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glibc  2.9
s_roundf.c
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00001 /* Round float to integer away from zero.
00002    Copyright (C) 1997 Free Software Foundation, Inc.
00003    This file is part of the GNU C Library.
00004    Contributed by Ulrich Drepper <drepper@cygnus.com>, 1997.
00005 
00006    The GNU C Library is free software; you can redistribute it and/or
00007    modify it under the terms of the GNU Lesser General Public
00008    License as published by the Free Software Foundation; either
00009    version 2.1 of the License, or (at your option) any later version.
00010 
00011    The GNU C Library is distributed in the hope that it will be useful,
00012    but WITHOUT ANY WARRANTY; without even the implied warranty of
00013    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
00014    Lesser General Public License for more details.
00015 
00016    You should have received a copy of the GNU Lesser General Public
00017    License along with the GNU C Library; if not, write to the Free
00018    Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
00019    02111-1307 USA.  */
00020 
00021 #include <math.h>
00022 
00023 #include "math_private.h"
00024 
00025 
00026 static const float huge = 1.0e30;
00027 
00028 
00029 float
00030 __roundf (float x)
00031 {
00032   int32_t i0, j0;
00033 
00034   GET_FLOAT_WORD (i0, x);
00035   j0 = ((i0 >> 23) & 0xff) - 0x7f;
00036   if (j0 < 23)
00037     {
00038       if (j0 < 0)
00039        {
00040          if (huge + x > 0.0F)
00041            {
00042              i0 &= 0x80000000;
00043              if (j0 == -1)
00044               i0 |= 0x3f800000;
00045            }
00046        }
00047       else
00048        {
00049          u_int32_t i = 0x007fffff >> j0;
00050          if ((i0 & i) == 0)
00051            /* X is integral.  */
00052            return x;
00053          if (huge + x > 0.0F)
00054            {
00055              /* Raise inexact if x != 0.  */
00056              i0 += 0x00400000 >> j0;
00057              i0 &= ~i;
00058            }
00059        }
00060     }
00061   else
00062     {
00063       if (j0 == 0x80)
00064        /* Inf or NaN.  */
00065        return x + x;
00066       else
00067        return x;
00068     }
00069 
00070   SET_FLOAT_WORD (x, i0);
00071   return x;
00072 }
00073 weak_alias (__roundf, roundf)