pragma solidity ^0.8.9; /** * @dev Contract module that helps prevent reentrant calls to a function. * * Inheriting from `ReentrancyGuard` will make the `nonReentrant` modifier * available, which can be aplied to functions to make sure there are no nested * (reentrant) calls to them. * * Note that because there is a single `nonReentrant` guard, functions marked as * `nonReentrant` may not call one another. This can be worked around by making * those functions `private`, and then adding `external` `nonReentrant` entry * points to them. */ contract ReentrancyGuard { /// @dev counter to allow mutex lock with only one SSTORE operation uint256 private _guardCounter; constructor() { // The counter starts at one to prevent changing it from zero to a non-zero // value, which is a more expensive operation. _guardCounter = 1; } /** * @dev Prevents a contract from calling itself, directly or indirectly. * Calling a `nonReentrant` function from another `nonReentrant` * function is not supported. It is possible to prevent this from happening * by making the `nonReentrant` function external, and make it call a * `private` function that does the actual work. */ modifier nonReentrant() { _guardCounter += 1; uint256 localCounter = _guardCounter; _; require(localCounter == _guardCounter, "ReentrancyGuard: reentrant call"); } }