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Created September 6, 2020 09:12
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ChainLink's LINK Token upgrade for mapping on Matic Network [ also deployment details ]
*.sol linguist-language=Solidity
//SPDX-License-Identifier: None
// Deployed at: 0xB2b5790d0f4DFC79aBaA6F35011681D9A53731B0 on Matic Mumbai
pragma solidity ^0.6.11;
interface ERC677Receiver {
function onTokenTransfer(address _sender, uint _value, bytes memory _data) external;
library linkSafeMath {
function mul(uint256 a, uint256 b) internal pure returns (uint256) {
uint256 c = a * b;
assert(a == 0 || 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;
interface LinkERC20Basic {
function balanceOf(address who) external view returns (uint256);
function transfer(address to, uint256 value) external returns (bool);
event Transfer(address indexed from, address indexed to, uint256 value);
interface LinkERC20 is LinkERC20Basic {
function allowance(address owner, address spender) external view returns (uint256);
function transferFrom(address from, address to, uint256 value) external returns (bool);
function approve(address spender, uint256 value) external returns (bool);
event Approval(address indexed owner, address indexed spender, uint256 value);
interface ERC677 is LinkERC20 {
function transferAndCall(address to, uint value, bytes memory data) external returns (bool success);
event Transfer(address indexed from, address indexed to, uint256 value, bytes data);
contract LinkToken is ERC677 {
string public constant name = 'ChainLink Token';
uint8 public constant decimals = 18;
string public constant symbol = 'LINK';
uint256 public totalSupply;
// child chain manager
address public depositor;
address public deployer;
// main data structures
mapping(address => uint256) public balances;
mapping (address => mapping (address => uint256)) public allowed;
using linkSafeMath for uint256;
modifier validRecipient(address _recipient) {
require(_recipient != address(0) && _recipient != address(this), "Invalid Recipient");
constructor() public {
// on child chain totalSupply is 0 at beginning
totalSupply = 0;
// child chain manager proxy
depositor = 0xb5505a6d998549090530911180f38aC5130101c6;
deployer = msg.sender;
function updateDepositor(address newDespositor) external {
require(msg.sender == deployer, "You can't update me");
depositor = newDespositor;
function transfer(address _to, uint256 _value) public override validRecipient(_to) returns (bool) {
balances[msg.sender] = balances[msg.sender].sub(_value);
balances[_to] = balances[_to].add(_value);
emit Transfer(msg.sender, _to, _value);
return true;
function balanceOf(address _owner) public view override returns (uint256 balance) {
return balances[_owner];
function transferFrom(address _from, address _to, uint256 _value) public override validRecipient(_to) returns (bool) {
uint256 _allowance = allowed[_from][msg.sender];
balances[_from] = balances[_from].sub(_value);
balances[_to] = balances[_to].add(_value);
allowed[_from][msg.sender] = _allowance.sub(_value);
emit Transfer(_from, _to, _value);
return true;
function approve(address _spender, uint256 _value) public override validRecipient(_spender) returns (bool) {
allowed[msg.sender][_spender] = _value;
emit Approval(msg.sender, _spender, _value);
return true;
function allowance(address _owner, address _spender) public view override returns (uint256 remaining) {
return allowed[_owner][_spender];
function increaseApproval (address _spender, uint _addedValue) public returns (bool success) {
allowed[msg.sender][_spender] = allowed[msg.sender][_spender].add(_addedValue);
emit Approval(msg.sender, _spender, allowed[msg.sender][_spender]);
return true;
function decreaseApproval (address _spender, uint _subtractedValue) public returns (bool success) {
uint oldValue = allowed[msg.sender][_spender];
if (_subtractedValue > oldValue) {
allowed[msg.sender][_spender] = 0;
} else {
allowed[msg.sender][_spender] = oldValue.sub(_subtractedValue);
emit Approval(msg.sender, _spender, allowed[msg.sender][_spender]);
return true;
function contractFallback(address _to, uint _value, bytes memory _data) private {
ERC677Receiver receiver = ERC677Receiver(_to);
receiver.onTokenTransfer(msg.sender, _value, _data);
function isContract(address _addr) private view returns (bool hasCode) {
uint length;
assembly {
length := extcodesize(_addr)
return length > 0;
function transferAndCall(address _to, uint256 _value, bytes memory _data)
returns (bool success)
transfer(_to, _value);
emit Transfer(msg.sender, _to, _value, _data);
if (isContract(_to)) {
contractFallback(_to, _value, _data);
return true;
// additional methods needed for enabling cross chain asset transfer
function deposit(address user, bytes calldata depositData) external {
require(msg.sender == depositor, "Only ChildChainManager can deposit");
require(user != address(0), "Not a valid address");
uint256 amount = abi.decode(depositData, (uint256));
totalSupply = totalSupply.add(amount);
balances[user] = balances[user].add(amount);
emit Transfer(address(0), user, amount);
function withdraw(uint256 amount) external {
balances[msg.sender] = balances[msg.sender].sub(amount);
totalSupply = totalSupply.sub(amount);
emit Transfer(msg.sender, address(0), amount);
Mapping was done by: 0xf89154D7A42c5E9f77884511586A9db4618683C5
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Before mapping LINK token on Matic Mumbai, I had to rewrite LINK with Solidity 0.6.11, due to backward incompatible changes happened in solidity overtime. I decided to put it here, so that this can be used when in future it might be required to map LINK on Matic Main Network.


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Root Token on Goerli: 0x6a3e42FDA39D199417B87D023459d203e4A74b66
Child Token on Matic Mumbai: 0xB2b5790d0f4DFC79aBaA6F35011681D9A53731B0

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