contract TimedCrowdsale is Crowdsale {
    using SafeMath for uint256;

    uint256 public openingTime;
    uint256 public closingTime;

    /**
    * @dev Reverts if not in crowdsale time range.
    */
    modifier onlyWhileOpen {
        // solium-disable-next-line security/no-block-members
        require(block.timestamp >= openingTime && block.timestamp <= closingTime);
        _;
    }

    /**
    * @dev Constructor, takes crowdsale opening and closing times.
    * @param _openingTime Crowdsale opening time
    * @param _closingTime Crowdsale closing time
    */
    constructor(uint256 _openingTime, uint256 _closingTime) public {
        // solium-disable-next-line security/no-block-members
        require(_openingTime >= block.timestamp);
        require(_closingTime > _openingTime);

        openingTime = _openingTime;
        closingTime = _closingTime;
    }

    /**
    * @dev Checks whether the period in which the crowdsale is open has already elapsed.
    * @return Whether crowdsale period has elapsed
    */
    function hasClosed() public view returns (bool) {
        // solium-disable-next-line security/no-block-members
        return block.timestamp > closingTime;
    }

    /**
    * @dev Extend parent behavior requiring to be within contributing period
    * @param _beneficiary Token purchaser
    * @param _weiAmount Amount of wei contributed
    * @param _tokenAmount Amount of token purchased
    */
    function _preValidatePurchase(
        address _beneficiary,
        uint256 _weiAmount,
        uint256 _tokenAmount
    )
        internal
        onlyWhileOpen
    {
        super._preValidatePurchase(_beneficiary, _weiAmount, _tokenAmount);
    }

}
/**
 * @title TimedCrowdsale
 * @dev Crowdsale accepting contributions only within a time frame.
 */
function _preValidatePurchase(
        address _beneficiary,
        uint256 _weiAmount,
        uint256 _tokenAmount
    )
        internal
        onlyWhileOpen
    {
        super._preValidatePurchase(_beneficiary, _weiAmount, _tokenAmount);
    }
/**
 * @dev Extend parent behavior requiring to be within contributing period
 * @param _beneficiary Token purchaser
 * @param _weiAmount Amount of wei contributed
 * @param _tokenAmount Amount of token purchased
 */