sysdeps/ieee754/dbl-64/s_lround.c

   1 /* Round double value to long int.
   2    Copyright (C) 1997, 2004 Free Software Foundation, Inc.
   3    This file is part of the GNU C Library.
   4    Contributed by Ulrich Drepper <drepper@cygnus.com>, 1997.
   5
   6    The GNU C Library is free software; you can redistribute it and/or
   7    modify it under the terms of the GNU Lesser General Public
   8    License as published by the Free Software Foundation; either
   9    version 2.1 of the License, or (at your option) any later version.
  10
  11    The GNU C Library is distributed in the hope that it will be useful,
  12    but WITHOUT ANY WARRANTY; without even the implied warranty of
  13    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  14    Lesser General Public License for more details.
  15
  16    You should have received a copy of the GNU Lesser General Public
  17    License along with the GNU C Library; if not, write to the Free
  18    Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
  19    02111-1307 USA.  */
  20
  21 #include <math.h>
  22
  23 #include "math_private.h"
  24
  25
  26 long int
  27 __lround (double x)
  28 {
  29   int32_t j0;
  30   u_int32_t i1, i0;
  31   long int result;
  32   int sign;
  33
  34   EXTRACT_WORDS (i0, i1, x);
  35   j0 = ((i0 >> 20) & 0x7ff) - 0x3ff;
  36   sign = (i0 & 0x80000000) != 0 ? -1 : 1;
  37   i0 &= 0xfffff;
  38   i0 |= 0x100000;
  39
  40   if (j0 < 20)
  41     {
  42       if (j0 < 0)
  43         return j0 < -1 ? 0 : sign;
  44       else
  45         {
  46           i0 += 0x80000 >> j0;
  47
  48           result = i0 >> (20 - j0);
  49         }
  50     }
  51   else if (j0 < (int32_t) (8 * sizeof (long int)) - 1)
  52     {
  53       if (j0 >= 52)
  54         result = ((long int) i0 << (j0 - 20)) | (i1 << (j0 - 52));
  55       else
  56         {
  57           u_int32_t j = i1 + (0x80000000 >> (j0 - 20));
  58           if (j < i1)
  59             ++i0;
  60
  61           if (j0 == 20)
  62             result = (long int) i0;
  63           else
  64             result = ((long int) i0 << (j0 - 20)) | (j >> (52 - j0));
  65         }
  66     }
  67   else
  68     {
  69       /* The number is too large.  It is left implementation defined
  70          what happens.  */
  71       return (long int) x;
  72     }
  73
  74   return sign * result;
  75 }
  76
  77 weak_alias (__lround, lround)
  78 #ifdef NO_LONG_DOUBLE
  79 strong_alias (__lround, __lroundl)
  80 weak_alias (__lround, lroundl)
  81 #endif