Hello World for LuaJIT FFI/C++ binding.

hello.cpp

// Act as a source file in existing project.

#include "hello.h"

const char* Hello::World()
{
    return "Hello World!\n";
}

hello.h

// Act as a header file in existing project.

class Hello {
    public:
        const char* World();
};

hello.lua

-- Lua part binding, load necessary interface.

ffi = require('ffi')
ffi.cdef[[
    typedef struct Hello Hello;

    Hello* Hello_new();
    const char* Hello_World(Hello*);
    void Hello_gc(Hello*);
]]
hello = ffi.load('hello')

hello_index = {
    World = hello.Hello_World
}
hello_mt = ffi.metatype('Hello', {
    __index = hello_index
})
Hello = ffi.gc(hello.Hello_new(), hello.Hello_gc)
return Hello

libhello.cpp

// C++ part binding, expose necessary interface to C.

#include "hello.h"

extern "C" {
    Hello* Hello_new(){
        return new Hello;
    }
    const char* Hello_World(Hello* self){
        return self->World();
    }
    void Hello_gc(Hello* self) {
        delete self;
    }
}

main.lua

-- Demo how to use binding in lua project.

hello = require('hello')
ffi = require('ffi')
io.write(ffi.string(hello:World()))

Makefile

all: lib run

lib:
    g++ -shared -fPIC -o libhello.so libhello.cpp hello.cpp
run:
    luajit main.lua
clean:
    rm *.so