early-access version 1255
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218
externals/libressl/crypto/bn/bn_shift.c
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externals/libressl/crypto/bn/bn_shift.c
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/* $OpenBSD: bn_shift.c,v 1.13 2014/10/28 07:35:58 jsg 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 <string.h>
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#include "bn_lcl.h"
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int
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BN_lshift1(BIGNUM *r, const BIGNUM *a)
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{
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BN_ULONG *ap, *rp, t, c;
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int i;
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bn_check_top(r);
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bn_check_top(a);
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if (r != a) {
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r->neg = a->neg;
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if (bn_wexpand(r, a->top + 1) == NULL)
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return (0);
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r->top = a->top;
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} else {
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if (bn_wexpand(r, a->top + 1) == NULL)
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return (0);
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}
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ap = a->d;
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rp = r->d;
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c = 0;
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for (i = 0; i < a->top; i++) {
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t= *(ap++);
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*(rp++) = ((t << 1) | c) & BN_MASK2;
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c = (t & BN_TBIT) ? 1 : 0;
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}
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if (c) {
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*rp = 1;
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r->top++;
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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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int
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BN_rshift1(BIGNUM *r, const BIGNUM *a)
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{
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BN_ULONG *ap, *rp, t, c;
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int i, j;
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bn_check_top(r);
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bn_check_top(a);
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if (BN_is_zero(a)) {
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BN_zero(r);
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return (1);
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}
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i = a->top;
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ap = a->d;
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j = i - (ap[i - 1]==1);
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if (a != r) {
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if (bn_wexpand(r, j) == NULL)
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return (0);
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r->neg = a->neg;
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}
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rp = r->d;
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t = ap[--i];
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c = (t & 1) ? BN_TBIT : 0;
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if (t >>= 1)
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rp[i] = t;
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while (i > 0) {
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t = ap[--i];
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rp[i] = ((t >> 1) & BN_MASK2) | c;
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c = (t & 1) ? BN_TBIT : 0;
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}
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r->top = j;
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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_lshift(BIGNUM *r, const BIGNUM *a, int n)
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{
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int i, nw, lb, rb;
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BN_ULONG *t, *f;
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BN_ULONG l;
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bn_check_top(r);
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bn_check_top(a);
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r->neg = a->neg;
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nw = n / BN_BITS2;
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if (bn_wexpand(r, a->top + nw + 1) == NULL)
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return (0);
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lb = n % BN_BITS2;
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rb = BN_BITS2 - lb;
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f = a->d;
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t = r->d;
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t[a->top + nw] = 0;
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if (lb == 0)
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for (i = a->top - 1; i >= 0; i--)
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t[nw + i] = f[i];
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else
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for (i = a->top - 1; i >= 0; i--) {
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l = f[i];
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t[nw + i + 1] |= (l >> rb) & BN_MASK2;
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t[nw + i] = (l << lb) & BN_MASK2;
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}
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memset(t, 0, nw * sizeof(t[0]));
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/* for (i=0; i<nw; i++)
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t[i]=0;*/
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r->top = a->top + nw + 1;
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bn_correct_top(r);
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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_rshift(BIGNUM *r, const BIGNUM *a, int n)
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{
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int i, j, nw, lb, rb;
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BN_ULONG *t, *f;
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BN_ULONG l, tmp;
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bn_check_top(r);
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bn_check_top(a);
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nw = n / BN_BITS2;
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rb = n % BN_BITS2;
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lb = BN_BITS2 - rb;
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if (nw >= a->top || a->top == 0) {
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BN_zero(r);
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return (1);
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}
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i = (BN_num_bits(a) - n + (BN_BITS2 - 1)) / BN_BITS2;
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if (r != a) {
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r->neg = a->neg;
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if (bn_wexpand(r, i) == NULL)
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return (0);
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} else {
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if (n == 0)
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return 1; /* or the copying loop will go berserk */
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}
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f = &(a->d[nw]);
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t = r->d;
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j = a->top - nw;
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r->top = i;
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if (rb == 0) {
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for (i = j; i != 0; i--)
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*(t++) = *(f++);
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} else {
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l = *(f++);
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for (i = j - 1; i != 0; i--) {
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tmp = (l >> rb) & BN_MASK2;
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l = *(f++);
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*(t++) = (tmp|(l << lb)) & BN_MASK2;
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}
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if ((l = (l >> rb) & BN_MASK2))
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*(t) = l;
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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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