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glibc  2.9
s_roundl.c
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00001 /* Round long double to integer away from zero.
00002    Copyright (C) 1997, 1999 Free Software Foundation, Inc.
00003    This file is part of the GNU C Library.
00004    Contributed by Ulrich Drepper <drepper@cygnus.com>, 1997 and
00005                 Jakub Jelinek <jj@ultra.linux.cz>, 1999.
00006 
00007    The GNU C Library is free software; you can redistribute it and/or
00008    modify it under the terms of the GNU Lesser General Public
00009    License as published by the Free Software Foundation; either
00010    version 2.1 of the License, or (at your option) any later version.
00011 
00012    The GNU C Library is distributed in the hope that it will be useful,
00013    but WITHOUT ANY WARRANTY; without even the implied warranty of
00014    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
00015    Lesser General Public License for more details.
00016 
00017    You should have received a copy of the GNU Lesser General Public
00018    License along with the GNU C Library; if not, write to the Free
00019    Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
00020    02111-1307 USA.  */
00021 
00022 #include <math.h>
00023 
00024 #include "math_private.h"
00025 
00026 
00027 static const long double huge = 1.0E4930L;
00028 
00029 
00030 long double
00031 __roundl (long double x)
00032 {
00033   int32_t j0;
00034   u_int64_t i1, i0;
00035 
00036   GET_LDOUBLE_WORDS64 (i0, i1, x);
00037   j0 = ((i0 >> 48) & 0x7fff) - 0x3fff;
00038   if (j0 < 31)
00039     {
00040       if (j0 < 0)
00041        {
00042          if (huge + x > 0.0)
00043            {
00044              i0 &= 0x8000000000000000ULL;
00045              if (j0 == -1)
00046               i0 |= 0x3fff000000000000LL;
00047              i1 = 0;
00048            }
00049        }
00050       else
00051        {
00052          u_int64_t i = 0x0000ffffffffffffLL >> j0;
00053          if (((i0 & i) | i1) == 0)
00054            /* X is integral.  */
00055            return x;
00056          if (huge + x > 0.0)
00057            {
00058              /* Raise inexact if x != 0.  */
00059              i0 += 0x0000800000000000LL >> j0;
00060              i0 &= ~i;
00061              i1 = 0;
00062            }
00063        }
00064     }
00065   else if (j0 > 111)
00066     {
00067       if (j0 == 0x4000)
00068        /* Inf or NaN.  */
00069        return x + x;
00070       else
00071        return x;
00072     }
00073   else
00074     {
00075       u_int64_t i = -1ULL >> (j0 - 48);
00076       if ((i1 & i) == 0)
00077        /* X is integral.  */
00078        return x;
00079 
00080       if (huge + x > 0.0)
00081        {
00082          /* Raise inexact if x != 0.  */
00083          u_int64_t j = i1 + (1LL << (111 - j0));
00084          if (j < i1)
00085            i0 += 1;
00086          i1 = j;
00087        }
00088       i1 &= ~i;
00089     }
00090 
00091   SET_LDOUBLE_WORDS64 (x, i0, i1);
00092   return x;
00093 }
00094 weak_alias (__roundl, roundl)