Contract Source Code:
// SPDX-License-Identifier: MIT
pragma solidity 0.6.11;
pragma experimental ABIEncoderV2;
//import "hardhat/console.sol";
//import "@openzeppelin/contracts/math/SafeMath.sol";
contract EPNS {
/// @notice EIP-20 token name for this token
string public constant name = "Ethereum Push Notification Service";
/// @notice EIP-20 token symbol for this token
string public constant symbol = "PUSH";
/// @notice EIP-20 token decimals for this token
uint8 public constant decimals = 18;
/// @notice Total number of tokens in circulation
uint public totalSupply = 100_000_000e18; // 100 million PUSH
/// @notice block number when tokens came into circulation
uint public born;
/// @dev Allowance amounts on behalf of others
mapping (address => mapping (address => uint96)) internal allowances;
/// @dev Official record of token balances for each account
mapping (address => uint96) internal balances;
/// @notice Official record of the token block information for the holder
mapping (address => uint) public holderWeight;
/// @notice Allows holder weight to be reset by other adddresses
mapping (address => mapping(address => bool)) public holderDelegation;
/// @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 an account changes its total token weight
event HolderWeightChanged(address indexed holder, uint256 amount, uint weight);
/// @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 PUSH token
* @param account The initial account to grant all the tokens
*/
constructor(address account) public {
balances[account] = uint96(totalSupply);
emit Transfer(address(0), account, totalSupply);
// holder weight initial adjustments
holderWeight[account] = block.number;
born = block.number;
}
/**
* @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(uint96(-1))) {
amount = uint96(-1);
} else {
amount = safe96(rawAmount, "Push::approve: 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 | Approve by signature
* @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, "Push::permit: 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), "Push::permit: invalid signature");
require(signatory == owner, "Push::permit: unauthorized");
require(now <= deadline, "Push::permit: 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, "Push::transfer: 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, "Push::approve: amount exceeds 96 bits");
if (spender != src && spenderAllowance != uint96(-1)) {
uint96 newAllowance = sub96(spenderAllowance, amount, "Push::transferFrom: transfer amount exceeds spender allowance");
allowances[src][spender] = newAllowance;
emit Approval(src, spender, newAllowance);
}
_transferTokens(src, dst, amount);
return true;
}
/**
* @notice Return holder units
*/
function returnHolderUnits(address account, uint atBlock) external view returns (uint) {
return mul256(balances[account], sub256(atBlock, holderWeight[account], "Push::returnHolderUnits: atBlock should be greater than holderWeight"), "Push::returnHolderUnits: ratio exceeds max range");
}
/**
* @notice toggle holder whitelist
*/
function returnHolderDelegation(address account, address delegate) external view returns (bool) {
return holderDelegation[account][delegate];
}
/**
* @notice toggle holder whitelist
*/
function setHolderDelegation(address delegate, bool value) external {
holderDelegation[msg.sender][delegate] = value;
}
/**
* @notice Reset holder weight to current block
*/
function resetHolderWeight(address holder) external {
require(holderDelegation[holder][msg.sender] == true || holder == msg.sender, "Push::resetHolderWeight: unauthorized");
holderWeight[holder] = block.number;
emit HolderWeightChanged(holder, balances[holder], block.number);
}
/**
* @notice Destory `RawAmount` of tokens from a holder `account`
* @param rawAmount The number of tokens
*/
function burn(uint256 rawAmount) external {
address account = msg.sender;
uint96 balance = balances[account];
uint96 amount = safe96(rawAmount, "Push::burn: amount exceeds 96 bits");
balances[account] = sub96(balance, amount, "Push::burn: burn amount exceeds balance");
totalSupply = sub256(totalSupply, rawAmount, "Push::burn: supply underflow");
emit Transfer(account, address(0), amount);
}
/**
* @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), "Push::delegateBySig: invalid signature");
require(nonce == nonces[signatory]++, "Push::delegateBySig: invalid nonce");
require(now <= expiry, "Push::delegateBySig: 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, "Push::getPriorVotes: not yet determined");
uint32 nCheckpoints = numCheckpoints[account];
if (nCheckpoints == 0) {
return 0;
}
Checkpoint memory lastCheckpoint = checkpoints[account][nCheckpoints - 1];
// First check most recent balance
if (lastCheckpoint.fromBlock <= blockNumber) {
return lastCheckpoint.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), "Push::_transferTokens: cannot transfer from the zero address");
require(dst != address(0), "Push::_transferTokens: cannot transfer to the zero address");
// adjust holder weight
_adjustHolderWeight(src, dst, amount);
// update balance
balances[src] = sub96(balances[src], amount, "Push::_transferTokens: transfer amount exceeds balance");
balances[dst] = add96(balances[dst], amount, "Push::_transferTokens: transfer amount overflows");
emit Transfer(src, dst, amount);
_moveDelegates(delegates[src], delegates[dst], amount);
}
function _adjustHolderWeight(address src, address dst, uint96 amount) internal {
// change holderWeight block
uint96 balance = balances[dst];
if (balance == 0) {
holderWeight[dst] = holderWeight[src];
}
else {
uint256 dstWeight = mul256(holderWeight[dst], balance, "Push::_adjustHolderWeight: holder dst weight exceeded limit");
uint256 srcWeight = mul256(holderWeight[src], amount, "Push::_adjustHolderWeight: holder src weight exceeded limit");
uint256 totalWeight = add256(dstWeight, srcWeight, "Push::_adjustHolderWeight: total weight exceeded limit");
uint256 totalAmount = add256(balance, amount, "Push::_adjustHolderWeight: total amount exceeded limit");
uint256 totalAmountBy2 = div256(totalAmount, 2, "");
uint256 roundUpWeight = add256(totalWeight, totalAmountBy2, "Push::_adjustHolderWeight: round up amount exceeded limit");
holderWeight[dst] = div256(roundUpWeight, totalAmount, "Push::_adjustHolderWeight: adjusted holder negative divide");
}
}
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, "Push::_moveVotes: 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, "Push::_moveVotes: vote amount overflows");
_writeCheckpoint(dstRep, dstRepNum, dstRepOld, dstRepNew);
}
}
}
function _writeCheckpoint(address delegatee, uint32 nCheckpoints, uint96 oldVotes, uint96 newVotes) internal {
uint32 blockNumber = safe32(block.number, "Push::_writeCheckpoint: 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 add256(uint256 a, uint256 b, string memory errorMessage) internal pure returns (uint256) {
uint256 c = a + b;
require(c >= a, errorMessage);
return c;
}
function sub256(uint256 a, uint256 b, string memory errorMessage) internal pure returns (uint256) {
require(b <= a, errorMessage);
uint256 c = a - b;
return c;
}
function mul256(uint256 a, uint256 b, string memory errorMessage) internal pure returns (uint256) {
// Gas optimization: this is cheaper than requiring 'a' not being zero, but the
// benefit is lost if 'b' is also tested.
// See: https://github.com/OpenZeppelin/openzeppelin-contracts/pull/522
if (a == 0) {
return 0;
}
uint256 c = a * b;
require(c / a == b, errorMessage);
return c;
}
function div256(uint256 a, uint256 b, string memory errorMessage) internal pure returns (uint256) {
// Solidity only automatically asserts when dividing by 0
require(b > 0, errorMessage);
uint256 c = a / b;
// assert(a == b * c + a % b); // There is no case in which this doesn't hold
return c;
}
function getChainId() internal pure returns (uint) {
uint256 chainId;
assembly { chainId := chainid() }
return chainId;
}
}