new functions mpfr_fits_* and mpfr_get_[us]i

git-svn-id: svn://scm.gforge.inria.fr/svn/mpfr/trunk@2235 280ebfd0-de03-0410-8827-d642c229c3f4

1 files changed, 57 insertions, 0 deletions

diff --git a/get_ui.c b/get_ui.c
new file mode 100644
index 000000000..b89619206
--- /dev/null
+++ b/get_ui.c
@@ -0,0 +1,57 @@
+/* mpfr_get_ui -- convert a floating-point number to an unsigned long.
+
+Copyright 2003 Free Software Foundation, Inc.
+
+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"
+
+unsigned long
+mpfr_get_ui (mpfr_srcptr f, mp_rnd_t rnd)
+{
+  mp_prec_t prec;
+  unsigned long s;
+  mpfr_t x;
+  mp_size_t n;
+  mp_exp_t exp;
+
+  if (!mpfr_fits_ulong_p (f, rnd) || MPFR_IS_ZERO(f))
+    return (long) 0;
+
+  /* determine prec of unsigned long */
+  for (s = ULONG_MAX, prec = 0; s != 0; s /= 2, prec ++);
+
+  /* first round to prec bits */
+  mpfr_init2 (x, prec);
+  mpfr_set (x, f, rnd);
+
+  ASSERT(GMP_NAIL_BITS == 0); /* otherwise we may have to consider two or
+				 more limbs */
+
+  /* now the result is in the most significant limb of x */
+  exp = MPFR_EXP(x); /* since |x| >= 1, exp >= 1 */
+  n = MPFR_ABSSIZE(x);
+  s = MPFR_MANT(x)[n - 1] >> (GMP_NUMB_BITS - exp);
+
+  mpfr_clear (x);
+
+  return s;
+}