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, write to the Free
  18    Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
  19    02111-1307 USA.  */
  20
  21 #include <math.h>
  22 #include "math_private.h"
  23
  24 double
  25 trunc (double x)
  26 {
  27   int32_t i0, j0;
  28   u_int32_t i1;
  29   int sx;
  30
  31   EXTRACT_WORDS (i0, i1, x);
  32   sx = i0 & 0x80000000;
  33   j0 = ((i0 >> 20) & 0x7ff) - 0x3ff;
  34   if (j0 < 20)
  35     {
  36       if (j0 < 0)
  37         /* The magnitude of the number is < 1 so the result is +-0.  */
  38         INSERT_WORDS (x, sx, 0);
  39       else
  40         INSERT_WORDS (x, sx | (i0 & ~(0x000fffff >> j0)), 0);
  41     }
  42   else if (j0 > 51)
  43     {
  44       if (j0 == 0x400)
  45         /* x is inf or NaN.  */
  46         return x + x;
  47     }
  48   else
  49     {
  50       INSERT_WORDS (x, i0, i1 & ~(0xffffffffu >> (j0 - 20)));
  51     }
  52
  53   return x;
  54 }
  55 libm_hidden_def(trunc)