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[lsnes.git] / include / library / luabase.hpp

#ifndef _library__luabase__hpp__included__
#define _library__luabase__hpp__included__

#include <string>
#include <stdexcept>
#include <map>
#include <set>
#include <list>
#include <cassert>
#include "string.hpp"
#include "utf8.hpp"
extern "C"
{
#include <lua.h>
}

class lua_state;

struct luaclass_methods
{
        bool (*is)(lua_state& state, int index);
        const std::string& (*name)();
        std::string (*print)(lua_state& state, int index);
};

std::list<luaclass_methods>& userdata_recogn_fns();
std::string try_recognize_userdata(lua_state& state, int index);
std::string try_print_userdata(lua_state& state, int index);

struct lua_function;

/**
 * Group of functions.
 */
class lua_function_group
{
public:
/**
 * Create a group.
 */
        lua_function_group();
/**
 * Destroy a group.
 */
        ~lua_function_group();
/**
 * Add a function to group.
 */
        void do_register(const std::string& name, lua_function& fun);
/**
 * Drop a function from group.
 */
        void do_unregister(const std::string& name);
/**
 * Request callbacks on all currently registered functions.
 */
        void request_callback(std::function<void(std::string, lua_function*)> cb);
/**
 * Bind a callback.
 *
 * Callbacks for all registered functions are immediately called.
 */
        int add_callback(std::function<void(std::string, lua_function*)> cb,
                std::function<void(lua_function_group*)> dcb);
/**
 * Unbind a calback.
 */
        void drop_callback(int handle);
private:
        int next_handle;
        std::map<std::string, lua_function*> functions;
        std::map<int, std::function<void(std::string, lua_function*)>> callbacks;
        std::map<int, std::function<void(lua_function_group*)>> dcallbacks;
};

/**
 * Lua state object.
 */
class lua_state
{
public:
        //Auxillary type for store-tag.
        template<typename T> struct _store_tag
        {
                T& addr;
                T val;
                _store_tag(T& a, T v) : addr(a), val(v) {}
        };
        //Auxillary type for vararg-tag.
        struct vararg_tag
        {
                std::list<std::string> args;
                vararg_tag(std::list<std::string>& _args) : args(_args) {}
                int pushargs(lua_state& L);
        };

        //Auxillary type for numeric-tag.
        template<typename T> struct _numeric_tag
        {
                T val;
                _numeric_tag(T v) : val(v) {}
        };

        //Auxillary type for fnptr-tag.
        template<typename T> struct _fnptr_tag
        {
                int(*fn)(lua_state& L, T v);
                T val;
                _fnptr_tag(int (*f)(lua_state& L, T v), T v) : fn(f), val(v) {}
        };

        //Auxillary type for fn-tag.
        template<typename T> struct _fn_tag
        {
                T fn;
                _fn_tag(T f) : fn(f) {}
        };

        /**
         * Callback parameter: Don't pass any real parameter, but instead store specified value in specified
         * location.
         *
         * Parameter a: The location to store value to.
         * Parameter v: The value to store.
         * Returns: The parameter structure.
         */
        template<typename T> static struct _store_tag<T> store_tag(T& a, T v) { return _store_tag<T>(a, v); }
        /**
         * Callback parameter: Pass numeric value.
         *
         * Parameter v: The value to pass.
         * Returns: The parameter structure.
         */
        template<typename T> static struct _numeric_tag<T> numeric_tag(T v) { return _numeric_tag<T>(v); }

        /**
         * Callback parameter: Execute function to push more parameters.
         *
         * Parameter f: The function to execute. The return value is number of additional parameters pushed.
         * Parameter v: The value to pass to function.
         * Returns: The parameter structure.
         */
        template<typename T> static struct _fnptr_tag<T> fnptr_tag(int (*f)(lua_state& L, T v), T v)
        {
                return _fnptr_tag<T>(f, v);
        }

        /**
         * Callback parameter: Execute function to push more parameters.
         *
         * Parameter v: The functor to execute. Passed reference to the Lua state. The return value is number of
         *      additional parameters pushed.
         * Returns: The parameter structure.
         */
        template<typename T> static struct _fn_tag<T> fn_tag(T v) { return _fn_tag<T>(v); }

        /**
         * Callback parameter: Pass boolean argument.
         *
         * Parameter v: The boolean value to pass.
         */
        struct boolean_tag { bool val; boolean_tag(bool v) : val(v) {}};

        /**
         * Callback parameter: Pass string argument.
         *
         * Parameter v: The string value to pass.
         */
        struct string_tag { std::string val; string_tag(const std::string& v) : val(v) {}};

        /**
         * Callback parameter: Pass nil argument.
         */
        struct nil_tag { nil_tag() {}};
private:
        template<typename U, typename... T> void _callback(int argc, _store_tag<U> tag, T... args)
        {
                tag.addr = tag.val;
                _callback(argc, args...);
                tag.addr = NULL;
        }

        template<typename... T> void _callback(int argc, vararg_tag tag, T... args)
        {
                int e = tag.pushargs(*this);
                _callback(argc + e, args...);
        }

        template<typename... T> void _callback(int argc, nil_tag tag, T... args)
        {
                pushnil();
                _callback(argc + 1, args...);
        }

        template<typename... T> void _callback(int argc, boolean_tag tag, T... args)
        {
                pushboolean(tag.val);
                _callback(argc + 1, args...);
        }

        template<typename... T> void _callback(int argc, string_tag tag, T... args)
        {
                pushlstring(tag.val.c_str(), tag.val.length());
                _callback(argc + 1, args...);
        }

        template<typename U, typename... T> void _callback(int argc, _numeric_tag<U> tag, T... args)
        {
                pushnumber(tag.val);
                _callback(argc + 1, args...);
        }

        template<typename U, typename... T> void _callback(int argc, _fnptr_tag<U> tag, T... args)
        {
                int extra = tag.fn(*this, tag.val);
                _callback(argc + extra, args...);
        }

        template<typename U, typename... T> void _callback(int argc, _fn_tag<U> tag, T... args)
        {
                int extra = tag.fn(*this);
                _callback(argc + extra, args...);
        }

        void _callback(int argc)
        {
                int r = pcall(argc, 0, 0);
                if(r == LUA_ERRRUN) {
                        (stringfmt() << "Error running Lua callback: " << tostring(-1)).throwex();
                        pop(1);
                }
                if(r == LUA_ERRMEM) {
                        (stringfmt() << "Error running Lua callback: Out of memory").throwex();
                        pop(1);
                }
                if(r == LUA_ERRERR) {
                        (stringfmt() << "Error running Lua callback: Double Fault???").throwex();
                        pop(1);
                }
        }
public:
/**
 * Create a new state.
 */
        lua_state() throw(std::bad_alloc);
/**
 * Create a new state with specified master state.
 */
        lua_state(lua_state& _master, lua_State* L);
/**
 * Destroy a state.
 */
        ~lua_state() throw();
/**
 * Get the internal state object.
 *
 * Return value: Internal state.
 */
        lua_State* handle() { return lua_handle; }
/**
 * Get the master state.
 */
        lua_state& get_master() { return master ? master->get_master() : *this; }
/**
 * Set the internal state object.
 */
        void handle(lua_State* l) { lua_handle = l; }
/**
 * Set OOM handler.
 */
        void set_oom_handler(void (*oom)()) { oom_handler = oom ? oom : builtin_oom; }
/**
 * Reset the state.
 */
        void reset() throw(std::runtime_error, std::bad_alloc);
/**
 * Deinit the state.
 */
        void deinit() throw();
/**
 * Get a string argument.
 *
 * Parameter argindex: The stack index.
 * Parameter fname: The name of function to use in error messages.
 * Returns: The string.
 * Throws std::runtime_error: The specified argument is not a string.
 */
        std::string get_string(int argindex, const std::string& fname) throw(std::runtime_error, std::bad_alloc)
        {
                if(lua_isnone(lua_handle, argindex))
                        (stringfmt() << "argument #" << argindex << " to " << fname << " must be string").throwex();
                size_t len;
                const char* f = lua_tolstring(lua_handle, argindex, &len);
                if(!f)
                        (stringfmt() << "argument #" << argindex << " to " << fname << " must be string").throwex();
                return std::string(f, f + len);
        }
/**
 * Get a boolean argument.
 *
 * Parameter argindex: The stack index.
 * Parameter fname: The name of function to use in error messages.
 * Returns: The string.
 * Throws std::runtime_error: The specified argument is not a boolean.
 */
        bool get_bool(int argindex, const std::string& fname) throw(std::runtime_error, std::bad_alloc)
        {
                if(lua_isnone(lua_handle, argindex) || !lua_isboolean(lua_handle, argindex))
                        (stringfmt() << "argument #" << argindex << " to " << fname << " must be boolean").throwex();
                return (lua_toboolean(lua_handle, argindex) != 0);
        }
/**
 * Get a mandatory numeric argument.
 *
 * Parameter argindex: The stack index.
 * Parameter fname: The name of function to use in error messages.
 * Returns: The parsed number.
 * Throws std::runtime_error: Bad type.
 */
        template<typename T>
        T get_numeric_argument(int argindex, const std::string& fname)
        {
                if(lua_isnone(lua_handle, argindex) || !lua_isnumber(lua_handle, argindex))
                        (stringfmt() << "Argunment #" << argindex << " to " << fname << " must be numeric").throwex();
                return static_cast<T>(lua_tonumber(lua_handle, argindex));
        }
/**
 * Get a optional numeric argument.
 *
 * Parameter argindex: The stack index.
 * Parameter value: The place to store the value.
 * Parameter fname: The name of function to use in error messages.
 * Throws std::runtime_error: Bad type.
 */
        template<typename T>
        void get_numeric_argument(unsigned argindex, T& value, const std::string& fname)
        {
                if(lua_isnoneornil(lua_handle, argindex))
                        return;
                if(lua_isnone(lua_handle, argindex) || !lua_isnumber(lua_handle, argindex))
                        (stringfmt() << "Argunment #" << argindex << " to " << fname << " must be numeric if "
                                "present").throwex();
                value = static_cast<T>(lua_tonumber(lua_handle, argindex));
        }
/**
 * Do a callback.
 *
 * Parameter name: The name of the callback.
 * Parameter args: Arguments to pass to the callback.
 */
        template<typename... T>
        bool callback(const std::string& name, T... args)
        {
                getglobal(name.c_str());
                int t = type(-1);
                if(t != LUA_TFUNCTION) {
                        pop(1);
                        return false;
                }
                _callback(0, args...);
                return true;
        }
/**
 * Do a callback.
 *
 * Parameter cblist: List of environment keys to do callbacks.
 * Parameter args: Arguments to pass to the callback.
 */
        template<typename... T>
        bool callback(const std::list<char>& cblist, T... args)
        {
                bool any = false;
                for(auto& i : cblist) {
                        pushlightuserdata(const_cast<char*>(&i));
                        rawget(LUA_REGISTRYINDEX);
                        int t = type(-1);
                        if(t != LUA_TFUNCTION) {
                                pop(1);
                        } else {
                                _callback(0, args...);
                                any = true;
                        }
                }
                return any;
        }
/**
 * Add a group of functions.
 */
        void add_function_group(lua_function_group& group);
/**
 * Function callback.
 */
        void function_callback(const std::string& name, lua_function* func);
/**
 * Do something just once per VM.
 *
 * Parameter key: The do-once key value.
 * Returns: True if called the first time for given key on given VM, false otherwise.
 */
        bool do_once(void* key);
/**
 * Callback list.
 */
        class lua_callback_list
        {
        public:
                lua_callback_list(lua_state& L, const std::string& name, const std::string& fn_cbname = "");
                ~lua_callback_list();
                void _register(lua_state& L);   //Reads callback from top of lua stack.
                void _unregister(lua_state& L); //Reads callback from top of lua stack.
                template<typename... T> bool callback(T... args) {
                        bool any = L.callback(callbacks, args...);
                        if(fn_cbname != "" && L.callback(fn_cbname, args...))
                                any = true;
                        return any;
                }
                const std::string& get_name() { return name; }
                void clear() { callbacks.clear(); }
        private:
                lua_callback_list(const lua_callback_list&);
                lua_callback_list& operator=(const lua_callback_list&);
                std::list<char> callbacks;
                lua_state& L;
                std::string name;
                std::string fn_cbname;
        };
/**
 * Enumerate all callbacks.
 */
        std::list<lua_callback_list*> get_callbacks()
        {
                if(master)
                        return master->get_callbacks();
                std::list<lua_callback_list*> r;
                for(auto i : callbacks)
                        r.push_back(i.second);
                return r;
        }
/**
 * Register a callback.
 */
        class callback_proxy
        {
        public:
                callback_proxy(lua_state& _L) : parent(_L) {}
                void do_register(const std::string& name, lua_callback_list& callback)
                {
                        parent.do_register_cb(name, callback);
                }
/**
 * Unregister a callback.
 */
                void do_unregister(const std::string& name)
                {
                        parent.do_unregister_cb(name);
                }
        private:
                lua_state& parent;
        };

        void do_register_cb(const std::string& name, lua_callback_list& callback)
        {
                callbacks[name] = &callback;
        }

        void do_unregister_cb(const std::string& name)
        {
                callbacks.erase(name);
        }

        //All kinds of Lua API functions.
        void pop(int n) { lua_pop(lua_handle, n); }
        void* newuserdata(size_t size) { return lua_newuserdata(lua_handle, size); }
        int setmetatable(int index) { return lua_setmetatable(lua_handle, index); }
        int type(int index) { return lua_type(lua_handle, index); }
        int getmetatable(int index) { return lua_getmetatable(lua_handle, index); }
        int rawequal(int index1, int index2) { return lua_rawequal(lua_handle, index1, index2); }
        void* touserdata(int index) { return lua_touserdata(lua_handle, index); }
        const void* topointer(int index) { return lua_topointer(lua_handle, index); }
        int gettop() { return lua_gettop(lua_handle); }
        void pushvalue(int index) { lua_pushvalue(lua_handle, index); }
        void pushlightuserdata(void* p) { lua_pushlightuserdata(lua_handle, p); }
        void rawset(int index) { lua_rawset(lua_handle, index); }
        void pushnil() { lua_pushnil(lua_handle); }
        void pushstring(const char* s) { lua_pushstring(lua_handle, s); }
        void rawget(int index) { lua_rawget(lua_handle, index); }
        int isnil(int index) { return lua_isnil(lua_handle, index); }
        void newtable() { lua_newtable(lua_handle); }
        void pushcclosure(lua_CFunction fn, int n) { lua_pushcclosure(lua_handle, fn, n); }
        void pushcfunction(lua_CFunction fn) { lua_pushcfunction(lua_handle, fn); }
        void setfield(int index, const char* k) { lua_setfield(lua_handle, index, k); }
        void getfield(int index, const char* k) { lua_getfield(lua_handle, index, k); }
        void getglobal(const char* name) { lua_getglobal(lua_handle, name); }
        void setglobal(const char* name) { lua_setglobal(lua_handle, name); }
        void insert(int index) { lua_insert(lua_handle, index); }
        void settable(int index) { lua_settable(lua_handle, index); }
        int isnone(int index) { return lua_isnone(lua_handle, index); }
        void pushnumber(lua_Number n) { return lua_pushnumber(lua_handle, n); }
        int isnumber(int index) { return lua_isnumber(lua_handle, index); }
        int isboolean(int index) { return lua_isboolean(lua_handle, index); }
        int toboolean(int index) { return lua_toboolean(lua_handle, index); }
        const char* tolstring(int index, size_t *len) { return lua_tolstring(lua_handle, index, len); }
        void pushboolean(int b) { lua_pushboolean(lua_handle, b); }
        lua_Number tonumber(int index) { return lua_tonumber(lua_handle, index); }
        void gettable(int index) { lua_gettable(lua_handle, index); }
#if LUA_VERSION_NUM == 501
        int load(lua_Reader reader, void* data, const char* chunkname) { return lua_load(lua_handle, reader, data,
                chunkname); }
#endif
#if LUA_VERSION_NUM == 502
        int load(lua_Reader reader, void* data, const char* chunkname, const char* mode) { return lua_load(lua_handle,
                reader, data, chunkname, mode); }
#endif
        const char* tostring(int index) { return lua_tostring(lua_handle, index); }
        const char* tolstring(int index, size_t& len) { return lua_tolstring(lua_handle, index, &len); }
        void pushlstring(const char* s, size_t len) { lua_pushlstring(lua_handle, s, len); }
        void pushlstring(const std::string& s) { lua_pushlstring(lua_handle, s.c_str(), s.length()); }
        void pushlstring(const char32_t* s, size_t len) { pushlstring(to_u8string(std::u32string(s, len))); }
        int pcall(int nargs, int nresults, int errfunc) { return lua_pcall(lua_handle, nargs, nresults, errfunc); }
        int next(int index) { return lua_next(lua_handle, index); }
        int isnoneornil(int index) { return lua_isnoneornil(lua_handle, index); }
        lua_Integer tointeger(int index) { return lua_tointeger(lua_handle, index); }
        void rawgeti(int index, int n) { lua_rawgeti(lua_handle, index, n); }
        callback_proxy cbproxy;
private:
        static void builtin_oom();
        static void* builtin_alloc(void* user, void* old, size_t olds, size_t news);
        void (*oom_handler)();
        lua_state* master;
        lua_State* lua_handle;
        std::set<std::pair<lua_function_group*, int>> function_groups;
        std::map<std::string, lua_callback_list*> callbacks;
        lua_state(lua_state&);
        lua_state& operator=(lua_state&);
};

/**
 * Pin of an object against Lua GC.
 */
template<typename T> struct lua_obj_pin
{
/**
 * Create a null pin.
 */
        lua_obj_pin()
        {
                state = NULL;
                obj = NULL;
        }
/**
 * Create a new pin.
 *
 * Parameter _state: The state to pin the object in.
 * Parameter _object: The object to pin.
 */
        lua_obj_pin(lua_state& _state, T* _object)
                : state(&_state.get_master())
        {
                _state.pushlightuserdata(this);
                _state.pushvalue(-2);
                _state.rawset(LUA_REGISTRYINDEX);
                obj = _object;
        }
/**
 * Delete a pin.
 */
        ~lua_obj_pin() throw()
        {
                if(obj) {
                        state->pushlightuserdata(this);
                        state->pushnil();
                        state->rawset(LUA_REGISTRYINDEX);
                }
        }
/**
 * Copy ctor.
 */
        lua_obj_pin(const lua_obj_pin& p)
        {
                state = p.state;
                obj = p.obj;
                if(obj) {
                        state->pushlightuserdata(this);
                        state->pushlightuserdata(const_cast<lua_obj_pin*>(&p));
                        state->rawget(LUA_REGISTRYINDEX);
                        state->rawset(LUA_REGISTRYINDEX);
                }
        }
/**
 * Assignment operator.
 */
        lua_obj_pin& operator=(const lua_obj_pin& p)
        {
                if(state == p.state && obj == p.obj)
                        return *this;
                if(obj == p.obj)
                        throw std::logic_error("A Lua object can't be in two lua states at once");
                if(obj) {
                        state->pushlightuserdata(this);
                        state->pushnil();
                        state->rawset(LUA_REGISTRYINDEX);
                }
                state = p.state;
                if(p.obj) {
                        state->pushlightuserdata(this);
                        state->pushlightuserdata(const_cast<lua_obj_pin*>(&p));
                        state->rawget(LUA_REGISTRYINDEX);
                        state->rawset(LUA_REGISTRYINDEX);
                }
                obj = p.obj;
                return *this;
        }
/**
 * Clear a pinned object.
 */
        void clear()
        {
                if(obj) {
                        state->pushlightuserdata(this);
                        state->pushnil();
                        state->rawset(LUA_REGISTRYINDEX);
                }
                state = NULL;
                obj = NULL;
        }
/**
 * Get pointer to pinned object.
 *
 * Returns: The pinned object.
 */
        T* object() { return obj; }
/**
 * Is non-null?
 */
        operator bool() { return obj != NULL; }
/**
 * Smart pointer.
 */
        T& operator*() { if(obj) return *obj; throw std::runtime_error("Attempted to reference NULL Lua pin"); }
        T* operator->() { if(obj) return obj; throw std::runtime_error("Attempted to reference NULL Lua pin"); }
/**
 * Push Lua value.
 */
        void luapush(lua_state& state)
        {
                state.pushlightuserdata(this);
                state.rawget(LUA_REGISTRYINDEX);
        }
private:
        T* obj;
        lua_state* state;
};

template<typename T> void* unbox_any_pin(struct lua_obj_pin<T>* pin)
{
        return pin ? pin->object() : NULL;
}

/**
 * Helper class containing binding data for Lua class call.
 */
template<class T> struct lua_class_bind_data
{
/**
 * The pointer to call.
 */
        int (T::*fn)(lua_state& state, const std::string& _fname);
/**
 * The state to call it in.
 */
        lua_state* state;
/**
 * The name of the method to pass.
 */
        char fname[];
};

template<class T> class lua_class;

/**
 * Function to obtain class object for given Lua class.
 */
template<class T> lua_class<T>& objclass();

template<class T> struct lua_class_binding
{
/**
 * Name.
 */
        const char* name;
/**
 * Function.
 */
        int (T::*fn)(lua_state& LS, const std::string& fname);
};

/**
 * The type of Lua classes.
 */
template<class T> class lua_class
{
        template<typename... U> T* _create(lua_state& state, U... args)
        {
                void* obj = state.newuserdata(sizeof(T));
                load_metatable(state);
                state.setmetatable(-2);
                T* _obj = reinterpret_cast<T*>(obj);
                new(_obj) T(state, args...);
                return _obj;
        }

        static int class_bind_trampoline(lua_State* LS)
        {
                try {
                        lua_class_bind_data<T>* b = (lua_class_bind_data<T>*)lua_touserdata(LS, lua_upvalueindex(1));
                        lua_state L(*b->state, LS);
                        T* p = lua_class<T>::get(L, 1, b->fname);
                        return (p->*(b->fn))(L, b->fname);
                } catch(std::exception& e) {
                        std::string err = e.what();
                        lua_pushlstring(LS, err.c_str(), err.length());
                        lua_error(LS);
                }
        }

        T* _get(lua_state& state, int arg, const std::string& fname, bool optional = false)
        {
                if(state.type(arg) == LUA_TNONE || state.type(arg) == LUA_TNIL) {
                        if(optional)
                                return NULL;
                        else
                                goto badtype;
                }
                load_metatable(state);
                if(!state.getmetatable(arg))
                        goto badtype;
                if(!state.rawequal(-1, -2))
                        goto badtype;
                state.pop(2);
                return reinterpret_cast<T*>(state.touserdata(arg));
badtype:
                (stringfmt() << "argument #" << arg << " to " << fname << " must be " << name).throwex();
                return NULL;    //Never reached.
        }

        bool _is(lua_state& state, int arg)
        {
                if(state.type(arg) != LUA_TUSERDATA)
                        return false;
                load_metatable(state);
                if(!state.getmetatable(arg)) {
                        state.pop(1);
                        return false;
                }
                bool ret = state.rawequal(-1, -2);
                state.pop(2);
                return ret;
        }

        lua_obj_pin<T> _pin(lua_state& state, int arg, const std::string& fname)
        {
                T* obj = get(state, arg, fname);
                state.pushvalue(arg);
                return lua_obj_pin<T>(state, obj);
        }
public:
/**
 * Create a new Lua class.
 *
 * Parameter _name: The name of the class.
 */
        lua_class(const std::string& _name)
        {
                name = _name;
                luaclass_methods m;
                m.is = lua_class<T>::is;
                m.name = lua_class<T>::get_name;
                m.print = lua_class<T>::print;
                userdata_recogn_fns().push_back(m);
        }

/**
 * Create a new instance of object.
 *
 * Parameter state: The Lua state to create the object in.
 * Parameter args: The arguments to pass to class constructor.
 */
        template<typename... U> static T* create(lua_state& state, U... args)
        {
                return objclass<T>()._create(state, args...);
        }

/**
 * Bind a method to class.
 *
 * Parameter state: The state to do the binding in.
 * Parameter keyname: The name of the method.
 * Parameter fn: The method to call.
 * Parameter force: If true, overwrite existing method.
 */
        void bind(lua_state& state, const char* keyname, int (T::*fn)(lua_state& LS, const std::string& fname))
        {
                load_metatable(state);
                state.pushstring(keyname);
                std::string fname = name + std::string("::") + keyname;
                void* ptr = state.newuserdata(sizeof(lua_class_bind_data<T>) + fname.length() + 1);
                lua_class_bind_data<T>* bdata = reinterpret_cast<lua_class_bind_data<T>*>(ptr);
                bdata->fn = fn;
                bdata->state = &state.get_master();
                std::copy(fname.begin(), fname.end(), bdata->fname);
                bdata->fname[fname.length()] = 0;
                state.pushcclosure(class_bind_trampoline, 1);
                state.rawset(-3);
                state.pop(1);
        }
/**
 * Bind multiple at once.
 */
        void bind_multi(lua_state& state, std::initializer_list<lua_class_binding<T>> list, void* doonce_key = NULL)
        {
                static char once_key;
                if(state.do_once(doonce_key ? doonce_key : &once_key))
                        for(auto i : list)
                                bind(state, i.name, i.fn);
        }
/**
 * Get a pointer to the object.
 *
 * Parameter state: The Lua state.
 * Parameter arg: Argument index.
 * Parameter fname: The name of function for error messages.
 * Parameter optional: If true and argument is NIL or none, return NULL.
 * Throws std::runtime_error: Wrong type.
 */
        static T* get(lua_state& state, int arg, const std::string& fname, bool optional = false)
                throw(std::bad_alloc, std::runtime_error)
        {
                return objclass<T>()._get(state, arg, fname, optional);
        }

/**
 * Identify if object is of this type.
 *
 * Parameter state: The Lua state.
 * Parameter arg: Argument index.
 * Returns: True if object is of specified type, false if not.
 */
        static bool is(lua_state& state, int arg) throw()
        {
                return objclass<T>()._is(state, arg);
        }
/**
 * Get name of class.
 */
        static const std::string& get_name()
        {
                return objclass<T>().name;
        }
/**
 * Format instance of this class as string.
 */
        static std::string print(lua_state& state, int index)
        {
                T* obj = get(state, index, "__internal_print");
                return obj->print();
        }
/**
 * Get a pin of object against Lua GC.
 *
 * Parameter state: The Lua state.
 * Parameter arg: Argument index.
 * Parameter fname: Name of function for error message purposes.
 * Throws std::runtime_error: Wrong type.
 */
        static lua_obj_pin<T> pin(lua_state& state, int arg, const std::string& fname) throw(std::bad_alloc,
                std::runtime_error)
        {
                return objclass<T>()._pin(state, arg, fname);
        }
private:
        static int dogc(lua_State* LS)
        {
                T* obj = reinterpret_cast<T*>(lua_touserdata(LS, 1));
                obj->~T();
                return 0;
        }

        static int newindex(lua_State* LS)
        {
                lua_pushstring(LS, "Writing metatables of classes is not allowed");
                lua_error(LS);
                return 0;
        }

        static int index(lua_State* LS)
        {
                lua_getmetatable(LS, 1);
                lua_pushvalue(LS, 2);
                lua_rawget(LS, -2);
                return 1;
        }

        void load_metatable(lua_state& state)
        {
again:
                state.pushlightuserdata(this);
                state.rawget(LUA_REGISTRYINDEX);
                if(state.type(-1) == LUA_TNIL) {
                        state.pop(1);
                        state.pushlightuserdata(this);
                        state.newtable();
                        state.pushvalue(-1);
                        state.setmetatable(-2);
                        state.pushstring("__gc");
                        state.pushcfunction(&lua_class<T>::dogc);
                        state.rawset(-3);
                        state.pushstring("__newindex");
                        state.pushcfunction(&lua_class<T>::newindex);
                        state.rawset(-3);
                        state.pushstring("__index");
                        state.pushcfunction(&lua_class<T>::index);
                        state.rawset(-3);
                        state.rawset(LUA_REGISTRYINDEX);
                        goto again;
                }
        }
        std::string name;
        lua_class(const lua_class<T>&);
        lua_class& operator=(const lua_class<T>&);
};

#define DECLARE_LUACLASS(x, X) template<> lua_class< x >& objclass() { static lua_class< x > clazz( X ); \
        return clazz; }

/**
 * Function implemented in C++ exported to Lua.
 */
class lua_function
{
public:
/**
 * Register function.
 */
        lua_function(lua_function_group& group, const std::string& name) throw(std::bad_alloc);
/**
 * Unregister function.
 */
        virtual ~lua_function() throw();

/**
 * Invoke function.
 */
        virtual int invoke(lua_state& L) = 0;
protected:
        std::string fname;
        lua_function_group& group;
};

/**
 * Register function pointer as lua function.
 */
class function_ptr_luafun : public lua_function
{
public:
/**
 * Register.
 */
        function_ptr_luafun(lua_function_group& group, const std::string& name,
                int (*_fn)(lua_state& L, const std::string& fname))
                : lua_function(group, name)
        {
                fn = _fn;
        }
/**
 * Invoke function.
 */
        int invoke(lua_state& L)
        {
                return fn(L, fname);
        }
private:
        int (*fn)(lua_state& L, const std::string& fname);
};


#endif