| /* |
| * Copyright 1995-2020 The OpenSSL Project Authors. All Rights Reserved. |
| * |
| * Licensed under the Apache License 2.0 (the "License"). You may not use |
| * this file except in compliance with the License. You can obtain a copy |
| * in the file LICENSE in the source distribution or at |
| * https://www.openssl.org/source/license.html |
| */ |
| |
| #include "internal/cryptlib.h" |
| #include "bn_local.h" |
| |
| /* signed add of b to a. */ |
| int BN_add(BIGNUM *r, const BIGNUM *a, const BIGNUM *b) |
| { |
| int ret, r_neg, cmp_res; |
| |
| bn_check_top(a); |
| bn_check_top(b); |
| |
| if (a->neg == b->neg) { |
| r_neg = a->neg; |
| ret = BN_uadd(r, a, b); |
| } else { |
| cmp_res = BN_ucmp(a, b); |
| if (cmp_res > 0) { |
| r_neg = a->neg; |
| ret = BN_usub(r, a, b); |
| } else if (cmp_res < 0) { |
| r_neg = b->neg; |
| ret = BN_usub(r, b, a); |
| } else { |
| r_neg = 0; |
| BN_zero(r); |
| ret = 1; |
| } |
| } |
| |
| r->neg = r_neg; |
| bn_check_top(r); |
| return ret; |
| } |
| |
| /* signed sub of b from a. */ |
| int BN_sub(BIGNUM *r, const BIGNUM *a, const BIGNUM *b) |
| { |
| int ret, r_neg, cmp_res; |
| |
| bn_check_top(a); |
| bn_check_top(b); |
| |
| if (a->neg != b->neg) { |
| r_neg = a->neg; |
| ret = BN_uadd(r, a, b); |
| } else { |
| cmp_res = BN_ucmp(a, b); |
| if (cmp_res > 0) { |
| r_neg = a->neg; |
| ret = BN_usub(r, a, b); |
| } else if (cmp_res < 0) { |
| r_neg = !b->neg; |
| ret = BN_usub(r, b, a); |
| } else { |
| r_neg = 0; |
| BN_zero(r); |
| ret = 1; |
| } |
| } |
| |
| r->neg = r_neg; |
| bn_check_top(r); |
| return ret; |
| } |
| |
| /* unsigned add of b to a, r can be equal to a or b. */ |
| int BN_uadd(BIGNUM *r, const BIGNUM *a, const BIGNUM *b) |
| { |
| int max, min, dif; |
| const BN_ULONG *ap, *bp; |
| BN_ULONG *rp, carry, t1, t2; |
| |
| bn_check_top(a); |
| bn_check_top(b); |
| |
| if (a->top < b->top) { |
| const BIGNUM *tmp; |
| |
| tmp = a; |
| a = b; |
| b = tmp; |
| } |
| max = a->top; |
| min = b->top; |
| dif = max - min; |
| |
| if (bn_wexpand(r, max + 1) == NULL) |
| return 0; |
| |
| r->top = max; |
| |
| ap = a->d; |
| bp = b->d; |
| rp = r->d; |
| |
| carry = bn_add_words(rp, ap, bp, min); |
| rp += min; |
| ap += min; |
| |
| while (dif) { |
| dif--; |
| t1 = *(ap++); |
| t2 = (t1 + carry) & BN_MASK2; |
| *(rp++) = t2; |
| carry &= (t2 == 0); |
| } |
| *rp = carry; |
| r->top += carry; |
| |
| r->neg = 0; |
| bn_check_top(r); |
| 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, dif; |
| BN_ULONG t1, t2, borrow, *rp; |
| const BN_ULONG *ap, *bp; |
| |
| bn_check_top(a); |
| bn_check_top(b); |
| |
| max = a->top; |
| min = b->top; |
| dif = max - min; |
| |
| if (dif < 0) { /* hmm... should not be happening */ |
| ERR_raise(ERR_LIB_BN, BN_R_ARG2_LT_ARG3); |
| return 0; |
| } |
| |
| if (bn_wexpand(r, max) == NULL) |
| return 0; |
| |
| ap = a->d; |
| bp = b->d; |
| rp = r->d; |
| |
| borrow = bn_sub_words(rp, ap, bp, min); |
| ap += min; |
| rp += min; |
| |
| while (dif) { |
| dif--; |
| t1 = *(ap++); |
| t2 = (t1 - borrow) & BN_MASK2; |
| *(rp++) = t2; |
| borrow &= (t1 == 0); |
| } |
| |
| while (max && *--rp == 0) |
| max--; |
| |
| r->top = max; |
| r->neg = 0; |
| bn_pollute(r); |
| |
| return 1; |
| } |
| |