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