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[RTL]

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Add implementation of RtlFindLastBackwardRunClear from amd64 branch, thanks to Alex for noticing that it has never been merged.

svn path=/trunk/; revision=61872
This commit is contained in:
Timo Kreuzer 2014-01-28 21:55:30 +00:00
parent 91bacc4dc8
commit 55564f4975
1 changed files with 57 additions and 3 deletions
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60
reactos/lib/rtl/bitmap.c
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@ -709,7 +709,7 @@ RtlFindNextForwardRunSet(
*StartingRunIndex = FromIndex + Length;
/* Now return the length of the run */
return RtlpGetLengthOfRunSet(BitMapHeader, FromIndex, MAXINDEX);
return RtlpGetLengthOfRunSet(BitMapHeader, FromIndex + Length, MAXINDEX);
}
BITMAP_INDEX
@ -728,8 +728,62 @@ RtlFindLastBackwardRunClear(
_In_ BITMAP_INDEX FromIndex,
_Out_ PBITMAP_INDEX StartingRunIndex)
{
UNIMPLEMENTED;
return 0;
BITMAP_INDEX Value, InvValue, BitPos;
PBITMAP_BUFFER Buffer;
/* Make sure we don't go past the end */
FromIndex = min(FromIndex, BitMapHeader->SizeOfBitMap - 1);
/* Calculate positions */
Buffer = BitMapHeader->Buffer + FromIndex / _BITCOUNT;
BitPos = (_BITCOUNT - 1) - (FromIndex & (_BITCOUNT - 1));
/* Get the inversed value, clear bits that don't belong to the run */
InvValue = ~(*Buffer--) << BitPos >> BitPos;
/* Skip all set ULONGs */
while (InvValue == 0)
{
/* Did we already reach past the first ULONG? */
if (Buffer < BitMapHeader->Buffer)
{
/* Yes, nothing found */
return 0;
}
InvValue = ~(*Buffer--);
}
/* We hit a clear bit, check how many set bits are left */
BitScanReverse(&BitPos, InvValue);
/* Calculate last bit position */
FromIndex = (Buffer + 1 - BitMapHeader->Buffer) * _BITCOUNT + BitPos;
Value = ~InvValue << ((_BITCOUNT - 1) - BitPos) >> ((_BITCOUNT - 1) - BitPos);
/* Skip all clear ULONGs */
while (Value == 0 && Buffer >= BitMapHeader->Buffer)
{
Value = *Buffer--;
}
if (Value != 0)
{
/* We hit a set bit, check how many clear bits are left */
BitScanReverse(&BitPos, Value);
/* Calculate Starting Index */
*StartingRunIndex = (Buffer + 1 - BitMapHeader->Buffer) * _BITCOUNT + BitPos + 1;
}
else
{
/* We reached the start of the bitmap */
*StartingRunIndex = 0;
}
/* Return length of the run */
return FromIndex - *StartingRunIndex;
}