contrib/mpfr/src/fits_intmax.c

   1 /* mpfr_fits_intmax_p -- test whether an mpfr fits an intmax_t.
   2
   3 Copyright 2004, 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 #ifdef HAVE_CONFIG_H
  24 # include "config.h"            /* for a build within gmp */
  25 #endif
  26
  27 #include "mpfr-intmax.h"
  28 #include "mpfr-impl.h"
  29
  30 #ifdef _MPFR_H_HAVE_INTMAX_T
  31
  32 /* We can't use fits_s.h <= mpfr_cmp_ui */
  33 int
  34 mpfr_fits_intmax_p (mpfr_srcptr f, mpfr_rnd_t rnd)
  35 {
  36   mpfr_exp_t e;
  37   int prec;
  38   mpfr_t x, y;
  39   int neg;
  40   int res;
  41
  42   if (MPFR_UNLIKELY (MPFR_IS_SINGULAR (f)))
  43     /* Zero always fit */
  44     return MPFR_IS_ZERO (f) ? 1 : 0;
  45
  46   /* now it fits if either
  47      (a) MINIMUM <= f <= MAXIMUM
  48      (b) or MINIMUM <= round(f, prec(slong), rnd) <= MAXIMUM */
  49
  50   e = MPFR_EXP (f);
  51   if (e < 1)
  52     return 1; /* |f| < 1: always fits */
  53
  54   neg = MPFR_IS_NEG (f);
  55
  56   /* let EXTREMUM be MAXIMUM if f > 0, and MINIMUM if f < 0 */
  57
  58   /* first compute prec(EXTREMUM), this could be done at configure time,
  59      but the result can depend on neg (the loop is moved inside the "if"
  60      to give the compiler a better chance to compute prec statically) */
  61   if (neg)
  62     {
  63       uintmax_t s;
  64       /* In C89, the division on negative integers isn't well-defined. */
  65       s = SAFE_ABS (uintmax_t, MPFR_INTMAX_MIN);
  66       for (prec = 0; s != 0; s /= 2, prec ++);
  67     }
  68   else
  69     {
  70       intmax_t s;
  71       s = MPFR_INTMAX_MAX;
  72       for (prec = 0; s != 0; s /= 2, prec ++);
  73     }
  74
  75   /* EXTREMUM needs prec bits, i.e. 2^(prec-1) <= |EXTREMUM| < 2^prec */
  76
  77    /* if e <= prec - 1, then f < 2^(prec-1) <= |EXTREMUM| */
  78   if (e <= prec - 1)
  79     return 1;
  80
  81   /* if e >= prec + 1, then f >= 2^prec > |EXTREMUM| */
  82   if (e >= prec + 1)
  83     return 0;
  84
  85   MPFR_ASSERTD (e == prec);
  86
  87   /* hard case: first round to prec bits, then check */
  88   mpfr_init2 (x, prec);
  89   mpfr_set (x, f, rnd);
  90
  91   if (neg)
  92     {
  93       mpfr_init2 (y, prec);
  94       mpfr_set_sj (y, MPFR_INTMAX_MIN, MPFR_RNDN);
  95       res = mpfr_cmp (x, y) >= 0;
  96       mpfr_clear (y);
  97     }
  98   else
  99     {
 100       res = MPFR_GET_EXP (x) == e;
 101     }
 102
 103   mpfr_clear (x);
 104   return res;
 105 }
 106
 107 #endif