Annotation of OpenXM_contrib/gmp/mpz/gcdext.c, Revision 1.1.1.1
1.1 maekawa 1: /* mpz_gcdext(g, s, t, a, b) -- Set G to gcd(a, b), and S and T such that
2: g = as + bt.
3:
4: Copyright (C) 1991, 1993, 1994, 1995 Free Software Foundation, Inc.
5:
6: This file is part of the GNU MP Library.
7:
8: The GNU MP Library is free software; you can redistribute it and/or modify
9: it under the terms of the GNU Library General Public License as published by
10: the Free Software Foundation; either version 2 of the License, or (at your
11: option) any later version.
12:
13: The GNU MP Library is distributed in the hope that it will be useful, but
14: WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
15: or FITNESS FOR A PARTICULAR PURPOSE. See the GNU Library General Public
16: License for more details.
17:
18: You should have received a copy of the GNU Library General Public License
19: along with the GNU MP Library; see the file COPYING.LIB. If not, write to
20: the Free Software Foundation, Inc., 59 Temple Place - Suite 330, Boston,
21: MA 02111-1307, USA. */
22:
23: #include "gmp.h"
24: #include "gmp-impl.h"
25:
26: /* Botch: SLOW! */
27:
28: void
29: #if __STDC__
30: mpz_gcdext (mpz_ptr g, mpz_ptr s, mpz_ptr t, mpz_srcptr a, mpz_srcptr b)
31: #else
32: mpz_gcdext (g, s, t, a, b)
33: mpz_ptr g;
34: mpz_ptr s;
35: mpz_ptr t;
36: mpz_srcptr a;
37: mpz_srcptr b;
38: #endif
39: {
40: mpz_t s0, s1, q, r, x, d0, d1;
41:
42: mpz_init_set_ui (s0, 1L);
43: mpz_init_set_ui (s1, 0L);
44: mpz_init (q);
45: mpz_init (r);
46: mpz_init (x);
47: mpz_init_set (d0, a);
48: mpz_init_set (d1, b);
49:
50: while (d1->_mp_size != 0)
51: {
52: mpz_tdiv_qr (q, r, d0, d1);
53: mpz_set (d0, d1);
54: mpz_set (d1, r);
55:
56: mpz_mul (x, s1, q);
57: mpz_sub (x, s0, x);
58: mpz_set (s0, s1);
59: mpz_set (s1, x);
60: }
61:
62: if (t != NULL)
63: {
64: mpz_mul (x, s0, a);
65: mpz_sub (x, d0, x);
66: if (b->_mp_size == 0)
67: t->_mp_size = 0;
68: else
69: mpz_tdiv_q (t, x, b);
70: }
71: mpz_set (s, s0);
72: mpz_set (g, d0);
73: if (g->_mp_size < 0)
74: {
75: g->_mp_size = -g->_mp_size;
76: s->_mp_size = -s->_mp_size;
77: if (t != NULL)
78: t->_mp_size = -t->_mp_size;
79: }
80:
81: mpz_clear (s0);
82: mpz_clear (s1);
83: mpz_clear (q);
84: mpz_clear (r);
85: mpz_clear (x);
86: mpz_clear (d0);
87: mpz_clear (d1);
88: }
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