/*

    Copyright 2020 DODO ZOO.
    SPDX-License-Identifier: Apache-2.0

*/

pragma solidity 0.6.9;
pragma experimental ABIEncoderV2;

/**
 * @title ReentrancyGuard
 * @author DODO Breeder
 *
 * @notice Protect functions from Reentrancy Attack
 */
contract ReentrancyGuard {
    // https://solidity.readthedocs.io/en/latest/control-structures.html?highlight=zero-state#scoping-and-declarations
    // zero-state of _ENTERED_ is false
    bool private _ENTERED_;

    modifier preventReentrant() {
        require(!_ENTERED_, "REENTRANT");
        _ENTERED_ = true;
        _;
        _ENTERED_ = false;
    }
}