--- /dev/null
+/* Compute {up,n}^(-1).
+
+Copyright (C) 2007 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 Lesser General Public License as published by
+the Free Software Foundation; either version 3 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 Lesser General Public
+License for more details.
+
+You should have received a copy of the GNU Lesser General Public License
+along with the GNU MP Library. If not, see http://www.gnu.org/licenses/. */
+
+#include <stdlib.h>
+#include "gmp.h"
+#include "gmp-impl.h"
+
+/* Formulas:
+ z = 2z-(zz)d
+ z = 2z-(zd)z
+ z = z(2-zd)
+ z = z-z*(zd-1)
+ z = z+z*(1-zd)
+*/
+
+mp_size_t
+mpn_invert_itch (mp_size_t n)
+{
+ return 3 * n + 2;
+}
+
+void
+mpn_invert (mp_ptr ip, mp_srcptr dp, mp_size_t n, mp_ptr scratch)
+{
+ mp_ptr np, rp;
+ mp_size_t i;
+ TMP_DECL;
+
+ TMP_MARK;
+ if (scratch == NULL)
+ {
+ scratch = TMP_ALLOC_LIMBS (mpn_invert_itch (n));
+ }
+
+ np = scratch; /* 2 * n limbs */
+ rp = scratch + 2 * n; /* n + 2 limbs */
+ for (i = n - 1; i >= 0; i--)
+ np[i] = ~CNST_LIMB(0);
+ mpn_com_n (np + n, dp, n);
+ mpn_tdiv_qr (rp, ip, 0L, np, 2 * n, dp, n);
+ MPN_COPY (ip, rp, n);
+
+ TMP_FREE;
+}