Underflow semantics changed (not tested).

git-svn-id: svn://scm.gforge.inria.fr/svn/mpfr/trunk@1910 280ebfd0-de03-0410-8827-d642c229c3f4

1 files changed, 44 insertions, 0 deletions

diff --git a/powerof2.c b/powerof2.c
new file mode 100644
index 000000000..f4bf0d3c6
--- /dev/null
+++ b/powerof2.c
@@ -0,0 +1,44 @@
+/* mpfr_powerof2_raw -- test whether a floating-point number is a power of 2
+
+Copyright 2002 Free Software Foundation.
+
+This file is part of the MPFR Library.
+
+The MPFR 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 2.1 of the License, or (at your
+option) any later version.
+
+The MPFR 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 MPFR 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"
+#include "mpfr.h"
+#include "mpfr-impl.h"
+
+/* This is an internal function and one assumes that x is a real number. */
+
+int
+mpfr_powerof2_raw (mpfr_srcptr x)
+{
+  mp_limb_t *xp;
+  mp_size_t xn;
+
+  MPFR_ASSERTN(MPFR_IS_FP(x));
+  xp = MPFR_MANT(x);
+  xn = (MPFR_PREC(x) - 1) / BITS_PER_MP_LIMB;
+  if (NOT_POW2(xp[xn]))
+    return 0;
+  while (xn > 0)
+    if (xp[--xn] != 0)
+      return 0;
+  return 1;
+}