r->top=max;
sl@0: 
sl@0: 
sl@0: 	ap=a->d;
sl@0: 	bp=b->d;
sl@0: 	rp=r->d;
sl@0: 
sl@0: 	carry=bn_add_words(rp,ap,bp,min);
sl@0: 	rp+=min;
sl@0: 	ap+=min;
sl@0: 	bp+=min;
sl@0: 
sl@0: 	if (carry)
sl@0: 		{
sl@0: 		while (dif)
sl@0: 			{
sl@0: 			dif--;
sl@0: 			t1 = *(ap++);
sl@0: 			t2 = (t1+1) & BN_MASK2;
sl@0: 			*(rp++) = t2;
sl@0: 			if (t2)
sl@0: 				{
sl@0: 				carry=0;
sl@0: 				break;
sl@0: 				}
sl@0: 			}
sl@0: 		if (carry)
sl@0: 			{
sl@0: 			/* carry != 0 => dif == 0 */
sl@0: 			*rp = 1;
sl@0: 			r->top++;
sl@0: 			}
sl@0: 		}
sl@0: 	if (dif && rp != ap)
sl@0: 		while (dif--)
sl@0: 			/* copy remaining words if ap != rp */
sl@0: 			*(rp++) = *(ap++);
sl@0: 	r->neg = 0;
sl@0: 	bn_check_top(r);
sl@0: 	return 1;
sl@0: 	}
sl@0: 
sl@0: /* unsigned subtraction of b from a, a must be larger than b. */
sl@0: EXPORT_C int BN_usub(BIGNUM *r, const BIGNUM *a, const BIGNUM *b)
sl@0: 	{
sl@0: 	int max,min,dif;
sl@0: 	register BN_ULONG t1,t2,*ap,*bp,*rp;
sl@0: 	int i,carry;
sl@0: #if defined(IRIX_CC_BUG) && !defined(LINT)
sl@0: 	int dummy;
sl@0: #endif
sl@0: 
sl@0: 	bn_check_top(a);
sl@0: 	bn_check_top(b);
sl@0: 
sl@0: 	max = a->top;
sl@0: 	min = b->top;
sl@0: 	dif = max - min;
sl@0: 
sl@0: 	if (dif < 0)	/* hmm... should not be happening */
sl@0: 		{
sl@0: 		BNerr(BN_F_BN_USUB,BN_R_ARG2_LT_ARG3);
sl@0: 		return(0);
sl@0: 		}
sl@0: 
sl@0: 	if (bn_wexpand(r,max) == NULL) return(0);
sl@0: 
sl@0: 	ap=a->d;
sl@0: 	bp=b->d;
sl@0: 	rp=r->d;
sl@0: 
sl@0: #if 1
sl@0: 	carry=0;
sl@0: 	for (i = min; i != 0; i--)
sl@0: 		{
sl@0: 		t1= *(ap++);
sl@0: 		t2= *(bp++);
sl@0: 		if (carry)
sl@0: 			{
sl@0: 			carry=(t1 <= t2);
sl@0: 			t1=(t1-t2-1)&BN_MASK2;
sl@0: 			}
sl@0: 		else
sl@0: 			{
sl@0: 			carry=(t1 < t2);
sl@0: 			t1=(t1-t2)&BN_MASK2;
sl@0: 			}
sl@0: #if defined(IRIX_CC_BUG) && !defined(LINT)
sl@0: 		dummy=t1;
sl@0: #endif
sl@0: 		*(rp++)=t1&BN_MASK2;
sl@0: 		}
sl@0: #else
sl@0: 	carry=bn_sub_words(rp,ap,bp,min);
sl@0: 	ap+=min;
sl@0: 	bp+=min;
sl@0: 	rp+=min;
sl@0: #endif
sl@0: 	if (carry) /* subtracted */
sl@0: 		{
sl@0: 		if (!dif)
sl@0: 			/* error: a < b */
sl@0: 			return 0;
sl@0: 		while (dif)
sl@0: 			{
sl@0: 			dif--;
sl@0: 			t1 = *(ap++);
sl@0: 			t2 = (t1-1)&BN_MASK2;
sl@0: 			*(rp++) = t2;
sl@0: 			if (t1)
sl@0: 				break;
sl@0: 			}
sl@0: 		}
sl@0: #if 0
sl@0: 	memcpy(rp,ap,sizeof(*rp)*(max-i));
sl@0: #else
sl@0: 	if (rp != ap)
sl@0: 		{
sl@0: 		for (;;)
sl@0: 			{
sl@0: 			if (!dif--) break;
sl@0: 			rp[0]=ap[0];
sl@0: 			if (!dif--) break;
sl@0: 			rp[1]=ap[1];
sl@0: 			if (!dif--) break;
sl@0: 			rp[2]=ap[2];
sl@0: 			if (!dif--) break;
sl@0: 			rp[3]=ap[3];
sl@0: 			rp+=4;
sl@0: 			ap+=4;
sl@0: 			}
sl@0: 		}
sl@0: #endif
sl@0: 
sl@0: 	r->top=max;
sl@0: 	r->neg=0;
sl@0: 	bn_correct_top(r);
sl@0: 	return(1);
sl@0: 	}
sl@0: 
sl@0: EXPORT_C int BN_sub(BIGNUM *r, const BIGNUM *a, const BIGNUM *b)
sl@0: 	{
sl@0: 	int max;
sl@0: 	int add=0,neg=0;
sl@0: 	const BIGNUM *tmp;
sl@0: 
sl@0: 	bn_check_top(a);
sl@0: 	bn_check_top(b);
sl@0: 
sl@0: 	/*  a -  b	a-b
sl@0: 	 *  a - -b	a+b
sl@0: 	 * -a -  b	-(a+b)
sl@0: 	 * -a - -b	b-a
sl@0: 	 */
sl@0: 	if (a->neg)
sl@0: 		{
sl@0: 		if (b->neg)
sl@0: 			{ tmp=a; a=b; b=tmp; }
sl@0: 		else
sl@0: 			{ add=1; neg=1; }
sl@0: 		}
sl@0: 	else
sl@0: 		{
sl@0: 		if (b->neg) { add=1; neg=0; }
sl@0: 		}
sl@0: 
sl@0: 	if (add)
sl@0: 		{
sl@0: 		if (!BN_uadd(r,a,b)) return(0);
sl@0: 		r->neg=neg;
sl@0: 		return(1);
sl@0: 		}
sl@0: 
sl@0: 	/* We are actually doing a - b :-) */
sl@0: 
sl@0: 	max=(a->top > b->top)?a->top:b->top;
sl@0: 	if (bn_wexpand(r,max) == NULL) return(0);
sl@0: 	if (BN_ucmp(a,b) < 0)
sl@0: 		{
sl@0: 		if (!BN_usub(r,b,a)) return(0);
sl@0: 		r->neg=1;
sl@0: 		}
sl@0: 	else
sl@0: 		{
sl@0: 		if (!BN_usub(r,a,b)) return(0);
sl@0: 		r->neg=0;
sl@0: 		}
sl@0: 	bn_check_top(r);
sl@0: 	return(1);
sl@0: 	}
sl@0: