reactos/lib/kernel32/misc/muldiv.c

   1 /* $Id$
   2  *
   3  */
   4 #include <k32.h>
   5
   6
   7 /***********************************************************************
   8  *           MulDiv   (KERNEL32.@)
   9  * RETURNS
  10  *      Result of multiplication and division
  11  *      -1: Overflow occurred or Divisor was 0
  12  * FIXME! move to correct file
  13  *
  14  * @implemented
  15  */
  16 INT
  17 WINAPI
  18 MulDiv(INT nNumber,
  19        INT nNumerator,
  20        INT nDenominator)
  21 {
  22     LARGE_INTEGER Result;
  23     LONG Negative;
  24
  25     /* Find out if this will be a negative result */
  26     Negative = nNumber ^ nNumerator ^ nDenominator;
  27
  28     /* Turn all the parameters into absolute values */
  29     if (nNumber < 0) nNumber *= -1;
  30     if (nNumerator < 0) nNumerator *= -1;
  31     if (nDenominator < 0) nDenominator *= -1;
  32
  33     /* Calculate the result */
  34     Result.QuadPart = Int32x32To64(nNumber, nNumerator) + (nDenominator / 2);
  35
  36     /* Now check for overflow */
  37     if (nDenominator > Result.HighPart)
  38     {
  39         /* Divide the product to get the quotient and remainder */
  40         Result.LowPart = RtlEnlargedUnsignedDivide(*(PULARGE_INTEGER)&Result,
  41                                                    (ULONG)nDenominator,
  42                                                    &Result.HighPart);
  43
  44         /* Do the sign changes */
  45         if ((LONG)Result.LowPart >= 0)
  46         {
  47             return (Negative >= 0) ? Result.LowPart : -(LONG)Result.LowPart;
  48         }
  49     }
  50
  51     /* Return overflow */
  52     return - 1;
  53 }
  54