ru.serce.jnrfuse

Interface FuseFS

All Superinterfaces:

Mountable

All Known Implementing Classes:

AbstractFuseFS, FuseStubFS, HelloFuse, MemoryFS

public interface FuseFS
extends Mountable

Fuse file system. All documentation from "fuse.h"

Since:

27.05.15

See Also:

Most of these should work very similarly to the well known UNIX file system operations. A major exception is that instead of returning an error in 'errno', the operation should return the negated error value (-errno) directly.

All methods are optional, but some are essential for a useful filesystem (e.g. getattr). Open, flush, release, fsync, opendir, releasedir, fsyncdir, access, create, ftruncate, fgetattr, lock, init and destroy are special purpose methods, without which a full featured filesystem can still be implemented.

See http://fuse.sourceforge.net/wiki/ for more information.

Method Summary

Modifier and Type	Method and Description
int	access(java.lang.String path, int mask) Check file access permissions
int	bmap(java.lang.String path, long blocksize, long idx) Map block index within file to block index within device
int	chmod(java.lang.String path, long mode) Change the permission bits of a file
int	chown(java.lang.String path, long uid, long gid) Change the owner and group of a file
int	create(java.lang.String path, long mode, FuseFileInfo fi) Create and open a file
void	destroy(jnr.ffi.Pointer initResult) Clean up filesystem
int	fallocate(java.lang.String path, int mode, long off, long length, FuseFileInfo fi) Allocates space for an open file
int	fgetattr(java.lang.String path, FileStat stbuf, FuseFileInfo fi) Get attributes from an open file
int	flock(java.lang.String path, FuseFileInfo fi, int op) Perform BSD file locking operation
int	flush(java.lang.String path, FuseFileInfo fi) Possibly flush cached data
int	fsync(java.lang.String path, int isdatasync, FuseFileInfo fi) Synchronize file contents
int	fsyncdir(java.lang.String path, FuseFileInfo fi) Synchronize directory contents
int	ftruncate(java.lang.String path, long size, FuseFileInfo fi) Change the size of an open file
int	getattr(java.lang.String path, FileStat stat) Get file attributes.
int	getxattr(java.lang.String path, java.lang.String name, jnr.ffi.Pointer value, long size) Get the attribute NAME of the file pointed to by PATH to VALUE (which is SIZE bytes long).
jnr.ffi.Pointer	init(jnr.ffi.Pointer conn) Initialize filesystem
int	ioctl(java.lang.String path, int cmd, jnr.ffi.Pointer arg, FuseFileInfo fi, long flags, jnr.ffi.Pointer data) Ioctl
int	link(java.lang.String oldpath, java.lang.String newpath) Create a hard link to a file
int	listxattr(java.lang.String path, jnr.ffi.Pointer list, long size) List extended attributes
int	lock(java.lang.String path, FuseFileInfo fi, int cmd, Flock flock) Perform POSIX file locking operation
int	mkdir(java.lang.String path, long mode) Create a directory
int	mknod(java.lang.String path, long mode, long rdev) Create a file node
int	open(java.lang.String path, FuseFileInfo fi) File open operation
int	opendir(java.lang.String path, FuseFileInfo fi) Open directory
int	poll(java.lang.String path, FuseFileInfo fi, FusePollhandle ph, jnr.ffi.Pointer reventsp) Poll for IO readiness events
int	read_buf(java.lang.String path, jnr.ffi.Pointer bufp, long size, long off, FuseFileInfo fi) Store data from an open file in a buffer
int	read(java.lang.String path, jnr.ffi.Pointer buf, long size, long offset, FuseFileInfo fi) Read data from an open file
int	readdir(java.lang.String path, jnr.ffi.Pointer buf, FuseFillDir filter, long offset, FuseFileInfo fi) Read directory
int	readlink(java.lang.String path, jnr.ffi.Pointer buf, long size) Read the target of a symbolic link
int	release(java.lang.String path, FuseFileInfo fi) Release an open file
int	releasedir(java.lang.String path, FuseFileInfo fi) Release directory
int	removexattr(java.lang.String path, java.lang.String name) Remove the attribute NAME from the file pointed to by PATH.
int	rename(java.lang.String oldpath, java.lang.String newpath) Rename a file
int	rmdir(java.lang.String path) Remove a directory
int	setxattr(java.lang.String path, java.lang.String name, jnr.ffi.Pointer value, long size, int flags) Set the attribute NAME of the file pointed to by PATH to VALUE (which is SIZE bytes long).
int	statfs(java.lang.String path, Statvfs stbuf) Get file system statistics
int	symlink(java.lang.String oldpath, java.lang.String newpath) Create a symbolic link
int	truncate(java.lang.String path, long size) Change the size of a file
int	unlink(java.lang.String path) Remove a file
int	utimens(java.lang.String path, Timespec[] timespec) Change the access and modification times of a file with nanosecond resolution
int	write_buf(java.lang.String path, FuseBufvec buf, long off, FuseFileInfo fi) Write contents of buffer to an open file
int	write(java.lang.String path, jnr.ffi.Pointer buf, long size, long offset, FuseFileInfo fi) Write data to an open file

Methods inherited from interface ru.serce.jnrfuse.Mountable

mount, mount, mount, mount, umount

Method Detail

getattr

int getattr(java.lang.String path,
            FileStat stat)

Get file attributes.

Similar to stat(). The 'st_dev' and 'st_blksize' fields are ignored. The 'st_ino' field is ignored except if the 'use_ino' mount option is given.

readlink

int readlink(java.lang.String path,
             jnr.ffi.Pointer buf,
             long size)

Read the target of a symbolic link

The buffer should be filled with a null terminated string. The buffer size argument includes the space for the terminating null character. If the linkname is too long to fit in the buffer, it should be truncated. The return value should be 0 for success.

mknod

int mknod(java.lang.String path,
          long mode,
          long rdev)

Create a file node

This is called for creation of all non-directory, non-symlink nodes. If the filesystem defines a create() method, then for regular files that will be called instead.

Parameters:

mode - The argument mode specifies the permissions to use in case a new file is created. @see ru.serce.jnrfuse.struct.FileStat flags

mkdir

int mkdir(java.lang.String path,
          long mode)

Create a directory

Note that the mode argument may not have the type specification bits set, i.e. S_ISDIR(mode) can be false. To obtain the correct directory type bits use mode|S_IFDIR

Parameters:

mode - The argument mode specifies the permissions to use in case a new file is created. @see ru.serce.jnrfuse.struct.FileStat flags

unlink

int unlink(java.lang.String path)

Remove a file

rmdir

int rmdir(java.lang.String path)

Remove a directory

symlink

int symlink(java.lang.String oldpath,
            java.lang.String newpath)

Create a symbolic link

rename

int rename(java.lang.String oldpath,
           java.lang.String newpath)

Rename a file

link

int link(java.lang.String oldpath,
         java.lang.String newpath)

Create a hard link to a file

chmod

int chmod(java.lang.String path,
          long mode)

Change the permission bits of a file

Parameters:

mode - The argument mode specifies the permissions to use in case a new file is created. @see ru.serce.jnrfuse.struct.FileStat flags

chown

int chown(java.lang.String path,
          long uid,
          long gid)

Change the owner and group of a file

truncate

int truncate(java.lang.String path,
             long size)

Change the size of a file

open

int open(java.lang.String path,
         FuseFileInfo fi)

File open operation

No creation (O_CREAT, O_EXCL) and by default also no truncation (O_TRUNC) flags will be passed to open(). If an application specifies O_TRUNC, fuse first calls truncate() and then open(). Only if 'atomic_o_trunc' has been specified and kernel version is 2.6.24 or later, O_TRUNC is passed on to open.

Unless the 'default_permissions' mount option is given, open should check if the operation is permitted for the given flags. Optionally open may also return an arbitrary filehandle in the fuse_file_info structure, which will be passed to all file operations.

See Also:

OpenFlags

read

int read(java.lang.String path,
         jnr.ffi.Pointer buf,
         long size,
         long offset,
         FuseFileInfo fi)

Read data from an open file

Read should return exactly the number of bytes requested except on EOF or error, otherwise the rest of the data will be substituted with zeroes. An exception to this is when the 'direct_io' mount option is specified, in which case the return value of the read system call will reflect the return value of this operation.

write

int write(java.lang.String path,
          jnr.ffi.Pointer buf,
          long size,
          long offset,
          FuseFileInfo fi)

Write data to an open file

Write should return exactly the number of bytes requested except on error. An exception to this is when the 'direct_io' mount option is specified (see read operation).

statfs

int statfs(java.lang.String path,
           Statvfs stbuf)

Get file system statistics

The 'f_frsize', 'f_favail', 'f_fsid' and 'f_flag' fields are ignored

flush

int flush(java.lang.String path,
          FuseFileInfo fi)

Possibly flush cached data

BIG NOTE: This is not equivalent to fsync(). It's not a request to sync dirty data.

Flush is called on each close() of a file descriptor. So if a filesystem wants to return write errors in close() and the file has cached dirty data, this is a good place to write back data and return any errors. Since many applications ignore close() errors this is not always useful.

NOTE: The flush() method may be called more than once for each open(). This happens if more than one file descriptor refers to an opened file due to dup(), dup2() or fork() calls. It is not possible to determine if a flush is final, so each flush should be treated equally. Multiple write-flush sequences are relatively rare, so this shouldn't be a problem.

Filesystems shouldn't assume that flush will always be called after some writes, or that if will be called at all.

release

int release(java.lang.String path,
            FuseFileInfo fi)

Release an open file

Release is called when there are no more references to an open file: all file descriptors are closed and all memory mappings are unmapped.

For every open() call there will be exactly one release() call with the same flags and file descriptor. It is possible to have a file opened more than once, in which case only the last release will mean, that no more reads/writes will happen on the file. The return value of release is ignored.

fsync

int fsync(java.lang.String path,
          int isdatasync,
          FuseFileInfo fi)

Synchronize file contents

If the datasync parameter is non-zero, then only the user data should be flushed, not the meta data.

setxattr

int setxattr(java.lang.String path,
             java.lang.String name,
             jnr.ffi.Pointer value,
             long size,
             int flags)

Set the attribute NAME of the file pointed to by PATH to VALUE (which is SIZE bytes long).

Parameters:

flags - @see XAttrConstants

Returns:

Return 0 on success, -1 for errors.

getxattr

int getxattr(java.lang.String path,
             java.lang.String name,
             jnr.ffi.Pointer value,
             long size)

Get the attribute NAME of the file pointed to by PATH to VALUE (which is SIZE bytes long).

Returns:

Return 0 on success, -1 for errors.

listxattr

int listxattr(java.lang.String path,
              jnr.ffi.Pointer list,
              long size)

List extended attributes

The retrieved list is placed in list, a caller-allocated buffer whose size (in bytes) is specified in the argument size. The list is the set of (null-terminated) names, one after the other. Names of extended attributes to which the calling process does not have access may be omitted from the list. The length of the attribute name list is returned

removexattr

int removexattr(java.lang.String path,
                java.lang.String name)

Remove the attribute NAME from the file pointed to by PATH.

Returns:

Return 0 on success, -1 for errors.

opendir

int opendir(java.lang.String path,
            FuseFileInfo fi)

Open directory

Unless the 'default_permissions' mount option is given, this method should check if opendir is permitted for this directory. Optionally opendir may also return an arbitrary filehandle in the fuse_file_info structure, which will be passed to readdir, closedir and fsyncdir.

readdir

int readdir(java.lang.String path,
            jnr.ffi.Pointer buf,
            FuseFillDir filter,
            long offset,
            FuseFileInfo fi)

Read directory

This supersedes the old getdir() interface. New applications should use this.

The filesystem may choose between two modes of operation:

1) The readdir implementation ignores the offset parameter, and passes zero to the filler function's offset. The filler function will not return '1' (unless an error happens), so the whole directory is read in a single readdir operation. This works just like the old getdir() method.

2) The readdir implementation keeps track of the offsets of the directory entries. It uses the offset parameter and always passes non-zero offset to the filler function. When the buffer is full (or an error happens) the filler function will return '1'.

releasedir

int releasedir(java.lang.String path,
               FuseFileInfo fi)

Release directory

fsyncdir

int fsyncdir(java.lang.String path,
             FuseFileInfo fi)

Synchronize directory contents

If the datasync parameter is non-zero, then only the user data should be flushed, not the meta data

init

jnr.ffi.Pointer init(jnr.ffi.Pointer conn)

Initialize filesystem

The return value will passed in the private_data field of fuse_context to all file operations and as a parameter to the destroy() method.

destroy

void destroy(jnr.ffi.Pointer initResult)

Clean up filesystem

Called on filesystem exit.

access

int access(java.lang.String path,
           int mask)

Check file access permissions

This will be called for the access() system call. If the 'default_permissions' mount option is given, this method is not called.

This method is not called under Linux kernel versions 2.4.x

Parameters:

mask - see @{link ru.serce.jnrfuse.flags.AccessConstants}

Returns:

-ENOENT if the path doesn't exist, -EACCESS if the requested permission isn't available, or 0 for success

create

int create(java.lang.String path,
           long mode,
           FuseFileInfo fi)

Create and open a file

If the file does not exist, first create it with the specified mode, and then open it.

If this method is not implemented or under Linux kernel versions earlier than 2.6.15, the mknod() and open() methods will be called instead.

Parameters:

mode - The argument mode specifies the permissions to use in case a new file is created. See ru.serce.jnrfuse.struct.FileStat flags

ftruncate

int ftruncate(java.lang.String path,
              long size,
              FuseFileInfo fi)

Change the size of an open file

This method is called instead of the truncate() method if the truncation was invoked from an ftruncate() system call.

If this method is not implemented or under Linux kernel versions earlier than 2.6.15, the truncate() method will be called instead.

fgetattr

int fgetattr(java.lang.String path,
             FileStat stbuf,
             FuseFileInfo fi)

Get attributes from an open file

This method is called instead of the getattr() method if the file information is available.

Currently this is only called after the create() method if that is implemented (see above). Later it may be called for invocations of fstat() too.

lock

int lock(java.lang.String path,
         FuseFileInfo fi,
         int cmd,
         Flock flock)

Perform POSIX file locking operation

The cmd argument will be either F_GETLK, F_SETLK or F_SETLKW.

For the meaning of fields in 'struct flock' see the man page for fcntl(2). The l_whence field will always be set to SEEK_SET.

For checking lock ownership, the 'fuse_file_info->owner' argument must be used.

For F_GETLK operation, the library will first check currently held locks, and if a conflicting lock is found it will return information without calling this method. This ensures, that for local locks the l_pid field is correctly filled in. The results may not be accurate in case of race conditions and in the presence of hard links, but it's unlikely that an application would rely on accurate GETLK results in these cases. If a conflicting lock is not found, this method will be called, and the filesystem may fill out l_pid by a meaningful value, or it may leave this field zero.

For F_SETLK and F_SETLKW the l_pid field will be set to the pid of the process performing the locking operation.

Note: if this method is not implemented, the kernel will still allow file locking to work locally. Hence it is only interesting for network filesystems and similar.

Parameters:

cmd - see Fcntl

utimens

int utimens(java.lang.String path,
            Timespec[] timespec)

Change the access and modification times of a file with nanosecond resolution

This supersedes the old utime() interface. New applications should use this.

See the utimensat(2) man page for details.

bmap

int bmap(java.lang.String path,
         long blocksize,
         long idx)

Map block index within file to block index within device

Note: This makes sense only for block device backed filesystems mounted with the 'blkdev' option

Parameters:

idx - block index within file

blocksize - unit of block index

ioctl

int ioctl(java.lang.String path,
          int cmd,
          jnr.ffi.Pointer arg,
          FuseFileInfo fi,
          long flags,
          jnr.ffi.Pointer data)

Ioctl

flags will have FUSE_IOCTL_COMPAT set for 32bit ioctls in 64bit environment. The size and direction of data is determined by _IOC_*() decoding of cmd. For _IOC_NONE, data will be NULL, for _IOC_WRITE data is out area, for _IOC_READ in area and if both are set in/out area. In all non-NULL cases, the area is of _IOC_SIZE(cmd) bytes.

Parameters:

flags - See IoctlFlags

poll

int poll(java.lang.String path,
         FuseFileInfo fi,
         FusePollhandle ph,
         jnr.ffi.Pointer reventsp)

Poll for IO readiness events

Note: If ph is non-NULL, the client should notify when IO readiness events occur by calling fuse_notify_poll() with the specified ph.

Regardless of the number of times poll with a non-NULL ph is received, single notification is enough to clear all. Notifying more times incurs overhead but doesn't harm correctness.

The callee is responsible for destroying ph with fuse_pollhandle_destroy() when no longer in use.

Parameters:

reventsp - A pointer to a bitmask of the returned events satisfied.

write_buf

int write_buf(java.lang.String path,
              FuseBufvec buf,
              long off,
              FuseFileInfo fi)

Write contents of buffer to an open file

Similar to the write() method, but data is supplied in a generic buffer. Use fuse_buf_copy() to transfer data to the destination.

IMPORTANT: Is not enabled by default, for enabling use ru.serce.jnrfuse.AbstractFuseFS#isBufOperationsImplemented()

read_buf

int read_buf(java.lang.String path,
             jnr.ffi.Pointer bufp,
             long size,
             long off,
             FuseFileInfo fi)

Store data from an open file in a buffer

Similar to the read() method, but data is stored and returned in a generic buffer.

No actual copying of data has to take place, the source file descriptor may simply be stored in the buffer for later data transfer.

The buffer must be allocated dynamically and stored at the location pointed to by bufp. If the buffer contains memory regions, they too must be allocated using malloc(). The allocated memory will be freed by the caller.

IMPORTANT: Is not enabled by default, for enabling use ru.serce.jnrfuse.AbstractFuseFS#isBufOperationsImplemented()

flock

int flock(java.lang.String path,
          FuseFileInfo fi,
          int op)

Perform BSD file locking operation

The op argument will be either LOCK_SH, LOCK_EX or LOCK_UN

Nonblocking requests will be indicated by ORing LOCK_NB to the above operations

For more information see the flock(2) manual page.

Additionally fi->owner will be set to a value unique to this open file. This same value will be supplied to ->release() when the file is released.

Note: if this method is not implemented, the kernel will still allow file locking to work locally. Hence it is only interesting for network filesystems and similar.

Parameters:

op - see Flock

fallocate

int fallocate(java.lang.String path,
              int mode,
              long off,
              long length,
              FuseFileInfo fi)

Allocates space for an open file

This function ensures that required space is allocated for specified file. If this function returns success then any subsequent write request to specified range is guaranteed not to fail because of lack of space on the file system media.