sysdeps/ieee754/dbl-64/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
  23 #include "math_private.h"
  24
  25
  26 double
  27 __trunc (double x)
  28 {
  29   int32_t i0, j0;
  30   u_int32_t i1;
  31   int sx;
  32
  33   EXTRACT_WORDS (i0, i1, x);
  34   sx = i0 & 0x80000000;
  35   j0 = ((i0 >> 20) & 0x7ff) - 0x3ff;
  36   if (j0 < 20)
  37     {
  38       if (j0 < 0)
  39         /* The magnitude of the number is < 1 so the result is +-0.  */
  40         INSERT_WORDS (x, sx, 0);
  41       else
  42         INSERT_WORDS (x, sx | (i0 & ~(0x000fffff >> j0)), 0);
  43     }
  44   else if (j0 > 51)
  45     {
  46       if (j0 == 0x400)
  47         /* x is inf or NaN.  */
  48         return x + x;
  49     }
  50   else
  51     {
  52       INSERT_WORDS (x, i0, i1 & ~(0xffffffffu >> (j0 - 20)));
  53     }
  54
  55   return x;
  56 }
  57 weak_alias (__trunc, trunc)
  58 #ifdef NO_LONG_DOUBLE
  59 strong_alias (__trunc, __truncl)
  60 weak_alias (__trunc, truncl)
  61 #endif