/* mpi-gcd.c - MPI functions
* Copyright (C) 1998, 2001 Free Software Foundation, Inc.
*
* This file is part of Libgcrypt.
*
* Libgcrypt 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.
*
* Libgcrypt 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
#include
#include
#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
gcry_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( gcry_mpi_cmp_ui( b, 0 ) ) {
_gcry_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 !gcry_mpi_cmp_ui( g, 1);
}