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- Fix implementation of RtlFindSetBits to be able to return bits that are at lower location than the supplied hint.

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svn path=/trunk/; revision=11053
This commit is contained in:
Filip Navara 2004-09-25 20:49:57 +00:00
parent 91fea9194d
commit 3823d945f5
1 changed files with 48 additions and 25 deletions
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73
reactos/lib/rtl/bitmap.c
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@ -16,7 +16,7 @@
* along with this program; if not, write to the Free Software
* Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
*/
/* $Id: bitmap.c,v 1.3 2004/09/25 19:39:57 navaraf Exp $
/* $Id: bitmap.c,v 1.4 2004/09/25 20:49:57 navaraf Exp $
*
* COPYRIGHT: See COPYING in the top level directory
* PROJECT: ReactOS kernel
@ -600,6 +600,9 @@ RtlFindSetBits(PRTL_BITMAP BitMapHeader,
ULONG Count;
PULONG Ptr;
ULONG Mask;
ULONG Loop;
ULONG End;
ULONG OriginalHint = HintIndex;
Size = BitMapHeader->SizeOfBitMap;
if (NumberToFind > Size || NumberToFind == 0)
@ -608,40 +611,60 @@ RtlFindSetBits(PRTL_BITMAP BitMapHeader,
if (HintIndex >= Size)
HintIndex = 0;
/* Initialize the values to the hint location. */
Index = HintIndex;
Ptr = (PULONG)BitMapHeader->Buffer + (Index / 32);
Ptr = BitMapHeader->Buffer + (Index / 32);
Mask = 1 << (Index & 0x1F);
End = Size;
while (HintIndex < Size)
/* The outer loop does the magic of first searching from the
* hint to the bitmap end and then going again from beginning
* of the bitmap to the hint location.
*/
for (Loop = 0; Loop < 2; Loop++)
{
/* Count set bits */
for (Count = 0; Index < Size && *Ptr & Mask; Index++)
while (HintIndex < End)
{
if (++Count >= NumberToFind)
return HintIndex;
Mask <<= 1;
if (Mask == 0)
/* Count set bits */
for (Count = 0; Index < End && *Ptr & Mask; Index++)
{
Mask = 1;
Ptr++;
if (++Count >= NumberToFind)
return HintIndex;
Mask <<= 1;
if (Mask == 0)
{
Mask = 1;
Ptr++;
}
}
/* Skip clear bits */
for (; Index < End && ~*Ptr & Mask; Index++)
{
Mask <<= 1;
if (Mask == 0)
{
Mask = 1;
Ptr++;
}
}
HintIndex = Index;
}
/* Skip clear bits */
for (; Index < Size && ~*Ptr & Mask; Index++)
{
Mask <<= 1;
/* Optimalization */
if (OriginalHint == 0)
break;
if (Mask == 0)
{
Mask = 1;
Ptr++;
}
}
HintIndex = Index;
/* Initialize the values for the beginning -> hint loop. */
HintIndex = Index = 0;
End = OriginalHint + NumberToFind - 1;
End = End > Size ? Size : End;
Ptr = BitMapHeader->Buffer;
Mask = 1;
}
return (ULONG)-1;