usr/src/common/mpi/mplogic.c

   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
  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
 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  */
 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  */
 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  */
 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  */
 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                                                  */