FILE_COMPRESSION_INFORMATION structure (ntifs.h)
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:
| Value | Meaning |
|---|---|
| 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[3]
Reserved
Requirements
| Requirement | Value |
|---|---|
| Header | ntifs.h (include Ntifs.h, Fltkernel.h) |