The RtlFindClearBits routine searches for a range of clear bits of a requested size within a bitmap.
ULONG RtlFindClearBits( _In_ PRTL_BITMAP BitMapHeader, _In_ ULONG NumberToFind, _In_ ULONG HintIndex );
- BitMapHeader [in]
- NumberToFind [in]
Specifies how many contiguous clear bits will satisfy this request.
- HintIndex [in]
Specifies a zero-based bit position from which to start looking for a clear bit range of the given size.
RtlFindClearBits either returns the zero-based starting bit index for a clear bit range of at least the requested size, or it returns 0xFFFFFFFF if it cannot find such a range within the given bitmap.
For a successful call, the returned bit position is not necessarily equivalent to the given HintIndex. If necessary, RtlFindClearBits searches the whole bitmap to locate a clear bit range of the requested size. However, it starts searching for the requested range from HintIndex, so callers can find such a range more quickly when they can supply appropriate hints about where to start looking.
Callers of RtlFindClearBits must be running at IRQL <= APC_LEVEL if the memory that contains the bitmap variable is pageable or the memory at BitMapHeader is pageable. Otherwise, RtlFindClearBits can be called at any IRQL.
|Available starting with Windows 2000.|
|<= APC_LEVEL (See Remarks section)|