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A Field Guide to Lua Coroutines

• fab13n 13y ago
  Coroutine are a powerful low-level tool to build higher level, user friendly environments. That's true of most of Lua's advanced features, BTW: they tend to be complex tools letting you build simple-to-use stuff (as opposed e.g. to C++'s templates, where you need a fairly advanced understanding of C++ metaprogramming features to use even simple containers correctly). Anyway, coroutines are intended to let people build their own high-level concurrency system. It's used e.g. to share the CPU among scripted entities in video games. Mihini (http://www.eclipse.org/mihini/ http://www.eclipse.org/mihini/) offers higher-level concurrency within a single OS thread, primarily targetting Linux-based embedded communicating applications. Copas (https://github.com/keplerproject/copas https://github.com/keplerproject/copas) is much simpler, but probably sufficient if you only need to handle several sockets concurrently without wasting many OS threads. There are also some attempts to wrap luvit (https://github.com/luvit/luvit https://github.com/luvit/luvit), Lua's porting of libuv, with coroutines, getting callback-based performances without it's tendency to make one's code write-only. I don't know what's usable and maintained, nor even whether it really exists.
  • catwell 13y ago
    Luvit is not really a port of libuv, it is more a reimplementation of the NodeJS model that uses libuv. A more straightforward libuv binding by the same author is https://github.com/creationix/luv https://github.com/creationix/luv, and one using coroutines is https://github.com/hnakamur/couv https://github.com/hnakamur/couv
• vaughan0 13y ago
  > "The main limitation of Lua coroutines is that, since they are implemented with setjmp(3) and longjmp(3), you cannot use them to call from Lua into C code that calls back into Lua that calls back into C, because the nested longjmp will clobber the C function’s stack frames. (This is detected at runtime, rather than failing silently.)" Lua 5.2 provides a mechanism to help with this: http://www.lua.org/manual/5.2/manual.html#4.7 http://www.lua.org/manual/5.2/manual.html#4.7
  • silentbicycle 13y ago
    Thanks. :) I'm still mostly using Lua 5.1.4 most of the time, and I forgot to include that.
    • dottrap 13y ago
      There is also a modification patch for Lua 5.1 called Cocos that fixes this. It was written by Mike Pall, better known as the author of LuaJIT. http://coco.luajit.org http://coco.luajit.org
      • silentbicycle 13y ago
        I saw a patch he wrote for copying coroutines, for those who miss multi-shot continuations.
• beagle3 13y ago
  Relevant: super lightweight co-routines in C, with (limited) support for blocking as well: https://github.com/halayli/lthread https://github.com/halayli/lthread