get_si.c revision 1.1.1.1
1/* mpfr_get_si -- convert a floating-point number to a signed long. 2 3Copyright 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 25long 26mpfr_get_si (mpfr_srcptr f, mpfr_rnd_t rnd) 27{ 28 mpfr_prec_t prec; 29 long s; 30 mpfr_t x; 31 32 if (MPFR_UNLIKELY (!mpfr_fits_slong_p (f, rnd))) 33 { 34 MPFR_SET_ERANGE (); 35 return MPFR_IS_NAN (f) ? 0 : 36 MPFR_IS_NEG (f) ? LONG_MIN : LONG_MAX; 37 } 38 39 if (MPFR_IS_ZERO (f)) 40 return (long) 0; 41 42 /* determine prec of long */ 43 for (s = LONG_MIN, prec = 0; s != 0; s /= 2, prec++) 44 { } 45 46 /* first round to prec bits */ 47 mpfr_init2 (x, prec); 48 mpfr_rint (x, f, rnd); 49 50 /* warning: if x=0, taking its exponent is illegal */ 51 if (MPFR_UNLIKELY (MPFR_IS_ZERO(x))) 52 s = 0; 53 else 54 { 55 mp_limb_t a; 56 mp_size_t n; 57 mpfr_exp_t exp; 58 59 /* now the result is in the most significant limb of x */ 60 exp = MPFR_GET_EXP (x); /* since |x| >= 1, exp >= 1 */ 61 n = MPFR_LIMB_SIZE(x); 62 a = MPFR_MANT(x)[n - 1] >> (GMP_NUMB_BITS - exp); 63 s = MPFR_SIGN(f) > 0 ? a : a <= LONG_MAX ? - (long) a : LONG_MIN; 64 } 65 66 mpfr_clear (x); 67 68 return s; 69} 70