Contract Source Code:
// SPDX-License-Identifier: GPL-2.0-or-later
pragma solidity =0.7.6;
pragma experimental ABIEncoderV2;
// Forked from Uniswap's UNI
// Reference: https://etherscan.io/address/0x1f9840a85d5af5bf1d1762f925bdaddc4201f984#code
contract Rng {
/// @notice EIP-20 token name for this token
// solhint-disable-next-line const-name-snakecase
string public constant name = "Ring.Exchange";
/// @notice EIP-20 token symbol for this token
// solhint-disable-next-line const-name-snakecase
string public constant symbol = "RNG";
/// @notice EIP-20 token decimals for this token
// solhint-disable-next-line const-name-snakecase
uint8 public constant decimals = 18;
/// @notice Total number of tokens in circulation
// solhint-disable-next-line const-name-snakecase
uint public totalSupply = 1_000_000e18; // 1 million Ring
/// @notice Address which may mint new tokens
address public minter;
mapping (address => mapping (address => uint96)) internal allowances;
mapping (address => uint96) internal balances;
/// @notice A record of each accounts delegate
mapping (address => address) public delegates;
/// @notice A checkpoint for marking number of votes from a given block
struct Checkpoint {
uint32 fromBlock;
uint96 votes;
}
/// @notice A record of votes checkpoints for each account, by index
mapping (address => mapping (uint32 => Checkpoint)) public checkpoints;
/// @notice The number of checkpoints for each account
mapping (address => uint32) public numCheckpoints;
/// @notice The EIP-712 typehash for the contract's domain
bytes32 public constant DOMAIN_TYPEHASH = keccak256("EIP712Domain(string name,uint256 chainId,address verifyingContract)");
/// @notice The EIP-712 typehash for the delegation struct used by the contract
bytes32 public constant DELEGATION_TYPEHASH = keccak256("Delegation(address delegatee,uint256 nonce,uint256 expiry)");
/// @notice The EIP-712 typehash for the permit struct used by the contract
bytes32 public constant PERMIT_TYPEHASH = keccak256("Permit(address owner,address spender,uint256 value,uint256 nonce,uint256 deadline)");
/// @notice A record of states for signing / validating signatures
mapping (address => uint) public nonces;
/// @notice An event thats emitted when the minter address is changed
event MinterChanged(address minter, address newMinter);
/// @notice An event thats emitted when an account changes its delegate
event DelegateChanged(address indexed delegator, address indexed fromDelegate, address indexed toDelegate);
/// @notice An event thats emitted when a delegate account's vote balance changes
event DelegateVotesChanged(address indexed delegate, uint previousBalance, uint newBalance);
/// @notice The standard EIP-20 transfer event
event Transfer(address indexed from, address indexed to, uint256 amount);
/// @notice The standard EIP-20 approval event
event Approval(address indexed owner, address indexed spender, uint256 amount);
/**
* @notice Construct a new Ring token
* @param account The initial account to grant all the tokens
* @param minter_ The account with minting ability
*/
constructor(address account, address minter_) {
balances[account] = uint96(totalSupply);
emit Transfer(address(0), account, totalSupply);
minter = minter_;
emit MinterChanged(address(0), minter);
}
/**
* @notice Change the minter address
* @param minter_ The address of the new minter
*/
function setMinter(address minter_) external {
require(msg.sender == minter, "Ring: only the minter can change the minter address");
emit MinterChanged(minter, minter_);
minter = minter_;
}
/**
* @notice Mint new tokens
* @param dst The address of the destination account
* @param rawAmount The number of tokens to be minted
*/
function mint(address dst, uint rawAmount) external {
require(msg.sender == minter, "Ring: only the minter can mint");
require(dst != address(0), "Ring: cannot transfer to the zero address");
// mint the amount
uint96 amount = safe96(rawAmount, "Ring: amount exceeds 96 bits");
uint96 safeSupply = safe96(totalSupply, "Ring: totalSupply exceeds 96 bits");
totalSupply = add96(safeSupply, amount, "Ring: totalSupply exceeds 96 bits");
// transfer the amount to the recipient
balances[dst] = add96(balances[dst], amount, "Ring: transfer amount overflows");
emit Transfer(address(0), dst, amount);
// move delegates
_moveDelegates(address(0), delegates[dst], amount);
}
/**
* @notice Get the number of tokens `spender` is approved to spend on behalf of `account`
* @param account The address of the account holding the funds
* @param spender The address of the account spending the funds
* @return The number of tokens approved
*/
function allowance(address account, address spender) external view returns (uint) {
return allowances[account][spender];
}
/**
* @notice Approve `spender` to transfer up to `amount` from `src`
* @dev This will overwrite the approval amount for `spender`
* and is subject to issues noted [here](https://eips.ethereum.org/EIPS/eip-20#approve)
* @param spender The address of the account which may transfer tokens
* @param rawAmount The number of tokens that are approved (2^256-1 means infinite)
* @return Whether or not the approval succeeded
*/
function approve(address spender, uint rawAmount) external returns (bool) {
uint96 amount;
if (rawAmount == uint(-1)) {
amount = uint96(-1);
} else {
amount = safe96(rawAmount, "Ring: amount exceeds 96 bits");
}
allowances[msg.sender][spender] = amount;
emit Approval(msg.sender, spender, amount);
return true;
}
/**
* @notice Triggers an approval from owner to spends
* @param owner The address to approve from
* @param spender The address to be approved
* @param rawAmount The number of tokens that are approved (2^256-1 means infinite)
* @param deadline The time at which to expire the signature
* @param v The recovery byte of the signature
* @param r Half of the ECDSA signature pair
* @param s Half of the ECDSA signature pair
*/
function permit(address owner, address spender, uint rawAmount, uint deadline, uint8 v, bytes32 r, bytes32 s) external {
uint96 amount;
if (rawAmount == uint(-1)) {
amount = uint96(-1);
} else {
amount = safe96(rawAmount, "Ring: amount exceeds 96 bits");
}
bytes32 domainSeparator = keccak256(abi.encode(DOMAIN_TYPEHASH, keccak256(bytes(name)), getChainId(), address(this)));
bytes32 structHash = keccak256(abi.encode(PERMIT_TYPEHASH, owner, spender, rawAmount, nonces[owner]++, deadline));
bytes32 digest = keccak256(abi.encodePacked("\x19\x01", domainSeparator, structHash));
address signatory = ecrecover(digest, v, r, s);
require(signatory != address(0), "Ring: invalid signature");
require(signatory == owner, "Ring: unauthorized");
// solhint-disable-next-line not-rely-on-time
require(block.timestamp <= deadline, "Ring: signature expired");
allowances[owner][spender] = amount;
emit Approval(owner, spender, amount);
}
/**
* @notice Get the number of tokens held by the `account`
* @param account The address of the account to get the balance of
* @return The number of tokens held
*/
function balanceOf(address account) external view returns (uint) {
return balances[account];
}
/**
* @notice Transfer `amount` tokens from `msg.sender` to `dst`
* @param dst The address of the destination account
* @param rawAmount The number of tokens to transfer
* @return Whether or not the transfer succeeded
*/
function transfer(address dst, uint rawAmount) external returns (bool) {
uint96 amount = safe96(rawAmount, "Ring: amount exceeds 96 bits");
_transferTokens(msg.sender, dst, amount);
return true;
}
/**
* @notice Transfer `amount` tokens from `src` to `dst`
* @param src The address of the source account
* @param dst The address of the destination account
* @param rawAmount The number of tokens to transfer
* @return Whether or not the transfer succeeded
*/
function transferFrom(address src, address dst, uint rawAmount) external returns (bool) {
address spender = msg.sender;
uint96 spenderAllowance = allowances[src][spender];
uint96 amount = safe96(rawAmount, "Ring: amount exceeds 96 bits");
if (spender != src && spenderAllowance != uint96(-1)) {
uint96 newAllowance = sub96(spenderAllowance, amount, "Ring: transfer amount exceeds spender allowance");
allowances[src][spender] = newAllowance;
emit Approval(src, spender, newAllowance);
}
_transferTokens(src, dst, amount);
return true;
}
/**
* @notice Delegate votes from `msg.sender` to `delegatee`
* @param delegatee The address to delegate votes to
*/
function delegate(address delegatee) public {
return _delegate(msg.sender, delegatee);
}
/**
* @notice Delegates votes from signatory to `delegatee`
* @param delegatee The address to delegate votes to
* @param nonce The contract state required to match the signature
* @param expiry The time at which to expire the signature
* @param v The recovery byte of the signature
* @param r Half of the ECDSA signature pair
* @param s Half of the ECDSA signature pair
*/
function delegateBySig(address delegatee, uint nonce, uint expiry, uint8 v, bytes32 r, bytes32 s) public {
bytes32 domainSeparator = keccak256(abi.encode(DOMAIN_TYPEHASH, keccak256(bytes(name)), getChainId(), address(this)));
bytes32 structHash = keccak256(abi.encode(DELEGATION_TYPEHASH, delegatee, nonce, expiry));
bytes32 digest = keccak256(abi.encodePacked("\x19\x01", domainSeparator, structHash));
address signatory = ecrecover(digest, v, r, s);
require(signatory != address(0), "Ring: invalid signature");
require(nonce == nonces[signatory]++, "Ring: invalid nonce");
// solhint-disable-next-line not-rely-on-time
require(block.timestamp <= expiry, "Ring: signature expired");
return _delegate(signatory, delegatee);
}
/**
* @notice Gets the current votes balance for `account`
* @param account The address to get votes balance
* @return The number of current votes for `account`
*/
function getCurrentVotes(address account) external view returns (uint96) {
uint32 nCheckpoints = numCheckpoints[account];
return nCheckpoints > 0 ? checkpoints[account][nCheckpoints - 1].votes : 0;
}
/**
* @notice Determine the prior number of votes for an account as of a block number
* @dev Block number must be a finalized block or else this function will revert to prevent misinformation.
* @param account The address of the account to check
* @param blockNumber The block number to get the vote balance at
* @return The number of votes the account had as of the given block
*/
function getPriorVotes(address account, uint blockNumber) public view returns (uint96) {
require(blockNumber < block.number, "Ring: not yet determined");
uint32 nCheckpoints = numCheckpoints[account];
if (nCheckpoints == 0) {
return 0;
}
// First check most recent balance
if (checkpoints[account][nCheckpoints - 1].fromBlock <= blockNumber) {
return checkpoints[account][nCheckpoints - 1].votes;
}
// Next check implicit zero balance
if (checkpoints[account][0].fromBlock > blockNumber) {
return 0;
}
uint32 lower = 0;
uint32 upper = nCheckpoints - 1;
while (upper > lower) {
uint32 center = upper - (upper - lower) / 2; // ceil, avoiding overflow
Checkpoint memory cp = checkpoints[account][center];
if (cp.fromBlock == blockNumber) {
return cp.votes;
} else if (cp.fromBlock < blockNumber) {
lower = center;
} else {
upper = center - 1;
}
}
return checkpoints[account][lower].votes;
}
function _delegate(address delegator, address delegatee) internal {
address currentDelegate = delegates[delegator];
uint96 delegatorBalance = balances[delegator];
delegates[delegator] = delegatee;
emit DelegateChanged(delegator, currentDelegate, delegatee);
_moveDelegates(currentDelegate, delegatee, delegatorBalance);
}
function _transferTokens(address src, address dst, uint96 amount) internal {
require(src != address(0), "Ring: cannot transfer from the zero address");
require(dst != address(0), "Ring: cannot transfer to the zero address");
balances[src] = sub96(balances[src], amount, "Ring: transfer amount exceeds balance");
balances[dst] = add96(balances[dst], amount, "Ring: transfer amount overflows");
emit Transfer(src, dst, amount);
_moveDelegates(delegates[src], delegates[dst], amount);
}
function _moveDelegates(address srcRep, address dstRep, uint96 amount) internal {
if (srcRep != dstRep && amount > 0) {
if (srcRep != address(0)) {
uint32 srcRepNum = numCheckpoints[srcRep];
uint96 srcRepOld = srcRepNum > 0 ? checkpoints[srcRep][srcRepNum - 1].votes : 0;
uint96 srcRepNew = sub96(srcRepOld, amount, "Ring: vote amount underflows");
_writeCheckpoint(srcRep, srcRepNum, srcRepOld, srcRepNew);
}
if (dstRep != address(0)) {
uint32 dstRepNum = numCheckpoints[dstRep];
uint96 dstRepOld = dstRepNum > 0 ? checkpoints[dstRep][dstRepNum - 1].votes : 0;
uint96 dstRepNew = add96(dstRepOld, amount, "Ring: vote amount overflows");
_writeCheckpoint(dstRep, dstRepNum, dstRepOld, dstRepNew);
}
}
}
function _writeCheckpoint(address delegatee, uint32 nCheckpoints, uint96 oldVotes, uint96 newVotes) internal {
uint32 blockNumber = safe32(block.number, "Ring: block number exceeds 32 bits");
if (nCheckpoints > 0 && checkpoints[delegatee][nCheckpoints - 1].fromBlock == blockNumber) {
checkpoints[delegatee][nCheckpoints - 1].votes = newVotes;
} else {
checkpoints[delegatee][nCheckpoints] = Checkpoint(blockNumber, newVotes);
numCheckpoints[delegatee] = nCheckpoints + 1;
}
emit DelegateVotesChanged(delegatee, oldVotes, newVotes);
}
function safe32(uint n, string memory errorMessage) internal pure returns (uint32) {
require(n < 2**32, errorMessage);
return uint32(n);
}
function safe96(uint n, string memory errorMessage) internal pure returns (uint96) {
require(n < 2**96, errorMessage);
return uint96(n);
}
function add96(uint96 a, uint96 b, string memory errorMessage) internal pure returns (uint96) {
uint96 c = a + b;
require(c >= a, errorMessage);
return c;
}
function sub96(uint96 a, uint96 b, string memory errorMessage) internal pure returns (uint96) {
require(b <= a, errorMessage);
return a - b;
}
function getChainId() internal pure returns (uint) {
uint256 chainId;
// solhint-disable-next-line no-inline-assembly
assembly { chainId := chainid() }
return chainId;
}
}