public static NWProtocolDefinition CreateFramerDefinition(string identifier, NWFramerCreateFlags flags, Func <NWFramer, NWFramerStartResult> startCallback)
        {
            BlockLiteral block_handler = new BlockLiteral();

            block_handler.SetupBlockUnsafe(static_CreateFramerHandler, startCallback);
            try {
                return(new NWProtocolDefinition(nw_framer_create_definition(identifier, flags, ref block_handler), owns: true));
            } finally {
                block_handler.CleanupBlock();
            }
        }
 static extern unsafe OS_nw_protocol_definition nw_framer_create_definition(string identifier, NWFramerCreateFlags flags, ref BlockLiteral start_handler);