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ch1_mpi                 1 /* mpi-gcd.c  -  MPI functions
ch1_mpi 2 * Modified by No Such Labs. (C) 2015. See README.
ch1_mpi 3 *
ch1_mpi 4 * This file was originally part of Gnu Privacy Guard (GPG), ver. 1.4.10,
ch1_mpi 5 * SHA256(gnupg-1.4.10.tar.gz):
ch1_mpi 6 * 0bfd74660a2f6cedcf7d8256db4a63c996ffebbcdc2cf54397bfb72878c5a85a
ch1_mpi 7 * (C) 1994-2005 Free Software Foundation, Inc.
ch1_mpi 8 *
ch1_mpi 9 * This program is free software: you can redistribute it and/or modify
ch1_mpi 10 * it under the terms of the GNU General Public License as published by
ch1_mpi 11 * the Free Software Foundation, either version 3 of the License, or
ch1_mpi 12 * (at your option) any later version.
ch1_mpi 13 *
ch1_mpi 14 * This program is distributed in the hope that it will be useful,
ch1_mpi 15 * but WITHOUT ANY WARRANTY; without even the implied warranty of
ch1_mpi 16 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
ch1_mpi 17 * GNU General Public License for more details.
ch1_mpi 18 *
ch1_mpi 19 * You should have received a copy of the GNU General Public License
ch1_mpi 20 * along with this program. If not, see <http://www.gnu.org/licenses/>.
ch1_mpi 21 */
ch1_mpi 22
ch1_mpi 23 #include <stdio.h>
ch1_mpi 24 #include <stdlib.h>
ch1_mpi 25
ch1_mpi 26 #include "knobs.h"
ch1_mpi 27 #include "mpi-internal.h"
ch1_mpi 28
ch1_mpi 29 /****************
ch1_mpi 30 * Find the greatest common divisor G of A and B.
ch1_mpi 31 * Return: true if this 1, false in all other cases
ch1_mpi 32 */
ch1_mpi 33 int
ch1_mpi 34 mpi_gcd( MPI g, MPI xa, MPI xb )
ch1_mpi 35 {
ch1_mpi 36 MPI a, b;
ch1_mpi 37
ch1_mpi 38 a = mpi_copy(xa);
ch1_mpi 39 b = mpi_copy(xb);
ch1_mpi 40
ch1_mpi 41 /* TAOCP Vol II, 4.5.2, Algorithm A */
ch1_mpi 42 a->sign = 0;
ch1_mpi 43 b->sign = 0;
ch1_mpi 44 while( mpi_cmp_ui( b, 0 ) ) {
ch1_mpi 45 mpi_fdiv_r( g, a, b ); /* g used as temorary variable */
ch1_mpi 46 mpi_set(a,b);
ch1_mpi 47 mpi_set(b,g);
ch1_mpi 48 }
ch1_mpi 49 mpi_set(g, a);
ch1_mpi 50
ch1_mpi 51 mpi_free(a);
ch1_mpi 52 mpi_free(b);
ch1_mpi 53 return !mpi_cmp_ui( g, 1);
ch1_mpi 54 }
ch1_mpi 55
ch1_mpi 56
ch1_mpi 57