Function CacheScriptContainer

Plugins/UnLua/Source/UnLua/Private/LuaCore.cpp:496–528

* Find a cached script container or create a new one * * @return - null if container is already cached, or the new created userdata otherwise */

 * @return - null if container is already cached, or the new created userdata otherwise
 */
void* CacheScriptContainer(lua_State *L, void *Key, const FScriptContainerDesc &Desc)
{
    if (!Key)
    {
        UNLUA_LOGERROR(L, LogUnLua, Warning, TEXT("%s, Invalid key!"), ANSI_TO_TCHAR(__FUNCTION__));
        return nullptr;
    }

    // return null if container is already cached, or create/cache/return a new ud
    void *Userdata = nullptr;
    lua_getfield(L, LUA_REGISTRYINDEX, "ScriptContainerMap");
    lua_pushlightuserdata(L, Key);
    int32 Type = lua_rawget(L, -2);             
    if (Type == LUA_TNIL)
    {
        lua_pop(L, 1);

        Userdata = NewUserdataWithContainerTag(L, Desc.GetSize());      // create new userdata
        luaL_setmetatable(L, Desc.GetName());               // set metatable
        lua_pushlightuserdata(L, Key);
        lua_pushvalue(L, -2);
        lua_rawset(L, -4);                                  // cache it in 'ScriptContainerMap'
        UnLua::FLuaEnv::FindEnv(L)->GetDanglingCheck()->CaptureContainer(L, Key);
    }
#if UE_BUILD_DEBUG
    else
    {
        check(Type == LUA_TUSERDATA);
    }
#endif
    lua_remove(L, -2);
    return Userdata;            // return null if container is already cached, or the new created userdata otherwise
}

/**
 * Get a script container at the given stack index