reactos/win32ss/core/gdi/eng/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 INT
  25 APIENTRY
  26 EngMulDiv(
  27     _In_ INT iMultiplicand,
  28     _In_ INT iMultiplier,
  29     _In_ INT iDivisor)
  30 {
  31     INT64 i64Multiplied, i64Result;
  32
  33     /* Check for divide by zero */
  34     if (iDivisor == 0)
  35     {
  36         /* Quick sign check and return "infinite" */
  37         return ((iMultiplicand ^ iMultiplier) < 0) ? INT_MIN : INT_MAX;
  38     }
  39
  40     /* We want to deal with a positive divisor to simplify the logic. */
  41     if (iDivisor < 0)
  42     {
  43         iMultiplicand = -iMultiplicand;
  44         iDivisor = -iDivisor;
  45     }
  46
  47     /* Do the multiplication */
  48     i64Multiplied = Int32x32To64(iMultiplicand, iMultiplier);
  49
  50     /* If the result is positive, we add to round, else we subtract to round. */
  51     if (i64Multiplied >= 0)
  52     {
  53         i64Multiplied += (iDivisor / 2);
  54     }
  55     else
  56     {
  57         i64Multiplied -= (iDivisor / 2);
  58     }
  59
  60     /* Now do the divide */
  61     i64Result = i64Multiplied / iDivisor;
  62
  63     /* Check for positive overflow */
  64     if (i64Result > INT_MAX)
  65     {
  66         return INT_MAX;
  67     }
  68
  69     /* Check for negative overflow. */
  70     if (i64Result < INT_MIN)
  71     {
  72         return INT_MIN;
  73     }
  74
  75     return (INT)i64Result;
  76 }
  77