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+/*
+ * mplogic.c
+ *
+ * Bitwise logical operations on MPI values
+ *
+ * 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 Michael J. Fromberger are
+ * Copyright (C) 1998, 1999, 2000 Michael J. Fromberger.
+ * All Rights Reserved.
+ *
+ * Contributor(s):
+ *
+ * Alternatively, the contents of this file may be used under the
+ * terms of the GNU General Public License Version 2 or later (the
+ * "GPL"), in which case the provisions of the GPL are applicable
+ * instead of those above. If you wish to allow use of your
+ * version of this file only under the terms of the GPL and not to
+ * allow others to use your version of this file under the MPL,
+ * indicate your decision by deleting the provisions above and
+ * replace them with the notice and other provisions required by
+ * the GPL. If you do not delete the provisions above, a recipient
+ * may use your version of this file under either the MPL or the GPL.
+ *
+ * $Id$
+ */
+
+#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_not(a, b) - compute b = ~a
+ mpl_and(a, b, c) - compute c = a & b
+ mpl_or(a, b, c) - compute c = a | b
+ mpl_xor(a, b, c) - compute c = a ^ b
+ */
+
+/* {{{ mpl_not(a, b) */
+
+mp_err mpl_not(mp_int *a, mp_int *b)
+{
+ mp_err res;
+ int ix;
+
+ ARGCHK(a != NULL && b != NULL, MP_BADARG);
+
+ if((res = mp_copy(a, b)) != MP_OKAY)
+ return res;
+
+ /* This relies on the fact that the digit type is unsigned */
+ for(ix = 0; ix < USED(b); ix++)
+ DIGIT(b, ix) = ~DIGIT(b, ix);
+
+ s_mp_clamp(b);
+
+ return MP_OKAY;
+
+} /* end mpl_not() */
+
+/* }}} */
+
+/* {{{ mpl_and(a, b, c) */
+
+mp_err mpl_and(mp_int *a, mp_int *b, mp_int *c)
+{
+ mp_int *which, *other;
+ mp_err res;
+ int ix;
+
+ ARGCHK(a != NULL && b != NULL && c != NULL, MP_BADARG);
+
+ if(USED(a) <= USED(b)) {
+ which = a;
+ other = b;
+ } else {
+ which = b;
+ other = a;
+ }
+
+ if((res = mp_copy(which, c)) != MP_OKAY)
+ return res;
+
+ for(ix = 0; ix < USED(which); ix++)
+ DIGIT(c, ix) &= DIGIT(other, ix);
+
+ s_mp_clamp(c);
+
+ return MP_OKAY;
+
+} /* end mpl_and() */
+
+/* }}} */
+
+/* {{{ mpl_or(a, b, c) */
+
+mp_err mpl_or(mp_int *a, mp_int *b, mp_int *c)
+{
+ mp_int *which, *other;
+ mp_err res;
+ int ix;
+
+ ARGCHK(a != NULL && b != NULL && c != NULL, MP_BADARG);
+
+ if(USED(a) >= USED(b)) {
+ which = a;
+ other = b;
+ } else {
+ which = b;
+ other = a;
+ }
+
+ if((res = mp_copy(which, c)) != MP_OKAY)
+ return res;
+
+ for(ix = 0; ix < USED(which); ix++)
+ DIGIT(c, ix) |= DIGIT(other, ix);
+
+ return MP_OKAY;
+
+} /* end mpl_or() */
+
+/* }}} */
+
+/* {{{ mpl_xor(a, b, c) */
+
+mp_err mpl_xor(mp_int *a, mp_int *b, mp_int *c)
+{
+ mp_int *which, *other;
+ mp_err res;
+ int ix;
+
+ ARGCHK(a != NULL && b != NULL && c != NULL, MP_BADARG);
+
+ if(USED(a) >= USED(b)) {
+ which = a;
+ other = b;
+ } else {
+ which = b;
+ other = a;
+ }
+
+ if((res = mp_copy(which, c)) != MP_OKAY)
+ return res;
+
+ for(ix = 0; ix < USED(which); ix++)
+ DIGIT(c, ix) ^= DIGIT(other, ix);
+
+ s_mp_clamp(c);
+
+ return MP_OKAY;
+
+} /* end mpl_xor() */
+
+/* }}} */
+
+/*------------------------------------------------------------------------*/
+/*
+ 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_num_set(a, num)
+
+ Count the number of set bits in the binary representation of a.
+ Returns MP_OKAY and sets 'num' to be the number of such bits, if
+ possible. If num is NULL, the result is thrown away, but it is
+ not considered an error.
+
+ mpl_num_clear() does basically the same thing for clear bits.
+ */
+
+/* {{{ mpl_num_set(a, num) */
+
+mp_err mpl_num_set(mp_int *a, int *num)
+{
+ int ix, db, nset = 0;
+ mp_digit cur;
+ unsigned char reg;
+
+ ARGCHK(a != NULL, MP_BADARG);
+
+ for(ix = 0; ix < USED(a); ix++) {
+ cur = DIGIT(a, ix);
+
+ for(db = 0; db < sizeof(mp_digit); db++) {
+ reg = (unsigned char)(cur >> (CHAR_BIT * db));
+
+ nset += bitc[reg];
+ }
+ }
+
+ if(num)
+ *num = nset;
+
+ return MP_OKAY;
+
+} /* end mpl_num_set() */
+
+/* }}} */
+
+/* {{{ mpl_num_clear(a, num) */
+
+mp_err mpl_num_clear(mp_int *a, int *num)
+{
+ int ix, db, nset = 0;
+ mp_digit cur;
+ unsigned char reg;
+
+ ARGCHK(a != NULL, MP_BADARG);
+
+ for(ix = 0; ix < USED(a); ix++) {
+ cur = DIGIT(a, ix);
+
+ for(db = 0; db < sizeof(mp_digit); db++) {
+ reg = (unsigned char)(cur >> (CHAR_BIT * db));
+
+ nset += bitc[UCHAR_MAX - reg];
+ }
+ }
+
+ if(num)
+ *num = nset;
+
+ return MP_OKAY;
+
+
+} /* end mpl_num_clear() */
+
+/* }}} */
+
+/*------------------------------------------------------------------------*/
+/*
+ mpl_parity(a)
+
+ Determines the bitwise parity of the value given. Returns MP_EVEN
+ if an even number of digits are set, MP_ODD if an odd number are
+ set.
+ */
+
+/* {{{ mpl_parity(a) */
+
+mp_err mpl_parity(mp_int *a)
+{
+ int ix, par = 0;
+ mp_digit cur;
+
+ ARGCHK(a != NULL, MP_BADARG);
+
+ for(ix = 0; ix < USED(a); ix++) {
+ int shft = (sizeof(mp_digit) * CHAR_BIT) / 2;
+
+ cur = DIGIT(a, ix);
+
+ /* Compute parity for current digit */
+ while(shft != 0) {
+ cur ^= (cur >> shft);
+ shft >>= 1;
+ }
+ cur &= 1;
+
+ /* XOR with running parity so far */
+ par ^= cur;
+ }
+
+ if(par)
+ return MP_ODD;
+ else
+ return MP_EVEN;
+
+} /* end mpl_parity() */
+
+/* }}} */
+
+/*
+ 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 */
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