subsystems/win32/win32k/misc/math.c

   1 /* Math functions for i387.
   2    Copyright (C) 1995, 1996, 1997 Free Software Foundation, Inc.
   3    This file is part of the GNU C Library.
   4    Contributed by John C. Bowman <bowman@ipp-garching.mpg.de>, 1995.
   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., 51 Franklin Street, Fifth Floor,
  19    Boston, MA 02110-1301, USA.
  20 */
  21
  22 #include <win32k.h>
  23
  24 /*
  25  * FIXME! Is there a better algorithm. like FT_MulDiv
  26  *
  27  * @implemented
  28  */
  29 INT APIENTRY EngMulDiv(
  30              INT nMultiplicand,
  31              INT nMultiplier,
  32              INT nDivisor)
  33 {
  34 #if SIZEOF_LONG_LONG >= 8
  35     long long ret;
  36
  37     if (!nDivisor) return -1;
  38
  39     /* We want to deal with a positive divisor to simplify the logic. */
  40     if (nDivisor < 0)
  41     {
  42       nMultiplicand = - nMultiplicand;
  43       nDivisor = -nDivisor;
  44     }
  45
  46     /* If the result is positive, we "add" to round. else, we subtract to round. */
  47     if ( ( (nMultiplicand <  0) && (nMultiplier <  0) ) ||
  48          ( (nMultiplicand >= 0) && (nMultiplier >= 0) ) )
  49       ret = (((long long)nMultiplicand * nMultiplier) + (nDivisor/2)) / nDivisor;
  50     else
  51       ret = (((long long)nMultiplicand * nMultiplier) - (nDivisor/2)) / nDivisor;
  52
  53     if ((ret > 2147483647) || (ret < -2147483647)) return -1;
  54     return ret;
  55 #else
  56     if (!nDivisor) return -1;
  57
  58     /* We want to deal with a positive divisor to simplify the logic. */
  59     if (nDivisor < 0)
  60     {
  61       nMultiplicand = - nMultiplicand;
  62       nDivisor = -nDivisor;
  63     }
  64
  65     /* If the result is positive, we "add" to round. else, we subtract to round. */
  66     if ( ( (nMultiplicand <  0) && (nMultiplier <  0) ) ||
  67          ( (nMultiplicand >= 0) && (nMultiplier >= 0) ) )
  68       return ((nMultiplicand * nMultiplier) + (nDivisor/2)) / nDivisor;
  69
  70     return ((nMultiplicand * nMultiplier) - (nDivisor/2)) / nDivisor;
  71
  72 #endif
  73 }