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#pragma once
//http://lua-users.org/wiki/SimplerCppBinding
extern "C" {
#include "lua.h"
#include "lauxlib.h"
}
template <typename T> class Luna
{
typedef struct { T *pT; } userdataType;
public:
typedef int (T::*mfp)(lua_State *L);
typedef struct { const char *name; mfp mfunc; } RegType;
static void Register(lua_State *L)
{
lua_newtable(L);
int methods = lua_gettop(L);
luaL_newmetatable(L, T::className);
int metatable = lua_gettop(L);
// store method table in globals so that
// scripts can add functions written in Lua.
lua_pushstring(L, T::className);
lua_pushvalue(L, methods);
lua_settable(L, LUA_GLOBALSINDEX);
lua_pushliteral(L, "__metatable");
lua_pushvalue(L, methods);
lua_settable(L, metatable); // hide metatable from Lua getmetatable()
lua_pushliteral(L, "__index");
lua_pushvalue(L, methods);
lua_settable(L, metatable);
lua_pushliteral(L, "__tostring");
lua_pushcfunction(L, tostring_T);
lua_settable(L, metatable);
lua_pushliteral(L, "__gc");
lua_pushcfunction(L, gc_T);
lua_settable(L, metatable);
lua_newtable(L); // mt for method table
int mt = lua_gettop(L);
lua_pushliteral(L, "__call");
lua_pushcfunction(L, new_T);
lua_pushliteral(L, "new");
lua_pushvalue(L, -2); // dup new_T function
lua_settable(L, methods); // add new_T to method table
lua_settable(L, mt); // mt.__call = new_T
lua_setmetatable(L, methods);
// fill method table with methods from class T
for (RegType *l = T::methods; l->name; l++)
{
/* edited by Snaily: shouldn't it be const RegType *l ... ? */
lua_pushstring(L, l->name);
lua_pushlightuserdata(L, (void*)l);
lua_pushcclosure(L, thunk, 1);
lua_settable(L, methods);
}
lua_pop(L, 2); // drop metatable and method table
}
// get userdata from Lua stack and return pointer to T object
static T * check(lua_State * L, int narg)
{
userdataType *ud = static_cast<userdataType*>(luaL_checkudata(L, narg, T::className));
if(!ud)
luaL_typerror(L, narg, T::className);
return ud->pT; // pointer to T object
}
static void * tryGet(lua_State * L, int narg)
{
if(checkType(L, narg, T::className))
{
userdataType *ud = static_cast<userdataType*>(luaL_checkudata(L, narg, T::className));
if(!ud)
luaL_typerror(L, narg, T::className);
return ud; // pointer to T object
}
else
{
return NULL;
}
}
static bool checkType (lua_State * L, int idx, const char *name)
{
// returns true if a userdata is of a certain type
int res;
if (lua_type(L, idx) != LUA_TUSERDATA) return false;
lua_getmetatable(L, idx);
luaL_newmetatable (L, name);
res = lua_equal(L, -2, -1);
lua_pop(L, 2); // pop both tables (metatables) off
return res;
}
static inline T * get(void * userData)
{
return ((userdataType*)userData)->pT;
}
private:
Luna(); // hide default constructor
// member function dispatcher
static int thunk(lua_State * L)
{
// stack has userdata, followed by method args
T *obj = check(L, 1); // get 'self', or if you prefer, 'this'
lua_remove(L, 1); // remove self so member function args start at index 1
// get member function from upvalue
RegType *l = static_cast<RegType*>(lua_touserdata(L, lua_upvalueindex(1)));
return (obj->*(l->mfunc))(L); // call member function
}
// create a new T object and
// push onto the Lua stack a userdata containing a pointer to T object
static int new_T(lua_State * L)
{
lua_remove(L, 1); // use classname:new(), instead of classname.new()
T *obj = new T(L); // call constructor for T objects
userdataType *ud = static_cast<userdataType*>(lua_newuserdata(L, sizeof(userdataType)));
ud->pT = obj; // store pointer to object in userdata
obj->UserData = luaL_ref(L, LUA_REGISTRYINDEX);
lua_rawgeti(L, LUA_REGISTRYINDEX, obj->UserData);
luaL_getmetatable(L, T::className); // lookup metatable in Lua registry
lua_setmetatable(L, -2);
return 1; // userdata containing pointer to T object
}
// garbage collection metamethod
static int gc_T(lua_State *L)
{
userdataType *ud = static_cast<userdataType*>(lua_touserdata(L, 1));
T *obj = ud->pT;
delete obj; // call destructor for T objects
return 0;
}
static int tostring_T (lua_State * L)
{
char buff[32];
userdataType *ud = static_cast<userdataType*>(lua_touserdata(L, 1));
T *obj = ud->pT;
sprintf(buff, "%p", obj);
lua_pushfstring(L, "%s (%s)", T::className, buff);
return 1;
}
};
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