1 /* mpfr_fits_*_p -- test whether an mpfr fits a C signed type. 2 3 Copyright 2003-2018 Free Software Foundation, Inc. 4 Contributed by the AriC and Caramba 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_flags_t saved_flags; 33 mpfr_exp_t e; 34 int prec; 35 mpfr_t x; 36 int neg; 37 int res; 38 39 if (MPFR_UNLIKELY (MPFR_IS_SINGULAR (f))) 40 /* Zero always fit */ 41 return MPFR_IS_ZERO (f) ? 1 : 0; 42 43 /* now it fits if either 44 (a) MINIMUM <= f <= MAXIMUM 45 (b) or MINIMUM <= round(f, prec(slong), rnd) <= MAXIMUM */ 46 47 e = MPFR_GET_EXP (f); 48 if (e < 1) 49 return 1; /* |f| < 1: always fits */ 50 51 neg = MPFR_IS_NEG (f); 52 53 /* let EXTREMUM be MAXIMUM if f > 0, and MINIMUM if f < 0 */ 54 55 /* first compute prec(EXTREMUM), this could be done at configure time, 56 but the result can depend on neg (the loop is moved inside the "if" 57 to give the compiler a better chance to compute prec statically) */ 58 if (neg) 59 { 60 unsigned TYPE s; 61 /* In C89, the division on negative integers isn't well-defined. */ 62 s = SAFE_ABS (unsigned TYPE, MINIMUM); 63 for (prec = 0; s != 0; s /= 2, prec ++); 64 } 65 else 66 { 67 TYPE s; 68 s = MAXIMUM; 69 for (prec = 0; s != 0; s /= 2, prec ++); 70 } 71 72 /* EXTREMUM needs prec bits, i.e. 2^(prec-1) <= |EXTREMUM| < 2^prec */ 73 74 /* if e <= prec - 1, then f < 2^(prec-1) <= |EXTREMUM| */ 75 if (e <= prec - 1) 76 return 1; 77 78 /* if e >= prec + 1, then f >= 2^prec > |EXTREMUM| */ 79 if (e >= prec + 1) 80 return 0; 81 82 MPFR_ASSERTD (e == prec); 83 84 /* hard case: first round to prec bits, then check */ 85 saved_flags = __gmpfr_flags; 86 mpfr_init2 (x, prec); 87 /* for RNDF, it suffices to check it fits when rounded away from zero */ 88 mpfr_set (x, f, (rnd == MPFR_RNDF) ? MPFR_RNDA : rnd); 89 /* Warning! Due to the rounding, x can be an infinity. Here we use 90 the fact that singular numbers have a special exponent field, 91 thus well-defined and different from e, in which case this means 92 that the number does not fit. That's why we use MPFR_EXP, not 93 MPFR_GET_EXP. */ 94 res = neg ? (mpfr_cmp_si (x, MINIMUM) >= 0) : (MPFR_EXP (x) == e); 95 mpfr_clear (x); 96 __gmpfr_flags = saved_flags; 97 return res; 98 } 99