contract OwnedUpgradeabilityProxy is UpgradeabilityProxy {
    /**
    * @dev Event to show ownership has been transferred
    * @param previousOwner representing the address of the previous owner
    * @param newOwner representing the address of the new owner
    */
    event ProxyOwnershipTransferred(address previousOwner, address newOwner);

    // Storage position of the owner of the contract
    bytes32 private constant PROXY_OWNER_POSITION = keccak256("fixed.price.trade.proxy.owner");

    /**
    * @dev the constructor sets the original owner of the contract to the sender account.
    */
    constructor(address _implementation) public {
        _setUpgradeabilityOwner(msg.sender);
        _upgradeTo(_implementation);
    }

    /**
    * @dev Throws if called by any account other than the owner.
    */
    modifier onlyProxyOwner() {
        require(msg.sender == proxyOwner());
        _;
    }

    /**
    * @dev Tells the address of the owner
    * @return the address of the owner
    */
    function proxyOwner() public view returns (address owner) {
        bytes32 position = PROXY_OWNER_POSITION;
        assembly {
            owner := sload(position)
        }
    }

    /**
    * @dev Allows the current owner to transfer control of the contract to a newOwner.
    * @param _newOwner The address to transfer ownership to.
    */
    function transferProxyOwnership(address _newOwner) public onlyProxyOwner {
        require(_newOwner != address(0));
        _setUpgradeabilityOwner(_newOwner);
        emit ProxyOwnershipTransferred(proxyOwner(), _newOwner);
    }

    /**
    * @dev Allows the proxy owner to upgrade the current version of the proxy.
    * @param _implementation representing the address of the new implementation to be set.
    */
    function upgradeTo(address _implementation) public onlyProxyOwner {
        _upgradeTo(_implementation);
    }

    /**
     * @dev Sets the address of the owner
    */
    function _setUpgradeabilityOwner(address _newProxyOwner) internal {
        bytes32 position = PROXY_OWNER_POSITION;
        assembly {
            sstore(position, _newProxyOwner)
        }
    }
}
/**
 * @title OwnedUpgradeabilityProxy
 * @dev This contract combines an upgradeability proxy with basic authorization control functionalities
 */
function transferProxyOwnership(address _newOwner) public onlyProxyOwner {
    require(_newOwner != address(0));
    _setUpgradeabilityOwner(_newOwner);
    emit ProxyOwnershipTransferred(proxyOwner(), _newOwner);
}

/**
 * @dev Allows the current owner to transfer control of the contract to a newOwner.
 * @param _newOwner The address to transfer ownership to.
 */