Ada-Fuse

Ada-Fuse provides Ada bindings for Fuse. Our goal was to make it possible to use the Fuse operations with Ada-like types and functions.

You can install it with Alire.

You can use most of the Fuse operations. The missing operations are lock, utimens, bmap, ioctl and poll. For most file systems this should not be a problem, in fact we never saw a Fuse-Filesystem using these operations. Be aware that not all of the implemented functions are tested. Untested functions are marked in the source.

Ada-Fuse should work on 32-bit and 64-bit Linux and macOS. See "Known limitations/bugs" for more information.

Requirements

• FUSE (with dev files)
• Gnat 2012
• gprbuild

Package Layout

• Fuse: important types and constants

• Fuse.System: system specific declarations

• Fuse.General: general type and procedure declarations; depends on Fuse.System

• Fuse.Main: main, operations, wrapper; depends on Fuse.General and Fuse.System

• Fuse.Aux: procedures for fs implementation; is not needed by fuse lib

Getting started

Take a look at our example file systems. In a nutshell, you have to instantiate Fuse.Main, write the functions you want to implement and register them. Then you can call the main procedure, which mounts the filesystem. For a list of functions take a look at fuse-main.ads. As most of our documentation is only about Ada-Fuse but not Fuse in general, you should also have a look into the Fuse Wiki and their API reference. Also the corresponding pages in man 2 are helpful.

Known limitations/bugs

• We made no efforts to support multi threading. Some things might work but unless you know what you are doing you should always call your file system with the -s flag.

• Not much testing has been done yet. We tried to fix or at least document all the bugs we found, but there might still be major problems we didn't notice yet.

• Ada-Fuse was developed and tested under Linux x86_64. Most things should work on 32 bit Linux and Mac OS as well, but especially Fuse.Aux can be problematic, as Fuse uses many 64 bit types internally and importing C functions often doesn't work anymore.

• Fuse.Aux depends on some Ada and C functions that were probably not meant to be used that way. It should be seen as a quick way to get things running, however it is not yet suitable for a reliable file system.

• We cannot specify the Fuse version to use. We think that is why we get a warning when running a file system:

  fuse: warning: library too old, some operations may not not work
  

• When instantiating Fuse.Main we get warnings about not every byte being used. This is because of Fuse's data structures. Avoid these with

  pragma Warnings (Off, "* bits of * unused");
  package My_Fuse is new Fuse.Main (...);
  pragma Warnings (On, "* bits of * unused");

• There are functions that have wrappers implemented that have not been tested. There is a good chance they will not work the way they are. However they are marked and already registered everywhere, so fixing them should be easy.

• We have no implementations for lock, utimens, bmap, ioctl and poll.

TODO

• remaining representation clauses in Fuse.System

• lock, utimens, bmap, ioctl and poll

• test the untested functions, fix if necessary

• functions for Fuse.Aux, that will work on every OS

• a larger example filesystem would be nice

Useful Links

• Fuse Wiki
• Fuse-API reference
• Writing a FUSE Filesystem: a Tutorial by Joseph J. Pfeiffer, Jr., Ph.D.

Copyright

This program is free software: you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation, either version 3 of the License, or (at your option) any later version.

This program is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details.

You should have received a copy of the GNU General Public License along with this program. If not, see https://www.gnu.org/licenses/.