initially checkin

1 files changed, 54 insertions, 0 deletions

diff --git a/mpi/mpi-gcd.c b/mpi/mpi-gcd.c
new file mode 100644
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--- /dev/null
+++ b/mpi/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);
+}
+
+
+