pragma solidity 0.4.20;


/**
 * @title Helps contracts guard agains rentrancy attacks.
 * @author Remco Bloemen <remco@2π.com>
 * @notice If you mark a function `nonReentrant`, you should also mark it `external`.
 */
contract ReentrancyGuard {
    /**
     * @dev We use a single lock for the whole contract.
     */
    bool private rentrancyLock = false;

    /**
     * @dev Prevents a contract from calling itself, directly or indirectly.
     * @notice If you mark a function `nonReentrant`, you should also mark it `external`. Calling one nonReentrant function from another is not supported. Instead, you can implement a `private` function doing the actual work, and a `external` wrapper marked as `nonReentrant`.
     */
    modifier nonReentrant() {
        require(!rentrancyLock);
        rentrancyLock = true;
        _;
        rentrancyLock = false;
    }
}