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@nventuro @frangio @Aniket-Engg @balajipachai @abcoathup
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pragma solidity ^0.5.0;
* @dev Contract module that helps prevent reentrant calls to a function.
* Inheriting from `ReentrancyGuard` will make the {nonReentrant} modifier
* available, which can be applied 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 {
// counter to allow mutex lock with only one SSTORE operation
uint256 private _guardCounter;
constructor () internal {
// 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");
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