mirror of
https://github.com/rn10950/RetroZilla.git
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433 lines
8.8 KiB
C
433 lines
8.8 KiB
C
/*
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* mplogic.c
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*
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* Bitwise logical operations on MPI values
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*
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* This Source Code Form is subject to the terms of the Mozilla Public
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* License, v. 2.0. If a copy of the MPL was not distributed with this
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* file, You can obtain one at http://mozilla.org/MPL/2.0/. */
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#include "mpi-priv.h"
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#include "mplogic.h"
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/* {{{ Lookup table for population count */
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static unsigned char bitc[] = {
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0, 1, 1, 2, 1, 2, 2, 3, 1, 2, 2, 3, 2, 3, 3, 4,
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1, 2, 2, 3, 2, 3, 3, 4, 2, 3, 3, 4, 3, 4, 4, 5,
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1, 2, 2, 3, 2, 3, 3, 4, 2, 3, 3, 4, 3, 4, 4, 5,
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2, 3, 3, 4, 3, 4, 4, 5, 3, 4, 4, 5, 4, 5, 5, 6,
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1, 2, 2, 3, 2, 3, 3, 4, 2, 3, 3, 4, 3, 4, 4, 5,
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2, 3, 3, 4, 3, 4, 4, 5, 3, 4, 4, 5, 4, 5, 5, 6,
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2, 3, 3, 4, 3, 4, 4, 5, 3, 4, 4, 5, 4, 5, 5, 6,
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3, 4, 4, 5, 4, 5, 5, 6, 4, 5, 5, 6, 5, 6, 6, 7,
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1, 2, 2, 3, 2, 3, 3, 4, 2, 3, 3, 4, 3, 4, 4, 5,
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2, 3, 3, 4, 3, 4, 4, 5, 3, 4, 4, 5, 4, 5, 5, 6,
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2, 3, 3, 4, 3, 4, 4, 5, 3, 4, 4, 5, 4, 5, 5, 6,
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3, 4, 4, 5, 4, 5, 5, 6, 4, 5, 5, 6, 5, 6, 6, 7,
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2, 3, 3, 4, 3, 4, 4, 5, 3, 4, 4, 5, 4, 5, 5, 6,
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3, 4, 4, 5, 4, 5, 5, 6, 4, 5, 5, 6, 5, 6, 6, 7,
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3, 4, 4, 5, 4, 5, 5, 6, 4, 5, 5, 6, 5, 6, 6, 7,
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4, 5, 5, 6, 5, 6, 6, 7, 5, 6, 6, 7, 6, 7, 7, 8
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};
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/* }}} */
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/*------------------------------------------------------------------------*/
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/*
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mpl_not(a, b) - compute b = ~a
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mpl_and(a, b, c) - compute c = a & b
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mpl_or(a, b, c) - compute c = a | b
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mpl_xor(a, b, c) - compute c = a ^ b
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*/
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/* {{{ mpl_not(a, b) */
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mp_err mpl_not(mp_int *a, mp_int *b)
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{
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mp_err res;
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unsigned int ix;
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ARGCHK(a != NULL && b != NULL, MP_BADARG);
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if((res = mp_copy(a, b)) != MP_OKAY)
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return res;
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/* This relies on the fact that the digit type is unsigned */
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for(ix = 0; ix < USED(b); ix++)
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DIGIT(b, ix) = ~DIGIT(b, ix);
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s_mp_clamp(b);
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return MP_OKAY;
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} /* end mpl_not() */
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/* }}} */
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/* {{{ mpl_and(a, b, c) */
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mp_err mpl_and(mp_int *a, mp_int *b, mp_int *c)
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{
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mp_int *which, *other;
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mp_err res;
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unsigned int ix;
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ARGCHK(a != NULL && b != NULL && c != NULL, MP_BADARG);
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if(USED(a) <= USED(b)) {
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which = a;
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other = b;
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} else {
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which = b;
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other = a;
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}
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if((res = mp_copy(which, c)) != MP_OKAY)
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return res;
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for(ix = 0; ix < USED(which); ix++)
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DIGIT(c, ix) &= DIGIT(other, ix);
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s_mp_clamp(c);
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return MP_OKAY;
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} /* end mpl_and() */
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/* }}} */
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/* {{{ mpl_or(a, b, c) */
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mp_err mpl_or(mp_int *a, mp_int *b, mp_int *c)
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{
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mp_int *which, *other;
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mp_err res;
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unsigned int ix;
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ARGCHK(a != NULL && b != NULL && c != NULL, MP_BADARG);
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if(USED(a) >= USED(b)) {
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which = a;
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other = b;
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} else {
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which = b;
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other = a;
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}
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if((res = mp_copy(which, c)) != MP_OKAY)
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return res;
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for(ix = 0; ix < USED(which); ix++)
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DIGIT(c, ix) |= DIGIT(other, ix);
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return MP_OKAY;
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} /* end mpl_or() */
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/* }}} */
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/* {{{ mpl_xor(a, b, c) */
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mp_err mpl_xor(mp_int *a, mp_int *b, mp_int *c)
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{
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mp_int *which, *other;
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mp_err res;
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unsigned int ix;
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ARGCHK(a != NULL && b != NULL && c != NULL, MP_BADARG);
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if(USED(a) >= USED(b)) {
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which = a;
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other = b;
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} else {
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which = b;
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other = a;
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}
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if((res = mp_copy(which, c)) != MP_OKAY)
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return res;
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for(ix = 0; ix < USED(which); ix++)
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DIGIT(c, ix) ^= DIGIT(other, ix);
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s_mp_clamp(c);
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return MP_OKAY;
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} /* end mpl_xor() */
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/* }}} */
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/*------------------------------------------------------------------------*/
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/*
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mpl_rsh(a, b, d) - b = a >> d
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mpl_lsh(a, b, d) - b = a << d
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*/
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/* {{{ mpl_rsh(a, b, d) */
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mp_err mpl_rsh(const mp_int *a, mp_int *b, mp_digit d)
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{
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mp_err res;
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ARGCHK(a != NULL && b != NULL, MP_BADARG);
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if((res = mp_copy(a, b)) != MP_OKAY)
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return res;
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s_mp_div_2d(b, d);
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return MP_OKAY;
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} /* end mpl_rsh() */
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/* }}} */
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/* {{{ mpl_lsh(a, b, d) */
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mp_err mpl_lsh(const mp_int *a, mp_int *b, mp_digit d)
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{
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mp_err res;
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ARGCHK(a != NULL && b != NULL, MP_BADARG);
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if((res = mp_copy(a, b)) != MP_OKAY)
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return res;
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return s_mp_mul_2d(b, d);
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} /* end mpl_lsh() */
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/* }}} */
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/*------------------------------------------------------------------------*/
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/*
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mpl_num_set(a, num)
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Count the number of set bits in the binary representation of a.
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Returns MP_OKAY and sets 'num' to be the number of such bits, if
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possible. If num is NULL, the result is thrown away, but it is
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not considered an error.
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mpl_num_clear() does basically the same thing for clear bits.
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*/
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/* {{{ mpl_num_set(a, num) */
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mp_err mpl_num_set(mp_int *a, int *num)
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{
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unsigned int ix;
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int db, nset = 0;
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mp_digit cur;
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unsigned char reg;
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ARGCHK(a != NULL, MP_BADARG);
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for(ix = 0; ix < USED(a); ix++) {
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cur = DIGIT(a, ix);
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for(db = 0; db < sizeof(mp_digit); db++) {
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reg = (unsigned char)(cur >> (CHAR_BIT * db));
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nset += bitc[reg];
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}
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}
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if(num)
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*num = nset;
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return MP_OKAY;
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} /* end mpl_num_set() */
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/* }}} */
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/* {{{ mpl_num_clear(a, num) */
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mp_err mpl_num_clear(mp_int *a, int *num)
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{
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unsigned int ix;
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int db, nset = 0;
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mp_digit cur;
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unsigned char reg;
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ARGCHK(a != NULL, MP_BADARG);
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for(ix = 0; ix < USED(a); ix++) {
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cur = DIGIT(a, ix);
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for(db = 0; db < sizeof(mp_digit); db++) {
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reg = (unsigned char)(cur >> (CHAR_BIT * db));
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nset += bitc[UCHAR_MAX - reg];
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}
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}
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if(num)
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*num = nset;
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return MP_OKAY;
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} /* end mpl_num_clear() */
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/* }}} */
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/*------------------------------------------------------------------------*/
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/*
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mpl_parity(a)
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Determines the bitwise parity of the value given. Returns MP_EVEN
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if an even number of digits are set, MP_ODD if an odd number are
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set.
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*/
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/* {{{ mpl_parity(a) */
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mp_err mpl_parity(mp_int *a)
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{
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unsigned int ix;
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int par = 0;
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mp_digit cur;
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ARGCHK(a != NULL, MP_BADARG);
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for(ix = 0; ix < USED(a); ix++) {
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int shft = (sizeof(mp_digit) * CHAR_BIT) / 2;
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cur = DIGIT(a, ix);
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/* Compute parity for current digit */
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while(shft != 0) {
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cur ^= (cur >> shft);
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shft >>= 1;
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}
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cur &= 1;
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/* XOR with running parity so far */
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par ^= cur;
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}
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if(par)
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return MP_ODD;
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else
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return MP_EVEN;
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} /* end mpl_parity() */
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/* }}} */
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/*
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mpl_set_bit
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Returns MP_OKAY or some error code.
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Grows a if needed to set a bit to 1.
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*/
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mp_err mpl_set_bit(mp_int *a, mp_size bitNum, mp_size value)
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{
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mp_size ix;
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mp_err rv;
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mp_digit mask;
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ARGCHK(a != NULL, MP_BADARG);
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ix = bitNum / MP_DIGIT_BIT;
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if (ix + 1 > MP_USED(a)) {
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rv = s_mp_pad(a, ix + 1);
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if (rv != MP_OKAY)
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return rv;
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}
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bitNum = bitNum % MP_DIGIT_BIT;
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mask = (mp_digit)1 << bitNum;
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if (value)
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MP_DIGIT(a,ix) |= mask;
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else
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MP_DIGIT(a,ix) &= ~mask;
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s_mp_clamp(a);
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return MP_OKAY;
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}
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/*
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mpl_get_bit
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returns 0 or 1 or some (negative) error code.
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*/
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mp_err mpl_get_bit(const mp_int *a, mp_size bitNum)
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{
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mp_size bit, ix;
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mp_err rv;
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ARGCHK(a != NULL, MP_BADARG);
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ix = bitNum / MP_DIGIT_BIT;
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ARGCHK(ix <= MP_USED(a) - 1, MP_RANGE);
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bit = bitNum % MP_DIGIT_BIT;
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rv = (mp_err)(MP_DIGIT(a, ix) >> bit) & 1;
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return rv;
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}
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/*
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mpl_get_bits
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- Extracts numBits bits from a, where the least significant extracted bit
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is bit lsbNum. Returns a negative value if error occurs.
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- Because sign bit is used to indicate error, maximum number of bits to
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be returned is the lesser of (a) the number of bits in an mp_digit, or
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(b) one less than the number of bits in an mp_err.
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- lsbNum + numbits can be greater than the number of significant bits in
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integer a, as long as bit lsbNum is in the high order digit of a.
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*/
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mp_err mpl_get_bits(const mp_int *a, mp_size lsbNum, mp_size numBits)
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{
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mp_size rshift = (lsbNum % MP_DIGIT_BIT);
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mp_size lsWndx = (lsbNum / MP_DIGIT_BIT);
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mp_digit * digit = MP_DIGITS(a) + lsWndx;
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mp_digit mask = ((1 << numBits) - 1);
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ARGCHK(numBits < CHAR_BIT * sizeof mask, MP_BADARG);
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ARGCHK(MP_HOWMANY(lsbNum, MP_DIGIT_BIT) <= MP_USED(a), MP_RANGE);
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if ((numBits + lsbNum % MP_DIGIT_BIT <= MP_DIGIT_BIT) ||
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(lsWndx + 1 >= MP_USED(a))) {
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mask &= (digit[0] >> rshift);
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} else {
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mask &= ((digit[0] >> rshift) | (digit[1] << (MP_DIGIT_BIT - rshift)));
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}
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return (mp_err)mask;
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}
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/*
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mpl_significant_bits
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returns number of significnant bits in abs(a).
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returns 1 if value is zero.
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*/
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mp_err mpl_significant_bits(const mp_int *a)
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{
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mp_err bits = 0;
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int ix;
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ARGCHK(a != NULL, MP_BADARG);
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ix = MP_USED(a);
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for (ix = MP_USED(a); ix > 0; ) {
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mp_digit d;
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d = MP_DIGIT(a, --ix);
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if (d) {
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while (d) {
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++bits;
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d >>= 1;
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}
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break;
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}
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}
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bits += ix * MP_DIGIT_BIT;
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if (!bits)
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bits = 1;
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return bits;
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}
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/*------------------------------------------------------------------------*/
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/* HERE THERE BE DRAGONS */
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