mirror of https://github.com/macssh/macssh.git
138 lines
3.5 KiB
C
Executable File
138 lines
3.5 KiB
C
Executable File
/* 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, 1996, 1997, 2000 Free Software
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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 Lesser General Public License as published by
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the Free Software Foundation; either version 2.1 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 Lesser General Public
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License for more details.
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You should have received a copy of the GNU Lesser 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 <stdio.h> /* for NULL */
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#include "gmp.h"
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#include "gmp-impl.h"
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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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mp_size_t asize, bsize, usize, vsize;
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mp_srcptr ap, bp;
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mp_ptr up, vp;
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mp_size_t gsize, ssize, tmp_ssize;
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mp_ptr gp, sp, tmp_gp, tmp_sp;
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mpz_srcptr u, v;
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mpz_ptr ss, tt;
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__mpz_struct stmp, gtmp;
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TMP_DECL (marker);
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TMP_MARK (marker);
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/* mpn_gcdext requires that U >= V. Therefore, we often have to swap U and
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V. This in turn leads to a lot of complications. The computed cofactor
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will be the wrong one, so we have to fix that up at the end. */
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asize = ABS (SIZ (a));
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bsize = ABS (SIZ (b));
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ap = PTR (a);
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bp = PTR (b);
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if (asize > bsize || (asize == bsize && mpn_cmp (ap, bp, asize) > 0))
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{
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usize = asize;
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vsize = bsize;
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up = (mp_ptr) TMP_ALLOC ((usize + 1) * BYTES_PER_MP_LIMB);
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vp = (mp_ptr) TMP_ALLOC ((vsize + 1) * BYTES_PER_MP_LIMB);
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MPN_COPY (up, ap, usize);
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MPN_COPY (vp, bp, vsize);
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u = a;
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v = b;
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ss = s;
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tt = t;
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}
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else
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{
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usize = bsize;
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vsize = asize;
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up = (mp_ptr) TMP_ALLOC ((usize + 1) * BYTES_PER_MP_LIMB);
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vp = (mp_ptr) TMP_ALLOC ((vsize + 1) * BYTES_PER_MP_LIMB);
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MPN_COPY (up, bp, usize);
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MPN_COPY (vp, ap, vsize);
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u = b;
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v = a;
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ss = t;
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tt = s;
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}
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tmp_gp = (mp_ptr) TMP_ALLOC ((usize + 1) * BYTES_PER_MP_LIMB);
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tmp_sp = (mp_ptr) TMP_ALLOC ((usize + 1) * BYTES_PER_MP_LIMB);
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if (vsize == 0)
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{
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tmp_sp[0] = 1;
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tmp_ssize = 1;
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MPN_COPY (tmp_gp, up, usize);
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gsize = usize;
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}
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else
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gsize = mpn_gcdext (tmp_gp, tmp_sp, &tmp_ssize, up, usize, vp, vsize);
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ssize = ABS (tmp_ssize);
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PTR (>mp) = tmp_gp;
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SIZ (>mp) = gsize;
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PTR (&stmp) = tmp_sp;
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SIZ (&stmp) = (tmp_ssize ^ SIZ (u)) >= 0 ? ssize : -ssize;
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if (tt != NULL)
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{
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if (SIZ (v) == 0)
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SIZ (tt) = 0;
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else
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{
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mpz_t x;
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MPZ_TMP_INIT (x, ssize + usize + 1);
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mpz_mul (x, &stmp, u);
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mpz_sub (x, >mp, x);
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mpz_tdiv_q (tt, x, v);
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}
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}
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if (ss != NULL)
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{
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if (ALLOC (ss) < ssize)
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_mpz_realloc (ss, ssize);
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sp = PTR (ss);
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MPN_COPY (sp, tmp_sp, ssize);
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SIZ (ss) = SIZ (&stmp);
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}
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if (ALLOC (g) < gsize)
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_mpz_realloc (g, gsize);
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gp = PTR (g);
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MPN_COPY (gp, tmp_gp, gsize);
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SIZ (g) = gsize;
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TMP_FREE (marker);
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}
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