2 * Copyright 1995-2016 The OpenSSL Project Authors. All Rights Reserved.
4 * Licensed under the OpenSSL license (the "License"). You may not use
5 * this file except in compliance with the License. You can obtain a copy
6 * in the file LICENSE in the source distribution or at
7 * https://www.openssl.org/source/license.html
10 #include "internal/cryptlib.h"
14 int BN_add(BIGNUM *r, const BIGNUM *a, const BIGNUM *b)
17 int a_neg = a->neg, ret;
29 /* only one is negative */
36 /* we are now a - b */
38 if (BN_ucmp(a, b) < 0) {
39 if (!BN_usub(r, b, a))
43 if (!BN_usub(r, a, b))
50 ret = BN_uadd(r, a, b);
56 /* unsigned add of b to a */
57 int BN_uadd(BIGNUM *r, const BIGNUM *a, const BIGNUM *b)
60 const BN_ULONG *ap, *bp;
61 BN_ULONG *rp, carry, t1, t2;
67 if (a->top < b->top) {
76 if (bn_wexpand(r, max + 1) == NULL)
85 carry = bn_add_words(rp, ap, bp, min);
94 t2 = (t1 + 1) & BN_MASK2;
102 /* carry != 0 => dif == 0 */
109 /* copy remaining words if ap != rp */
116 /* unsigned subtraction of b from a, a must be larger than b. */
117 int BN_usub(BIGNUM *r, const BIGNUM *a, const BIGNUM *b)
120 register BN_ULONG t1, t2, *rp;
121 register const BN_ULONG *ap, *bp;
131 if (dif < 0) { /* hmm... should not be happening */
132 BNerr(BN_F_BN_USUB, BN_R_ARG2_LT_ARG3);
136 if (bn_wexpand(r, max) == NULL)
145 for (i = min; i != 0; i--) {
150 t1 = (t1 - t2 - 1) & BN_MASK2;
153 t1 = (t1 - t2) & BN_MASK2;
155 *(rp++) = t1 & BN_MASK2;
158 carry = bn_sub_words(rp, ap, bp, min);
163 if (carry) { /* subtracted */
170 t2 = (t1 - 1) & BN_MASK2;
177 memcpy(rp, ap, sizeof(*rp) * dif);
185 int BN_sub(BIGNUM *r, const BIGNUM *a, const BIGNUM *b)
188 int add = 0, neg = 0;
217 if (!BN_uadd(r, a, b))
223 /* We are actually doing a - b :-) */
225 max = (a->top > b->top) ? a->top : b->top;
226 if (bn_wexpand(r, max) == NULL)
228 if (BN_ucmp(a, b) < 0) {
229 if (!BN_usub(r, b, a))
233 if (!BN_usub(r, a, b))