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 #pragma ident "%Z%%M% %I% %E% SMI"
49
50 /* $Id: mplogic.c,v 1.15 2004/04/27 23:04:36 gerv%gerv.net Exp $ */
51
52 #include "mpi-priv.h"
53 #include "mplogic.h"
54
55 /* {{{ Lookup table for population count */
56
57 static unsigned char bitc[] = {
58 0, 1, 1, 2, 1, 2, 2, 3, 1, 2, 2, 3, 2, 3, 3, 4,
59 1, 2, 2, 3, 2, 3, 3, 4, 2, 3, 3, 4, 3, 4, 4, 5,
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 1, 2, 2, 3, 2, 3, 3, 4, 2, 3, 3, 4, 3, 4, 4, 5,
63 2, 3, 3, 4, 3, 4, 4, 5, 3, 4, 4, 5, 4, 5, 5, 6,
64 2, 3, 3, 4, 3, 4, 4, 5, 3, 4, 4, 5, 4, 5, 5, 6,
65 3, 4, 4, 5, 4, 5, 5, 6, 4, 5, 5, 6, 5, 6, 6, 7,
66 1, 2, 2, 3, 2, 3, 3, 4, 2, 3, 3, 4, 3, 4, 4, 5,
67 2, 3, 3, 4, 3, 4, 4, 5, 3, 4, 4, 5, 4, 5, 5, 6,
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 2, 3, 3, 4, 3, 4, 4, 5, 3, 4, 4, 5, 4, 5, 5, 6,
71 3, 4, 4, 5, 4, 5, 5, 6, 4, 5, 5, 6, 5, 6, 6, 7,
72 3, 4, 4, 5, 4, 5, 5, 6, 4, 5, 5, 6, 5, 6, 6, 7,
73 4, 5, 5, 6, 5, 6, 6, 7, 5, 6, 6, 7, 6, 7, 7, 8
74 };
75
76 /* }}} */
77
78 /*
79 mpl_rsh(a, b, d) - b = a >> d
80 mpl_lsh(a, b, d) - b = a << d
81 */
82
83 /* {{{ mpl_rsh(a, b, d) */
84
mpl_rsh(const mp_int * a,mp_int * b,mp_digit d)85 mp_err mpl_rsh(const mp_int *a, mp_int *b, mp_digit d)
86 {
87 mp_err res;
88
89 ARGCHK(a != NULL && b != NULL, MP_BADARG);
90
91 if((res = mp_copy(a, b)) != MP_OKAY)
92 return res;
93
94 s_mp_div_2d(b, d);
95
96 return MP_OKAY;
97
98 } /* end mpl_rsh() */
99
100 /* }}} */
101
102 /* {{{ mpl_lsh(a, b, d) */
103
mpl_lsh(const mp_int * a,mp_int * b,mp_digit d)104 mp_err mpl_lsh(const mp_int *a, mp_int *b, mp_digit d)
105 {
106 mp_err res;
107
108 ARGCHK(a != NULL && b != NULL, MP_BADARG);
109
110 if((res = mp_copy(a, b)) != MP_OKAY)
111 return res;
112
113 return s_mp_mul_2d(b, d);
114
115 } /* end mpl_lsh() */
116
117 /* }}} */
118
119 /*------------------------------------------------------------------------*/
120 /*
121 mpl_set_bit
122
123 Returns MP_OKAY or some error code.
124 Grows a if needed to set a bit to 1.
125 */
mpl_set_bit(mp_int * a,mp_size bitNum,mp_size value)126 mp_err mpl_set_bit(mp_int *a, mp_size bitNum, mp_size value)
127 {
128 mp_size ix;
129 mp_err rv;
130 mp_digit mask;
131
132 ARGCHK(a != NULL, MP_BADARG);
133
134 ix = bitNum / MP_DIGIT_BIT;
135 if (ix + 1 > MP_USED(a)) {
136 rv = s_mp_pad(a, ix + 1);
137 if (rv != MP_OKAY)
138 return rv;
139 }
140
141 bitNum = bitNum % MP_DIGIT_BIT;
142 mask = (mp_digit)1 << bitNum;
143 if (value)
144 MP_DIGIT(a,ix) |= mask;
145 else
146 MP_DIGIT(a,ix) &= ~mask;
147 s_mp_clamp(a);
148 return MP_OKAY;
149 }
150
151 /*
152 mpl_get_bit
153
154 returns 0 or 1 or some (negative) error code.
155 */
mpl_get_bit(const mp_int * a,mp_size bitNum)156 mp_err mpl_get_bit(const mp_int *a, mp_size bitNum)
157 {
158 mp_size bit, ix;
159 mp_err rv;
160
161 ARGCHK(a != NULL, MP_BADARG);
162
163 ix = bitNum / MP_DIGIT_BIT;
164 ARGCHK(ix <= MP_USED(a) - 1, MP_RANGE);
165
166 bit = bitNum % MP_DIGIT_BIT;
167 rv = (mp_err)(MP_DIGIT(a, ix) >> bit) & 1;
168 return rv;
169 }
170
171 /*
172 mpl_get_bits
173 - Extracts numBits bits from a, where the least significant extracted bit
174 is bit lsbNum. Returns a negative value if error occurs.
175 - Because sign bit is used to indicate error, maximum number of bits to
176 be returned is the lesser of (a) the number of bits in an mp_digit, or
177 (b) one less than the number of bits in an mp_err.
178 - lsbNum + numbits can be greater than the number of significant bits in
179 integer a, as long as bit lsbNum is in the high order digit of a.
180 */
mpl_get_bits(const mp_int * a,mp_size lsbNum,mp_size numBits)181 mp_err mpl_get_bits(const mp_int *a, mp_size lsbNum, mp_size numBits)
182 {
183 mp_size rshift = (lsbNum % MP_DIGIT_BIT);
184 mp_size lsWndx = (lsbNum / MP_DIGIT_BIT);
185 mp_digit * digit = MP_DIGITS(a) + lsWndx;
186 mp_digit mask = ((1 << numBits) - 1);
187
188 ARGCHK(numBits < CHAR_BIT * sizeof mask, MP_BADARG);
189 ARGCHK(MP_HOWMANY(lsbNum, MP_DIGIT_BIT) <= MP_USED(a), MP_RANGE);
190
191 if ((numBits + lsbNum % MP_DIGIT_BIT <= MP_DIGIT_BIT) ||
192 (lsWndx + 1 >= MP_USED(a))) {
193 mask &= (digit[0] >> rshift);
194 } else {
195 mask &= ((digit[0] >> rshift) | (digit[1] << (MP_DIGIT_BIT - rshift)));
196 }
197 return (mp_err)mask;
198 }
199
200 /*
201 mpl_significant_bits
202 returns number of significnant bits in abs(a).
203 returns 1 if value is zero.
204 */
mpl_significant_bits(const mp_int * a)205 mp_err mpl_significant_bits(const mp_int *a)
206 {
207 mp_err bits = 0;
208 int ix;
209
210 ARGCHK(a != NULL, MP_BADARG);
211
212 ix = MP_USED(a);
213 for (ix = MP_USED(a); ix > 0; ) {
214 mp_digit d;
215 d = MP_DIGIT(a, --ix);
216 if (d) {
217 while (d) {
218 ++bits;
219 d >>= 1;
220 }
221 break;
222 }
223 }
224 bits += ix * MP_DIGIT_BIT;
225 if (!bits)
226 bits = 1;
227 return bits;
228 }
229
230 /*------------------------------------------------------------------------*/
231 /* HERE THERE BE DRAGONS */
232