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224 lines
5.4 KiB
C
224 lines
5.4 KiB
C
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/* $OpenBSD: bn_add.c,v 1.13 2018/07/23 18:07:21 tb Exp $ */
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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 <openssl/err.h>
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#include "bn_lcl.h"
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int
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BN_add(BIGNUM *r, const BIGNUM *a, const BIGNUM *b)
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{
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int ret, r_neg;
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bn_check_top(a);
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bn_check_top(b);
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if (a->neg == b->neg) {
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r_neg = a->neg;
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ret = BN_uadd(r, a, b);
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} else {
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int cmp = BN_ucmp(a, b);
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if (cmp > 0) {
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r_neg = a->neg;
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ret = BN_usub(r, a, b);
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} else if (cmp < 0) {
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r_neg = b->neg;
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ret = BN_usub(r, b, a);
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} else {
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r_neg = 0;
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BN_zero(r);
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ret = 1;
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}
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}
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r->neg = r_neg;
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bn_check_top(r);
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return ret;
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}
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int
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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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const BN_ULONG *ap, *bp;
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BN_ULONG *rp, carry, t1, t2;
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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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const BIGNUM *tmp;
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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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while (dif) {
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dif--;
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t1 = *(ap++);
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t2 = (t1 + carry) & BN_MASK2;
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*(rp++) = t2;
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carry &= (t2 == 0);
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}
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*rp = carry;
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r->top += carry;
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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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int
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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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const BN_ULONG *ap, *bp;
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BN_ULONG t1, t2, borrow, *rp;
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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) {
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BNerror(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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borrow = bn_sub_words(rp, ap, bp, min);
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ap += min;
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rp += min;
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while (dif) {
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dif--;
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t1 = *(ap++);
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t2 = (t1 - borrow) & BN_MASK2;
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*(rp++) = t2;
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borrow &= (t1 == 0);
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}
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while (max > 0 && *--rp == 0)
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max--;
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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
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BN_sub(BIGNUM *r, const BIGNUM *a, const BIGNUM *b)
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{
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int ret, r_neg;
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bn_check_top(a);
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bn_check_top(b);
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if (a->neg != b->neg) {
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r_neg = a->neg;
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ret = BN_uadd(r, a, b);
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} else {
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int cmp = BN_ucmp(a, b);
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if (cmp > 0) {
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r_neg = a->neg;
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ret = BN_usub(r, a, b);
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} else if (cmp < 0) {
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r_neg = !b->neg;
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ret = BN_usub(r, b, a);
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} else {
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r_neg = 0;
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BN_zero(r);
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ret = 1;
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}
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}
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r->neg = r_neg;
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bn_check_top(r);
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return ret;
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}
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