/* crypto/bn/bn_add.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 "workaround.h"/* r can == a or b */int BN_add(BIGNUM * r, const BIGNUM * a, const BIGNUM * b){    const BIGNUM *tmp;    bn_check_top(a);    bn_check_top(b);    /*  a +  b      a+b     *  a + -b      a-b     * -a +  b      b-a     * -a + -b      -(a+b)     */    if (a->neg ^ b->neg) {	/* only one is negative */	if (a->neg) {	    tmp = a;	    a = b;	    b = tmp;	}	/* we are now a - b */	if (BN_ucmp(a, b) < 0) {	    if (!BN_usub(r, b, a))		return (0);	    r->neg = 1;	} else {	    if (!BN_usub(r, a, b))		return (0);	    r->neg = 0;	}	return (1);    }    if (a->neg)			/* both are neg */	r->neg = 1;    else	r->neg = 0;    if (!BN_uadd(r, a, b))	return (0);    return (1);}/* unsigned add of b to a, r must be large enough */int BN_uadd(BIGNUM * r, const BIGNUM * a, const BIGNUM * b){    register int i;    int max, min;    BN_ULONG *ap, *bp, *rp, carry, t1;    const BIGNUM *tmp;    bn_check_top(a);    bn_check_top(b);    if (a->top < b->top) {	tmp = a;	a = b;	b = tmp;    }    max = a->top;    min = b->top;    if (bn_wexpand(r, max + 1) == NULL)	return (0);    r->top = max;    ap = a->d;    bp = b->d;    rp = r->d;    carry = 0;    carry = bn_add_words(rp, ap, bp, min);    rp += min;    ap += min;    bp += min;    i = min;    if (carry) {	while (i < max) {	    i++;	    t1 = *(ap++);	    if ((*(rp++) = (t1 + 1) & BN_MASK2) >= t1) {		carry = 0;		break;	    }	}	if ((i >= max) && carry) {	    *(rp++) = 1;	    r->top++;	}    }    if (rp != ap) {	for (; i < max; i++)	    *(rp++) = *(ap++);    }    /* hss_memcpy(rp,ap,sizeof(*ap)*(max-i)); */    return (1);}/* unsigned subtraction of b from a, a must be larger than b. */int BN_usub(BIGNUM * r, const BIGNUM * a, const BIGNUM * b){    int max, min;    register BN_ULONG t1, t2, *ap, *bp, *rp;    int i, carry;#if defined(IRIX_CC_BUG) && !defined(LINT)    int dummy;#endif    bn_check_top(a);    bn_check_top(b);    if (a->top < b->top) {	/* hmm... should not be happening */	BNerr(BN_F_BN_USUB, BN_R_ARG2_LT_ARG3);	return (0);    }    max = a->top;    min = b->top;    if (bn_wexpand(r, max) == NULL)	return (0);    ap = a->d;    bp = b->d;    rp = r->d;#if 1    carry = 0;    for (i = 0; i < min; i++) {	t1 = *(ap++);	t2 = *(bp++);	if (carry) {	    carry = (t1 <= t2);	    t1 = (t1 - t2 - 1) & BN_MASK2;	} else {	    carry = (t1 < t2);	    t1 = (t1 - t2) & BN_MASK2;	}#if defined(IRIX_CC_BUG) && !defined(LINT)	dummy = t1;#endif	*(rp++) = t1 & BN_MASK2;    }#else    carry = bn_sub_words(rp, ap, bp, min);    ap += min;    bp += min;    rp += min;    i = min;#endif    if (carry) {		/* subtracted */	while (i < max) {	    i++;	    t1 = *(ap++);	    t2 = (t1 - 1) & BN_MASK2;	    *(rp++) = t2;	    if (t1 > t2)		break;	}    }#if 0    hss_memcpy(rp, ap, sizeof(*rp) * (max - i));#else    if (rp != ap) {	for (;;) {	    if (i++ >= max)		break;	    rp[0] = ap[0];	    if (i++ >= max)		break;	    rp[1] = ap[1];	    if (i++ >= max)		break;	    rp[2] = ap[2];	    if (i++ >= max)		break;	    rp[3] = ap[3];	    rp += 4;	    ap += 4;	}    }#endif    r->top = max;    bn_fix_top(r);    return (1);}int BN_sub(BIGNUM * r, const BIGNUM * a, const BIGNUM * b){    int max;    int add = 0, neg = 0;    const BIGNUM *tmp;    bn_check_top(a);    bn_check_top(b);    /*  a -  b      a-b     *  a - -b      a+b     * -a -  b      -(a+b)     * -a - -b      b-a     */    if (a->neg) {	if (b->neg) {	    tmp = a;	    a = b;	    b = tmp;	} else {	    add = 1;	    neg = 1;	}    } else {	if (b->neg) {	    add = 1;	    neg = 0;	}    }    if (add) {	if (!BN_uadd(r, a, b))	    return (0);	r->neg = neg;	return (1);    }    /* We are actually doing a - b :-) */    max = (a->top > b->top) ? a->top : b->top;    if (bn_wexpand(r, max) == NULL)	return (0);    if (BN_ucmp(a, b) < 0) {	if (!BN_usub(r, b, a))	    return (0);	r->neg = 1;    } else {	if (!BN_usub(r, a, b))	    return (0);	r->neg = 0;    }    return (1);}