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Annotation of OpenXM_contrib/gmp/mpz/gcdext.c, Revision 1.1.1.3

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:
1.1.1.3 ! ohara       4: Copyright 1991, 1993, 1994, 1995, 1996, 1997, 2000, 2001 Free Software
1.1.1.2   maekawa     5: Foundation, Inc.
1.1       maekawa     6:
                      7: This file is part of the GNU MP Library.
                      8:
                      9: The GNU MP Library is free software; you can redistribute it and/or modify
1.1.1.2   maekawa    10: it under the terms of the GNU Lesser General Public License as published by
                     11: the Free Software Foundation; either version 2.1 of the License, or (at your
1.1       maekawa    12: option) any later version.
                     13:
                     14: The GNU MP Library is distributed in the hope that it will be useful, but
                     15: WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
1.1.1.2   maekawa    16: or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU Lesser General Public
1.1       maekawa    17: License for more details.
                     18:
1.1.1.2   maekawa    19: You should have received a copy of the GNU Lesser General Public License
1.1       maekawa    20: along with the GNU MP Library; see the file COPYING.LIB.  If not, write to
                     21: the Free Software Foundation, Inc., 59 Temple Place - Suite 330, Boston,
                     22: MA 02111-1307, USA. */
                     23:
1.1.1.2   maekawa    24: #include <stdio.h> /* for NULL */
1.1       maekawa    25: #include "gmp.h"
                     26: #include "gmp-impl.h"
                     27:
                     28: void
                     29: mpz_gcdext (mpz_ptr g, mpz_ptr s, mpz_ptr t, mpz_srcptr a, mpz_srcptr b)
                     30: {
1.1.1.2   maekawa    31:   mp_size_t asize, bsize, usize, vsize;
                     32:   mp_srcptr ap, bp;
                     33:   mp_ptr up, vp;
                     34:   mp_size_t gsize, ssize, tmp_ssize;
                     35:   mp_ptr gp, sp, tmp_gp, tmp_sp;
                     36:   mpz_srcptr u, v;
                     37:   mpz_ptr ss, tt;
                     38:   __mpz_struct stmp, gtmp;
                     39:   TMP_DECL (marker);
                     40:
                     41:   TMP_MARK (marker);
                     42:
                     43:   /* mpn_gcdext requires that U >= V.  Therefore, we often have to swap U and
                     44:      V.  This in turn leads to a lot of complications.  The computed cofactor
                     45:      will be the wrong one, so we have to fix that up at the end.  */
                     46:
                     47:   asize = ABS (SIZ (a));
                     48:   bsize = ABS (SIZ (b));
                     49:   ap = PTR (a);
                     50:   bp = PTR (b);
                     51:   if (asize > bsize || (asize == bsize && mpn_cmp (ap, bp, asize) > 0))
                     52:     {
                     53:       usize = asize;
                     54:       vsize = bsize;
                     55:       up = (mp_ptr) TMP_ALLOC ((usize + 1) * BYTES_PER_MP_LIMB);
                     56:       vp = (mp_ptr) TMP_ALLOC ((vsize + 1) * BYTES_PER_MP_LIMB);
                     57:       MPN_COPY (up, ap, usize);
                     58:       MPN_COPY (vp, bp, vsize);
                     59:       u = a;
                     60:       v = b;
                     61:       ss = s;
                     62:       tt = t;
                     63:     }
                     64:   else
                     65:     {
                     66:       usize = bsize;
                     67:       vsize = asize;
                     68:       up = (mp_ptr) TMP_ALLOC ((usize + 1) * BYTES_PER_MP_LIMB);
                     69:       vp = (mp_ptr) TMP_ALLOC ((vsize + 1) * BYTES_PER_MP_LIMB);
                     70:       MPN_COPY (up, bp, usize);
                     71:       MPN_COPY (vp, ap, vsize);
                     72:       u = b;
                     73:       v = a;
                     74:       ss = t;
                     75:       tt = s;
                     76:     }
1.1       maekawa    77:
1.1.1.2   maekawa    78:   tmp_gp = (mp_ptr) TMP_ALLOC ((usize + 1) * BYTES_PER_MP_LIMB);
                     79:   tmp_sp = (mp_ptr) TMP_ALLOC ((usize + 1) * BYTES_PER_MP_LIMB);
1.1       maekawa    80:
1.1.1.2   maekawa    81:   if (vsize == 0)
1.1       maekawa    82:     {
1.1.1.2   maekawa    83:       tmp_sp[0] = 1;
                     84:       tmp_ssize = 1;
                     85:       MPN_COPY (tmp_gp, up, usize);
                     86:       gsize = usize;
1.1       maekawa    87:     }
1.1.1.2   maekawa    88:   else
                     89:     gsize = mpn_gcdext (tmp_gp, tmp_sp, &tmp_ssize, up, usize, vp, vsize);
                     90:   ssize = ABS (tmp_ssize);
1.1       maekawa    91:
1.1.1.2   maekawa    92:   PTR (&gtmp) = tmp_gp;
                     93:   SIZ (&gtmp) = gsize;
                     94:
                     95:   PTR (&stmp) = tmp_sp;
                     96:   SIZ (&stmp) = (tmp_ssize ^ SIZ (u)) >= 0 ? ssize : -ssize;
                     97:
                     98:   if (tt != NULL)
1.1       maekawa    99:     {
1.1.1.2   maekawa   100:       if (SIZ (v) == 0)
                    101:        SIZ (tt) = 0;
1.1       maekawa   102:       else
1.1.1.2   maekawa   103:        {
                    104:          mpz_t x;
                    105:          MPZ_TMP_INIT (x, ssize + usize + 1);
                    106:          mpz_mul (x, &stmp, u);
                    107:          mpz_sub (x, &gtmp, x);
                    108:          mpz_tdiv_q (tt, x, v);
                    109:        }
1.1       maekawa   110:     }
1.1.1.2   maekawa   111:
                    112:   if (ss != NULL)
1.1       maekawa   113:     {
1.1.1.2   maekawa   114:       if (ALLOC (ss) < ssize)
                    115:        _mpz_realloc (ss, ssize);
                    116:       sp = PTR (ss);
                    117:       MPN_COPY (sp, tmp_sp, ssize);
                    118:       SIZ (ss) = SIZ (&stmp);
1.1       maekawa   119:     }
                    120:
1.1.1.2   maekawa   121:   if (ALLOC (g) < gsize)
                    122:     _mpz_realloc (g, gsize);
                    123:   gp = PTR (g);
                    124:   MPN_COPY (gp, tmp_gp, gsize);
                    125:   SIZ (g) = gsize;
                    126:
                    127:   TMP_FREE (marker);
1.1       maekawa   128: }