yuzu/externals/libressl/crypto/bn/bn_add.c

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2020-12-28 19:15:37 +04:00
/* $OpenBSD: bn_add.c,v 1.13 2018/07/23 18:07:21 tb Exp $ */
/* 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 <openssl/err.h>
#include "bn_lcl.h"
int
BN_add(BIGNUM *r, const BIGNUM *a, const BIGNUM *b)
{
int ret, r_neg;
bn_check_top(a);
bn_check_top(b);
if (a->neg == b->neg) {
r_neg = a->neg;
ret = BN_uadd(r, a, b);
} else {
int cmp = BN_ucmp(a, b);
if (cmp > 0) {
r_neg = a->neg;
ret = BN_usub(r, a, b);
} else if (cmp < 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;
}
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;
}
int
BN_usub(BIGNUM *r, const BIGNUM *a, const BIGNUM *b)
{
int max, min, dif;
const BN_ULONG *ap, *bp;
BN_ULONG t1, t2, borrow, *rp;
bn_check_top(a);
bn_check_top(b);
max = a->top;
min = b->top;
dif = max - min;
if (dif < 0) {
BNerror(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 > 0 && *--rp == 0)
max--;
r->top = max;
r->neg = 0;
bn_correct_top(r);
return 1;
}
int
BN_sub(BIGNUM *r, const BIGNUM *a, const BIGNUM *b)
{
int ret, r_neg;
bn_check_top(a);
bn_check_top(b);
if (a->neg != b->neg) {
r_neg = a->neg;
ret = BN_uadd(r, a, b);
} else {
int cmp = BN_ucmp(a, b);
if (cmp > 0) {
r_neg = a->neg;
ret = BN_usub(r, a, b);
} else if (cmp < 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;
}