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contracts/token/ERC20/utils/SafeERC20.sol

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+// SPDX-License-Identifier: MIT
+// OpenZeppelin Contracts (last updated v5.0.0-rc.0) (token/ERC20/utils/SafeERC20.sol)
+
+pragma solidity ^0.8.20;
+
+import {IERC20} from "../IERC20.sol";
+import {IERC20Permit} from "../extensions/IERC20Permit.sol";
+import {Address} from "../../../utils/Address.sol";
+
+/**
+ * @title SafeERC20
+ * @dev Wrappers around ERC20 operations that throw on failure (when the token
+ * contract returns false). Tokens that return no value (and instead revert or
+ * throw on failure) are also supported, non-reverting calls are assumed to be
+ * successful.
+ * To use this library you can add a `using SafeERC20 for IERC20;` statement to your contract,
+ * which allows you to call the safe operations as `token.safeTransfer(...)`, etc.
+ */
+library SafeERC20 {
+    using Address for address;
+
+    /**
+     * @dev An operation with an ERC20 token failed.
+     */
+    error SafeERC20FailedOperation(address token);
+
+    /**
+     * @dev Indicates a failed `decreaseAllowance` request.
+     */
+    error SafeERC20FailedDecreaseAllowance(address spender, uint256 currentAllowance, uint256 requestedDecrease);
+
+    /**
+     * @dev Transfer `value` amount of `token` from the calling contract to `to`. If `token` returns no value,
+     * non-reverting calls are assumed to be successful.
+     */
+    function safeTransfer(IERC20 token, address to, uint256 value) internal {
+        _callOptionalReturn(token, abi.encodeCall(token.transfer, (to, value)));
+    }
+
+    /**
+     * @dev Transfer `value` amount of `token` from `from` to `to`, spending the approval given by `from` to the
+     * calling contract. If `token` returns no value, non-reverting calls are assumed to be successful.
+     */
+    function safeTransferFrom(IERC20 token, address from, address to, uint256 value) internal {
+        _callOptionalReturn(token, abi.encodeCall(token.transferFrom, (from, to, value)));
+    }
+
+    /**
+     * @dev Increase the calling contract's allowance toward `spender` by `value`. If `token` returns no value,
+     * non-reverting calls are assumed to be successful.
+     */
+    function safeIncreaseAllowance(IERC20 token, address spender, uint256 value) internal {
+        uint256 oldAllowance = token.allowance(address(this), spender);
+        forceApprove(token, spender, oldAllowance + value);
+    }
+
+    /**
+     * @dev Decrease the calling contract's allowance toward `spender` by `requestedDecrease`. If `token` returns no
+     * value, non-reverting calls are assumed to be successful.
+     */
+    function safeDecreaseAllowance(IERC20 token, address spender, uint256 requestedDecrease) internal {
+        unchecked {
+            uint256 currentAllowance = token.allowance(address(this), spender);
+            if (currentAllowance < requestedDecrease) {
+                revert SafeERC20FailedDecreaseAllowance(spender, currentAllowance, requestedDecrease);
+            }
+            forceApprove(token, spender, currentAllowance - requestedDecrease);
+        }
+    }
+
+    /**
+     * @dev Set the calling contract's allowance toward `spender` to `value`. If `token` returns no value,
+     * non-reverting calls are assumed to be successful. Meant to be used with tokens that require the approval
+     * to be set to zero before setting it to a non-zero value, such as USDT.
+     */
+    function forceApprove(IERC20 token, address spender, uint256 value) internal {
+        bytes memory approvalCall = abi.encodeCall(token.approve, (spender, value));
+
+        if (!_callOptionalReturnBool(token, approvalCall)) {
+            _callOptionalReturn(token, abi.encodeCall(token.approve, (spender, 0)));
+            _callOptionalReturn(token, approvalCall);
+        }
+    }
+
+    /**
+     * @dev Imitates a Solidity high-level call (i.e. a regular function call to a contract), relaxing the requirement
+     * on the return value: the return value is optional (but if data is returned, it must not be false).
+     * @param token The token targeted by the call.
+     * @param data The call data (encoded using abi.encode or one of its variants).
+     */
+    function _callOptionalReturn(IERC20 token, bytes memory data) private {
+        // We need to perform a low level call here, to bypass Solidity's return data size checking mechanism, since
+        // we're implementing it ourselves. We use {Address-functionCall} to perform this call, which verifies that
+        // the target address contains contract code and also asserts for success in the low-level call.
+
+        bytes memory returndata = address(token).functionCall(data);
+        if (returndata.length != 0 && !abi.decode(returndata, (bool))) {
+            revert SafeERC20FailedOperation(address(token));
+        }
+    }
+
+    /**
+     * @dev Imitates a Solidity high-level call (i.e. a regular function call to a contract), relaxing the requirement
+     * on the return value: the return value is optional (but if data is returned, it must not be false).
+     * @param token The token targeted by the call.
+     * @param data The call data (encoded using abi.encode or one of its variants).
+     *
+     * This is a variant of {_callOptionalReturn} that silents catches all reverts and returns a bool instead.
+     */
+    function _callOptionalReturnBool(IERC20 token, bytes memory data) private returns (bool) {
+        // We need to perform a low level call here, to bypass Solidity's return data size checking mechanism, since
+        // we're implementing it ourselves. We cannot use {Address-functionCall} here since this should return false
+        // and not revert is the subcall reverts.
+
+        (bool success, bytes memory returndata) = address(token).call(data);
+        return success && (returndata.length == 0 || abi.decode(returndata, (bool))) && address(token).code.length > 0;
+    }
+}