Method get_object_internal

library/LuaWrapper.cpp:350–397

* Verify that the value matches the identity, and return ptr if so. */

 * Verify that the value matches the identity, and return ptr if so.
 */
void *LuaWrapper::get_object_internal(lua_State *state, const type_identity *type, int val_index, bool exact_type, bool in_method)
{
    /*
     * Non-userdata results in NULL; nil for NULL gets handled here too.
     */
    if (!lua_isuserdata(state, val_index))
        return NULL;

    /*
     * Light user data is allowed with null type; otherwise bail out.
     */
    if (!lua_getmetatable(state, val_index)) // () -> metatable?
    {
        if (!type && lua_islightuserdata(state, val_index))
            return lua_touserdata(state, val_index);

        return NULL;
    }

    /*
     * Verify that the metatable is known, and refers to the correct type.
     * Here doing reverse lookup of identity by metatable.
     */
    if (!LookupTypeInfo(state, in_method)) // metatable -> type?
        return NULL;

    if (type && lua_touserdata(state, -1) != type)
    {
        /*
         * If valid but different type, do an intelligent comparison.
         */
        lua_pop(state, 1); // type -> ()
        lua_getmetatable(state, val_index);

        if (!is_type_compatible(state, type, 0, lua_gettop(state), exact_type))
        {
            lua_pop(state, 1); // metatable -> ()
            return NULL;
        }
    }

    lua_pop(state, 1); // type -> ()

    /*
     * Finally decode the reference.
     */
    return get_object_ref(state, val_index);
}

/**
 * Check if the object and metatable are a valid DF reference or type.