1 files changed, 43 insertions, 0 deletions
diff --git a/mpz/invert.c b/mpz/invert.c
new file mode 100644
index 000000000..ff1d6d937
--- /dev/null
+++ b/mpz/invert.c
@@ -0,0 +1,43 @@
+/* mpz_invert (inv, x, n).  Find multiplicative inverse of X in Z(N).
+   If X has an inverse, return non-zero and store inverse in INVERSE,
+   otherwise, return 0 and put garbage in X.
+
+Copyright (C) 1996 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"
+
+int
+#if __STDC__
+mpz_invert (mpz_ptr inverse, mpz_srcptr x, mpz_srcptr n)
+#else
+mpz_invert (inverse, x, n)
+     mpz_ptr inverse;
+     mpz_srcptr x, n;
+#endif
+{
+  mpz_t gcd;
+  int rv;
+
+  mpz_init (gcd);
+  mpz_gcdext (gcd, inverse, (mpz_ptr) 0, x, n);
+  rv = gcd->_mp_size == 1 && (gcd->_mp_d)[0] == 1;
+  mpz_clear (gcd);
+  return rv;
+}