1 /* __gmpfr_ceil_exp2 - returns y >= 2^d 2 3 Copyright 1999, 2000, 2001, 2002, 2003, 2004, 2006, 2007, 2008, 2009, 2010, 2011 Free Software Foundation, Inc. 4 Contributed by the Arenaire and Caramel projects, INRIA. 5 6 This file is part of the GNU MPFR Library. 7 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. 12 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. 17 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. */ 22 23 #include "mpfr-impl.h" 24 25 /* returns y >= 2^d, assuming that d <= 1024 26 for d integer, returns exactly 2^d 27 */ 28 double 29 __gmpfr_ceil_exp2 (double d) 30 { 31 long exp; 32 #if _GMP_IEEE_FLOATS 33 union ieee_double_extract x; 34 #else 35 struct {double d;} x; 36 #endif 37 38 MPFR_ASSERTN(d <= 1024.0); 39 exp = (long) d; 40 if (d != (double) exp) 41 exp++; 42 /* now exp = ceil(d) */ 43 x.d = 1.0; 44 #if _GMP_IEEE_FLOATS 45 x.s.exp = exp <= -1022 ? 1 : 1023 + exp; 46 #else 47 if (exp >= 0) 48 { 49 while (exp != 0) 50 { 51 x.d *= 2.0; 52 exp--; 53 } 54 } 55 else 56 { 57 while (exp != 0) 58 { 59 x.d *= (1.0 / 2.0); 60 exp++; 61 } 62 } 63 #endif 64 return x.d; 65 } 66