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

   1 /* Truncate argument to nearest integral value not larger than the argument.
   2    Copyright (C) 1997-2014 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
  22 #include <math_private.h>
  23
  24
  25 double
  26 __trunc (double x)
  27 {
  28   int64_t i0, j0;
  29   int64_t sx;
  30
  31   EXTRACT_WORDS64 (i0, x);
  32   sx = i0 & UINT64_C(0x8000000000000000);
  33   j0 = ((i0 >> 52) & 0x7ff) - 0x3ff;
  34   if (j0 < 52)
  35     {
  36       if (j0 < 0)
  37         /* The magnitude of the number is < 1 so the result is +-0.  */
  38         INSERT_WORDS64 (x, sx);
  39       else
  40         INSERT_WORDS64 (x, sx | (i0 & ~(UINT64_C(0x000fffffffffffff) >> j0)));
  41     }
  42   else
  43     {
  44       if (j0 == 0x400)
  45         /* x is inf or NaN.  */
  46         return x + x;
  47     }
  48
  49   return x;
  50 }
  51 weak_alias (__trunc, trunc)
  52 #ifdef NO_LONG_DOUBLE
  53 strong_alias (__trunc, __truncl)
  54 weak_alias (__trunc, truncl)
  55 #endif