#ifndef _NTRTL_H

NTSYSAPI
NTSTATUS
NTAPI
RtlCompressChunks(
    _In_reads_bytes_(UncompressedBufferSize) PUCHAR UncompressedBuffer,
    _In_ ULONG UncompressedBufferSize,
    _Out_writes_bytes_(CompressedBufferSize) PUCHAR CompressedBuffer,
    _In_range_(>=, (UncompressedBufferSize - (UncompressedBufferSize / 16))) ULONG CompressedBufferSize,
    _Inout_updates_bytes_(CompressedDataInfoLength) PCOMPRESSED_DATA_INFO CompressedDataInfo,
    _In_range_(>, sizeof(COMPRESSED_DATA_INFO)) ULONG CompressedDataInfoLength,
    _In_ PVOID WorkSpace
    );

#endif
View code on GitHub

// ntifs.h

NTSYSAPI NTSTATUS RtlCompressChunks(
  PUCHAR                UncompressedBuffer,
  ULONG                 UncompressedBufferSize,
  PUCHAR                CompressedBuffer,
  ULONG                 CompressedBufferSize,
  PCOMPRESSED_DATA_INFO CompressedDataInfo,
  ULONG                 CompressedDataInfoLength,
  PVOID                 WorkSpace
);
View the official Windows Driver Kit DDI reference