libm/s_trunc.c

   1 /* Truncate argument to nearest integral value not larger than the argument.
   2    Copyright (C) 1997, 1998 Free Software Foundation, Inc.
   3    This file is part of the GNU C Library.
   4    Contributed by Ulrich Drepper <drepper@cygnus.com>, 1997.
   5
   6    The GNU C Library is free software; you can redistribute it and/or
   7    modify it under the terms of the GNU Lesser General Public
   8    License as published by the Free Software Foundation; either
   9    version 2.1 of the License, or (at your option) any later version.
  10
  11    The GNU C Library is distributed in the hope that it will be useful,
  12    but WITHOUT ANY WARRANTY; without even the implied warranty of
  13    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  14    Lesser General Public License for more details.
  15
  16    You should have received a copy of the GNU Lesser General Public
  17    License along with the GNU C Library; if not, see
  18    <http://www.gnu.org/licenses/>.  */
  19
  20 #include <math.h>
  21 #include "math_private.h"
  22
  23 double
  24 trunc (double x)
  25 {
  26   int32_t i0, _j0;
  27   u_int32_t i1;
  28   int sx;
  29
  30   EXTRACT_WORDS (i0, i1, x);
  31   sx = i0 & 0x80000000;
  32   _j0 = ((i0 >> 20) & 0x7ff) - 0x3ff;
  33   if (_j0 < 20)
  34     {
  35       if (_j0 < 0)
  36         /* The magnitude of the number is < 1 so the result is +-0.  */
  37         INSERT_WORDS (x, sx, 0);
  38       else
  39         INSERT_WORDS (x, sx | (i0 & ~(0x000fffff >> _j0)), 0);
  40     }
  41   else if (_j0 > 51)
  42     {
  43       if (_j0 == 0x400)
  44         /* x is inf or NaN.  */
  45         return x + x;
  46     }
  47   else
  48     {
  49       INSERT_WORDS (x, i0, i1 & ~(0xffffffffu >> (_j0 - 20)));
  50     }
  51
  52   return x;
  53 }
  54 libm_hidden_def(trunc)