RtlNumberOfClearBits function (wdm.h)

Article
02/22/2024

The RtlNumberOfClearBits routine returns a count of the clear bits in a given bitmap variable.

Syntax

NTSYSAPI ULONG RtlNumberOfClearBits(
  [in] PRTL_BITMAP BitMapHeader
);

Parameters

[in] BitMapHeader

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

Return value

RtlNumberOfClearBits returns the number of bits that are currently clear.

Remarks

Callers of RtlNumberOfClearBits 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, RtlNumberOfClearBits 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)