xref: /illumos-gate/usr/src/common/mpi/mplogic.c (revision c40a6cd785e883b3f052b122c332e21174fc1871)
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