1/* mpfr_div_2ui -- divide a floating-point number by a power of two 2 3Copyright 1999, 2001, 2002, 2003, 2004, 2005, 2006, 2007, 2008, 2009, 2010, 2011, 2012, 2013 Free Software Foundation, Inc. 4Contributed by the AriC and Caramel projects, INRIA. 5 6This file is part of the GNU MPFR Library. 7 8The GNU MPFR Library is free software; you can redistribute it and/or modify 9it under the terms of the GNU Lesser General Public License as published by 10the Free Software Foundation; either version 3 of the License, or (at your 11option) any later version. 12 13The GNU MPFR Library is distributed in the hope that it will be useful, but 14WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY 15or FITNESS FOR A PARTICULAR PURPOSE. See the GNU Lesser General Public 16License for more details. 17 18You should have received a copy of the GNU Lesser General Public License 19along with the GNU MPFR Library; see the file COPYING.LESSER. If not, see 20http://www.gnu.org/licenses/ or write to the Free Software Foundation, Inc., 2151 Franklin St, Fifth Floor, Boston, MA 02110-1301, USA. */ 22 23#include "mpfr-impl.h" 24 25int 26mpfr_div_2ui (mpfr_ptr y, mpfr_srcptr x, unsigned long n, mpfr_rnd_t rnd_mode) 27{ 28 int inexact; 29 30 MPFR_LOG_FUNC ( 31 ("x[%Pu]=%.*Rg n=%lu rnd=%d", mpfr_get_prec(x), mpfr_log_prec, x, n, 32 rnd_mode), 33 ("y[%Pu]=%.*Rg inexact=%d", mpfr_get_prec(y), mpfr_log_prec, y, inexact)); 34 35 if (MPFR_UNLIKELY (MPFR_IS_SINGULAR (x))) 36 return mpfr_set (y, x, rnd_mode); 37 else 38 { 39 mpfr_exp_t exp = MPFR_GET_EXP (x); 40 mpfr_uexp_t diffexp; 41 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 */ 45 { 46 if (rnd_mode == MPFR_RNDN && 47 (n > diffexp || (inexact >= 0 && mpfr_powerof2_raw (y)))) 48 rnd_mode = MPFR_RNDZ; 49 return mpfr_underflow (y, rnd_mode, MPFR_SIGN (y)); 50 } 51 /* exp - n >= emin (no underflow, no integer overflow) */ 52 while (n > LONG_MAX) 53 { 54 n -= LONG_MAX; 55 exp -= LONG_MAX; /* note: signed values */ 56 } 57 MPFR_SET_EXP (y, exp - (long) n); 58 } 59 60 MPFR_RET (inexact); 61} 62