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The following table shows the FSD IOCTLs along with a description of each.

Programming element Description
FSCTL_GET_COMPRESSION This IOCTL retrieves the current compression state of a file or directory on a volume whose file system supports per-stream compression.
FSCTL_GET_REGISTRY_INFO This IOCTL obtains information about a registry key.
FSCTL_QUERY_ALLOCATED_RANGES This IOCTL scans a file or alternate stream looking for ranges that may contain nonzero data. Only compressed or sparse files can have zeroed ranges known to the OS. For other files, the output buffer will contain only a single entry that contains the starting point and the length requested.
FSCTL_SET_COMPRESSION This IOCTL sets the compression state of a file or directory on a volume whose file system supports per-file and per-directory compression. You can use this IOCTL to compress or uncompress a file or directory on such a volume.
FSCTL_SET_SPARSE This IOCTL marks an indicated file as sparse. In a sparse file, large ranges of zeros may not require disk allocation. Space for nonzero data will be allocated as needed as the file is written.
FSCTL_SET_ZERO_DATA This IOCTL fills a specified range of a file with zeros.
FSCTL_USER This user-defined IOCTL can be used to define additional FSD IOCTLs.
FSSCTL_FLUSH_BUFFERS This IOCTL flushes all buffers on a specified file system.

See Also

FSD Reference

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