function erc165InterfaceSupported(address _contract, bytes4 _interfaceId) constant public returns (bool) {
        if (!erc165Cache[_contract][_interfaceId]) {
            erc165UpdateCache(_contract, _interfaceId);
        }
        return interfaces[_contract][_interfaceId] != 0;
    }

    function erc165UpdateCache(address _contract, bytes4 _interfaceId) public {
        interfaces[_contract][_interfaceId] =
            erc165InterfaceSupported_NoCache(_contract, _interfaceId) ? _contract : 0;
        erc165Cache[_contract][_interfaceId] = true;
    }