homeOcaml implementation of zlib Inflate algorithm
Posted on 29.12.07
In between the social duties usual during this time of the year I’ve been trying to work on and off on GLCaml. I’ve had some feedback from the (not very large) user base over the past few months and it’s clear that some changes are needed.
For instance, the use of enumerations is a pain, because OpenGL mixes enumerations and integers willy-nilly, and having to convert back-and-forth in Ocaml is just not worth the hassle. Also, although the use of Bigarrays is in my opinion mostly unavoidable, I’m trying to minimize usage where it is not strictly necessary.
A couple of weeks ago, Jon Harrop mailed that he had gotten GL shaders to work, albeit with some difficulty and hand tweaking. I’m taking the opportunity to test shaders and related bindings more thoroughly, but this will take some time.
I think the next release of GLCaml will have some fairly major changes; some cosmetic, some fundamental. Basically GL constants (glenums in GLcaml) will become ints, and as a result GL_ALL_CAPS notation will have to become gl_lower_case notation. But before I release it I’d like to test it reasonably well. Revise and revamp the documentation, examples and website as well. This might take a month or so, depending on free time.
What does all this have to do with Zlib’s inflate algorithm? Nothing. But about a month ago I implemented an Ocaml-only implementation of Zlib’s inflate algorithm (RFC 1951). It’s not the first one: Extlib has one, but using it requires pulling in a lot of other stuff as well. I was writing a pure-Ocaml PNG decoder (mostly done but very buggy, will finish it when I have the time), and needed a simple zlib decoder.
So I wrote one. The source code is available (under the BSD licence). It’s pretty compact: about 250 lines of code, including comments. Usage is very simple: pass a string containing data compressed with the zlib deflate algorithm, and a string large enough to contain the decompressed data, and it returns the same string with the decompressed data. uncompress -> string -> string -> string. I added a small, simple example to uncompress gzipped files.
The code is based more or less on the specs, with a peek every now and then at Andrew Church’s tinflate.c when I got stuck on some ambiguity or other. It’s pretty compact - 200 lines of code - and pretty slow: gunzip beats it by a factor of 10 to 100. Maybe if I have time I’ll try and optimize it. First I have to find the time to finish the PNG decoder. And GLCaml, of course.
Comments OffOcaml bindings for OpenGL and SDL
Posted on 30.06.06
UPDATE: This project has moved to glcaml.sourceforge.net.
In the interests of reinventing the wheel where possible, I wrote OCaml bindings for the SDL libraries and OpenGL libraries over a couple of weekends.
The (automatically generated) OpenGL bindings cover OpenGL 1.1, 1.2, 1.3, 1.4, 1.5, 2.0 and most current non-platform-specific extensions. There are no dependencies whatsoever: the system opengl shared library is loaded dynamically, and the functions are called dynamically, so there is no need to link against import libraries.
The SDL bindings are fairly but not wholly complete; they are hand-written and functions are bound on an as-needed-by me basis. They are only dependent on the SDL main library and not on the mixer, ttf or image libraries. Because I wanted to have basic sound capabilities, the SDL_Audio modules are implemented, along with extra functions for panning and pitch shifting audio buffers.
- The source code, in a tar gzipped file, along with around 20 examples
- The documentation, fairly complete for SDL
This has been tested and works on Windows 2000, Windows XP, and Ubuntu Linux running on AMD64.
On Windows I use the mingw Ocaml compiler suite along with the msys shell; the source tarball contains makefiles that work as-is on the Windows mingw/msys port and under Linux. It will probably work as-is for the cygwin port of Ocaml, and will definitely need some tweaking to work under the Visual-C port.