1 /* mpfr_fits_*_p -- test whether an mpfr fits a C signed type. 2 3 Copyright 2003, 2004, 2005, 2006, 2007, 2008, 2009, 2010, 2011, 2012, 2013 Free Software Foundation, Inc. 4 Contributed by the AriC 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 /* The original version of this file came from GMP's mpf/fits_s.h; 26 it has been adapted for MPFR. In particular, the result can be 27 rounded away from zero. */ 28 29 int 30 FUNCTION (mpfr_srcptr f, mpfr_rnd_t rnd) 31 { 32 mpfr_exp_t e; 33 int prec; 34 mpfr_t x; 35 int neg; 36 int res; 37 38 if (MPFR_UNLIKELY (MPFR_IS_SINGULAR (f))) 39 /* Zero always fit */ 40 return MPFR_IS_ZERO (f) ? 1 : 0; 41 42 /* now it fits if either 43 (a) MINIMUM <= f <= MAXIMUM 44 (b) or MINIMUM <= round(f, prec(slong), rnd) <= MAXIMUM */ 45 46 e = MPFR_GET_EXP (f); 47 if (e < 1) 48 return 1; /* |f| < 1: always fits */ 49 50 neg = MPFR_IS_NEG (f); 51 52 /* let EXTREMUM be MAXIMUM if f > 0, and MINIMUM if f < 0 */ 53 54 /* first compute prec(EXTREMUM), this could be done at configure time, 55 but the result can depend on neg (the loop is moved inside the "if" 56 to give the compiler a better chance to compute prec statically) */ 57 if (neg) 58 { 59 unsigned TYPE s; 60 /* In C89, the division on negative integers isn't well-defined. */ 61 s = SAFE_ABS (unsigned TYPE, MINIMUM); 62 for (prec = 0; s != 0; s /= 2, prec ++); 63 } 64 else 65 { 66 TYPE s; 67 s = MAXIMUM; 68 for (prec = 0; s != 0; s /= 2, prec ++); 69 } 70 71 /* EXTREMUM needs prec bits, i.e. 2^(prec-1) <= |EXTREMUM| < 2^prec */ 72 73 /* if e <= prec - 1, then f < 2^(prec-1) <= |EXTREMUM| */ 74 if (e <= prec - 1) 75 return 1; 76 77 /* if e >= prec + 1, then f >= 2^prec > |EXTREMUM| */ 78 if (e >= prec + 1) 79 return 0; 80 81 MPFR_ASSERTD (e == prec); 82 83 /* hard case: first round to prec bits, then check */ 84 mpfr_init2 (x, prec); 85 mpfr_set (x, f, rnd); 86 res = neg ? (mpfr_cmp_si (x, MINIMUM) >= 0) : (MPFR_GET_EXP (x) == e); 87 mpfr_clear (x); 88 return res; 89 } 90