Merge tag 'v2.2.0' of github.com:OpenZeppelin/openzeppelin-solidity

v2.2.0

contracts/drafts/Counter.sol

@@ -1,24 +0,0 @@
-pragma solidity ^0.5.0;
-
-/**
- * @title Counter
- * @author Matt Condon (@shrugs)
- * @dev Provides an incrementing uint256 id acquired by the `Counter#next` getter.
- * Use this for issuing ERC721 ids or keeping track of request ids, anything you want, really.
- *
- * Include with `using Counter for Counter.Counter;`
- * @notice Does not allow an Id of 0, which is popularly used to signify a null state in solidity.
- * Does not protect from overflows, but if you have 2^256 ids, you have other problems.
- * (But actually, it's generally impossible to increment a counter this many times, energy wise
- * so it's not something you have to worry about.)
- */
-library Counter {
-    struct Counter {
-        uint256 current; // default: 0
-    }
-
-    function next(Counter storage index) internal returns (uint256) {
-        index.current += 1;
-        return index.current;
-    }
-}

contracts/drafts/Counters.sol

@@ -0,0 +1,37 @@
+pragma solidity ^0.5.2;
+
+import "../math/SafeMath.sol";
+
+/**
+ * @title Counters
+ * @author Matt Condon (@shrugs)
+ * @dev Provides counters that can only be incremented or decremented by one. This can be used e.g. to track the number
+ * of elements in a mapping, issuing ERC721 ids, or counting request ids
+ *
+ * Include with `using Counters for Counters.Counter;`
+ * Since it is not possible to overflow a 256 bit integer with increments of one, `increment` can skip the SafeMath
+ * overflow check, thereby saving gas. This does assume however correct usage, in that the underlying `_value` is never
+ * directly accessed.
+ */
+library Counters {
+    using SafeMath for uint256;
+
+    struct Counter {
+        // This variable should never be directly accessed by users of the library: interactions must be restricted to
+        // the library's function. As of Solidity v0.5.2, this cannot be enforced, though there is a proposal to add
+        // this feature: see https://github.com/ethereum/solidity/issues/4637
+        uint256 _value; // default: 0
+    }
+
+    function current(Counter storage counter) internal view returns (uint256) {
+        return counter._value;
+    }
+
+    function increment(Counter storage counter) internal {
+        counter._value += 1;
+    }
+
+    function decrement(Counter storage counter) internal {
+        counter._value = counter._value.sub(1);
+    }
+}

contracts/drafts/ERC1046/ERC20Metadata.sol

@@ -1,4 +1,4 @@
-pragma solidity ^0.5.0;
+pragma solidity ^0.5.2;
 
 import "zos-lib/contracts/Initializable.sol";
 import "../../token/ERC20/IERC20.sol";
@@ -8,22 +8,20 @@ import "../../token/ERC20/IERC20.sol";
  * @dev See https://eips.ethereum.org/EIPS/eip-1046
  * @dev tokenURI must respond with a URI that implements https://eips.ethereum.org/EIPS/eip-1047
  */
-contract ERC20TokenMetadata is Initializable, IERC20 {
-    function tokenURI() external view returns (string memory);
-
-    uint256[50] private ______gap;
-}
-
-contract ERC20WithMetadata is Initializable, ERC20TokenMetadata {
+contract ERC20Metadata is Initializable {
     string private _tokenURI;
 
-    function initialize(string memory tokenURI) public {
-        _tokenURI = tokenURI;
+    function initialize(string memory tokenURI_) public {
+        _setTokenURI(tokenURI_);
     }
 
     function tokenURI() external view returns (string memory) {
         return _tokenURI;
     }
 
+    function _setTokenURI(string memory tokenURI_) internal {
+        _tokenURI = tokenURI_;
+    }
+
     uint256[50] private ______gap;
 }

contracts/drafts/ERC20Migrator.sol

@@ -1,4 +1,4 @@
-pragma solidity ^0.5.0;
+pragma solidity ^0.5.2;
 
 import "zos-lib/contracts/Initializable.sol";
 import "../token/ERC20/IERC20.sol";
@@ -18,7 +18,7 @@ import "../math/Math.sol";
  * OpenZeppelin's ERC20Mintable, but the only functions that are needed are
  * `isMinter(address)` and `mint(address, amount)`. The migrator will check
  * that it is a minter for the token.
- * The balance from the legacy token will be transfered to the migrator, as it
+ * The balance from the legacy token will be transferred to the migrator, as it
  * is migrated, and remain there forever.
  * Although this contract can be used in many different scenarios, the main
  * motivation was to provide a way to migrate ERC20 tokens into an upgradeable
@@ -66,14 +66,14 @@ contract ERC20Migrator is Initializable {
     /**
      * @dev Begins the migration by setting which is the new token that will be
      * minted. This contract must be a minter for the new token.
-     * @param newToken the token that will be minted
+     * @param newToken_ the token that will be minted
      */
-    function beginMigration(ERC20Mintable newToken) public {
+    function beginMigration(ERC20Mintable newToken_) public {
         require(address(_newToken) == address(0));
-        require(address(newToken) != address(0));
-        require(newToken.isMinter(address(this)));
+        require(address(newToken_) != address(0));
+        require(newToken_.isMinter(address(this)));
 
-        _newToken = newToken;
+        _newToken = newToken_;
     }
 
     /**
@@ -83,6 +83,7 @@ contract ERC20Migrator is Initializable {
      * @param amount amount of tokens to be migrated
      */
     function migrate(address account, uint256 amount) public {
+        require(address(_newToken) != address(0));
         _legacyToken.safeTransferFrom(account, address(this), amount);
         _newToken.mint(account, amount);
     }

contracts/drafts/ERC20Snapshot.sol

@@ -0,0 +1,140 @@
+pragma solidity ^0.5.2;
+
+import "zos-lib/contracts/Initializable.sol";
+import "../math/SafeMath.sol";
+import "../utils/Arrays.sol";
+import "../drafts/Counters.sol";
+import "../token/ERC20/ERC20.sol";
+
+/**
+ * @title ERC20 token with snapshots.
+ * @dev Inspired by Jordi Baylina's MiniMeToken to record historical balances:
+ * https://github.com/Giveth/minime/blob/ea04d950eea153a04c51fa510b068b9dded390cb/contracts/MiniMeToken.sol
+ * When a snapshot is made, the balances and totalSupply at the time of the snapshot are recorded for later
+ * access.
+ *
+ * To make a snapshot, call the `snapshot` function, which will emit the `Snapshot` event and return a snapshot id.
+ * To get the total supply from a snapshot, call the function `totalSupplyAt` with the snapshot id.
+ * To get the balance of an account from a snapshot, call the `balanceOfAt` function with the snapshot id and the
+ * account address.
+ * @author Validity Labs AG <info@validitylabs.org>
+ */
+contract ERC20Snapshot is Initializable, ERC20 {
+    using SafeMath for uint256;
+    using Arrays for uint256[];
+    using Counters for Counters.Counter;
+
+    // Snapshotted values have arrays of ids and the value corresponding to that id. These could be an array of a
+    // Snapshot struct, but that would impede usage of functions that work on an array.
+    struct Snapshots {
+        uint256[] ids;
+        uint256[] values;
+    }
+
+    mapping (address => Snapshots) private _accountBalanceSnapshots;
+    Snapshots private _totalSupplySnaphots;
+
+    // Snapshot ids increase monotonically, with the first value being 1. An id of 0 is invalid.
+    Counters.Counter private _currentSnapshotId;
+
+    event Snapshot(uint256 id);
+
+    // Creates a new snapshot id. Balances are only stored in snapshots on demand: unless a snapshot was taken, a
+    // balance change will not be recorded. This means the extra added cost of storing snapshotted balances is only paid
+    // when required, but is also flexible enough that it allows for e.g. daily snapshots.
+    function snapshot() public returns (uint256) {
+        _currentSnapshotId.increment();
+
+        uint256 currentId = _currentSnapshotId.current();
+        emit Snapshot(currentId);
+        return currentId;
+    }
+
+    function balanceOfAt(address account, uint256 snapshotId) public view returns (uint256) {
+        (bool snapshotted, uint256 value) = _valueAt(snapshotId, _accountBalanceSnapshots[account]);
+
+        return snapshotted ? value : balanceOf(account);
+    }
+
+    function totalSupplyAt(uint256 snapshotId) public view returns(uint256) {
+        (bool snapshotted, uint256 value) = _valueAt(snapshotId, _totalSupplySnaphots);
+
+        return snapshotted ? value : totalSupply();
+    }
+
+    // _transfer, _mint and _burn are the only functions where the balances are modified, so it is there that the
+    // snapshots are updated. Note that the update happens _before_ the balance change, with the pre-modified value.
+    // The same is true for the total supply and _mint and _burn.
+    function _transfer(address from, address to, uint256 value) internal {
+        _updateAccountSnapshot(from);
+        _updateAccountSnapshot(to);
+
+        super._transfer(from, to, value);
+    }
+
+    function _mint(address account, uint256 value) internal {
+        _updateAccountSnapshot(account);
+        _updateTotalSupplySnapshot();
+
+        super._mint(account, value);
+    }
+
+    function _burn(address account, uint256 value) internal {
+        _updateAccountSnapshot(account);
+        _updateTotalSupplySnapshot();
+
+        super._burn(account, value);
+    }
+
+    // When a valid snapshot is queried, there are three possibilities:
+    //  a) The queried value was not modified after the snapshot was taken. Therefore, a snapshot entry was never
+    //  created for this id, and all stored snapshot ids are smaller than the requested one. The value that corresponds
+    //  to this id is the current one.
+    //  b) The queried value was modified after the snapshot was taken. Therefore, there will be an entry with the
+    //  requested id, and its value is the one to return.
+    //  c) More snapshots were created after the requested one, and the queried value was later modified. There will be
+    //  no entry for the requested id: the value that corresponds to it is that of the smallest snapshot id that is
+    //  larger than the requested one.
+    //
+    // In summary, we need to find an element in an array, returning the index of the smallest value that is larger if
+    // it is not found, unless said value doesn't exist (e.g. when all values are smaller). Arrays.findUpperBound does
+    // exactly this.
+    function _valueAt(uint256 snapshotId, Snapshots storage snapshots)
+        private view returns (bool, uint256)
+    {
+        require(snapshotId > 0);
+        require(snapshotId <= _currentSnapshotId.current());
+
+        uint256 index = snapshots.ids.findUpperBound(snapshotId);
+
+        if (index == snapshots.ids.length) {
+            return (false, 0);
+        } else {
+            return (true, snapshots.values[index]);
+        }
+    }
+
+    function _updateAccountSnapshot(address account) private {
+        _updateSnapshot(_accountBalanceSnapshots[account], balanceOf(account));
+    }
+
+    function _updateTotalSupplySnapshot() private {
+        _updateSnapshot(_totalSupplySnaphots, totalSupply());
+    }
+
+    function _updateSnapshot(Snapshots storage snapshots, uint256 currentValue) private {
+        uint256 currentId = _currentSnapshotId.current();
+        if (_lastSnapshotId(snapshots.ids) < currentId) {
+            snapshots.ids.push(currentId);
+            snapshots.values.push(currentValue);
+        }
+    }
+
+    function _lastSnapshotId(uint256[] storage ids) private view returns (uint256) {
+        if (ids.length == 0) {
+            return 0;
+        } else {
+            return ids[ids.length - 1];
+        }
+    }
+}

contracts/drafts/SignatureBouncer.sol

@@ -1,4 +1,4 @@
-pragma solidity ^0.5.0;
+pragma solidity ^0.5.2;
 
 import "zos-lib/contracts/Initializable.sol";
 import "../access/roles/SignerRole.sol";
@@ -30,7 +30,7 @@ import "../cryptography/ECDSA.sol";
  * @notice A method that uses the `onlyValidSignatureAndData` modifier must make
  * the _signature parameter the "last" parameter. You cannot sign a message that
  * has its own signature in it so the last 128 bytes of msg.data (which
- * represents the length of the _signature data and the _signaature data itself)
+ * represents the length of the _signature data and the _signature data itself)
  * is ignored when validating. Also non fixed sized parameters make constructing
  * the data in the signature much more complex.
  * See https://ethereum.stackexchange.com/a/50616 for more details.
@@ -57,7 +57,7 @@ contract SignatureBouncer is Initializable, SignerRole {
     }
 
     /**
-     * @dev requires that a valid signature with a specifed method of a signer was provided
+     * @dev requires that a valid signature with a specified method of a signer was provided
      */
     modifier onlyValidSignatureAndMethod(bytes memory signature) {
         require(_isValidSignatureAndMethod(msg.sender, signature));
@@ -65,7 +65,7 @@ contract SignatureBouncer is Initializable, SignerRole {
     }
 
     /**
-     * @dev requires that a valid signature with a specifed method and params of a signer was provided
+     * @dev requires that a valid signature with a specified method and params of a signer was provided
      */
     modifier onlyValidSignatureAndData(bytes memory signature) {
         require(_isValidSignatureAndData(msg.sender, signature));
@@ -73,7 +73,7 @@ contract SignatureBouncer is Initializable, SignerRole {
     }
 
     /**
-     * @dev is the signature of `this + sender` from a signer?
+     * @dev is the signature of `this + account` from a signer?
      * @return bool
      */
     function _isValidSignature(address account, bytes memory signature) internal view returns (bool) {
@@ -81,7 +81,7 @@ contract SignatureBouncer is Initializable, SignerRole {
     }
 
     /**
-     * @dev is the signature of `this + sender + methodId` from a signer?
+     * @dev is the signature of `this + account + methodId` from a signer?
      * @return bool
      */
     function _isValidSignatureAndMethod(address account, bytes memory signature) internal view returns (bool) {
@@ -93,10 +93,10 @@ contract SignatureBouncer is Initializable, SignerRole {
     }
 
     /**
-        * @dev is the signature of `this + sender + methodId + params(s)` from a signer?
-        * @notice the signature parameter of the method being validated must be the "last" parameter
-        * @return bool
-        */
+     * @dev is the signature of `this + account + methodId + params(s)` from a signer?
+     * @notice the signature parameter of the method being validated must be the "last" parameter
+     * @return bool
+     */
     function _isValidSignatureAndData(address account, bytes memory signature) internal view returns (bool) {
         require(msg.data.length > _SIGNATURE_SIZE);
 

contracts/drafts/SignedSafeMath.sol

@@ -1,4 +1,4 @@
-pragma solidity ^0.5.0;
+pragma solidity ^0.5.2;
 
 /**
  * @title SignedSafeMath
@@ -8,8 +8,8 @@ library SignedSafeMath {
     int256 constant private INT256_MIN = -2**255;
 
     /**
-    * @dev Multiplies two signed integers, reverts on overflow.
-    */
+     * @dev Multiplies two signed integers, reverts on overflow.
+     */
     function mul(int256 a, int256 b) internal pure returns (int256) {
         // Gas optimization: this is cheaper than requiring 'a' not being zero, but the
         // benefit is lost if 'b' is also tested.
@@ -27,8 +27,8 @@ library SignedSafeMath {
     }
 
     /**
-    * @dev Integer division of two signed integers truncating the quotient, reverts on division by zero.
-    */
+     * @dev Integer division of two signed integers truncating the quotient, reverts on division by zero.
+     */
     function div(int256 a, int256 b) internal pure returns (int256) {
         require(b != 0); // Solidity only automatically asserts when dividing by 0
         require(!(b == -1 && a == INT256_MIN)); // This is the only case of overflow
@@ -39,8 +39,8 @@ library SignedSafeMath {
     }
 
     /**
-    * @dev Subtracts two signed integers, reverts on overflow.
-    */
+     * @dev Subtracts two signed integers, reverts on overflow.
+     */
     function sub(int256 a, int256 b) internal pure returns (int256) {
         int256 c = a - b;
         require((b >= 0 && c <= a) || (b < 0 && c > a));
@@ -49,8 +49,8 @@ library SignedSafeMath {
     }
 
     /**
-    * @dev Adds two signed integers, reverts on overflow.
-    */
+     * @dev Adds two signed integers, reverts on overflow.
+     */
     function add(int256 a, int256 b) internal pure returns (int256) {
         int256 c = a + b;
         require((b >= 0 && c >= a) || (b < 0 && c < a));

contracts/drafts/TokenVesting.sol

@@ -1,4 +1,4 @@
-pragma solidity ^0.5.0;
+pragma solidity ^0.5.2;
 
 import "zos-lib/contracts/Initializable.sol";
 import "../token/ERC20/SafeERC20.sol";
@@ -14,8 +14,8 @@ import "../math/SafeMath.sol";
 contract TokenVesting is Initializable, Ownable {
     // The vesting schedule is time-based (i.e. using block timestamps as opposed to e.g. block numbers), and is
     // therefore sensitive to timestamp manipulation (which is something miners can do, to a certain degree). Therefore,
-    // it is recommended to avoid using short time durations (less than a minute). Typical vesting schemes, with a cliff
-    // period of a year and a duration of four years, are safe to use.
+    // it is recommended to avoid using short time durations (less than a minute). Typical vesting schemes, with a
+    // cliff period of a year and a duration of four years, are safe to use.
     // solhint-disable not-rely-on-time
 
     using SafeMath for uint256;