StakeDAO

1*Submitted for verification at Etherscan.io on 2021-01-20
2*/
3
4// SPDX-License-Identifier: MIT
5
6pragma solidity 0.6.12;
7
8
9
10// Part: Address
11
12/**
13 * @dev Collection of functions related to the address type
14 */
15library Address {
16    /**
17     * @dev Returns true if `account` is a contract.
18     *
19     * [IMPORTANT]
20     * ====
21     * It is unsafe to assume that an address for which this function returns
22     * false is an externally-owned account (EOA) and not a contract.
23     *
24     * Among others, `isContract` will return false for the following
25     * types of addresses:
26     *
27     *  - an externally-owned account
28     *  - a contract in construction
29     *  - an address where a contract will be created
30     *  - an address where a contract lived, but was destroyed
31     * ====
32     */
33    function isContract(address account) internal view returns (bool) {
34        // This method relies on extcodesize, which returns 0 for contracts in
35        // construction, since the code is only stored at the end of the
36        // constructor execution.
37
38        uint256 size;
39        // solhint-disable-next-line no-inline-assembly
40        assembly {
41            size := extcodesize(account)
42        }
43        return size > 0;
44    }
45
46    /**
47     * @dev Replacement for Solidity's `transfer`: sends `amount` wei to
48     * `recipient`, forwarding all available gas and reverting on errors.
49     *
50     * https://eips.ethereum.org/EIPS/eip-1884[EIP1884] increases the gas cost
51     * of certain opcodes, possibly making contracts go over the 2300 gas limit
52     * imposed by `transfer`, making them unable to receive funds via
53     * `transfer`. {sendValue} removes this limitation.
54     *
55     * https://diligence.consensys.net/posts/2019/09/stop-using-soliditys-transfer-now/[Learn more].
56     *
57     * IMPORTANT: because control is transferred to `recipient`, care must be
58     * taken to not create reentrancy vulnerabilities. Consider using
59     * {ReentrancyGuard} or the
60     * https://solidity.readthedocs.io/en/v0.5.11/security-considerations.html#use-the-checks-effects-interactions-pattern[checks-effects-interactions pattern].
61     */
62    function sendValue(address payable recipient, uint256 amount) internal {
63        require(
64            address(this).balance >= amount,
65            "Address: insufficient balance"
66        );
67
68        // solhint-disable-next-line avoid-low-level-calls, avoid-call-value
69        (bool success, ) = recipient.call{value: amount}("");
70        require(
71            success,
72            "Address: unable to send value, recipient may have reverted"
73        );
74    }
75
76    /**
77     * @dev Performs a Solidity function call using a low level `call`. A
78     * plain`call` is an unsafe replacement for a function call: use this
79     * function instead.
80     *
81     * If `target` reverts with a revert reason, it is bubbled up by this
82     * function (like regular Solidity function calls).
83     *
84     * Returns the raw returned data. To convert to the expected return value,
85     * use https://solidity.readthedocs.io/en/latest/units-and-global-variables.html?highlight=abi.decode#abi-encoding-and-decoding-functions[`abi.decode`].
86     *
87     * Requirements:
88     *
89     * - `target` must be a contract.
90     * - calling `target` with `data` must not revert.
91     *
92     * _Available since v3.1._
93     */
94    function functionCall(address target, bytes memory data)
95        internal
96        returns (bytes memory)
97    {
98        return functionCall(target, data, "Address: low-level call failed");
99    }
100
101    /**
102     * @dev Same as {xref-Address-functionCall-address-bytes-}[`functionCall`], but with
103     * `errorMessage` as a fallback revert reason when `target` reverts.
104     *
105     * _Available since v3.1._
106     */
107    function functionCall(
108        address target,
109        bytes memory data,
110        string memory errorMessage
111    ) internal returns (bytes memory) {
112        return functionCallWithValue(target, data, 0, errorMessage);
113    }
114
115    /**
116     * @dev Same as {xref-Address-functionCall-address-bytes-}[`functionCall`],
117     * but also transferring `value` wei to `target`.
118     *
119     * Requirements:
120     *
121     * - the calling contract must have an ETH balance of at least `value`.
122     * - the called Solidity function must be `payable`.
123     *
124     * _Available since v3.1._
125     */
126    function functionCallWithValue(
127        address target,
128        bytes memory data,
129        uint256 value
130    ) internal returns (bytes memory) {
131        return
132            functionCallWithValue(
133                target,
134                data,
135                value,
136                "Address: low-level call with value failed"
137            );
138    }
139
140    /**
141     * @dev Same as {xref-Address-functionCallWithValue-address-bytes-uint256-}[`functionCallWithValue`], but
142     * with `errorMessage` as a fallback revert reason when `target` reverts.
143     *
144     * _Available since v3.1._
145     */
146    function functionCallWithValue(
147        address target,
148        bytes memory data,
149        uint256 value,
150        string memory errorMessage
151    ) internal returns (bytes memory) {
152        require(
153            address(this).balance >= value,
154            "Address: insufficient balance for call"
155        );
156        require(isContract(target), "Address: call to non-contract");
157
158        // solhint-disable-next-line avoid-low-level-calls
159        (bool success, bytes memory returndata) = target.call{value: value}(
160            data
161        );
162        return _verifyCallResult(success, returndata, errorMessage);
163    }
164
165    /**
166     * @dev Same as {xref-Address-functionCall-address-bytes-}[`functionCall`],
167     * but performing a static call.
168     *
169     * _Available since v3.3._
170     */
171    function functionStaticCall(address target, bytes memory data)
172        internal
173        view
174        returns (bytes memory)
175    {
176        return
177            functionStaticCall(
178                target,
179                data,
180                "Address: low-level static call failed"
181            );
182    }
183
184    /**
185     * @dev Same as {xref-Address-functionCall-address-bytes-string-}[`functionCall`],
186     * but performing a static call.
187     *
188     * _Available since v3.3._
189     */
190    function functionStaticCall(
191        address target,
192        bytes memory data,
193        string memory errorMessage
194    ) internal view returns (bytes memory) {
195        require(isContract(target), "Address: static call to non-contract");
196
197        // solhint-disable-next-line avoid-low-level-calls
198        (bool success, bytes memory returndata) = target.staticcall(data);
199        return _verifyCallResult(success, returndata, errorMessage);
200    }
201
202    /**
203     * @dev Same as {xref-Address-functionCall-address-bytes-}[`functionCall`],
204     * but performing a delegate call.
205     *
206     * _Available since v3.3._
207     */
208    function functionDelegateCall(address target, bytes memory data)
209        internal
210        returns (bytes memory)
211    {
212        return
213            functionDelegateCall(
214                target,
215                data,
216                "Address: low-level delegate call failed"
217            );
218    }
219
220    /**
221     * @dev Same as {xref-Address-functionCall-address-bytes-string-}[`functionCall`],
222     * but performing a delegate call.
223     *
224     * _Available since v3.3._
225     */
226    function functionDelegateCall(
227        address target,
228        bytes memory data,
229        string memory errorMessage
230    ) internal returns (bytes memory) {
231        require(isContract(target), "Address: delegate call to non-contract");
232
233        // solhint-disable-next-line avoid-low-level-calls
234        (bool success, bytes memory returndata) = target.delegatecall(data);
235        return _verifyCallResult(success, returndata, errorMessage);
236    }