RtlFindSetBitsAndClear function (wdm.h)

The RtlFindSetBitsAndClear routine searches for a range of set bits of a requested size within a bitmap and clears all bits in the range when it has been located.

Syntax

NTSYSAPI ULONG RtlFindSetBitsAndClear(
  [in] PRTL_BITMAP BitMapHeader,
  [in] ULONG       NumberToFind,
  [in] ULONG       HintIndex
);

Parameters

[in] BitMapHeader

A pointer to the RTL_BITMAP structure that describes the bitmap. This structure must have been initialized by the RtlInitializeBitMap routine.

[in] NumberToFind

Specifies how many contiguous set bits will satisfy this request.

[in] HintIndex

Specifies a zero-based bit position around which to start looking for a set bit range of the given size.

Return value

RtlFindSetBitsAndClear either returns the zero-based starting bit index for a set bit range of the requested size that it cleared, or it returns 0xFFFFFFFF if it cannot find such a range within the given bitmap variable.

Remarks

For a successful call, the returned bit position is not necessarily equivalent to the given HintIndex. If necessary, RtlFindSetBitsAndClear searches the whole bitmap to locate a set bit range of the requested size. However, it starts searching for the requested range near HintIndex, so callers can clear such a range more quickly when they can supply appropriate hints about where to start looking.

Callers of RtlFindSetBitsAndClear 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, RtlFindSetBitsAndClear can be called at any IRQL.

Requirements

See also

RTL_BITMAP

RtlAreBitsSet

RtlClearAllBits

RtlClearBits

RtlFindSetBits

RtlInitializeBitMap

RtlNumberOfSetBits