sysdeps/ieee754/dbl-64/s_trunc.c

   1 /* Truncate argument to nearest integral value not larger than the argument.
   2    Copyright (C) 1997-2019 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 #define NO_MATH_REDIRECT
  21 #include <math.h>
  22
  23 #include <math_private.h>
  24 #include <libm-alias-double.h>
  25
  26
  27 double
  28 __trunc (double x)
  29 {
  30   int32_t i0, j0;
  31   uint32_t i1;
  32   int sx;
  33
  34   EXTRACT_WORDS (i0, i1, x);
  35   sx = i0 & 0x80000000;
  36   j0 = ((i0 >> 20) & 0x7ff) - 0x3ff;
  37   if (j0 < 20)
  38     {
  39       if (j0 < 0)
  40         /* The magnitude of the number is < 1 so the result is +-0.  */
  41         INSERT_WORDS (x, sx, 0);
  42       else
  43         INSERT_WORDS (x, sx | (i0 & ~(0x000fffff >> j0)), 0);
  44     }
  45   else if (j0 > 51)
  46     {
  47       if (j0 == 0x400)
  48         /* x is inf or NaN.  */
  49         return x + x;
  50     }
  51   else
  52     {
  53       INSERT_WORDS (x, i0, i1 & ~(0xffffffffu >> (j0 - 20)));
  54     }
  55
  56   return x;
  57 }
  58 #ifndef __trunc
  59 libm_alias_double (__trunc, trunc)
  60 #endif