/* mpi-bit.c  -  MPI bit level fucntions * Copyright (C) 1998, 1999 Free Software Foundation, Inc. * * This file is part of GnuPG. * * GnuPG is free software; you can redistribute it and/or modify * it under the terms of the GNU General Public License as published by * the Free Software Foundation; either version 2 of the License, or * (at your option) any later version. * * GnuPG is distributed in the hope that it will be useful, * but WITHOUT ANY WARRANTY; without even the implied warranty of * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the * GNU General Public License for more details. * * You should have received a copy of the GNU General Public License * along with this program; if not, write to the Free Software * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA */ #include "mpi-internal.h"#include "longlong.h" #define A_LIMB_1 ((mpi_limb_t) 1) /**************** * Sometimes we have MSL (most significant limbs) which are 0; * this is for some reasons not good, so this function removes them. */void mpi_normalize(MPI a){	for (; a->nlimbs && !a->d[a->nlimbs - 1]; a->nlimbs--)		;} /**************** * Return the number of bits in A. */unsigned mpi_get_nbits(MPI a){	unsigned n; 	mpi_normalize(a); 	if (a->nlimbs) {		mpi_limb_t alimb = a->d[a->nlimbs - 1];		if (alimb)			count_leading_zeros(n, alimb);		else			n = BITS_PER_MPI_LIMB;		n = BITS_PER_MPI_LIMB - n + (a->nlimbs - 1) * BITS_PER_MPI_LIMB;	} else		n = 0;	return n;}EXPORT_SYMBOL_GPL(mpi_get_nbits); /**************** * Test whether bit N is set. */int mpi_test_bit(MPI a, unsigned n){	unsigned limbno, bitno;	mpi_limb_t limb; 	limbno = n / BITS_PER_MPI_LIMB;	bitno = n % BITS_PER_MPI_LIMB; 	if (limbno >= a->nlimbs)		return 0;	/* too far left: this is a 0 */	limb = a->d[limbno];	return (limb & (A_LIMB_1 << bitno)) ? 1 : 0;} /**************** * Set bit N of A. */int mpi_set_bit(MPI a, unsigned n){	unsigned limbno, bitno; 	limbno = n / BITS_PER_MPI_LIMB;	bitno = n % BITS_PER_MPI_LIMB; 	if (limbno >= a->nlimbs) {	/* resize */		if (a->alloced >= limbno)			if (mpi_resize(a, limbno + 1) < 0)				return -ENOMEM;		a->nlimbs = limbno + 1;	}	a->d[limbno] |= (A_LIMB_1 << bitno);	return 0;} /**************** * Set bit N of A. and clear all bits above */int mpi_set_highbit(MPI a, unsigned n){	unsigned limbno, bitno; 	limbno = n / BITS_PER_MPI_LIMB;	bitno = n % BITS_PER_MPI_LIMB; 	if (limbno >= a->nlimbs) {	/* resize */		if (a->alloced >= limbno)			if (mpi_resize(a, limbno + 1) < 0)				return -ENOMEM;		a->nlimbs = limbno + 1;	}	a->d[limbno] |= (A_LIMB_1 << bitno);	for (bitno++; bitno < BITS_PER_MPI_LIMB; bitno++)		a->d[limbno] &= ~(A_LIMB_1 << bitno);	a->nlimbs = limbno + 1;	return 0;} /**************** * clear bit N of A and all bits above */void mpi_clear_highbit(MPI a, unsigned n){	unsigned limbno, bitno; 	limbno = n / BITS_PER_MPI_LIMB;	bitno = n % BITS_PER_MPI_LIMB; 	if (limbno >= a->nlimbs)		return;		/* not allocated, so need to clear bits :-) */ 	for (; bitno < BITS_PER_MPI_LIMB; bitno++)		a->d[limbno] &= ~(A_LIMB_1 << bitno);	a->nlimbs = limbno + 1;} /**************** * Clear bit N of A. */void mpi_clear_bit(MPI a, unsigned n){	unsigned limbno, bitno; 	limbno = n / BITS_PER_MPI_LIMB;	bitno = n % BITS_PER_MPI_LIMB; 	if (limbno >= a->nlimbs)		return;		/* don't need to clear this bit, it's to far to left */	a->d[limbno] &= ~(A_LIMB_1 << bitno);} /**************** * Shift A by N bits to the right * FIXME: should use alloc_limb if X and A are same. */int mpi_rshift(MPI x, MPI a, unsigned n){	mpi_ptr_t xp;	mpi_size_t xsize; 	xsize = a->nlimbs;	x->sign = a->sign;	if (RESIZE_IF_NEEDED(x, (size_t) xsize) < 0)		return -ENOMEM;	xp = x->d; 	if (xsize) {		mpihelp_rshift(xp, a->d, xsize, n);		MPN_NORMALIZE(xp, xsize);	}	x->nlimbs = xsize;	return 0;} /**************** * Shift A by COUNT limbs to the left * This is used only within the MPI library */int mpi_lshift_limbs(MPI a, unsigned int count){	const int n = a->nlimbs;	mpi_ptr_t ap;	int i; 	if (!count || !n)		return 0; 	if (RESIZE_IF_NEEDED(a, n + count) < 0)		return -ENOMEM; 	ap = a->d;	for (i = n - 1; i >= 0; i--)		ap[i + count] = ap[i];	for (i = 0; i < count; i++)		ap[i] = 0;	a->nlimbs += count;	return 0;} /**************** * Shift A by COUNT limbs to the right * This is used only within the MPI library */void mpi_rshift_limbs(MPI a, unsigned int count){	mpi_ptr_t ap = a->d;	mpi_size_t n = a->nlimbs;	unsigned int i; 	if (count >= n) {		a->nlimbs = 0;		return;	} 	for (i = 0; i < n - count; i++)		ap[i] = ap[i + count];	ap[i] = 0;	a->nlimbs -= count;}