reactos/lib/kernel32/misc/muldiv.c

   1 /* $Id$
   2  *
   3  */
   4 #include <windows.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 STDCALL MulDiv(
  17              INT nMultiplicand,
  18              INT nMultiplier,
  19              INT nDivisor)
  20 {
  21 #if SIZEOF_LONG_LONG >= 8
  22     long long ret;
  23
  24     if (!nDivisor) return -1;
  25
  26     /* We want to deal with a positive divisor to simplify the logic. */
  27     if (nDivisor < 0)
  28     {
  29       nMultiplicand = - nMultiplicand;
  30       nDivisor = -nDivisor;
  31     }
  32
  33     /* If the result is positive, we "add" to round. else, we subtract to round. */
  34     if ( ( (nMultiplicand <  0) && (nMultiplier <  0) ) ||
  35          ( (nMultiplicand >= 0) && (nMultiplier >= 0) ) )
  36       ret = (((long long)nMultiplicand * nMultiplier) + (nDivisor/2)) / nDivisor;
  37     else
  38       ret = (((long long)nMultiplicand * nMultiplier) - (nDivisor/2)) / nDivisor;
  39
  40     if ((ret > 2147483647) || (ret < -2147483647)) return -1;
  41     return ret;
  42 #else
  43     if (!nDivisor) return -1;
  44
  45     /* We want to deal with a positive divisor to simplify the logic. */
  46     if (nDivisor < 0)
  47     {
  48       nMultiplicand = - nMultiplicand;
  49       nDivisor = -nDivisor;
  50     }
  51
  52     /* If the result is positive, we "add" to round. else, we subtract to round. */
  53     if ( ( (nMultiplicand <  0) && (nMultiplier <  0) ) ||
  54          ( (nMultiplicand >= 0) && (nMultiplier >= 0) ) )
  55       return ((nMultiplicand * nMultiplier) + (nDivisor/2)) / nDivisor;
  56
  57     return ((nMultiplicand * nMultiplier) - (nDivisor/2)) / nDivisor;
  58
  59 #endif
  60 }