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// SPDX-License-Identifier: MIT pragma solidity ^0.8.0; /* * @dev Provides information about the current execution context, including the * sender of the transaction and its data. While these are generally available * via msg.sender and msg.data, they should not be accessed in such a direct * manner, since when dealing with meta-transactions the account sending and * paying for execution may not be the actual sender (as far as an application * is concerned). * * This contract is only required for intermediate, library-like contracts. */ abstract contract Context { function _msgSender() internal view virtual returns (address) { return msg.sender; } function _msgData() internal view virtual returns (bytes calldata) { this; // silence state mutability warning without generating bytecode - see https://github.com/ethereum/solidity/issues/2691 return msg.data; } } pragma solidity ^0.8.0; /** * @dev Contract module which provides a basic access control mechanism, where * there is an account (an owner) that can be granted exclusive access to * specific functions. * * By default, the owner account will be the one that deploys the contract. This * can later be changed with {transferOwnership}. * * This module is used through inheritance. It will make available the modifier * `onlyOwner`, which can be applied to your functions to restrict their use to * the owner. */ abstract contract Ownable is Context { address private _owner; event OwnershipTransferred(address indexed previousOwner, address indexed newOwner); /** * @dev Initializes the contract setting the deployer as the initial owner. */ constructor () { address msgSender = _msgSender(); _owner = msgSender; emit OwnershipTransferred(address(0), msgSender); } /** * @dev Returns the address of the current owner. */ function owner() public view virtual returns (address) { return _owner; } /** * @dev Throws if called by any account other than the owner. */ modifier onlyOwner() { require(owner() == _msgSender(), "Ownable: caller is not the owner"); _; } /** * @dev Leaves the contract without owner. It will not be possible to call * `onlyOwner` functions anymore. Can only be called by the current owner. * * NOTE: Renouncing ownership will leave the contract without an owner, * thereby removing any functionality that is only available to the owner. */ function renounceOwnership() public virtual onlyOwner { emit OwnershipTransferred(_owner, address(0)); _owner = address(0); } /** * @dev Transfers ownership of the contract to a new account (`newOwner`). * Can only be called by the current owner. */ function transferOwnership(address newOwner) public virtual onlyOwner { require(newOwner != address(0), "Ownable: new owner is the zero address"); emit OwnershipTransferred(_owner, newOwner); _owner = newOwner; } } pragma solidity ^0.8.0; /** * @dev Collection of functions related to the address type */ library Address { /** * @dev Returns true if `account` is a contract. * * [IMPORTANT] * ==== * It is unsafe to assume that an address for which this function returns * false is an externally-owned account (EOA) and not a contract. * * Among others, `isContract` will return false for the following * types of addresses: * * - an externally-owned account * - a contract in construction * - an address where a contract will be created * - an address where a contract lived, but was destroyed * ==== */ function isContract(address account) internal view returns (bool) { // This method relies on extcodesize, which returns 0 for contracts in // construction, since the code is only stored at the end of the // constructor execution. uint256 size; // solhint-disable-next-line no-inline-assembly assembly { size := extcodesize(account) } return size > 0; } /** * @dev Replacement for Solidity's `transfer`: sends `amount` wei to * `recipient`, forwarding all available gas and reverting on errors. * * https://eips.ethereum.org/EIPS/eip-1884[EIP1884] increases the gas cost * of certain opcodes, possibly making contracts go over the 2300 gas limit * imposed by `transfer`, making them unable to receive funds via * `transfer`. {sendValue} removes this limitation. * * https://diligence.consensys.net/posts/2019/09/stop-using-soliditys-transfer-now/[Learn more]. * * IMPORTANT: because control is transferred to `recipient`, care must be * taken to not create reentrancy vulnerabilities. Consider using * {ReentrancyGuard} or the * https://solidity.readthedocs.io/en/v0.5.11/security-considerations.html#use-the-checks-effects-interactions-pattern[checks-effects-interactions pattern]. */ function sendValue(address payable recipient, uint256 amount) internal { require(address(this).balance >= amount, "Address: insufficient balance"); // solhint-disable-next-line avoid-low-level-calls, avoid-call-value (bool success, ) = recipient.call{ value: amount }(""); require(success, "Address: unable to send value, recipient may have reverted"); } /** * @dev Performs a Solidity function call using a low level `call`. A * plain`call` is an unsafe replacement for a function call: use this * function instead. * * If `target` reverts with a revert reason, it is bubbled up by this * function (like regular Solidity function calls). * * Returns the raw returned data. To convert to the expected return value, * use https://solidity.readthedocs.io/en/latest/units-and-global-variables.html?highlight=abi.decode#abi-encoding-and-decoding-functions[`abi.decode`]. * * Requirements: * * - `target` must be a contract. * - calling `target` with `data` must not revert. * * _Available since v3.1._ */ function functionCall(address target, bytes memory data) internal returns (bytes memory) { return functionCall(target, data, "Address: low-level call failed"); } /** * @dev Same as {xref-Address-functionCall-address-bytes-}[`functionCall`], but with * `errorMessage` as a fallback revert reason when `target` reverts. * * _Available since v3.1._ */ function functionCall(address target, bytes memory data, string memory errorMessage) internal returns (bytes memory) { return functionCallWithValue(target, data, 0, errorMessage); } /** * @dev Same as {xref-Address-functionCall-address-bytes-}[`functionCall`], * but also transferring `value` wei to `target`. * * Requirements: * * - the calling contract must have an ETH balance of at least `value`. * - the called Solidity function must be `payable`. * * _Available since v3.1._ */ function functionCallWithValue(address target, bytes memory data, uint256 value) internal returns (bytes memory) { return functionCallWithValue(target, data, value, "Address: low-level call with value failed"); } /** * @dev Same as {xref-Address-functionCallWithValue-address-bytes-uint256-}[`functionCallWithValue`], but * with `errorMessage` as a fallback revert reason when `target` reverts. * * _Available since v3.1._ */ function functionCallWithValue(address target, bytes memory data, uint256 value, string memory errorMessage) internal returns (bytes memory) { require(address(this).balance >= value, "Address: insufficient balance for call"); require(isContract(target), "Address: call to non-contract"); // solhint-disable-next-line avoid-low-level-calls (bool success, bytes memory returndata) = target.call{ value: value }(data); return _verifyCallResult(success, returndata, errorMessage); } /** * @dev Same as {xref-Address-functionCall-address-bytes-}[`functionCall`], * but performing a static call. * * _Available since v3.3._ */ function functionStaticCall(address target, bytes memory data) internal view returns (bytes memory) { return functionStaticCall(target, data, "Address: low-level static call failed"); } /** * @dev Same as {xref-Address-functionCall-address-bytes-string-}[`functionCall`], * but performing a static call. * * _Available since v3.3._ */ function functionStaticCall(address target, bytes memory data, string memory errorMessage) internal view returns (bytes memory) { require(isContract(target), "Address: static call to non-contract"); // solhint-disable-next-line avoid-low-level-calls (bool success, bytes memory returndata) = target.staticcall(data); return _verifyCallResult(success, returndata, errorMessage); } /** * @dev Same as {xref-Address-functionCall-address-bytes-}[`functionCall`], * but performing a delegate call. * * _Available since v3.4._ */ function functionDelegateCall(address target, bytes memory data) internal returns (bytes memory) { return functionDelegateCall(target, data, "Address: low-level delegate call failed"); } /** * @dev Same as {xref-Address-functionCall-address-bytes-string-}[`functionCall`], * but performing a delegate call. * * _Available since v3.4._ */ function functionDelegateCall(address target, bytes memory data, string memory errorMessage) internal returns (bytes memory) { require(isContract(target), "Address: delegate call to non-contract"); // solhint-disable-next-line avoid-low-level-calls (bool success, bytes memory returndata) = target.delegatecall(data); return _verifyCallResult(success, returndata, errorMessage); } function _verifyCallResult(bool success, bytes memory returndata, string memory errorMessage) private pure returns(bytes memory) { if (success) { return returndata; } else { // Look for revert reason and bubble it up if present if (returndata.length > 0) { // The easiest way to bubble the revert reason is using memory via assembly // solhint-disable-next-line no-inline-assembly assembly { let returndata_size := mload(returndata) revert(add(32, returndata), returndata_size) } } else { revert(errorMessage); } } } } pragma solidity ^0.8.0; /** * @title Escrow * @dev Base escrow contract, holds funds designated for a payee until they * withdraw them. * * Intended usage: This contract (and derived escrow contracts) should be a * standalone contract, that only interacts with the contract that instantiated * it. That way, it is guaranteed that all Ether will be handled according to * the `Escrow` rules, and there is no need to check for payable functions or * transfers in the inheritance tree. The contract that uses the escrow as its * payment method should be its owner, and provide public methods redirecting * to the escrow's deposit and withdraw. */ contract Escrow is Ownable { using Address for address payable; event Deposited(address indexed payee, uint256 weiAmount); event Withdrawn(address indexed payee, uint256 weiAmount); mapping(address => uint256) private _deposits; function depositsOf(address payee) public view returns (uint256) { return _deposits[payee]; } /** * @dev Stores the sent amount as credit to be withdrawn. * @param payee The destination address of the funds. */ function deposit(address payee) public payable virtual onlyOwner { uint256 amount = msg.value; _deposits[payee] = _deposits[payee] + amount; emit Deposited(payee, amount); } /** * @dev Withdraw accumulated balance for a payee, forwarding all gas to the * recipient. * * WARNING: Forwarding all gas opens the door to reentrancy vulnerabilities. * Make sure you trust the recipient, or are either following the * checks-effects-interactions pattern or using {ReentrancyGuard}. * * @param payee The address whose funds will be withdrawn and transferred to. */ function withdraw(address payable payee) public virtual onlyOwner { uint256 payment = _deposits[payee]; _deposits[payee] = 0; payee.sendValue(payment); emit Withdrawn(payee, payment); } } pragma solidity ^0.8.0; // main smart contract contract PaymentGateway{ Escrow immutable private escrow; constructor(){ escrow = new Escrow(); } //Receives payment on sale function sendPayment(address dest) public payable { require(msg.value > 0, "PaymentGateway: Cannot send a value of zero"); escrow.deposit{value: msg.value}(dest); } //to withdrawl funds function withdraw() public { escrow.withdraw(payable(msg.sender)); } // checks balance available to withdraw of msg.sender // @return the balance function balance() public view returns (uint256) { return escrow.depositsOf(msg.sender); } }
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