| /* mpfr_div_2si -- divide a floating-point number by a power of two |
| |
| Copyright 1999, 2001, 2002, 2003, 2004, 2005, 2006, 2007, 2008, 2009 Free Software Foundation, Inc. |
| Contributed by the Arenaire and Cacao projects, INRIA. |
| |
| This file is part of the GNU MPFR Library. |
| |
| The GNU 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 GNU 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 GNU MPFR Library; see the file COPYING.LIB. If not, write to |
| the Free Software Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, |
| MA 02110-1301, USA. */ |
| |
| #include "mpfr-impl.h" |
| |
| int |
| mpfr_div_2si (mpfr_ptr y, mpfr_srcptr x, long int n, mp_rnd_t rnd_mode) |
| { |
| int inexact; |
| |
| MPFR_LOG_FUNC (("x[%#R]=%R n=%ld rnd=%d", x, x, n, rnd_mode), |
| ("y[%#R]=%R inexact=%d", y, y, inexact)); |
| |
| inexact = MPFR_UNLIKELY(y != x) ? mpfr_set (y, x, rnd_mode) : 0; |
| |
| if (MPFR_LIKELY( MPFR_IS_PURE_FP(y) )) |
| { |
| mp_exp_t exp = MPFR_GET_EXP (y); |
| if (MPFR_UNLIKELY( n > 0 && (__gmpfr_emin > MPFR_EMAX_MAX - n || |
| exp < __gmpfr_emin + n)) ) |
| { |
| if (rnd_mode == GMP_RNDN && |
| (__gmpfr_emin > MPFR_EMAX_MAX - (n - 1) || |
| exp < __gmpfr_emin + (n - 1) || |
| (inexact >= 0 && mpfr_powerof2_raw (y)))) |
| rnd_mode = GMP_RNDZ; |
| return mpfr_underflow (y, rnd_mode, MPFR_SIGN(y)); |
| } |
| |
| if (MPFR_UNLIKELY(n < 0 && (__gmpfr_emax < MPFR_EMIN_MIN - n || |
| exp > __gmpfr_emax + n)) ) |
| return mpfr_overflow (y, rnd_mode, MPFR_SIGN(y)); |
| |
| MPFR_SET_EXP (y, exp - n); |
| } |
| |
| return inexact; |
| } |