mplogic.c

/* *********************************************************************
 *
 * Sun elects to have this file available under and governed by the
 * Mozilla Public License Version 1.1 ("MPL") (see
 * http://www.mozilla.org/MPL/ for full license text). For the avoidance
 * of doubt and subject to the following, Sun also elects to allow
 * licensees to use this file under the MPL, the GNU General Public
 * License version 2 only or the Lesser General Public License version
 * 2.1 only. Any references to the "GNU General Public License version 2
 * or later" or "GPL" in the following shall be construed to mean the
 * GNU General Public License version 2 only. Any references to the "GNU
 * Lesser General Public License version 2.1 or later" or "LGPL" in the
 * following shall be construed to mean the GNU Lesser General Public
 * License version 2.1 only. However, the following notice accompanied
 * the original version of this file:
 *
 *
 *  Bitwise logical operations on MPI values
 *
 * Version: MPL 1.1/GPL 2.0/LGPL 2.1
 *
 * The contents of this file are subject to the Mozilla Public License Version
 * 1.1 (the "License"); you may not use this file except in compliance with
 * the License. You may obtain a copy of the License at
 * http://www.mozilla.org/MPL/
 *
 * Software distributed under the License is distributed on an "AS IS" basis,
 * WITHOUT WARRANTY OF ANY KIND, either express or implied. See the License
 * for the specific language governing rights and limitations under the
 * License.
 *
 * The Original Code is the MPI Arbitrary Precision Integer Arithmetic library.
 *
 * The Initial Developer of the Original Code is
 * Michael J. Fromberger.
 * Portions created by the Initial Developer are Copyright (C) 1998
 * the Initial Developer. All Rights Reserved.
 *
 * Contributor(s):
 *
 * Alternatively, the contents of this file may be used under the terms of
 * either the GNU General Public License Version 2 or later (the "GPL"), or
 * the GNU Lesser General Public License Version 2.1 or later (the "LGPL"),
 * in which case the provisions of the GPL or the LGPL are applicable instead
 * of those above. If you wish to allow use of your version of this file only
 * under the terms of either the GPL or the LGPL, and not to allow others to
 * use your version of this file under the terms of the MPL, indicate your
 * decision by deleting the provisions above and replace them with the notice
 * and other provisions required by the GPL or the LGPL. If you do not delete
 * the provisions above, a recipient may use your version of this file under
 * the terms of any one of the MPL, the GPL or the LGPL.
 *
 *********************************************************************** */
/*
 * Copyright (c) 2007, Oracle and/or its affiliates. All rights reserved.
 * Use is subject to license terms.
 */

/* $Id: mplogic.c,v 1.15 2004/04/27 23:04:36 gerv%gerv.net Exp $ */

#include "mpi-priv.h"
#include "mplogic.h"

/* {{{ Lookup table for population count */

static unsigned char bitc[] = {
   0, 1, 1, 2, 1, 2, 2, 3, 1, 2, 2, 3, 2, 3, 3, 4,
   1, 2, 2, 3, 2, 3, 3, 4, 2, 3, 3, 4, 3, 4, 4, 5,
   1, 2, 2, 3, 2, 3, 3, 4, 2, 3, 3, 4, 3, 4, 4, 5,
   2, 3, 3, 4, 3, 4, 4, 5, 3, 4, 4, 5, 4, 5, 5, 6,
   1, 2, 2, 3, 2, 3, 3, 4, 2, 3, 3, 4, 3, 4, 4, 5,
   2, 3, 3, 4, 3, 4, 4, 5, 3, 4, 4, 5, 4, 5, 5, 6,
   2, 3, 3, 4, 3, 4, 4, 5, 3, 4, 4, 5, 4, 5, 5, 6,
   3, 4, 4, 5, 4, 5, 5, 6, 4, 5, 5, 6, 5, 6, 6, 7,
   1, 2, 2, 3, 2, 3, 3, 4, 2, 3, 3, 4, 3, 4, 4, 5,
   2, 3, 3, 4, 3, 4, 4, 5, 3, 4, 4, 5, 4, 5, 5, 6,
   2, 3, 3, 4, 3, 4, 4, 5, 3, 4, 4, 5, 4, 5, 5, 6,
   3, 4, 4, 5, 4, 5, 5, 6, 4, 5, 5, 6, 5, 6, 6, 7,
   2, 3, 3, 4, 3, 4, 4, 5, 3, 4, 4, 5, 4, 5, 5, 6,
   3, 4, 4, 5, 4, 5, 5, 6, 4, 5, 5, 6, 5, 6, 6, 7,
   3, 4, 4, 5, 4, 5, 5, 6, 4, 5, 5, 6, 5, 6, 6, 7,
   4, 5, 5, 6, 5, 6, 6, 7, 5, 6, 6, 7, 6, 7, 7, 8
};

/* }}} */

/*
  mpl_rsh(a, b, d)     - b = a >> d
  mpl_lsh(a, b, d)     - b = a << d
 */

/* {{{ mpl_rsh(a, b, d) */

mp_err mpl_rsh(const mp_int *a, mp_int *b, mp_digit d)
{
  mp_err   res;

  ARGCHK(a != NULL && b != NULL, MP_BADARG);

  if((res = mp_copy(a, b)) != MP_OKAY)
    return res;

  s_mp_div_2d(b, d);

  return MP_OKAY;

} /* end mpl_rsh() */

/* }}} */

/* {{{ mpl_lsh(a, b, d) */

mp_err mpl_lsh(const mp_int *a, mp_int *b, mp_digit d)
{
  mp_err   res;

  ARGCHK(a != NULL && b != NULL, MP_BADARG);

  if((res = mp_copy(a, b)) != MP_OKAY)
    return res;

  return s_mp_mul_2d(b, d);

} /* end mpl_lsh() */

/* }}} */

/*------------------------------------------------------------------------*/
/*
  mpl_set_bit

  Returns MP_OKAY or some error code.
  Grows a if needed to set a bit to 1.
 */
mp_err mpl_set_bit(mp_int *a, mp_size bitNum, mp_size value)
{
  mp_size      ix;
  mp_err       rv;
  mp_digit     mask;

  ARGCHK(a != NULL, MP_BADARG);

  ix = bitNum / MP_DIGIT_BIT;
  if (ix + 1 > MP_USED(a)) {
    rv = s_mp_pad(a, ix + 1);
    if (rv != MP_OKAY)
      return rv;
  }

  bitNum = bitNum % MP_DIGIT_BIT;
  mask = (mp_digit)1 << bitNum;
  if (value)
    MP_DIGIT(a,ix) |= mask;
  else
    MP_DIGIT(a,ix) &= ~mask;
  s_mp_clamp(a);
  return MP_OKAY;
}

/*
  mpl_get_bit

  returns 0 or 1 or some (negative) error code.
 */
mp_err mpl_get_bit(const mp_int *a, mp_size bitNum)
{
  mp_size      bit, ix;
  mp_err       rv;

  ARGCHK(a != NULL, MP_BADARG);

  ix = bitNum / MP_DIGIT_BIT;
  ARGCHK(ix <= MP_USED(a) - 1, MP_RANGE);

  bit   = bitNum % MP_DIGIT_BIT;
  rv = (mp_err)(MP_DIGIT(a, ix) >> bit) & 1;
  return rv;
}

/*
  mpl_get_bits
  - Extracts numBits bits from a, where the least significant extracted bit
  is bit lsbNum.  Returns a negative value if error occurs.
  - Because sign bit is used to indicate error, maximum number of bits to
  be returned is the lesser of (a) the number of bits in an mp_digit, or
  (b) one less than the number of bits in an mp_err.
  - lsbNum + numbits can be greater than the number of significant bits in
  integer a, as long as bit lsbNum is in the high order digit of a.
 */
mp_err mpl_get_bits(const mp_int *a, mp_size lsbNum, mp_size numBits)
{
  mp_size    rshift = (lsbNum % MP_DIGIT_BIT);
  mp_size    lsWndx = (lsbNum / MP_DIGIT_BIT);
  mp_digit * digit  = MP_DIGITS(a) + lsWndx;
  mp_digit   mask   = ((1 << numBits) - 1);

  ARGCHK(numBits < CHAR_BIT * sizeof mask, MP_BADARG);
  ARGCHK(MP_HOWMANY(lsbNum, MP_DIGIT_BIT) <= MP_USED(a), MP_RANGE);

  if ((numBits + lsbNum % MP_DIGIT_BIT <= MP_DIGIT_BIT) ||
      (lsWndx + 1 >= MP_USED(a))) {
    mask &= (digit[0] >> rshift);
  } else {
    mask &= ((digit[0] >> rshift) | (digit[1] << (MP_DIGIT_BIT - rshift)));
  }
  return (mp_err)mask;
}

/*
  mpl_significant_bits
  returns number of significnant bits in abs(a).
  returns 1 if value is zero.
 */
mp_err mpl_significant_bits(const mp_int *a)
{
  mp_err bits   = 0;
  int    ix;

  ARGCHK(a != NULL, MP_BADARG);

  ix = MP_USED(a);
  for (ix = MP_USED(a); ix > 0; ) {
    mp_digit d;
    d = MP_DIGIT(a, --ix);
    if (d) {
      while (d) {
        ++bits;
        d >>= 1;
      }
      break;
    }
  }
  bits += ix * MP_DIGIT_BIT;
  if (!bits)
    bits = 1;
  return bits;
}

/*------------------------------------------------------------------------*/
/* HERE THERE BE DRAGONS                                                  */