What can you do in 2k lines of C?

02 Feb 2011

Plain Old Awesome C

A few weeks ago I ran across some of Sean Barrett’s awesome C code.

It started with stb_image.c because it’s just crazy useful and avoids so much hassle in small demo programs. But that was just the gateway…

Check out stb_truetype.h too: TrueType font rendering in one ~1200 line header file. Do you remember how much of a pain in the ass it was the last time you had to try to integrate FreeType 2? Or <shudder> FontFusion? If you think about it for a second, you realize that TrueType rasterization can’t be that hard because printers were doing it long ago on crappy little embedded processors, but the default is just to fall back on the big ugly library, and then wrap it and pretend it’s not there. How about instead, just write some good code?

There’s also stb_vorbis.c (a Vorbis decoder) which I haven’t tried yet, but I fully expect it to Do What I Want, if someday I need it.

And, on top of that Sean’s released these as public domain (partially thanks to RAD it seems). Not MIT or BSD, and certainly not LGPL, GPL, or some other pain in the ass, but straight up public domain. So much easier when you’re embedded in Big Corp, but even if you’re not.

So, #1, use them. And #2, let’s all copy Sean.

So, what can you do in 1-2k?

Those libraries are standalone. Zero dependencies other than the C standard library. There’s no build files to screw with. There’s no licenses to get approved by your legal department*. There’s no attribution clauses to add to your “About” box. Just all buttery working-out-of-the-box convenient awesomeness.

I got to thinking: What else could be stuffed in 1-2k lines of plain C?

• An JSON / XML / YAML parser?
• Shading?
• A database?
• A GUI library?
• A web server?
• Rendering?

Since I’ve been language-obsessed the last few years, my first 1-2k LOC project is a programming language, appropriately named “twok”. Calling it something that sounds like poop dropping into a toilet probably means that no one will want to use it, but that’s probably for the best anyway; there’s lots of languages out there.

The question is, how much functionality can you get into 2k lines of code? So far, twok’s features are:

• Python-style syntax
• The “basics”: arithmetic, bit ops, logic ops, functions, if, for, etc.
• Native compilation to x64 (and supporting both Windows and SysV Mac/Linux ABIs) so you can call back and forth with C code
• List syntax/manipulation
• Simple zone-based GC
• Varargs functions
• Basic structs

And, it’s just a hair over 1k LOC, and of course, all in one easy-to-use header. My plan for the second half of the code:

• Some sort of macros
• More standard library functions
• List comprehension syntax
• Integration with the new GDB debugging-support-for-JITted-languages
• A backend for ARM, and maybe an interpreter backend for consoles

… Or other fun suggestions. I’m not sure if all of that will fit in 2k, but I think it should be close.

Certainly this is will not be the next C# or Ruby. And it’s not as practical as image loading, font rendering, or audio decoding. But, I think it’s interesting how much a hard constraint on size and a clear goal helps focus and at the same time find a way to stuff in the functionality you want.

So, what awesome library could you write in 1-2k lines of C?

Do it!

It’s fun!

And release it as public domain.

Programmers everywhere will love you.

_{*: yeah, I know that’s probably still not true, unfortunately.}

Copyright © Scott Graham.