Ethereum-Crowdsale-Beispiel – festgefahrene Token (wie man spart)

Ich habe einen Crowdsale-Vertrag mit der Quelle von ethereum.org bereitgestellt und ihn mit einigen Token geladen. Es funktioniert wie erwartet, außer dass es keinen Code hat, um die nicht verkauften Token an den Begünstigten zurückzugeben.

Gibt es eine Möglichkeit, diese Token zu speichern?

Hier ist die Vertragsquelle

pragma solidity ^0.4.16;

interface token {
    function transfer(address receiver, uint amount);
}

contract Crowdsale {
    address public beneficiary;
    uint public fundingGoal;
    uint public amountRaised;
    uint public deadline;
    uint public price;
    token public tokenReward;
    mapping(address => uint256) public balanceOf;
    bool fundingGoalReached = false;
    bool crowdsaleClosed = false;

    event GoalReached(address recipient, uint totalAmountRaised);
    event FundTransfer(address backer, uint amount, bool isContribution);

    /**
     * Constrctor function
     *
     * Setup the owner
     */
    function Crowdsale(
        address ifSuccessfulSendTo,
        uint fundingGoalInEthers,
        uint durationInMinutes,
        uint etherCostOfEachToken,
        address addressOfTokenUsedAsReward
    ) {
        beneficiary = ifSuccessfulSendTo;
        fundingGoal = fundingGoalInEthers * 1 ether;
        deadline = now + durationInMinutes * 1 minutes;
        price = etherCostOfEachToken * 1 ether;
        tokenReward = token(addressOfTokenUsedAsReward);
    }

    /**
     * Fallback function
     *
     * The function without name is the default function that is called whenever anyone sends funds to a contract
     */
    function () payable {
        require(!crowdsaleClosed);
        uint amount = msg.value;
        balanceOf[msg.sender] += amount;
        amountRaised += amount;
        tokenReward.transfer(msg.sender, amount / price);
        FundTransfer(msg.sender, amount, true);
    }

    modifier afterDeadline() { if (now >= deadline) _; }

    /**
     * Check if goal was reached
     *
     * Checks if the goal or time limit has been reached and ends the campaign
     */
    function checkGoalReached() afterDeadline {
        if (amountRaised >= fundingGoal){
            fundingGoalReached = true;
            GoalReached(beneficiary, amountRaised);
        }
        crowdsaleClosed = true;
    }


    /**
     * Withdraw the funds
     *
     * Checks to see if goal or time limit has been reached, and if so, and the funding goal was reached,
     * sends the entire amount to the beneficiary. If goal was not reached, each contributor can withdraw
     * the amount they contributed.
     */
    function safeWithdrawal() afterDeadline {
        if (!fundingGoalReached) {
            uint amount = balanceOf[msg.sender];
            balanceOf[msg.sender] = 0;
            if (amount > 0) {
                if (msg.sender.send(amount)) {
                    FundTransfer(msg.sender, amount, false);
                } else {
                    balanceOf[msg.sender] = amount;
                }
            }
        }

        if (fundingGoalReached && beneficiary == msg.sender) {
            if (beneficiary.send(amountRaised)) {
                FundTransfer(beneficiary, amountRaised, false);
            } else {
                //If we fail to send the funds to beneficiary, unlock funders balance
                fundingGoalReached = false;
            }
        }
    }
}