1 files changed, 40 insertions, 0 deletions
diff --git a/sysdeps/ieee754/isinf.c b/sysdeps/ieee754/isinf.c
new file mode 100644
index 0000000000..79be916432
--- /dev/null
+++ b/sysdeps/ieee754/isinf.c
@@ -0,0 +1,40 @@
+/* Copyright (C) 1991, 1992, 1995 Free Software Foundation, Inc.
+This file is part of the GNU C Library.
+
+The GNU C 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 C 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 C Library; see the file COPYING.LIB.  If
+not, write to the Free Software Foundation, Inc., 675 Mass Ave,
+Cambridge, MA 02139, USA.  */
+
+#include <ansidecl.h>
+#include <math.h>
+#include "ieee754.h"
+
+/* Return 0 if VALUE is finite or NaN, +1 if it
+   is +Infinity, -1 if it is -Infinity.  */
+int
+DEFUN(__isinf, (value), double value)
+{
+  union ieee754_double u;
+
+  u.d = value;
+  /* An IEEE 754 infinity has an exponent with the
+     maximum possible value and a zero mantissa.  */
+  if ((u.ieee.exponent & 0x7ff) == 0x7ff &&
+      u.ieee.mantissa0 == 0 && u.ieee.mantissa1 == 0)
+    return u.ieee.negative ? -1 : 1;
+
+  return 0;
+}
+
+weak_alias (__isinf, isinf)