Execute & bind Ruby by LuaJIT

ruby_interpreter.lua

-- Load foreign functions interface
local ffi = require("ffi")

-- Load Ruby library & define function headers
local ruby = ffi.load("msvcrt-ruby210")
ffi.cdef([[
typedef uintptr_t RUBY_VALUE;
enum{
	RUBY_Qfalse = 0,
	RUBY_Qtrue = 2,
	RUBY_Qnil = 4
};
enum{
	RUBY_T_STRING = 0x05,
	RUBY_T_MASK = 0x1f,
	RUBY_IMMEDIATE_MASK = 0x03,
	RUBY_RSTRING_NOEMBED = 1 << 13
};
typedef struct{
	RUBY_VALUE flags;
	const RUBY_VALUE klass;
}RBasic;
typedef struct{
	RBasic basic;
	union{
		struct{
			long len;
			char *ptr;
		}heap;
		char ary[sizeof(RUBY_VALUE)*3/sizeof(char)];
	}as;
}RString;

int ruby_setup(void);
RUBY_VALUE rb_define_module(const char*);
void rb_define_module_function(RUBY_VALUE, const char*, void*, int);
void* ruby_options(int, char**);
int ruby_run_node(void*);
]])

-- Test data
local args = {"-v", "test.rb"}

-- Lua load in Ruby
local function eval_str(mod, x)
	local band = bit.band
	if x == ffi.C.RUBY_Qnil or x == ffi.C.RUBY_Qfalse or
		band(x, ffi.C.RUBY_IMMEDIATE_MASK) ~= 0 or
		band(ffi.cast("RBasic*", x)[0].flags, ffi.C.RUBY_T_MASK) ~= ffi.C.RUBY_T_STRING then
		error("String expected", 1)
	end
	local code = band(ffi.cast("RBasic*", x)[0].flags, ffi.C.RUBY_RSTRING_NOEMBED) ~= 0 and
					load(ffi.string(ffi.cast("RString*", x)[0].as.heap.ptr)) or
					load(ffi.string(ffi.cast("RString*", x)[0].as.ary))
	return code and (code() and ffi.C.RUBY_Qtrue or ffi.C.RUBY_Qfalse) or ffi.C.RUBY_Qnil
end

-- Initialize Ruby
if ruby.ruby_setup() == 0 then
	-- Extend Ruby environment
	local ruby_module_lua = ruby.rb_define_module("Lua")
	ruby.rb_define_module_function(ruby_module_lua, "eval_str", ffi.cast("RUBY_VALUE(*)(RUBY_VALUE, RUBY_VALUE)", eval_str), 1)
	-- Build Ruby options
	local args_n = #args
	local options = ffi.new("char*[?]", 1 + args_n)
	options[0] = ffi.cast("char*", "rubylua")
	for i=1, args_n do
		options[i] = ffi.cast("char*", args[i])
	end
	-- Run Ruby with options
	local status = ruby.ruby_run_node(ruby.ruby_options(1 + args_n, options))
	if status ~= 0 then
		error("Ruby error code: " .. status)
	end
else
	error("Couldn't setup Ruby!")
end

test.rb

puts Lua::eval_str "print(\"Hello from Lua in Ruby!\")"