81 lines
1.9 KiB
C
81 lines
1.9 KiB
C
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/* 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 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 General Public License as published by
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the Free Software Foundation; either version 2, or (at your option)
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any later version.
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The GNU MP Library 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 General Public License for more details.
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You should have received a copy of the GNU General Public License
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along with the GNU MP Library; see the file COPYING. If not, write to
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the Free Software Foundation, 675 Mass Ave, Cambridge, MA 02139, 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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#ifdef __STDC__
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mpz_gcdext (MP_INT *g, MP_INT *s, MP_INT *t, const MP_INT *a, const MP_INT *b)
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#else
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mpz_gcdext (g, s, t, a, b)
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MP_INT *g;
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MP_INT *s;
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MP_INT *t;
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const MP_INT *a;
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const MP_INT *b;
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#endif
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{
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MP_INT s0, s1, q, r, x, d0, d1;
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mpz_init_set_ui (&s0, 1);
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mpz_init_set_ui (&s1, 0);
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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.size != 0)
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{
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mpz_divmod (&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->size == 0)
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t->size = 0;
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else
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mpz_div (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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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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