1 /*
2 * mplogic.c
3 *
4 * Bitwise logical operations on MPI values
5 *
6 * ***** BEGIN LICENSE BLOCK *****
7 * Version: MPL 1.1/GPL 2.0/LGPL 2.1
8 *
9 * The contents of this file are subject to the Mozilla Public License Version
10 * 1.1 (the "License"); you may not use this file except in compliance with
11 * the License. You may obtain a copy of the License at
12 * http://www.mozilla.org/MPL/
13 *
14 * Software distributed under the License is distributed on an "AS IS" basis,
15 * WITHOUT WARRANTY OF ANY KIND, either express or implied. See the License
16 * for the specific language governing rights and limitations under the
17 * License.
18 *
19 * The Original Code is the MPI Arbitrary Precision Integer Arithmetic library.
20 *
21 * The Initial Developer of the Original Code is
22 * Michael J. Fromberger.
23 * Portions created by the Initial Developer are Copyright (C) 1998
24 * the Initial Developer. All Rights Reserved.
25 *
26 * Contributor(s):
27 *
28 * Alternatively, the contents of this file may be used under the terms of
29 * either the GNU General Public License Version 2 or later (the "GPL"), or
30 * the GNU Lesser General Public License Version 2.1 or later (the "LGPL"),
31 * in which case the provisions of the GPL or the LGPL are applicable instead
32 * of those above. If you wish to allow use of your version of this file only
33 * under the terms of either the GPL or the LGPL, and not to allow others to
34 * use your version of this file under the terms of the MPL, indicate your
35 * decision by deleting the provisions above and replace them with the notice
36 * and other provisions required by the GPL or the LGPL. If you do not delete
37 * the provisions above, a recipient may use your version of this file under
38 * the terms of any one of the MPL, the GPL or the LGPL.
39 *
40 * ***** END LICENSE BLOCK ***** */
41 /*
42 * Copyright 2007 Sun Microsystems, Inc. All rights reserved.
43 * Use is subject to license terms.
44 *
45 * Sun elects to use this software under the MPL license.
46 */
47
48 /* $Id: mplogic.c,v 1.15 2004/04/27 23:04:36 gerv%gerv.net Exp $ */
49
50 #include "mpi-priv.h"
51 #include "mplogic.h"
52
53 /* {{{ Lookup table for population count */
54
55 static unsigned char bitc[] = {
56 0, 1, 1, 2, 1, 2, 2, 3, 1, 2, 2, 3, 2, 3, 3, 4,
57 1, 2, 2, 3, 2, 3, 3, 4, 2, 3, 3, 4, 3, 4, 4, 5,
58 1, 2, 2, 3, 2, 3, 3, 4, 2, 3, 3, 4, 3, 4, 4, 5,
59 2, 3, 3, 4, 3, 4, 4, 5, 3, 4, 4, 5, 4, 5, 5, 6,
60 1, 2, 2, 3, 2, 3, 3, 4, 2, 3, 3, 4, 3, 4, 4, 5,
61 2, 3, 3, 4, 3, 4, 4, 5, 3, 4, 4, 5, 4, 5, 5, 6,
62 2, 3, 3, 4, 3, 4, 4, 5, 3, 4, 4, 5, 4, 5, 5, 6,
63 3, 4, 4, 5, 4, 5, 5, 6, 4, 5, 5, 6, 5, 6, 6, 7,
64 1, 2, 2, 3, 2, 3, 3, 4, 2, 3, 3, 4, 3, 4, 4, 5,
65 2, 3, 3, 4, 3, 4, 4, 5, 3, 4, 4, 5, 4, 5, 5, 6,
66 2, 3, 3, 4, 3, 4, 4, 5, 3, 4, 4, 5, 4, 5, 5, 6,
67 3, 4, 4, 5, 4, 5, 5, 6, 4, 5, 5, 6, 5, 6, 6, 7,
68 2, 3, 3, 4, 3, 4, 4, 5, 3, 4, 4, 5, 4, 5, 5, 6,
69 3, 4, 4, 5, 4, 5, 5, 6, 4, 5, 5, 6, 5, 6, 6, 7,
70 3, 4, 4, 5, 4, 5, 5, 6, 4, 5, 5, 6, 5, 6, 6, 7,
71 4, 5, 5, 6, 5, 6, 6, 7, 5, 6, 6, 7, 6, 7, 7, 8
72 };
73
74 /* }}} */
75
76 /*
77 mpl_rsh(a, b, d) - b = a >> d
78 mpl_lsh(a, b, d) - b = a << d
79 */
80
81 /* {{{ mpl_rsh(a, b, d) */
82
mpl_rsh(const mp_int * a,mp_int * b,mp_digit d)83 mp_err mpl_rsh(const mp_int *a, mp_int *b, mp_digit d)
84 {
85 mp_err res;
86
87 ARGCHK(a != NULL && b != NULL, MP_BADARG);
88
89 if((res = mp_copy(a, b)) != MP_OKAY)
90 return res;
91
92 s_mp_div_2d(b, d);
93
94 return MP_OKAY;
95
96 } /* end mpl_rsh() */
97
98 /* }}} */
99
100 /* {{{ mpl_lsh(a, b, d) */
101
mpl_lsh(const mp_int * a,mp_int * b,mp_digit d)102 mp_err mpl_lsh(const mp_int *a, mp_int *b, mp_digit d)
103 {
104 mp_err res;
105
106 ARGCHK(a != NULL && b != NULL, MP_BADARG);
107
108 if((res = mp_copy(a, b)) != MP_OKAY)
109 return res;
110
111 return s_mp_mul_2d(b, d);
112
113 } /* end mpl_lsh() */
114
115 /* }}} */
116
117 /*------------------------------------------------------------------------*/
118 /*
119 mpl_set_bit
120
121 Returns MP_OKAY or some error code.
122 Grows a if needed to set a bit to 1.
123 */
mpl_set_bit(mp_int * a,mp_size bitNum,mp_size value)124 mp_err mpl_set_bit(mp_int *a, mp_size bitNum, mp_size value)
125 {
126 mp_size ix;
127 mp_err rv;
128 mp_digit mask;
129
130 ARGCHK(a != NULL, MP_BADARG);
131
132 ix = bitNum / MP_DIGIT_BIT;
133 if (ix + 1 > MP_USED(a)) {
134 rv = s_mp_pad(a, ix + 1);
135 if (rv != MP_OKAY)
136 return rv;
137 }
138
139 bitNum = bitNum % MP_DIGIT_BIT;
140 mask = (mp_digit)1 << bitNum;
141 if (value)
142 MP_DIGIT(a,ix) |= mask;
143 else
144 MP_DIGIT(a,ix) &= ~mask;
145 s_mp_clamp(a);
146 return MP_OKAY;
147 }
148
149 /*
150 mpl_get_bit
151
152 returns 0 or 1 or some (negative) error code.
153 */
mpl_get_bit(const mp_int * a,mp_size bitNum)154 mp_err mpl_get_bit(const mp_int *a, mp_size bitNum)
155 {
156 mp_size bit, ix;
157 mp_err rv;
158
159 ARGCHK(a != NULL, MP_BADARG);
160
161 ix = bitNum / MP_DIGIT_BIT;
162 ARGCHK(ix <= MP_USED(a) - 1, MP_RANGE);
163
164 bit = bitNum % MP_DIGIT_BIT;
165 rv = (mp_err)(MP_DIGIT(a, ix) >> bit) & 1;
166 return rv;
167 }
168
169 /*
170 mpl_get_bits
171 - Extracts numBits bits from a, where the least significant extracted bit
172 is bit lsbNum. Returns a negative value if error occurs.
173 - Because sign bit is used to indicate error, maximum number of bits to
174 be returned is the lesser of (a) the number of bits in an mp_digit, or
175 (b) one less than the number of bits in an mp_err.
176 - lsbNum + numbits can be greater than the number of significant bits in
177 integer a, as long as bit lsbNum is in the high order digit of a.
178 */
mpl_get_bits(const mp_int * a,mp_size lsbNum,mp_size numBits)179 mp_err mpl_get_bits(const mp_int *a, mp_size lsbNum, mp_size numBits)
180 {
181 mp_size rshift = (lsbNum % MP_DIGIT_BIT);
182 mp_size lsWndx = (lsbNum / MP_DIGIT_BIT);
183 mp_digit * digit = MP_DIGITS(a) + lsWndx;
184 mp_digit mask = ((1 << numBits) - 1);
185
186 ARGCHK(numBits < CHAR_BIT * sizeof mask, MP_BADARG);
187 ARGCHK(MP_HOWMANY(lsbNum, MP_DIGIT_BIT) <= MP_USED(a), MP_RANGE);
188
189 if ((numBits + lsbNum % MP_DIGIT_BIT <= MP_DIGIT_BIT) ||
190 (lsWndx + 1 >= MP_USED(a))) {
191 mask &= (digit[0] >> rshift);
192 } else {
193 mask &= ((digit[0] >> rshift) | (digit[1] << (MP_DIGIT_BIT - rshift)));
194 }
195 return (mp_err)mask;
196 }
197
198 /*
199 mpl_significant_bits
200 returns number of significnant bits in abs(a).
201 returns 1 if value is zero.
202 */
mpl_significant_bits(const mp_int * a)203 mp_err mpl_significant_bits(const mp_int *a)
204 {
205 mp_err bits = 0;
206 int ix;
207
208 ARGCHK(a != NULL, MP_BADARG);
209
210 ix = MP_USED(a);
211 for (ix = MP_USED(a); ix > 0; ) {
212 mp_digit d;
213 d = MP_DIGIT(a, --ix);
214 if (d) {
215 while (d) {
216 ++bits;
217 d >>= 1;
218 }
219 break;
220 }
221 }
222 bits += ix * MP_DIGIT_BIT;
223 if (!bits)
224 bits = 1;
225 return bits;
226 }
227
228 /*------------------------------------------------------------------------*/
229 /* HERE THERE BE DRAGONS */
230