System.Posix.HFuse

FuseOperations contains a field for each filesystem operations that can be called by FUSE. Think like if you were implementing a file system inside the Linux kernel.

Each actions must return a POSIX error code, also called Errno reflecting operation relult. For actions not using Either, you should return eOK in case of success.

Read and writes are done with Haskell String type. Even if this representation is known to have drawbacks, the binding try to be coherent with current Haskell libraries.

module Foreign.C.Error

data FuseOperations

Source

This record, given to fuseMain, binds each required file system operations.

Each field is named against System.Posix names. Matching Linux system calls are also given as a reference.

fuseGetFileStat implements System.Posix.Files.getSymbolicLinkStatus operation (POSIX lstat(2)).
fuseReadSymbolicLink implements System.Posix.Files.readSymbolicLink operation (POSIX readlink(2)). The returned FilePath might be truncated depending on caller buffer size.
fuseGetDirectoryContents implements System.Directory.getDirectoryContents (POSIX readddir(2)).
fuseCreateDevice implements System.Posix.Files.createDevice (POSIX mknod(2)). This function will also be called for regular file creation.
fuseCreateDirectory implements System.Posix.Directory.createDirectory (POSIX mkdir(2)).
fuseRemoveLink implements System.Posix.Files.removeLink (POSIX unlink(2)).
fuseRemoveDirectory implements System.Posix.Directory.removeDirectory (POSIX rmdir(2)).
fuseCreateSymbolicLink implements System.Posix.Files.createSymbolicLink (POSIX symlink(2)).
fuseRename implements System.Posix.Files.rename (POSIX rename(2)).
fuseCreateLink implements System.Posix.Files.createLink (POSIX link(2)).
fuseSetFileMode implements System.Posix.Files.setFileMode (POSIX chmod(2)).
fuseSetOwnerAndGroup implements System.Posix.Files.setOwnerAndGroup (POSIX chown(2)).
fuseSetFileSize implements System.Posix.Files.setFileSize (POSIX truncate(2)).
fuseSetFileTimes implements System.Posix.Files.setFileTimes (POSIX utime(2)).
fuseOpen implements System.Posix.Files.openFd (POSIX open(2)), but this does not actually returns a file handle but eOK if the operation is permitted with the given flags. No creation, exclusive access or truncating flags will be passed.
fuseRead implements Unix98 pread(2). It differs from System.Posix.Files.fdRead by the explicit FileOffset argument.
fuseWrite implements Unix98 pwrite(2). It differs from System.Posix.Files.fdWrite by the explicit FileOffset argument.
fuseGetFileSystemStats implements statfs(2).
fuseFlush is called when close(2) has been called on an open file. Note: this does not mean that the file is released. This function may be called more than once for each open(2). The return value is passed on to the close(2) system call.
fuseRelease is called when an open file has all file descriptors closed and all memory mappings unmapped. For every open call there will be exactly one release call with the same flags. It is possible to have a file opened more than once, in which case only the last release will mean, that no more reads or writes will happen on the file.
fuseSynchronizeFile implements fsync(2).

Constructors

FuseOperations

fuseGetFileStat :: FilePath -> IO (Either Errno FileStat)
fuseReadSymbolicLink :: FilePath -> IO (Either Errno FilePath)
fuseGetDirectoryContents :: FilePath -> IO (Either Errno [(FilePath, EntryType)])
fuseCreateDevice :: FilePath -> EntryType -> FileMode -> DeviceID -> IO Errno
fuseCreateDirectory :: FilePath -> FileMode -> IO Errno
fuseRemoveLink :: FilePath -> IO Errno
fuseRemoveDirectory :: FilePath -> IO Errno
fuseCreateSymbolicLink :: FilePath -> FilePath -> IO Errno
fuseRename :: FilePath -> FilePath -> IO Errno
fuseCreateLink :: FilePath -> FilePath -> IO Errno
fuseSetFileMode :: FilePath -> FileMode -> IO Errno
fuseSetOwnerAndGroup :: FilePath -> UserID -> GroupID -> IO Errno
fuseSetFileSize :: FilePath -> FileOffset -> IO Errno
fuseSetFileTimes :: FilePath -> EpochTime -> EpochTime -> IO Errno
fuseOpen :: FilePath -> OpenMode -> OpenFileFlags -> IO Errno
fuseRead :: FilePath -> ByteCount -> FileOffset -> IO (Either Errno (String, ByteCount))
fuseWrite :: FilePath -> String -> FileOffset -> IO (Either Errno ByteCount)
fuseGetFileSystemStats :: String -> IO (Either Errno FileSystemStats)
fuseFlush :: FilePath -> IO Errno
fuseRelease :: FilePath -> Int -> IO ()
fuseSynchronizeFile :: FilePath -> SyncType -> IO Errno
fuseOpenDirectory :: FilePath -> IO Errno
fuseReleaseDirectory :: FilePath -> IO Errno
fuseSynchronizeDirectory :: FilePath -> SyncType -> IO Errno
fuseInit :: IO ()
fuseDestroy :: IO ()

defaultFuseOps :: FuseOperations

Source

Empty / default versions of the FUSE operations.

fuseMain :: FuseOperations -> (Exception -> IO Errno) -> IO ()

Source

Main function of FUSE. This is all that has to be called from the main function. On top of the FuseOperations record with filesystem implementation, you must give an exception handler converting Haskell exceptions to Errno.

This function does the following:

parses command line options (-d, -s and -h) ;
passes all options after -- to the fusermount program ;
mounts the filesystem by calling fusermount ;
installs signal handlers for System.Posix.Signals.keyboardSignal, System.Posix.Signals.lostConnection, System.Posix.Signals.softwareTermination and System.Posix.Signals.openEndedPipe ;
registers an exit handler to unmount the filesystem on program exit ;
registers the operations ;
calls FUSE event loop.

defaultExceptionHandler :: Exception -> IO Errno

Source

Default exception handler. Print the exception on error output and returns eFAULT.

Operations datatypes

data FileStat

Source

Used by fuseGetFileStat.

Constructors

FileStat

statEntryType :: EntryType
statFileMode :: FileMode
statLinkCount :: LinkCount
statFileOwner :: UserID
statFileGroup :: GroupID
statSpecialDeviceID :: DeviceID
statFileSize :: FileOffset
statBlocks :: Integer
statAccessTime :: EpochTime
statModificationTime :: EpochTime
statStatusChangeTime :: EpochTime

data EntryType

Source

Used by fuseGetDirectoryContents implementation to specify the type of a directory entry.

Constructors

Unknown	Unknown entry type
NamedPipe
CharacterSpecial
Directory
BlockSpecial
RegularFile
SymbolicLink
Socket

data FileSystemStats

Source

Type used by the fuseGetFileSystemStats.

Constructors

FileSystemStats

fsStatBlockSize :: Integer	Optimal transfer block size. FUSE default is 512.
fsStatBlockCount :: Integer	Total data blocks in file system.
fsStatBlocksFree :: Integer	Free blocks in file system.
fsStatBlocksAvailable :: Integer	Free blocks available to non-superusers.
fsStatFileCount :: Integer	Total file nodes in file system.
fsStatFilesFree :: Integer	Free file nodes in file system.
fsStatMaxNameLength :: Integer	Maximum length of filenames. FUSE default is 255.