openssl1.0/crypto/bn/bn_shift.c
2019-08-09 10:00:55 +02:00

225 lines
6.5 KiB
C

/* crypto/bn/bn_shift.c */
/* 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 "cryptlib.h"
#include "bn_lcl.h"
int BN_lshift1(BIGNUM *r, const BIGNUM *a)
{
register BN_ULONG *ap, *rp, t, c;
int i;
bn_check_top(r);
bn_check_top(a);
if (r != a) {
r->neg = a->neg;
if (bn_wexpand(r, a->top + 1) == NULL)
return (0);
r->top = a->top;
} else {
if (bn_wexpand(r, a->top + 1) == NULL)
return (0);
}
ap = a->d;
rp = r->d;
c = 0;
for (i = 0; i < a->top; i++) {
t = *(ap++);
*(rp++) = ((t << 1) | c) & BN_MASK2;
c = (t & BN_TBIT) ? 1 : 0;
}
if (c) {
*rp = 1;
r->top++;
}
bn_check_top(r);
return (1);
}
int BN_rshift1(BIGNUM *r, const BIGNUM *a)
{
BN_ULONG *ap, *rp, t, c;
int i, j;
bn_check_top(r);
bn_check_top(a);
if (BN_is_zero(a)) {
BN_zero(r);
return (1);
}
i = a->top;
ap = a->d;
j = i - (ap[i - 1] == 1);
if (a != r) {
if (bn_wexpand(r, j) == NULL)
return (0);
r->neg = a->neg;
}
rp = r->d;
t = ap[--i];
c = (t & 1) ? BN_TBIT : 0;
if (t >>= 1)
rp[i] = t;
while (i > 0) {
t = ap[--i];
rp[i] = ((t >> 1) & BN_MASK2) | c;
c = (t & 1) ? BN_TBIT : 0;
}
r->top = j;
bn_check_top(r);
return (1);
}
int BN_lshift(BIGNUM *r, const BIGNUM *a, int n)
{
int i, nw, lb, rb;
BN_ULONG *t, *f;
BN_ULONG l;
bn_check_top(r);
bn_check_top(a);
if (n < 0) {
BNerr(BN_F_BN_LSHIFT, BN_R_INVALID_SHIFT);
return 0;
}
r->neg = a->neg;
nw = n / BN_BITS2;
if (bn_wexpand(r, a->top + nw + 1) == NULL)
return (0);
lb = n % BN_BITS2;
rb = BN_BITS2 - lb;
f = a->d;
t = r->d;
t[a->top + nw] = 0;
if (lb == 0)
for (i = a->top - 1; i >= 0; i--)
t[nw + i] = f[i];
else
for (i = a->top - 1; i >= 0; i--) {
l = f[i];
t[nw + i + 1] |= (l >> rb) & BN_MASK2;
t[nw + i] = (l << lb) & BN_MASK2;
}
memset(t, 0, nw * sizeof(t[0]));
/*
* for (i=0; i<nw; i++) t[i]=0;
*/
r->top = a->top + nw + 1;
bn_correct_top(r);
bn_check_top(r);
return (1);
}
int BN_rshift(BIGNUM *r, const BIGNUM *a, int n)
{
int i, j, nw, lb, rb;
BN_ULONG *t, *f;
BN_ULONG l, tmp;
bn_check_top(r);
bn_check_top(a);
if (n < 0) {
BNerr(BN_F_BN_RSHIFT, BN_R_INVALID_SHIFT);
return 0;
}
nw = n / BN_BITS2;
rb = n % BN_BITS2;
lb = BN_BITS2 - rb;
if (nw >= a->top || a->top == 0) {
BN_zero(r);
return (1);
}
i = (BN_num_bits(a) - n + (BN_BITS2 - 1)) / BN_BITS2;
if (r != a) {
r->neg = a->neg;
if (bn_wexpand(r, i) == NULL)
return (0);
} else {
if (n == 0)
return 1; /* or the copying loop will go berserk */
}
f = &(a->d[nw]);
t = r->d;
j = a->top - nw;
r->top = i;
if (rb == 0) {
for (i = j; i != 0; i--)
*(t++) = *(f++);
} else {
l = *(f++);
for (i = j - 1; i != 0; i--) {
tmp = (l >> rb) & BN_MASK2;
l = *(f++);
*(t++) = (tmp | (l << lb)) & BN_MASK2;
}
if ((l = (l >> rb) & BN_MASK2))
*(t) = l;
}
bn_check_top(r);
return (1);
}