/// <summary>
/// Initializes a new instance of the <see cref="ObjectBinder"/> class for the given <see cref="Lua"/> environment.
/// </summary>
/// <param name="lua">The <see cref="Lua"/> environment.</param>
public ObjectBinder(Lua lua)
{
_lua = lua;
// The __index metamethod can be cached in certain situations, such as methods and events. This can significantly improve
// performance.
var wrapIndexFunction = (LuaFunction)lua.DoString(@"
local error = error
local cache = setmetatable({}, { __mode = 'k' })
return function(fn)
return function(obj, index)
local objcache = cache[obj]
if objcache == nil then
objcache = {}
cache[obj] = objcache
end
if objcache[index] ~= nil then
return objcache[index]
end
local success, iscached, result = fn(obj, index)
if not success then
error(iscached, 2)
end
if iscached then
objcache[index] = result
end
return result
end
end")[0];
// To raise Lua errors, we will do so directly in Lua. Doing so by P/Invoking luaL_error is problematic because luaL_error
// performs a longjmp, which can destroy stack information.
_wrapFunction = (LuaFunction)lua.DoString(@"
local error = error
local function helper(success, ...)
if not success then
error(..., 2)
end
return ...
end
return function(fn)
return function(...)
return helper(fn(...))
end
end")[0];
// Storing the LuaCFunction delegates prevents the .NET GC from garbage collecting them.
_objectMetamethods = new Dictionary <string, LuaCFunction> {
["__call"] = CallObject,
["__index"] = IndexObject,
["__newindex"] = NewIndexObject,
["__add"] = AddObject,
["__sub"] = SubObject,
["__mul"] = MulObject,
["__div"] = DivObject,
["__mod"] = ModObject,
["__band"] = BandObject,
["__bor"] = BorObject,
["__bxor"] = BxorObject,
["__shr"] = ShrObject,
["__shl"] = ShlObject,
["__eq"] = EqObject,
["__lt"] = LtObject,
["__le"] = LeObject,
["__unm"] = UnmObject,
["__bnot"] = BnotObject,
["__gc"] = Gc,
["__tostring"] = ToString
};
_proxyCallObjectDelegate = ProxyCallObject;
_typeMetamethods = new Dictionary <string, LuaCFunction> {
["__call"] = CallType,
["__index"] = IndexType,
["__newindex"] = NewIndexType,
["__gc"] = Gc,
["__tostring"] = ToString
};
_proxyCallTypeDelegate = ProxyCallType;
NewMetatable(ObjectMetatable, _objectMetamethods);
NewMetatable(TypeMetatable, _typeMetamethods);
void NewMetatable(string name, Dictionary <string, LuaCFunction> metamethods)
{
LuaApi.NewMetatable(lua.MainState, name);
foreach (var kvp in metamethods)
{
LuaApi.PushString(lua.MainState, kvp.Key);
var isWrapped = kvp.Key != "__gc" && kvp.Key != "__tostring";
if (kvp.Key == "__index")
{
wrapIndexFunction.PushOnto(lua.MainState);
}
else if (isWrapped)
{
_wrapFunction.PushOnto(lua.MainState);
}
LuaApi.PushCClosure(lua.MainState, kvp.Value, 0);
if (isWrapped)
{
LuaApi.PCallK(lua.MainState, 1, 1);
}
LuaApi.SetTable(lua.MainState, -3);
}
// Setting __metatable to false will hide the metatable, protecting it from getmetatable and setmetatable.
LuaApi.PushString(lua.MainState, "__metatable");
LuaApi.PushBoolean(lua.MainState, false);
LuaApi.SetTable(lua.MainState, -3);
LuaApi.Pop(lua.MainState, 1);
}
}
