sysdeps/ieee754/dbl-64/wordsize-64/s_trunc.c

   1 /* Truncate argument to nearest integral value not larger than the argument.
   2    Copyright (C) 1997, 1998, 2009 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   int64_t i0, j0;
  30   int64_t sx;
  31
  32   EXTRACT_WORDS64 (i0, x);
  33   sx = i0 & UINT64_C(0x8000000000000000);
  34   j0 = ((i0 >> 52) & 0x7ff) - 0x3ff;
  35   if (j0 < 52)
  36     {
  37       if (j0 < 0)
  38         /* The magnitude of the number is < 1 so the result is +-0.  */
  39         INSERT_WORDS64 (x, sx);
  40       else
  41         INSERT_WORDS64 (x, sx | (i0 & ~(UINT64_C(0x000fffffffffffff) >> j0)));
  42     }
  43   else
  44     {
  45       if (j0 == 0x400)
  46         /* x is inf or NaN.  */
  47         return x + x;
  48     }
  49
  50   return x;
  51 }
  52 weak_alias (__trunc, trunc)
  53 #ifdef NO_LONG_DOUBLE
  54 strong_alias (__trunc, __truncl)
  55 weak_alias (__trunc, truncl)
  56 #endif