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, 74 insertions, 0 deletions

diff --git a/fits_u.h b/fits_u.h
new file mode 100644
index 000000000..43101cb6b
--- /dev/null
+++ b/fits_u.h
@@ -0,0 +1,74 @@
+/* mpfr_fits_*_p -- test whether an mpfr fits a C unsigned type.
+
+Copyright 2003 Free Software Foundation.
+Contributed by the Spaces project, INRIA Lorraine.
+
+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"
+
+int
+FUNCTION (mpfr_srcptr f, mp_rnd_t rnd)
+{
+  mp_exp_t exp;
+  mp_prec_t prec;
+  TYPE s;
+  mpfr_t x;
+  int res;
+
+  if (MPFR_IS_NAN(f) || MPFR_IS_INF(f) || MPFR_SIGN(f) < 0)
+    return 0; /* does not fit */
+
+  if (MPFR_IS_ZERO(f))
+    return 1; /* zero always fits */
+
+  /* now it fits if 
+     (a) f <= MAXIMUM
+     (b) round(f, prec(slong), rnd) <= MAXIMUM */
+
+  exp = MPFR_EXP(f);
+  if (exp < 1)
+    return 1; /* |f| < 1: always fits */
+
+  /* first compute prec(MAXIMUM) */
+  for (s = MAXIMUM, prec = 0; s != 0; s /= 2, prec ++);
+
+  /* MAXIMUM needs prec bits, i.e. 2^(prec-1) <= |MAXIMUM| < 2^prec */
+
+   /* if exp < prec - 1, then f < 2^(prec-1) < |MAXIMUM| */
+  if (exp < prec - 1)
+    return 1;
+
+  /* if exp > prec + 1, then f >= 2^prec > MAXIMUM */
+  if (exp > prec + 1)
+    return 0;
+
+  /* remains cases exp = prec-1 to prec+1 */
+
+  /* hard case: first round to prec bits, then check */
+  mpfr_init2 (x, prec);
+  mpfr_set (x, f, rnd);
+  res = mpfr_cmp_ui (x, MAXIMUM) <= 0;
+  mpfr_clear (x);
+
+  return res;
+}
+