dll/win32/kernel32/misc/muldiv.c

   1 /* $Id$
   2  *
   3  * COPYRIGHT:       See COPYING in the top level directory
   4  * PROJECT:         ReactOS system libraries
   5  * FILE:            dll/win32/kernel32/misc/muldiv.c
   6  * PURPOSE:
   7  * PROGRAMMER:      Casper S. Hornstrup
   8  *                  Gunnar Andre Dalsnes
   9  * UPDATE HISTORY:
  10  *                  Created 06/12/2002
  11  */
  12
  13 #include <k32.h>
  14
  15
  16 /***********************************************************************
  17  *           MulDiv   (KERNEL32.@)
  18  * RETURNS
  19  *      Result of multiplication and division
  20  *      -1: Overflow occurred or Divisor was 0
  21  * FIXME! move to correct file
  22  *
  23  * @implemented
  24  */
  25 INT
  26 WINAPI
  27 MulDiv(INT nNumber,
  28        INT nNumerator,
  29        INT nDenominator)
  30 {
  31     LARGE_INTEGER Result;
  32     LONG Negative;
  33
  34     /* Find out if this will be a negative result */
  35     Negative = nNumber ^ nNumerator ^ nDenominator;
  36
  37     /* Turn all the parameters into absolute values */
  38     if (nNumber < 0) nNumber *= -1;
  39     if (nNumerator < 0) nNumerator *= -1;
  40     if (nDenominator < 0) nDenominator *= -1;
  41
  42     /* Calculate the result */
  43     Result.QuadPart = Int32x32To64(nNumber, nNumerator) + (nDenominator / 2);
  44
  45     /* Now check for overflow */
  46     if (nDenominator > Result.HighPart)
  47     {
  48         /* Divide the product to get the quotient and remainder */
  49         Result.LowPart = RtlEnlargedUnsignedDivide(*(PULARGE_INTEGER)&Result,
  50                                                    (ULONG)nDenominator,
  51                                                    (PULONG)&Result.HighPart);
  52
  53         /* Do the sign changes */
  54         if ((LONG)Result.LowPart >= 0)
  55         {
  56             return (Negative >= 0) ? (LONG)Result.LowPart : -(LONG)Result.LowPart;
  57         }
  58     }
  59
  60     /* Return overflow */
  61     return - 1;
  62 }
  63