89 lines
2.1 KiB
C
89 lines
2.1 KiB
C
/* mpz_gcdext(g, s, t, a, b) -- Set G to gcd(a, b), and S and T such that
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g = as + bt.
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Copyright (C) 1991, 1993, 1994, 1995 Free Software Foundation, Inc.
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This file is part of the GNU MP Library.
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The GNU MP Library is free software; you can redistribute it and/or modify
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it under the terms of the GNU Library General Public License as published by
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the Free Software Foundation; either version 2 of the License, or (at your
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option) any later version.
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The GNU MP Library is distributed in the hope that it will be useful, but
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WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
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or FITNESS FOR A PARTICULAR PURPOSE. See the GNU Library General Public
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License for more details.
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You should have received a copy of the GNU Library General Public License
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along with the GNU MP Library; see the file COPYING.LIB. If not, write to
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the Free Software Foundation, Inc., 59 Temple Place - Suite 330, Boston,
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MA 02111-1307, USA. */
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#include "gmp.h"
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#include "gmp-impl.h"
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/* Botch: SLOW! */
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void
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#if __STDC__
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mpz_gcdext (mpz_ptr g, mpz_ptr s, mpz_ptr t, mpz_srcptr a, mpz_srcptr b)
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#else
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mpz_gcdext (g, s, t, a, b)
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mpz_ptr g;
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mpz_ptr s;
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mpz_ptr t;
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mpz_srcptr a;
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mpz_srcptr b;
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#endif
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{
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mpz_t s0, s1, q, r, x, d0, d1;
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mpz_init_set_ui (s0, 1L);
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mpz_init_set_ui (s1, 0L);
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mpz_init (q);
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mpz_init (r);
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mpz_init (x);
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mpz_init_set (d0, a);
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mpz_init_set (d1, b);
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while (d1->_mp_size != 0)
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{
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mpz_tdiv_qr (q, r, d0, d1);
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mpz_set (d0, d1);
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mpz_set (d1, r);
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mpz_mul (x, s1, q);
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mpz_sub (x, s0, x);
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mpz_set (s0, s1);
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mpz_set (s1, x);
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}
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if (t != NULL)
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{
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mpz_mul (x, s0, a);
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mpz_sub (x, d0, x);
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if (b->_mp_size == 0)
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t->_mp_size = 0;
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else
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mpz_tdiv_q (t, x, b);
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}
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mpz_set (s, s0);
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mpz_set (g, d0);
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if (g->_mp_size < 0)
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{
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g->_mp_size = -g->_mp_size;
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s->_mp_size = -s->_mp_size;
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if (t != NULL)
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t->_mp_size = -t->_mp_size;
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}
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mpz_clear (s0);
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mpz_clear (s1);
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mpz_clear (q);
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mpz_clear (r);
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mpz_clear (x);
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mpz_clear (d0);
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mpz_clear (d1);
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}
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