#ifndef _NTRTL_H
NTSYSAPI
VOID
NTAPI
RtlClearBits(
_In_ PRTL_BITMAP BitMapHeader,
_In_range_(0, BitMapHeader->SizeOfBitMap - NumberToClear) ULONG StartingIndex,
_In_range_(0, BitMapHeader->SizeOfBitMap - StartingIndex) ULONG NumberToClear
);
View code on GitHub
This function is documented in Windows Driver Kit.