RtlFindClearBitsAndSet function (wdm.h)

Article
02/22/2024

The RtlFindClearBitsAndSet routine searches for a range of clear bits of a requested size within a bitmap and sets all bits in the range when it has been located.

Syntax

NTSYSAPI ULONG RtlFindClearBitsAndSet(
  [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 clear bits will satisfy this request.

[in] HintIndex

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

Return value

RtlFindClearBitsAndSet either returns the zero-based starting bit index for a clear bit range of the requested size that it set, 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, RtlFindClearBitsAndSet 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 have such a range reset more quickly when they can supply appropriate hints about where to start looking.

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

Requirements

Requirement	Value
Minimum supported client	Available starting with Windows 2000.
Target Platform	Universal
Header	wdm.h (include Wdm.h, Ntddk.h, Ntifs.h)
Library	NtosKrnl.lib
DLL	NtosKrnl.exe
IRQL	<= APC_LEVEL (See Remarks section)