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Diffstat (limited to 'mpi/mpi-gcd.c')
| -rw-r--r-- | mpi/mpi-gcd.c | 55 |
1 files changed, 55 insertions, 0 deletions
diff --git a/mpi/mpi-gcd.c b/mpi/mpi-gcd.c new file mode 100644 index 0000000..6f384ce --- /dev/null +++ b/mpi/mpi-gcd.c @@ -0,0 +1,55 @@ +/* mpi-gcd.c - MPI functions + * Copyright (C) 1998, 1999, 2000, 2001 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., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, + * 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); +} + + + |