get_ui.c revision 1.1.1.3
1/* mpfr_get_ui -- convert a floating-point number to an unsigned long. 2 3Copyright 2003-2004, 2006-2018 Free Software Foundation, Inc. 4Contributed by the AriC and Caramba 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 25unsigned long 26mpfr_get_ui (mpfr_srcptr f, mpfr_rnd_t rnd) 27{ 28 mpfr_prec_t prec; 29 unsigned long s; 30 mpfr_t x; 31 mp_size_t n; 32 mpfr_exp_t exp; 33 MPFR_SAVE_EXPO_DECL (expo); 34 35 if (MPFR_UNLIKELY (!mpfr_fits_ulong_p (f, rnd))) 36 { 37 MPFR_SET_ERANGEFLAG (); 38 return MPFR_IS_NAN (f) || MPFR_IS_NEG (f) ? 39 (unsigned long) 0 : ULONG_MAX; 40 } 41 42 if (MPFR_IS_ZERO (f)) 43 return (unsigned long) 0; 44 45 for (s = ULONG_MAX, prec = 0; s != 0; s /= 2, prec ++) 46 { } 47 48 MPFR_SAVE_EXPO_MARK (expo); 49 50 /* first round to prec bits */ 51 mpfr_init2 (x, prec); 52 mpfr_rint (x, f, rnd); 53 54 /* The flags from mpfr_rint are the wanted ones. In particular, 55 it sets the inexact flag when necessary. */ 56 MPFR_SAVE_EXPO_UPDATE_FLAGS (expo, __gmpfr_flags); 57 58 /* warning: if x=0, taking its exponent is illegal */ 59 if (MPFR_IS_ZERO(x)) 60 s = 0; 61 else 62 { 63 /* now the result is in the most significant limb of x */ 64 exp = MPFR_GET_EXP (x); /* since |x| >= 1, exp >= 1 */ 65 n = MPFR_LIMB_SIZE(x); 66 s = MPFR_MANT(x)[n - 1] >> (GMP_NUMB_BITS - exp); 67 } 68 69 mpfr_clear (x); 70 71 MPFR_SAVE_EXPO_FREE (expo); 72 73 return s; 74} 75