Added logb from glibc math.h file

svn path=/trunk/; revision=306

reactos/lib/crtdll/float/logb.c

@@ -0,0 +1,31 @@
+/* Math functions for i387.
+   Copyright (C) 1995, 1996, 1997 Free Software Foundation, Inc.
+   This file is part of the GNU C Library.
+   Contributed by John C. Bowman <[email protected]>, 1995.
+
+   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., 59 Temple Place - Suite 330,
+   Boston, MA 02111-1307, USA.  */
+
+double logb (double __x);
+
+double logb (double __x)
+{
+  register double __value, __junk;
+  __asm __volatile__
+    ("fxtract\n\t"
+     : "=t" (__junk), "=u" (__value) : "0" (__x));
+
+  return __value;
+}