How to implement a Lua container (virtual file system) module loader in C#

Question

Sounds a little bit scary isn\'t it?

Some background information, I want to load a tar archive which contains some lua modules into my C# application using LuaInterface.

Answer 1

I finally got the trick ;-)

One Problem I currently not really understand is that my loader should not return any string. Here is my solution:

The loader Class itself:

namespace LuaInterfaceTest
{
class LuaTarModuleLoader
{
    private LuaTarModuleLoader() { }
    ~LuaTarModuleLoader()
    {
        in_stream_.Close();
    }
    public LuaTarModuleLoader(Stream in_stream,Lua lua )
    {
        in_stream_ = in_stream;
        lua_ = lua;
    }

    public LuaFunction load(string modulename)
    {
        string lua_chunk = "";
        string filename = modulename + ".lua";
        in_stream_.Position = 0; // rewind
        Stream gzipStream = new BZip2InputStream(in_stream_);
        TarInputStream tar = new TarInputStream(gzipStream);
        TarEntry tarEntry;
        LuaFunction func = null;
        while ((tarEntry = tar.GetNextEntry()) != null)
        {
            if (tarEntry.IsDirectory)
            {
                continue;
            }
            if (filename == tarEntry.Name)
            {
                MemoryStream out_stream = new MemoryStream();
                tar.CopyEntryContents(out_stream);
                out_stream.Position = 0; // rewind
                StreamReader stream_reader = new StreamReader(out_stream);
                lua_chunk = stream_reader.ReadToEnd();
                func = lua_.LoadString(lua_chunk, modulename);
                string dum = func.ToString();
                break;
            }
        }
        return func;
    }
    private Stream in_stream_;
    private Lua lua_;
}

}

And how to use the loader, I am not sure if all the package stuff is really needed. But I had to wrap up the call with ":" notation and hide it behind my "load_wrapper" function.

        string load_wrapper = "local function load_wrapper(modname)\n return container_module_loader:load(modname)\n end";
        Lua lua = new Lua();
        GC.Collect();
        Stream inStream = File.OpenRead("c:\\tmp\\lua_scripts.tar.bz2");
        LuaTarModuleLoader tar_loader = new LuaTarModuleLoader(inStream, lua);
        lua.DoString("require 'CLRPackage'");
        lua.DoString("import \"System\"");
        lua["container_module_loader"] = tar_loader;
        lua.DoString(load_wrapper);

        string loader_package = "module('my_loader', package.seeall) \n";
        loader_package += load_wrapper + "\n";
        loader_package += "table.insert(package.loaders, 2, load_wrapper)";
        lua.DoString(loader_package);
        lua.DoFile("./load_modules.lua");

I hope this may also helps some other

Answer 2

In LÖVE they have that working. All Lua files are inside one zip file, and they work, even if ... is used. The library they use is PhysicsFS.

Have a look at the source. Probably /modules/filesystem will get you started.