mpi-gcd.c
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mpi-gcd.c
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	/* mpi-gcd.c - MPI functions
	* Copyright (c) 1997 by Werner Koch (dd9jn)
	*
	* This file is part of G10.
	*
	* G10 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.
	*
	* G10 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 <config.h>
	#include <stdio.h>
	#include <stdlib.h>
	#include "mpi-internal.h"

	/****************
	* Find the greatest common divisor G of A and B.
	* Return: true if this 1, false in all other cases
	*/
	int
	mpi_gcd( MPI g, MPI xa, MPI xb )
	{
	MPI a, b;

	a = mpi_copy(xa);
	b = mpi_copy(xb);

	/* TAOCP Vol II, 4.5.2, Algorithm A */
	a->sign = 0;
	b->sign = 0;
	while( mpi_cmp_ui( b, 0 ) ) {
	mpi_fdiv_r( g, a, b ); /* g used as temorary variable */
	mpi_set(a,b);
	mpi_set(b,g);
	}
	mpi_set(g, a);

	mpi_free(a);
	mpi_free(b);
	return !mpi_cmp_ui( g, 1);
	}