Initial revision

1 files changed, 88 insertions, 0 deletions

diff --git a/mpz/gcdext.c b/mpz/gcdext.c
new file mode 100644
index 000000000..adf66b04a
--- /dev/null
+++ b/mpz/gcdext.c
@@ -0,0 +1,88 @@
+/* mpz_gcdext(g, s, t, a, b) -- Set G to gcd(a, b), and S and T such that
+   g = as + bt.
+
+Copyright (C) 1991, 1993, 1994, 1995 Free Software Foundation, Inc.
+
+This file is part of the GNU MP Library.
+
+The GNU MP Library is free software; you can redistribute it and/or modify
+it under the terms of the GNU Library General Public License as published by
+the Free Software Foundation; either version 2 of the License, or (at your
+option) any later version.
+
+The GNU MP Library is distributed in the hope that it will be useful, but
+WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
+or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU Library General Public
+License for more details.
+
+You should have received a copy of the GNU Library General Public License
+along with the GNU MP Library; see the file COPYING.LIB.  If not, write to
+the Free Software Foundation, Inc., 59 Temple Place - Suite 330, Boston,
+MA 02111-1307, USA. */
+
+#include "gmp.h"
+#include "gmp-impl.h"
+
+/* Botch:  SLOW!  */
+
+void
+#if __STDC__
+mpz_gcdext (mpz_ptr g, mpz_ptr s, mpz_ptr t, mpz_srcptr a, mpz_srcptr b)
+#else
+mpz_gcdext (g, s, t, a, b)
+     mpz_ptr g;
+     mpz_ptr s;
+     mpz_ptr t;
+     mpz_srcptr a;
+     mpz_srcptr b;
+#endif
+{
+  mpz_t s0, s1, q, r, x, d0, d1;
+
+  mpz_init_set_ui (s0, 1L);
+  mpz_init_set_ui (s1, 0L);
+  mpz_init (q);
+  mpz_init (r);
+  mpz_init (x);
+  mpz_init_set (d0, a);
+  mpz_init_set (d1, b);
+
+  while (d1->_mp_size != 0)
+    {
+      mpz_tdiv_qr (q, r, d0, d1);
+      mpz_set (d0, d1);
+      mpz_set (d1, r);
+
+      mpz_mul (x, s1, q);
+      mpz_sub (x, s0, x);
+      mpz_set (s0, s1);
+      mpz_set (s1, x);
+    }
+
+  if (t != NULL)
+    {
+      mpz_mul (x, s0, a);
+      mpz_sub (x, d0, x);
+      if (b->_mp_size == 0)
+	t->_mp_size = 0;
+      else
+	mpz_tdiv_q (t, x, b);
+    }
+  mpz_set (s, s0);
+  mpz_set (g, d0);
+  if (g->_mp_size < 0)
+    {
+      g->_mp_size = -g->_mp_size;
+      s->_mp_size = -s->_mp_size;
+      if (t != NULL)
+	t->_mp_size = -t->_mp_size;
+    }
+
+  mpz_clear (s0);
+  mpz_clear (s1);
+  mpz_clear (q);
+  mpz_clear (r);
+  mpz_clear (x);
+  mpz_clear (d0);
+  mpz_clear (d1);
+}