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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: }