COMPRESSED_DATA_INFO - NtDoc

#ifndef _NTRTL_H

typedef struct _COMPRESSED_DATA_INFO
{
    //
    //  Code for the compression format (and engine) as
    //  defined in ntrtl.h.  Note that COMPRESSION_FORMAT_NONE
    //  and COMPRESSION_FORMAT_DEFAULT are invalid if
    //  any of the described chunks are compressed.
    //

    USHORT CompressionFormatAndEngine;

    //
    //  Since chunks and compression units are expected to be
    //  powers of 2 in size, we express then log2.  So, for
    //  example (1 << ChunkShift) == ChunkSizeInBytes.  The
    //  ClusterShift indicates how much space must be saved
    //  to successfully compress a compression unit - each
    //  successfully compressed compression unit must occupy
    //  at least one cluster less in bytes than an uncompressed
    //  compression unit.
    //

    UCHAR CompressionUnitShift;
    UCHAR ChunkShift;
    UCHAR ClusterShift;
    UCHAR Reserved;

    //
    //  This is the number of entries in the CompressedChunkSizes
    //  array.
    //

    USHORT NumberOfChunks;

    //
    //  This is an array of the sizes of all chunks resident
    //  in the compressed data buffer.  There must be one entry
    //  in this array for each chunk possible in the uncompressed
    //  buffer size.  A size of FSRTL_CHUNK_SIZE indicates the
    //  corresponding chunk is uncompressed and occupies exactly
    //  that size.  A size of 0 indicates that the corresponding
    //  chunk contains nothing but binary 0's, and occupies no
    //  space in the compressed data.  All other sizes must be
    //  less than FSRTL_CHUNK_SIZE, and indicate the exact size
    //  of the compressed data in bytes.
    //

    ULONG CompressedChunkSizes[ANYSIZE_ARRAY];
} COMPRESSED_DATA_INFO, *PCOMPRESSED_DATA_INFO;

#endif
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