s_llroundl.c

Glibc 2.3.2源代码(解压后有100多M)

/* Round long double value to long long int.
   Copyright (C) 1997, 1999 Free Software Foundation, Inc.
   This file is part of the GNU C Library.
   Contributed by Ulrich Drepper <[e-mail]>, 1997 and
   		  Jakub Jelinek <[e-mail]>, 1999.

   The GNU C Library is free software; you can redistribute it and/or
   modify it under the terms of the GNU Lesser General Public
   License as published by the Free Software Foundation; either
   version 2.1 of the License, or (at your option) any later version.

   The GNU C Library is distributed in the hope that it will be useful,
   but WITHOUT ANY WARRANTY; without even the implied warranty of
   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
   Lesser General Public License for more details.

   You should have received a copy of the GNU Lesser General Public
   License along with the GNU C Library; if not, write to the Free
   Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
   02111-1307 USA.  */

#include <math.h>

#include "math_private.h"


long long int
__llroundl (long double x)
{
  int64_t j0;
  u_int64_t i1, i0;
  long long int result;
  int sign;

  GET_LDOUBLE_WORDS64 (i0, i1, x);
  j0 = ((i0 >> 48) & 0x7fff) - 0x3fff;
  sign = (i0 & 0x8000000000000000ULL) != 0 ? -1 : 1;
  i0 &= 0x0000ffffffffffffLL;
  i0 |= 0x0001000000000000LL;

  if (j0 < 48)
    {
      if (j0 < 0)
	return j0 < -1 ? 0 : sign;
      else
	{
	  i0 += 0x0000800000000000LL >> j0;
	  result = i0 >> (48 - j0);
	}
    }
  else if (j0 < (int32_t) (8 * sizeof (long long int)) - 1)
    {
      if (j0 >= 112)
	result = ((long long int) i0 << (j0 - 48)) | (i1 << (j0 - 112));
      else
	{
	  u_int64_t j = i1 + (0x8000000000000000ULL >> (j0 - 48));
	  if (j < i1)
	    ++i0;

	  result = ((long long int) i0 << (j0 - 48)) | (j >> (112 - j0));
	}
    }
  else
    {
      /* The number is too large.  It is left implementation defined
	 what happens.  */
      return (long long int) x;
    }

  return sign * result;
}

weak_alias (__llroundl, llroundl)