52 lines
1.5 KiB
C
52 lines
1.5 KiB
C
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/* mpi-gcd.c - MPI functions
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* Copyright (C) 1998, 2001, 2002, 2003 Free Software Foundation, Inc.
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*
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* This file is part of Libgcrypt.
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*
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* Libgcrypt is free software; you can redistribute it and/or modify
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* it under the terms of the GNU Lesser General Public License as
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* published by the Free Software Foundation; either version 2.1 of
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* the License, or (at your option) any later version.
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*
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* Libgcrypt is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU Lesser General Public License for more details.
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*
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* You should have received a copy of the GNU Lesser General Public
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* License along with this program; if not, write to the Free Software
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* Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA
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*/
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#include <config.h>
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#include <stdio.h>
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#include <stdlib.h>
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#include "mpi-internal.h"
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/****************
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* Find the greatest common divisor G of A and B.
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* Return: true if this 1, false in all other cases
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*/
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int
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gcry_mpi_gcd( gcry_mpi_t g, gcry_mpi_t xa, gcry_mpi_t xb )
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{
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gcry_mpi_t a, b;
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a = mpi_copy(xa);
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b = mpi_copy(xb);
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/* TAOCP Vol II, 4.5.2, Algorithm A */
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a->sign = 0;
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b->sign = 0;
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while( gcry_mpi_cmp_ui( b, 0 ) ) {
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_gcry_mpi_fdiv_r( g, a, b ); /* g used as temorary variable */
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mpi_set(a,b);
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mpi_set(b,g);
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}
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mpi_set(g, a);
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mpi_free(a);
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mpi_free(b);
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return !gcry_mpi_cmp_ui( g, 1);
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}
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