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[WIN32K]

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Rewrite EngMulDiv.

svn path=/trunk/; revision=58082
This commit is contained in:
Timo Kreuzer 2013-01-01 12:09:53 +00:00
parent 46da747829
commit 5b8a6dd3cc
1 changed files with 42 additions and 38 deletions
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82
reactos/win32ss/gdi/eng/math.c
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@ -21,53 +21,57 @@
#include <win32k.h>
/*
* FIXME: Is there a better algorithm, like FT_MulDiv?
*
* @implemented
*/
INT APIENTRY EngMulDiv(
INT nMultiplicand,
INT nMultiplier,
INT nDivisor)
INT
APIENTRY
EngMulDiv(
_In_ INT iMultiplicand,
_In_ INT iMultiplier,
_In_ INT iDivisor)
{
#if SIZEOF_LONG_LONG >= 8
long long ret;
INT64 i64Multiplied, i64Result;
if (!nDivisor) return -1;
/* We want to deal with a positive divisor to simplify the logic. */
if (nDivisor < 0)
/* Check for divide by zero */
if (iDivisor == 0)
{
nMultiplicand = - nMultiplicand;
nDivisor = -nDivisor;
/* Quick sign check and return "infinite" */
return ((iMultiplicand ^ iMultiplier) < 0) ? INT_MIN : INT_MAX;
}
/* If the result is positive, we "add" to round. else, we subtract to round. */
if ( ( (nMultiplicand < 0) && (nMultiplier < 0) ) ||
( (nMultiplicand >= 0) && (nMultiplier >= 0) ) )
ret = (((long long)nMultiplicand * nMultiplier) + (nDivisor/2)) / nDivisor;
/* We want to deal with a positive divisor to simplify the logic. */
if (iDivisor < 0)
{
iMultiplicand = -iMultiplicand;
iDivisor = -iDivisor;
}
/* Do the multiplication */
i64Multiplied = Int32x32To64(iMultiplicand, iMultiplier);
/* If the result is positive, we add to round, else we subtract to round. */
if (i64Multiplied >= 0)
{
i64Multiplied += (iDivisor / 2);
}
else
ret = (((long long)nMultiplicand * nMultiplier) - (nDivisor/2)) / nDivisor;
if ((ret > 2147483647) || (ret < -2147483647)) return -1;
return ret;
#else
if (!nDivisor) return -1;
/* We want to deal with a positive divisor to simplify the logic. */
if (nDivisor < 0)
{
nMultiplicand = - nMultiplicand;
nDivisor = -nDivisor;
i64Multiplied -= (iDivisor / 2);
}
/* If the result is positive, we "add" to round. else, we subtract to round. */
if ( ( (nMultiplicand < 0) && (nMultiplier < 0) ) ||
( (nMultiplicand >= 0) && (nMultiplier >= 0) ) )
return ((nMultiplicand * nMultiplier) + (nDivisor/2)) / nDivisor;
/* Now do the divide */
i64Result = i64Multiplied / iDivisor;
return ((nMultiplicand * nMultiplier) - (nDivisor/2)) / nDivisor;
#endif
/* Check for positive overflow */
if (i64Result > INT_MAX)
{
return INT_MAX;
}
/* Check for negative overflow. */
if (i64Result < INT_MIN)
{
return INT_MIN;
}
return (INT)i64Result;
}