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glibc  2.9
s_lround.c
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00001 /* Round double value to long int.
00002    Copyright (C) 1997, 2004 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 long int
00027 __lround (double x)
00028 {
00029   int32_t j0;
00030   u_int32_t i1, i0;
00031   long int result;
00032   int sign;
00033 
00034   EXTRACT_WORDS (i0, i1, x);
00035   j0 = ((i0 >> 20) & 0x7ff) - 0x3ff;
00036   sign = (i0 & 0x80000000) != 0 ? -1 : 1;
00037   i0 &= 0xfffff;
00038   i0 |= 0x100000;
00039 
00040   if (j0 < 20)
00041     {
00042       if (j0 < 0)
00043        return j0 < -1 ? 0 : sign;
00044       else
00045        {
00046          i0 += 0x80000 >> j0;
00047 
00048          result = i0 >> (20 - j0);
00049        }
00050     }
00051   else if (j0 < (int32_t) (8 * sizeof (long int)) - 1)
00052     {
00053       if (j0 >= 52)
00054        result = ((long int) i0 << (j0 - 20)) | (i1 << (j0 - 52));
00055       else
00056        {
00057          u_int32_t j = i1 + (0x80000000 >> (j0 - 20));
00058          if (j < i1)
00059            ++i0;
00060 
00061          if (j0 == 20)
00062            result = (long int) i0;
00063          else
00064            result = ((long int) i0 << (j0 - 20)) | (j >> (52 - j0));
00065        }
00066     }
00067   else
00068     {
00069       /* The number is too large.  It is left implementation defined
00070         what happens.  */
00071       return (long int) x;
00072     }
00073 
00074   return sign * result;
00075 }
00076 
00077 weak_alias (__lround, lround)
00078 #ifdef NO_LONG_DOUBLE
00079 strong_alias (__lround, __lroundl)
00080 weak_alias (__lround, lroundl)
00081 #endif