FILE_COMPRESSION_INFORMATION structure

The FILE_COMPRESSION_INFORMATION structure describes the state of a compressed data buffer.

Syntax


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;

Members

CompressedFileSize

The size, in bytes, of the compressed file.

CompressionFormat

The compression format. This member must have one of the following values:

ValueMeaning

COMPRESSION_FORMAT_NONE

No compression format.

COMPRESSION_FORMAT_DEFAULT

Default compression format.

COMPRESSION_FORMAT_LZNT1

LZNT1 compression format.

 

CompressionUnitShift

The log, base 2, of the number of clusters per compression

unit. In the NTFS file system, this value is NTFS_CLUSTERS_PER_COMPRESSION.

ChunkShift

The log, base 2, of the number of bytes in a chunk. In other words, the size in bytes of the chunk is 2 ** ChunkShift, or (1 << ChunkShift).

ClusterShift

The log, base 2, of the minimum number of clusters by which compression must reduce the size of the compression unit. If compression does not reduce the size of the compression unit by at least 2 ** ClusterShift clusters (or 1 << ClusterShift clusters), compression will not occur. Each compression unit must occupy at least one cluster less than the uncompressed data would occupy.

Reserved

Reserved

Requirements

Header

Ntifs.h (include Ntifs.h or Fltkernel.h)

See also

FLT_PARAMETERS for IRP_MJ_QUERY_INFORMATION
FltQueryInformationFile
IRP_MJ_QUERY_INFORMATION

 

 

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