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Rewrote RtlFind{Most,Least}SignificantBit in a more portable way.

This commit is contained in:
Alexandre Julliard 2003-03-07 23:15:52 +00:00
parent 361e691961
commit b5d8f532db
1 changed files with 44 additions and 48 deletions
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92
dlls/ntdll/rtlbitmap.c
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@ -50,8 +50,8 @@ static const BYTE NTDLL_leastSignificant[16] = {
};
/* Last set bit in a nibble; used for determining most significant bit */
static const BYTE NTDLL_mostSignificant[16] = {
0, 0, 1, 1, 2, 2, 2, 2, 3, 3, 3, 3, 3, 3, 3, 3
static const signed char NTDLL_mostSignificant[16] = {
-1, 0, 1, 1, 2, 2, 2, 2, 3, 3, 3, 3, 3, 3, 3, 3
};
/*************************************************************************
@ -568,37 +568,35 @@ ULONG WINAPI RtlNumberOfClearBits(PCRTL_BITMAP lpBits)
*
* Find the most significant bit in a 64 bit integer.
*
* PARAMS
* lpBits [I] Bitmap pointer
* ulStart [I] First bit to search from
*
* RETURNS
* The position of the most significant bit.
*/
CCHAR WINAPI RtlFindMostSignificantBit(ULONGLONG ulLong)
{
LONG lCount = 64;
LPBYTE lpOut = (LPBYTE)&ulLong + 7;
signed char ret = 32;
DWORD dw;
TRACE("(%lld)\n", ulLong);
if (!(ulLong & 0xffffffff00000000ul))
{
lpOut -= 4;
lCount -= 32;
}
for (; lCount > 0; lCount -= 8)
{
if (*lpOut)
if (!(dw = (ulLong >> 32)))
{
if (*lpOut & 0xf0)
return lCount - 4 + NTDLL_mostSignificant[*lpOut >> 4];
return lCount - 8 + NTDLL_mostSignificant[*lpOut & 0x0f];
ret = 0;
dw = (DWORD)ulLong;
}
lpOut--;
}
return -1;
if (dw & 0xffff0000)
{
dw >>= 16;
ret += 16;
}
if (dw & 0xff00)
{
dw >>= 8;
ret += 8;
}
if (dw & 0xf0)
{
dw >>= 4;
ret += 4;
}
return ret + NTDLL_mostSignificant[dw];
}
/*************************************************************************
@ -606,37 +604,35 @@ CCHAR WINAPI RtlFindMostSignificantBit(ULONGLONG ulLong)
*
* Find the least significant bit in a 64 bit integer.
*
* PARAMS
* lpBits [I] Bitmap pointer
* ulStart [I] First bit to search from
*
* RETURNS
* The position of the least significant bit.
*/
CCHAR WINAPI RtlFindLeastSignificantBit(ULONGLONG ulLong)
{
ULONG ulCount = 0;
LPBYTE lpOut = (LPBYTE)&ulLong;
signed char ret = 0;
DWORD dw;
TRACE("(%lld)\n", ulLong);
if (!(ulLong & 0xffffffff))
{
lpOut += 4;
ulCount = 32;
}
for (; ulCount < 64; ulCount += 8)
{
if (*lpOut)
if (!(dw = (DWORD)ulLong))
{
if (*lpOut & 0x0f)
return ulCount + NTDLL_leastSignificant[*lpOut & 0x0f];
return ulCount + 4 + NTDLL_leastSignificant[*lpOut >> 4];
ret = 32;
if (!(dw = ulLong >> 32)) return -1;
}
lpOut++;
}
return -1;
if (!(dw & 0xffff))
{
dw >>= 16;
ret += 16;
}
if (!(dw & 0xff))
{
dw >>= 8;
ret += 8;
}
if (!(dw & 0x0f))
{
dw >>= 4;
ret += 4;
}
return ret + NTDLL_leastSignificant[dw & 0x0f];
}
/*************************************************************************