Back to index

glibc  2.9
s_lrintf.c
Go to the documentation of this file.
00001 /* Round argument to nearest integral value according to current rounding
00002    direction.
00003    Copyright (C) 1997, 2006 Free Software Foundation, Inc.
00004    This file is part of the GNU C Library.
00005    Contributed by Ulrich Drepper <drepper@cygnus.com>, 1997.
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 static const float two23[2] =
00027 {
00028   8.3886080000e+06, /* 0x4B000000 */
00029  -8.3886080000e+06, /* 0xCB000000 */
00030 };
00031 
00032 
00033 long int
00034 __lrintf (float x)
00035 {
00036   int32_t j0;
00037   u_int32_t i0;
00038   volatile float w;
00039   float t;
00040   long int result;
00041   int sx;
00042 
00043   GET_FLOAT_WORD (i0, x);
00044 
00045   sx = i0 >> 31;
00046   j0 = ((i0 >> 23) & 0xff) - 0x7f;
00047   i0 &= 0x7fffff;
00048   i0 |= 0x800000;
00049 
00050   if (j0 < (int32_t) (sizeof (long int) * 8) - 1)
00051     {
00052       if (j0 >= 23)
00053        result = (long int) i0 << (j0 - 23);
00054       else
00055        {
00056          w = two23[sx] + x;
00057          t = w - two23[sx];
00058          GET_FLOAT_WORD (i0, t);
00059          j0 = ((i0 >> 23) & 0xff) - 0x7f;
00060          i0 &= 0x7fffff;
00061          i0 |= 0x800000;
00062 
00063          result = (j0 < 0 ? 0 : i0 >> (23 - j0));
00064        }
00065     }
00066   else
00067     {
00068       /* The number is too large.  It is left implementation defined
00069         what happens.  */
00070       return (long int) x;
00071     }
00072 
00073   return sx ? -result : result;
00074 }
00075 
00076 weak_alias (__lrintf, lrintf)