bn_shift.c revision 296341 
1/* crypto/bn/bn_shift.c */
2/* Copyright (C) 1995-1998 Eric Young (eay@cryptsoft.com)
3 * All rights reserved.
4 *
5 * This package is an SSL implementation written
6 * by Eric Young (eay@cryptsoft.com).
7 * The implementation was written so as to conform with Netscapes SSL.
8 *
9 * This library is free for commercial and non-commercial use as long as
10 * the following conditions are aheared to.  The following conditions
11 * apply to all code found in this distribution, be it the RC4, RSA,
12 * lhash, DES, etc., code; not just the SSL code.  The SSL documentation
13 * included with this distribution is covered by the same copyright terms
14 * except that the holder is Tim Hudson (tjh@cryptsoft.com).
15 *
16 * Copyright remains Eric Young's, and as such any Copyright notices in
17 * the code are not to be removed.
18 * If this package is used in a product, Eric Young should be given attribution
19 * as the author of the parts of the library used.
20 * This can be in the form of a textual message at program startup or
21 * in documentation (online or textual) provided with the package.
22 *
23 * Redistribution and use in source and binary forms, with or without
24 * modification, are permitted provided that the following conditions
25 * are met:
26 * 1. Redistributions of source code must retain the copyright
27 *    notice, this list of conditions and the following disclaimer.
28 * 2. Redistributions in binary form must reproduce the above copyright
29 *    notice, this list of conditions and the following disclaimer in the
30 *    documentation and/or other materials provided with the distribution.
31 * 3. All advertising materials mentioning features or use of this software
32 *    must display the following acknowledgement:
33 *    "This product includes cryptographic software written by
34 *     Eric Young (eay@cryptsoft.com)"
35 *    The word 'cryptographic' can be left out if the rouines from the library
36 *    being used are not cryptographic related :-).
37 * 4. If you include any Windows specific code (or a derivative thereof) from
38 *    the apps directory (application code) you must include an acknowledgement:
39 *    "This product includes software written by Tim Hudson (tjh@cryptsoft.com)"
40 *
41 * THIS SOFTWARE IS PROVIDED BY ERIC YOUNG ``AS IS'' AND
42 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
43 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
44 * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
45 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
46 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
47 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
48 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
49 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
50 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
51 * SUCH DAMAGE.
52 *
53 * The licence and distribution terms for any publically available version or
54 * derivative of this code cannot be changed.  i.e. this code cannot simply be
55 * copied and put under another distribution licence
56 * [including the GNU Public Licence.]
57 */
58
59#include <stdio.h>
60#include "cryptlib.h"
61#include "bn_lcl.h"
62
63int BN_lshift1(BIGNUM *r, const BIGNUM *a)
64{
65    register BN_ULONG *ap, *rp, t, c;
66    int i;
67
68    bn_check_top(r);
69    bn_check_top(a);
70
71    if (r != a) {
72        r->neg = a->neg;
73        if (bn_wexpand(r, a->top + 1) == NULL)
74            return (0);
75        r->top = a->top;
76    } else {
77        if (bn_wexpand(r, a->top + 1) == NULL)
78            return (0);
79    }
80    ap = a->d;
81    rp = r->d;
82    c = 0;
83    for (i = 0; i < a->top; i++) {
84        t = *(ap++);
85        *(rp++) = ((t << 1) | c) & BN_MASK2;
86        c = (t & BN_TBIT) ? 1 : 0;
87    }
88    if (c) {
89        *rp = 1;
90        r->top++;
91    }
92    bn_check_top(r);
93    return (1);
94}
95
96int BN_rshift1(BIGNUM *r, const BIGNUM *a)
97{
98    BN_ULONG *ap, *rp, t, c;
99    int i, j;
100
101    bn_check_top(r);
102    bn_check_top(a);
103
104    if (BN_is_zero(a)) {
105        BN_zero(r);
106        return (1);
107    }
108    i = a->top;
109    ap = a->d;
110    j = i - (ap[i - 1] == 1);
111    if (a != r) {
112        if (bn_wexpand(r, j) == NULL)
113            return (0);
114        r->neg = a->neg;
115    }
116    rp = r->d;
117    t = ap[--i];
118    c = (t & 1) ? BN_TBIT : 0;
119    if (t >>= 1)
120        rp[i] = t;
121    while (i > 0) {
122        t = ap[--i];
123        rp[i] = ((t >> 1) & BN_MASK2) | c;
124        c = (t & 1) ? BN_TBIT : 0;
125    }
126    r->top = j;
127    bn_check_top(r);
128    return (1);
129}
130
131int BN_lshift(BIGNUM *r, const BIGNUM *a, int n)
132{
133    int i, nw, lb, rb;
134    BN_ULONG *t, *f;
135    BN_ULONG l;
136
137    bn_check_top(r);
138    bn_check_top(a);
139
140    if (n < 0) {
141        BNerr(BN_F_BN_LSHIFT, BN_R_INVALID_SHIFT);
142        return 0;
143    }
144
145    r->neg = a->neg;
146    nw = n / BN_BITS2;
147    if (bn_wexpand(r, a->top + nw + 1) == NULL)
148        return (0);
149    lb = n % BN_BITS2;
150    rb = BN_BITS2 - lb;
151    f = a->d;
152    t = r->d;
153    t[a->top + nw] = 0;
154    if (lb == 0)
155        for (i = a->top - 1; i >= 0; i--)
156            t[nw + i] = f[i];
157    else
158        for (i = a->top - 1; i >= 0; i--) {
159            l = f[i];
160            t[nw + i + 1] |= (l >> rb) & BN_MASK2;
161            t[nw + i] = (l << lb) & BN_MASK2;
162        }
163    memset(t, 0, nw * sizeof(t[0]));
164    /*
165     * for (i=0; i<nw; i++) t[i]=0;
166     */
167    r->top = a->top + nw + 1;
168    bn_correct_top(r);
169    bn_check_top(r);
170    return (1);
171}
172
173int BN_rshift(BIGNUM *r, const BIGNUM *a, int n)
174{
175    int i, j, nw, lb, rb;
176    BN_ULONG *t, *f;
177    BN_ULONG l, tmp;
178
179    bn_check_top(r);
180    bn_check_top(a);
181
182    if (n < 0) {
183        BNerr(BN_F_BN_RSHIFT, BN_R_INVALID_SHIFT);
184        return 0;
185    }
186
187    nw = n / BN_BITS2;
188    rb = n % BN_BITS2;
189    lb = BN_BITS2 - rb;
190    if (nw >= a->top || a->top == 0) {
191        BN_zero(r);
192        return (1);
193    }
194    i = (BN_num_bits(a) - n + (BN_BITS2 - 1)) / BN_BITS2;
195    if (r != a) {
196        r->neg = a->neg;
197        if (bn_wexpand(r, i) == NULL)
198            return (0);
199    } else {
200        if (n == 0)
201            return 1;           /* or the copying loop will go berserk */
202    }
203
204    f = &(a->d[nw]);
205    t = r->d;
206    j = a->top - nw;
207    r->top = i;
208
209    if (rb == 0) {
210        for (i = j; i != 0; i--)
211            *(t++) = *(f++);
212    } else {
213        l = *(f++);
214        for (i = j - 1; i != 0; i--) {
215            tmp = (l >> rb) & BN_MASK2;
216            l = *(f++);
217            *(t++) = (tmp | (l << lb)) & BN_MASK2;
218        }
219        if ((l = (l >> rb) & BN_MASK2))
220            *(t) = l;
221    }
222    bn_check_top(r);
223    return (1);
224}
225