1 /* mpfr_div_2ui -- divide a floating-point number by a power of two
3 Copyright 1999, 2001, 2002, 2003, 2004, 2005, 2006, 2007, 2008, 2009, 2010, 2011, 2012, 2013 Free Software Foundation, Inc.
4 Contributed by the AriC and Caramel projects, INRIA.
6 This file is part of the GNU MPFR Library.
8 The GNU MPFR Library is free software; you can redistribute it and/or modify
9 it under the terms of the GNU Lesser General Public License as published by
10 the Free Software Foundation; either version 3 of the License, or (at your
11 option) any later version.
13 The GNU MPFR Library is distributed in the hope that it will be useful, but
14 WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
15 or FITNESS FOR A PARTICULAR PURPOSE. See the GNU Lesser General Public
16 License for more details.
18 You should have received a copy of the GNU Lesser General Public License
19 along with the GNU MPFR Library; see the file COPYING.LESSER. If not, see
20 http://www.gnu.org/licenses/ or write to the Free Software Foundation, Inc.,
21 51 Franklin St, Fifth Floor, Boston, MA 02110-1301, USA. */
23 #include "mpfr-impl.h"
26 mpfr_div_2ui (mpfr_ptr y
, mpfr_srcptr x
, unsigned long n
, mpfr_rnd_t rnd_mode
)
31 ("x[%Pu]=%.*Rg n=%lu rnd=%d", mpfr_get_prec(x
), mpfr_log_prec
, x
, n
,
33 ("y[%Pu]=%.*Rg inexact=%d", mpfr_get_prec(y
), mpfr_log_prec
, y
, inexact
));
35 if (MPFR_UNLIKELY (MPFR_IS_SINGULAR (x
)))
36 return mpfr_set (y
, x
, rnd_mode
);
39 mpfr_exp_t exp
= MPFR_GET_EXP (x
);
42 MPFR_SETRAW (inexact
, y
, x
, exp
, rnd_mode
);
43 diffexp
= (mpfr_uexp_t
) exp
- (mpfr_uexp_t
) (__gmpfr_emin
- 1);
44 if (MPFR_UNLIKELY (n
>= diffexp
)) /* exp - n <= emin - 1 */
46 if (rnd_mode
== MPFR_RNDN
&&
47 (n
> diffexp
|| (inexact
>= 0 && mpfr_powerof2_raw (y
))))
49 return mpfr_underflow (y
, rnd_mode
, MPFR_SIGN (y
));
51 /* exp - n >= emin (no underflow, no integer overflow) */
55 exp
-= LONG_MAX
; /* note: signed values */
57 MPFR_SET_EXP (y
, exp
- (long) n
);