#ifndef _NTRTL_H
NTSYSAPI
ULONG
NTAPI
RtlFindClearRuns(
_In_ PRTL_BITMAP BitMapHeader,
_Out_writes_to_(SizeOfRunArray, return) PRTL_BITMAP_RUN RunArray,
_In_range_(>, 0) ULONG SizeOfRunArray,
_In_ BOOLEAN LocateLongestRuns
);
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This function is documented in Windows Driver Kit.