RtlClearBits - NtDoc

Native API online documentation, based on the System Informer (formerly Process Hacker) phnt headers
#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
    );

#endif

View code on GitHub

This function is documented in Windows Driver Kit.