| Platform SDK: Files and I/O |
On NTFS volumes, each file and directory has a compression attribute. Other file systems may also implement a compression attribute for individual files and directories.
You can determine whether a file system supports a compression attribute for files and directories by calling the GetVolumeInformation function and examining the FS_FILE_COMPRESSION bit flag.
Use the GetFileAttributes or GetFileAttributesEx function to determine the compression attribute of a file or directory.
If a file's compression attribute is set (FILE_ATTRIBUTE_COMPRESSED), all data in the file is compressed. If the attribute is clear, none of the data in the file is compressed. There is no partially compressed state. The compression attribute is a simple Boolean indicator of compression state.
A directory's compression attribute provides a default compression attribute for newly created files and subdirectories. When you call CreateFile or CreateDirectory to create a new file or directory, the new file or directory inherits the compression attribute of its parent directory.