shift.c revision d5c2215355e1ae960be386b0d69aed228102cdae 
1/* Copyright (C) 1995-1998 Eric Young (eay@cryptsoft.com)
2 * All rights reserved.
3 *
4 * This package is an SSL implementation written
5 * by Eric Young (eay@cryptsoft.com).
6 * The implementation was written so as to conform with Netscapes SSL.
7 *
8 * This library is free for commercial and non-commercial use as long as
9 * the following conditions are aheared to.  The following conditions
10 * apply to all code found in this distribution, be it the RC4, RSA,
11 * lhash, DES, etc., code; not just the SSL code.  The SSL documentation
12 * included with this distribution is covered by the same copyright terms
13 * except that the holder is Tim Hudson (tjh@cryptsoft.com).
14 *
15 * Copyright remains Eric Young's, and as such any Copyright notices in
16 * the code are not to be removed.
17 * If this package is used in a product, Eric Young should be given attribution
18 * as the author of the parts of the library used.
19 * This can be in the form of a textual message at program startup or
20 * in documentation (online or textual) provided with the package.
21 *
22 * Redistribution and use in source and binary forms, with or without
23 * modification, are permitted provided that the following conditions
24 * are met:
25 * 1. Redistributions of source code must retain the copyright
26 *    notice, this list of conditions and the following disclaimer.
27 * 2. Redistributions in binary form must reproduce the above copyright
28 *    notice, this list of conditions and the following disclaimer in the
29 *    documentation and/or other materials provided with the distribution.
30 * 3. All advertising materials mentioning features or use of this software
31 *    must display the following acknowledgement:
32 *    "This product includes cryptographic software written by
33 *     Eric Young (eay@cryptsoft.com)"
34 *    The word 'cryptographic' can be left out if the rouines from the library
35 *    being used are not cryptographic related :-).
36 * 4. If you include any Windows specific code (or a derivative thereof) from
37 *    the apps directory (application code) you must include an acknowledgement:
38 *    "This product includes software written by Tim Hudson (tjh@cryptsoft.com)"
39 *
40 * THIS SOFTWARE IS PROVIDED BY ERIC YOUNG ``AS IS'' AND
41 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
42 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
43 * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
44 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
45 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
46 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
47 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
48 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
49 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
50 * SUCH DAMAGE.
51 *
52 * The licence and distribution terms for any publically available version or
53 * derivative of this code cannot be changed.  i.e. this code cannot simply be
54 * copied and put under another distribution licence
55 * [including the GNU Public Licence.] */
56
57#include <openssl/bn.h>
58
59#include <string.h>
60
61#include <openssl/err.h>
62
63#include "internal.h"
64
65
66int BN_lshift(BIGNUM *r, const BIGNUM *a, int n) {
67  int i, nw, lb, rb;
68  BN_ULONG *t, *f;
69  BN_ULONG l;
70
71  if (n < 0) {
72    OPENSSL_PUT_ERROR(BN, BN_R_NEGATIVE_NUMBER);
73    return 0;
74  }
75
76  r->neg = a->neg;
77  nw = n / BN_BITS2;
78  if (!bn_wexpand(r, a->top + nw + 1)) {
79    return 0;
80  }
81  lb = n % BN_BITS2;
82  rb = BN_BITS2 - lb;
83  f = a->d;
84  t = r->d;
85  t[a->top + nw] = 0;
86  if (lb == 0) {
87    for (i = a->top - 1; i >= 0; i--) {
88      t[nw + i] = f[i];
89    }
90  } else {
91    for (i = a->top - 1; i >= 0; i--) {
92      l = f[i];
93      t[nw + i + 1] |= l >> rb;
94      t[nw + i] = l << lb;
95    }
96  }
97  OPENSSL_memset(t, 0, nw * sizeof(t[0]));
98  r->top = a->top + nw + 1;
99  bn_correct_top(r);
100
101  return 1;
102}
103
104int BN_lshift1(BIGNUM *r, const BIGNUM *a) {
105  BN_ULONG *ap, *rp, t, c;
106  int i;
107
108  if (r != a) {
109    r->neg = a->neg;
110    if (!bn_wexpand(r, a->top + 1)) {
111      return 0;
112    }
113    r->top = a->top;
114  } else {
115    if (!bn_wexpand(r, a->top + 1)) {
116      return 0;
117    }
118  }
119  ap = a->d;
120  rp = r->d;
121  c = 0;
122  for (i = 0; i < a->top; i++) {
123    t = *(ap++);
124    *(rp++) = (t << 1) | c;
125    c = t >> (BN_BITS2 - 1);
126  }
127  if (c) {
128    *rp = 1;
129    r->top++;
130  }
131
132  return 1;
133}
134
135int BN_rshift(BIGNUM *r, const BIGNUM *a, int n) {
136  int i, j, nw, lb, rb;
137  BN_ULONG *t, *f;
138  BN_ULONG l, tmp;
139
140  if (n < 0) {
141    OPENSSL_PUT_ERROR(BN, BN_R_NEGATIVE_NUMBER);
142    return 0;
143  }
144
145  nw = n / BN_BITS2;
146  rb = n % BN_BITS2;
147  lb = BN_BITS2 - rb;
148  if (nw >= a->top || a->top == 0) {
149    BN_zero(r);
150    return 1;
151  }
152  i = (BN_num_bits(a) - n + (BN_BITS2 - 1)) / BN_BITS2;
153  if (r != a) {
154    r->neg = a->neg;
155    if (!bn_wexpand(r, i)) {
156      return 0;
157    }
158  } else {
159    if (n == 0) {
160      return 1;  // or the copying loop will go berserk
161    }
162  }
163
164  f = &(a->d[nw]);
165  t = r->d;
166  j = a->top - nw;
167  r->top = i;
168
169  if (rb == 0) {
170    for (i = j; i != 0; i--) {
171      *(t++) = *(f++);
172    }
173  } else {
174    l = *(f++);
175    for (i = j - 1; i != 0; i--) {
176      tmp = l >> rb;
177      l = *(f++);
178      *(t++) = tmp | (l << lb);
179    }
180    l >>= rb;
181    if (l) {
182      *(t) = l;
183    }
184  }
185
186  if (r->top == 0) {
187    r->neg = 0;
188  }
189
190  return 1;
191}
192
193int BN_rshift1(BIGNUM *r, const BIGNUM *a) {
194  BN_ULONG *ap, *rp, t, c;
195  int i, j;
196
197  if (BN_is_zero(a)) {
198    BN_zero(r);
199    return 1;
200  }
201  i = a->top;
202  ap = a->d;
203  j = i - (ap[i - 1] == 1);
204  if (a != r) {
205    if (!bn_wexpand(r, j)) {
206      return 0;
207    }
208    r->neg = a->neg;
209  }
210  rp = r->d;
211  t = ap[--i];
212  c = t << (BN_BITS2 - 1);
213  if (t >>= 1) {
214    rp[i] = t;
215  }
216  while (i > 0) {
217    t = ap[--i];
218    rp[i] = (t >> 1) | c;
219    c = t << (BN_BITS2 - 1);
220  }
221  r->top = j;
222
223  if (r->top == 0) {
224    r->neg = 0;
225  }
226
227  return 1;
228}
229
230int BN_set_bit(BIGNUM *a, int n) {
231  if (n < 0) {
232    return 0;
233  }
234
235  int i = n / BN_BITS2;
236  int j = n % BN_BITS2;
237  if (a->top <= i) {
238    if (!bn_wexpand(a, i + 1)) {
239      return 0;
240    }
241    for (int k = a->top; k < i + 1; k++) {
242      a->d[k] = 0;
243    }
244    a->top = i + 1;
245  }
246
247  a->d[i] |= (((BN_ULONG)1) << j);
248
249  return 1;
250}
251
252int BN_clear_bit(BIGNUM *a, int n) {
253  int i, j;
254
255  if (n < 0) {
256    return 0;
257  }
258
259  i = n / BN_BITS2;
260  j = n % BN_BITS2;
261  if (a->top <= i) {
262    return 0;
263  }
264
265  a->d[i] &= (~(((BN_ULONG)1) << j));
266  bn_correct_top(a);
267  return 1;
268}
269
270int BN_is_bit_set(const BIGNUM *a, int n) {
271  if (n < 0) {
272    return 0;
273  }
274  int i = n / BN_BITS2;
275  int j = n % BN_BITS2;
276  if (a->top <= i) {
277    return 0;
278  }
279
280  return (a->d[i]>>j)&1;
281}
282
283int BN_mask_bits(BIGNUM *a, int n) {
284  if (n < 0) {
285    return 0;
286  }
287
288  int w = n / BN_BITS2;
289  int b = n % BN_BITS2;
290  if (w >= a->top) {
291    return 0;
292  }
293  if (b == 0) {
294    a->top = w;
295  } else {
296    a->top = w + 1;
297    a->d[w] &= ~(BN_MASK2 << b);
298  }
299
300  bn_correct_top(a);
301  return 1;
302}
303