FILE_COMPRESSION_INFORMATION - NtDoc

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

typedef struct _FILE_COMPRESSION_INFORMATION
{
    LARGE_INTEGER CompressedFileSize;
    USHORT CompressionFormat;
    UCHAR CompressionUnitShift;
    UCHAR ChunkShift;
    UCHAR ClusterShift;
    UCHAR Reserved[3];
} FILE_COMPRESSION_INFORMATION, *PFILE_COMPRESSION_INFORMATION;

#endif

View code on GitHub

This structure is documented in Windows Driver Kit.