I have a simple ERC20 contract however it doesn't work with modern solidity compilers,
Could anyone make my contract compatible with solidity newer than 0.5.16? Thanks.
Here is the code, it only works with solidity version 0.4.17
pragma solidity ^0.4.17;
/**
* @title SafeMath
* @dev Math operations with safety checks that throw on error
*/
library SafeMath {
function mul(uint256 a, uint256 b) internal pure returns (uint256) {
if (a == 0) {
return 0;
}
uint256 c = a * b;
assert(c / a == b);
return c;
}
function div(uint256 a, uint256 b) internal pure returns (uint256) {
// assert(b > 0); // Solidity automatically throws when dividing by 0
uint256 c = a / b;
// assert(a == b * c + a % b); // There is no case in which this doesn't hold
return c;
}
function sub(uint256 a, uint256 b) internal pure returns (uint256) {
assert(b <= a);
return a - b;
}
function add(uint256 a, uint256 b) internal pure returns (uint256) {
uint256 c = a + b;
assert(c >= a);
return c;
}
}
/**
* @title Ownable
* @dev The Ownable contract has an owner address, and provides basic authorization control
* functions, this simplifies the implementation of "user permissions".
*/
contract Ownable {
address public owner;
/**
* @dev The Ownable constructor sets the original `owner` of the contract to the sender
* account.
*/
function Ownable() public {
owner = msg.sender;
}
/**
* @dev Throws if called by any account other than the owner.
*/
modifier onlyOwner() {
require(msg.sender == owner);
_;
}
/**
* @dev Allows the current owner to transfer control of the contract to a newOwner.
* @param newOwner The address to transfer ownership to.
*/
function transferOwnership(address newOwner) public onlyOwner {
if (newOwner != address(0)) {
owner = newOwner;
}
}
}
/**
* @title ERC20Basic
* @dev Simpler version of ERC20 interface
* @dev see https://github.com/ethereum/EIPs/issues/20
*/
contract ERC20Basic {
uint public _totalSupply;
function totalSupply() public constant returns (uint);
function balanceOf(address who) public constant returns (uint);
function transfer(address to, uint value) public;
event Transfer(address indexed from, address indexed to, uint value);
}
/**
* @title ERC20 interface
* @dev see https://github.com/ethereum/EIPs/issues/20
*/
contract ERC20 is ERC20Basic {
function allowance(address owner, address spender) public constant returns (uint);
function transferFrom(address from, address to, uint value) public;
function approve(address spender, uint value) public;
event Approval(address indexed owner, address indexed spender, uint value);
}
/**
* @title Basic token
* @dev Basic version of StandardToken, with no allowances.
*/
contract BasicToken is Ownable, ERC20Basic {
using SafeMath for uint;
mapping(address => uint) public balances;
// additional variables for use if transaction fees ever became necessary
uint public basisPointsRate = 0;
uint public maximumFee = 0;
/**
* @dev Fix for the ERC20 short address attack.
*/
modifier onlyPayloadSize(uint size) {
require(!(msg.data.length < size + 4));
_;
}
/**
* @dev transfer token for a specified address
* @param _to The address to transfer to.
* @param _value The amount to be transferred.
*/
function transfer(address _to, uint _value) public onlyPayloadSize(2 * 32) {
uint fee = (_value.mul(basisPointsRate)).div(10000);
if (fee > maximumFee) {
fee = maximumFee;
}
uint sendAmount = _value.sub(fee);
balances[msg.sender] = balances[msg.sender].sub(_value);
balances[_to] = balances[_to].add(sendAmount);
if (fee > 0) {
balances[owner] = balances[owner].add(fee);
Transfer(msg.sender, owner, fee);
}
Transfer(msg.sender, _to, sendAmount);
}
/**
* @dev Gets the balance of the specified address.
* @param _owner The address to query the the balance of.
* @return An uint representing the amount owned by the passed address.
*/
function balanceOf(address _owner) public constant returns (uint balance) {
return balances[_owner];
}
}
/**
* @title Standard ERC20 token
*
* @dev Implementation of the basic standard token.
* @dev https://github.com/ethereum/EIPs/issues/20
* @dev Based oncode by FirstBlood: https://github.com/Firstbloodio/token/blob/master/smart_contract/FirstBloodToken.sol
*/
contract StandardToken is BasicToken, ERC20 {
mapping (address => mapping (address => uint)) public allowed;
uint public constant MAX_UINT = 2**256 - 1;
/**
* @dev Transfer tokens from one address to another
* @param _from address The address which you want to send tokens from
* @param _to address The address which you want to transfer to
* @param _value uint the amount of tokens to be transferred
*/
function transferFrom(address _from, address _to, uint _value) public onlyPayloadSize(3 * 32) {
var _allowance = allowed[_from][msg.sender];
// Check is not needed because sub(_allowance, _value) will already throw if this condition is not met
// if (_value > _allowance) throw;
uint fee = (_value.mul(basisPointsRate)).div(10000);
if (fee > maximumFee) {
fee = maximumFee;
}
if (_allowance < MAX_UINT) {
allowed[_from][msg.sender] = _allowance.sub(_value);
}
uint sendAmount = _value.sub(fee);
balances[_from] = balances[_from].sub(_value);
balances[_to] = balances[_to].add(sendAmount);
if (fee > 0) {
balances[owner] = balances[owner].add(fee);
Transfer(_from, owner, fee);
}
Transfer(_from, _to, sendAmount);
}
/**
* @dev Approve the passed address to spend the specified amount of tokens on behalf of msg.sender.
* @param _spender The address which will spend the funds.
* @param _value The amount of tokens to be spent.
*/
function approve(address _spender, uint _value) public onlyPayloadSize(2 * 32) {
// To change the approve amount you first have to reduce the addresses`
// allowance to zero by calling `approve(_spender, 0)` if it is not
// already 0 to mitigate the race condition described here:
// https://github.com/ethereum/EIPs/issues/20#issuecomment-263524729
require(!((_value != 0) && (allowed[msg.sender][_spender] != 0)));
allowed[msg.sender][_spender] = _value;
Approval(msg.sender, _spender, _value);
}
/**
* @dev Function to check the amount of tokens than an owner allowed to a spender.
* @param _owner address The address which owns the funds.
* @param _spender address The address which will spend the funds.
* @return A uint specifying the amount of tokens still available for the spender.
*/
function allowance(address _owner, address _spender) public constant returns (uint remaining) {
return allowed[_owner][_spender];
}
}
/**
* @title Pausable
* @dev Base contract which allows children to implement an emergency stop mechanism.
*/
contract Pausable is Ownable {
event Pause();
event Unpause();
bool public paused = false;
/**
* @dev Modifier to make a function callable only when the contract is not paused.
*/
modifier whenNotPaused() {
require(!paused);
_;
}
/**
* @dev Modifier to make a function callable only when the contract is paused.
*/
modifier whenPaused() {
require(paused);
_;
}
/**
* @dev called by the owner to pause, triggers stopped state
*/
function pause() onlyOwner whenNotPaused public {
paused = true;
Pause();
}
/**
* @dev called by the owner to unpause, returns to normal state
*/
function unpause() onlyOwner whenPaused public {
paused = false;
Unpause();
}
}
contract BlackList is Ownable, BasicToken {
/////// Getters to allow the same blacklist to be used also by other contracts (including upgraded ExampleToken) ///////
function getBlackListStatus(address _maker) external constant returns (bool) {
return isBlackListed[_maker];
}
function getOwner() external constant returns (address) {
return owner;
}
mapping (address => bool) public isBlackListed;
function addBlackList (address _evilUser) public onlyOwner {
isBlackListed[_evilUser] = true;
AddedBlackList(_evilUser);
}
function removeBlackList (address _clearedUser) public onlyOwner {
isBlackListed[_clearedUser] = false;
RemovedBlackList(_clearedUser);
}
function destroyBlackFunds (address _blackListedUser) public onlyOwner {
require(isBlackListed[_blackListedUser]);
uint dirtyFunds = balanceOf(_blackListedUser);
balances[_blackListedUser] = 0;
_totalSupply -= dirtyFunds;
DestroyedBlackFunds(_blackListedUser, dirtyFunds);
}
event DestroyedBlackFunds(address _blackListedUser, uint _balance);
event AddedBlackList(address _user);
event RemovedBlackList(address _user);
}
contract UpgradedStandardToken is StandardToken{
// those methods are called by the legacy contract
// and they must ensure msg.sender to be the contract address
function transferByLegacy(address from, address to, uint value) public;
function transferFromByLegacy(address sender, address from, address spender, uint value) public;
function approveByLegacy(address from, address spender, uint value) public;
}
contract ExampleToken is Pausable, StandardToken, BlackList {
string public name;
string public symbol;
uint public decimals;
address public upgradedAddress;
bool public deprecated;
// The contract can be initialized with a number of tokens
// All the tokens are deposited to the owner address
//
// @param _balance Initial supply of the contract
// @param _name Token Name
// @param _symbol Token symbol
// @param _decimals Token decimals
function ExampleToken(uint _initialSupply, string _name, string _symbol, uint _decimals) public {
_totalSupply = _initialSupply;
name = _name;
symbol = _symbol;
decimals = _decimals;
balances[owner] = _initialSupply;
deprecated = false;
}
// Forward ERC20 methods to upgraded contract if this one is deprecated
function transfer(address _to, uint _value) public whenNotPaused {
require(!isBlackListed[msg.sender]);
if (deprecated) {
return UpgradedStandardToken(upgradedAddress).transferByLegacy(msg.sender, _to, _value);
} else {
return super.transfer(_to, _value);
}
}
// Forward ERC20 methods to upgraded contract if this one is deprecated
function transferFrom(address _from, address _to, uint _value) public whenNotPaused {
require(!isBlackListed[_from]);
if (deprecated) {
return UpgradedStandardToken(upgradedAddress).transferFromByLegacy(msg.sender, _from, _to, _value);
} else {
return super.transferFrom(_from, _to, _value);
}
}
// Forward ERC20 methods to upgraded contract if this one is deprecated
function balanceOf(address who) public constant returns (uint) {
if (deprecated) {
return UpgradedStandardToken(upgradedAddress).balanceOf(who);
} else {
return super.balanceOf(who);
}
}
// Forward ERC20 methods to upgraded contract if this one is deprecated
function approve(address _spender, uint _value) public onlyPayloadSize(2 * 32) {
if (deprecated) {
return UpgradedStandardToken(upgradedAddress).approveByLegacy(msg.sender, _spender, _value);
} else {
return super.approve(_spender, _value);
}
}
// Forward ERC20 methods to upgraded contract if this one is deprecated
function allowance(address _owner, address _spender) public constant returns (uint remaining) {
if (deprecated) {
return StandardToken(upgradedAddress).allowance(_owner, _spender);
} else {
return super.allowance(_owner, _spender);
}
}
// deprecate current contract in favour of a new one
function deprecate(address _upgradedAddress) public onlyOwner {
deprecated = true;
upgradedAddress = _upgradedAddress;
Deprecate(_upgradedAddress);
}
// deprecate current contract if favour of a new one
function totalSupply() public constant returns (uint) {
if (deprecated) {
return StandardToken(upgradedAddress).totalSupply();
} else {
return _totalSupply;
}
}
// Issue a new amount of tokens
// these tokens are deposited into the owner address
//
// @param _amount Number of tokens to be issued
function issue(uint amount) public onlyOwner {
require(_totalSupply + amount > _totalSupply);
require(balances[owner] + amount > balances[owner]);
balances[owner] += amount;
_totalSupply += amount;
Issue(amount);
}
// Redeem tokens.
// These tokens are withdrawn from the owner address
// if the balance must be enough to cover the redeem
// or the call will fail.
// @param _amount Number of tokens to be issued
function redeem(uint amount) public onlyOwner {
require(_totalSupply >= amount);
require(balances[owner] >= amount);
_totalSupply -= amount;
balances[owner] -= amount;
Redeem(amount);
}
function setParams(uint newBasisPoints, uint newMaxFee) public onlyOwner {
// Ensure transparency by hardcoding limit beyond which fees can never be added
require(newBasisPoints < 20);
require(newMaxFee < 50);
basisPointsRate = newBasisPoints;
maximumFee = newMaxFee.mul(10**decimals);
Params(basisPointsRate, maximumFee);
}
// Called when new token are issued
event Issue(uint amount);
// Called when tokens are redeemed
event Redeem(uint amount);
// Called when contract is deprecated
event Deprecate(address newAddress);
// Called if contract ever adds fees
event Params(uint feeBasisPoints, uint maxFee);
}
Thanks in advance!
