[Tcl-soc2008] tcl-fuse: project status update

[Alexandros S. <al...@gm...>]

Hi all,

This is a status update for the Tcl-Fuse project
(https://sourceforge.net/projects/tcl-fuse).

For those that don't know what tcl-fuse is:

It's a Tcl interface to the linux kernel's FUSE subsystem. It provides a
Tcl extension that exports the full functionality of the underlying FUSE
kernel feature to the Tcl programming language.

FUSE, which stands for File-System in User-Space, is a kernel subsystem
and accompanying library that allows regular programs to implement a
filesystem completely in userspace. The filesystem operations are
received by the kernel via the standard Linux VFS interface, and are
dispatched to a resident user process for handling (daemon).

This extension will enable for:
  * Easy creation of FUSE filesystem written solely in Tcl
  * Export of the Tcl VFS via FUSE for all system processes to take
advantage.

THE DESIGN:

The entry point is a new Tcl command named "fuse". This command
establishes a binding between FUSE operations and Tcl procedures. It
creates a new command for every FUSE filesystem, that can be used to
mount it on a specific filesystem directory.

There is a proxy C function for every FUSE operation. The proxy function
is invoked by FUSE and its job is to translate the C API to a Tcl API,
and vice versa for the return value of the Tcl procedure.

Currently the level of integration with FUSE is low. This will be
improved in due course. For instance, mount parameters are parsed by
FUSE, whereas the FUSE events are not handled by Tcl's event loop (which
remains stalled).

CURRENT STATUS:

  * Created a TEA build tree and adapted it for the needs
    of this Project.
  * Completed a first version of the extension with
    support for the "getattr", "readdir", "read", "open"
    and "rename" FUSE operations.
  * Ported the example hello FUSE filesystem
    (examples/hello.c in FUSE's source tree) to Tcl
    (examples/hello.tcl in tcl-fuse's source).
  * Created a preliminary TclVFS to FUSE Tcl interface
(examples/fusevfs.tcl in tcl-fuse's source), that
    is limited to the aforementioned FUSE operations.

WHAT'S COMING NEXT:

  * Implement the proxy functions for the remaining FUSE
    operations.
  * Implement a few subcommands for the "fuse" command, namely:
    version, unmount, info, context
  * Create Tcl cleanup procedures to automatically erase state.
  * Integration of FUSE events to Tcl's event loop
    and threading model.
  * Complete the FuseVFS extension.
  * Documentation (man page).

TO FETCH

svn checkout https://tcl-fuse.svn.sourceforge.net/svnroot/tcl-fuse

TO COMPILE

On 32bit:
    autoconf
    ./configure --prefix=/usr/local
    make
    sudo make install

On 64bit systems:
    autoconf
    PKG_CFLAGS="-D_FILE_OFFSET_BITS=64" \
     ./configure --with-tcl=/usr/lib64
    make
    sudo make install

Detailed instructions in README.tclfuse.

REQUIREMENTS:

  * Kernel with FUSE enabled (CONFIG_FUSE_FS)
  * Tcl 8.5

TO TRY IT OUT:

To mount the "hello" filesystem:

    cd <root of source code tree>
    tclsh examples/hello.tcl

To mount the FuseVFS filesystem that maps the root of Tcl's VFS:

    cd <root of source code tree>
    tclsh examples/test_fusevfs.tcl

In both cases the examples/mnt directory is where the filesystems will
get mounted.

I'm looking forward to feedback.

Alexandros