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diff --git a/community/gsoc/project_ideas/language_bindings.mdwn b/community/gsoc/project_ideas/language_bindings.mdwn new file mode 100644 index 00000000..a96f4569 --- /dev/null +++ b/community/gsoc/project_ideas/language_bindings.mdwn @@ -0,0 +1,90 @@ +[[meta copyright="Copyright © 2008, 2009 Free Software Foundation, Inc."]] + +[[meta license="""[[toggle id="license" text="GFDL 1.2+"]][[toggleable +id="license" text="Permission is granted to copy, distribute and/or modify this +document under the terms of the GNU Free Documentation License, Version 1.2 or +any later version published by the Free Software Foundation; with no Invariant +Sections, no Front-Cover Texts, and no Back-Cover Texts. A copy of the license +is included in the section entitled +[[GNU_Free_Documentation_License|/fdl]]."]]"""]] + +[[meta title="Bindings to Other Programming Languages"]] + +The main idea of the Hurd design is giving users the ability to easily +modify/extend the system's functionality ([[extensible_system|extensibility]]). +This is done by creating [[filesystem_translators|hurd/translator]] and other +kinds of Hurd servers. + +However, in practice this is not as easy as it should, because creating +translators and other servers is quite involved -- the interfaces for doing +that are not exactly simple, and available only for C programs. Being able to +easily create simple translators in RAD languages is highly desirable, to +really be able to reap the advantages of the Hurd architecture. + +Originally Lisp was meant to be the second system language besides C in the GNU +system; but that doesn't mean we are bound to Lisp. Bindings for any popular +high-level language, that helps quickly creating simple programs, are highly +welcome. + +Several approaches are possible when creating such bindings. One way is simply +to provide wrappers to all the available C libraries ([[hurd/libtrivfs]], [[hurd/libnetfs]] +etc.). While this is easy (it requires relatively little consideration), it may +not be the optimal solution. It is preferable to hook in at a lower level, thus +being able te create interfaces that are specially adapted to make good use of +the features available in the respective language. + +These more specialised bindings could hook in at some of the lower level +library interfaces ([[hurd/libports]], [[hurd/glibc]], etc.); use the +[[microkernel/mach/MIG]]-provided [[microkernel/mach/RPC]] stubs directly; or +even create native stubs directly from the interface definitions. + +The task is to create easy to use Hurd bindings for a language of the student's +choice, and some example servers to prove that it works well in practice. This +project will require gaining a very good understanding of the various Hurd +interfaces. Skills in designing nice programming interfaces are a must. + +There has already been some [earlier work on Python +bindings](http://www.sigill.org/files/pytrivfs-20060724-ro-test1.tar.bz2), that +perhaps can be re-used. Also some work on [Perl +bindings](http://www.nongnu.org/hurdextras/#pith) is availabled. + +# Lisp + +Most Lisp implementations provide a Foreign Function Interface (FFI) that +enables the Lisp code to call functions written in another language. +Specifically, most implementations provide an FFI to the C ABI (hence giving +access to C, Fortran and possibly C++). + +Common Lisp has even a portability layer for such FFI, +[CFFI](http://common-lisp.net/project/cffi/), so that you can write bindings +purely in Lisp and use the same binding code on any implementation supported by +CFFI. + +Many Scheme implementation also provide an FFI. [Scheme48](http://www.s48.org/) +is even the implementation used to run scsh, a Scheme shell designed to provide +instant access to POSIX functions. +[Guile](http://www.gnu.org/software/guile/guile.html) is the GNU project's +Scheme implementation, meant to be embeddable and provide access to C. At least +[Gambit](http://dynamo.iro.umontreal.ca/~gambit/), +[Chicken](http://www.call-with-current-continuation.org/), +[Bigloo](http://www-sop.inria.fr/mimosa/fp/Bigloo/) and +[PLT](http://www.plt-scheme.org/) are known to provide an FFI too. + +With respect to the packaging and dependencies, the good news is that Debian +comes handy: 5 Common Lisp implementations are packaged, one of which has +already been ported to Hurd (ECL), and CFFI is also packaged. As far as Scheme +is concerned, 14 [R5RS](http://www.schemers.org/Documents/Standards/R5RS/) +implementations are provided and 1 [R6RS](http://www.r6rs.org/). + +Possible mentors: Pierre THIERRY (nowhere_man) for Common Lisp or Scheme, and perhaps Python + +Exercise: Write some simple program(s) using Hurd-specific interfaces in the +language you intend to work on. For a start, you could try printing the system +uptime. A more advanced task is writing a simple variant of the hello +translator (you can use the existing C imlementation as reference), +implementing only open() and read() calls. Don't only write an implementations +using the existing C libraries (libps, libtrivfs), but also try to work with +the MiG-generated stubs directly. If you are ambitious, you could even try to +write your own stubs... + +*Status*: Flavio Cruz has completed [[Lisp_bindings|flaviocruz]] for GSoC 2008! |