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lua5.1.js: Lua 5.1, emscriptinized to JavaScript, with low-level API

lua5.1.js: Copyright (c) 2013, LogicEditor <[email protected]>
           Copyright (c) 2013, le-dsl-fsm authors (see `AUTHORS`)

Contains original Lua 5.1.5 implementation:

Lua 5.1:  Copyright (c) 1994-2012 Lua.org, PUC-Rio (http://lua.org)

See file COPYRIGHT for the license.

Project status:

Current version v0.9.1 is a community preview version.

This project is in early stages of its development. Early adopters are welcome. Production users should probably wait for a next release with better test coverage and more stable API.

API:

Pretty much all Lua C API should be supported. (Much of it untested though.) See the TODO file for a list of unsupported API items.

TODO: Document API properly.

Convention: all C numeric types are JS numbers, all C strings are JS strings, all other C pointers (including function pointers) are JS numbers.

To use function pointers, you have to call Emscripten's Runtime.addFunction().

API usage example:

var C = Lua5_1.C;

var L = C.lua_open();
C.luaL_openlibs(L);

C.lua_pushcfunction(
    L,
    Lua5_1.Runtime.addFunction(
        function(L)
        {
          var str = C.luaL_checkstring(L, 1);
          alert("{Lua} " + str);
          return 0;
        }
      )
  );
C.lua_setglobal(L, "ALERT");

if (C.luaL_dostring(L, "ALERT('Hello, world')") != 0)
{
  var err = C.lua_tostring(L, -1);
  C.lua_close(L);
  L = 0;
  throw new Error("Lua error: " + err);
}

Refer to Emscripten docs if you need more information:

https://github.com/kripken/emscripten/wiki/Interacting-with-code

Note: Pull requests to improve this document are very welcome.

Bundling files for use with lua5.1.js

A simple packer tool, lua5.1.js-file-packer is provided to bundle files for use with the library.

You can run it from bin/ or install to your system with LuaRocks:

sudo luarocks install lua5.1.js-file-packer

The lua5.1.js-file-packer packs a bunch of files to a JavaScript bundle file, which, when loaded, makes them available for lua5.1.js internal filesystem.

You should include the bundle file after you include lua5.1.js itself.

Run the tool as follows:

lua5.1.js-file-packer \
  lua-nucleo.lua5.1.js \   # The bunle filename
  /lua-nucleo/ \           # The base-path for packed files in JavaScript
  ./ \                     # The base-path for local files
  ./lua-nucleo/*.lua       # List of files to pack

Resulting file path in JavaScript is local file path, moved from its local base path to the JavaScript base path.

For example, for the command above, local file ./lua-nucleo/table.lua would be available for JavaScript code as /lua-nucleo/table.lua. Default "working directory" in lua5.1.js internal filesystem is the root, /, so you can require table.lua with the usual:

require 'lua-nucleo.table.lua'

See also example/packer/.

How to build lua5.1.5.js:

NOTE: You do not need to build lua5.1.5.js to use it. Just grab a minified file from src/min/, and go.

To rebuild src/min/lua5.1.5-*.js:

1. Install Lua 5.1.
2. Run ./make.sh.

If you want to rebuild the Lua VM itself, you need to do a few extra steps:

(Note that you're most likely do not need to do that to contribute to the project -- just change files in src/js/ and run ./make.sh without arguments.)

Instructions for a recent Ubuntu OS:

1. Install emscripten as described here:

   https://github.com/kripken/emscripten/wiki/Getting-Started-on-Ubuntu-12.10

   (You're advised to do that in a clean lxc container, Emscripten and dependencies are rather brittle. Unclean system can complicate things.)

2. Check ./make.sh for environment variables you might want to change.

3. Run ./make.sh --run-emscripten.

FAQ:

1. Q: The code in src/min/ does not look minified.

   A: Because it is not minified. But minification of emscriptenized code is tricky. We'll get there when (if) emcc -O2 itself will output minified code. Meanwhile, enable compression in your HTTP server or try building with EMCCFLAGS=-O1.

   Note that, for the reason outlined above, it is recommended that you keep this library in a separate file, not bundle it with other JS code.

2. Q: Why not lua.vm.js (https://github.com/kripken/lua.vm.js)?

   • The lua.vm.js is Lua 5.2, we need Lua 5.1.

   • The lua.vm.js code is pretty much a prototype, which has to be heavily refactored to be useful in production. Better to start from scratch.

See also:

File TODO in the distribution and issues at GitHub.