Smart contract for decoding State Sync data from Ethereum to Matic

Decoder.sol

// SPDX-License-Identifier: MIT

pragma solidity 0.8.0;

contract Decoder {
    
    bytes32 public constant DEPOSIT = keccak256("DEPOSIT");
    bytes32 public constant MAP_TOKEN = keccak256("MAP_TOKEN");
    
    enum SyncType {Deposit, TokenMapping, Unsupported}
    
    function getSyncTypeAndData(bytes memory data) internal pure returns(bytes32, bytes memory) {
        (bytes32 syncType, bytes memory syncData) = abi.decode(data, (bytes32, bytes));
        
        return (syncType, syncData);
    }
    
    function decodeStateSyncData(bytes calldata data) external pure returns (SyncType, address, address, bytes memory){
        (bytes32 syncType, bytes memory syncData) = getSyncTypeAndData(data);
        
        if (syncType == MAP_TOKEN) {
            (address root, address child, ) = abi.decode(syncData, (address, address, bytes32));
            
            return (SyncType.TokenMapping, root, child, "");
        }
        
        if (syncType == DEPOSIT) {
            (address depositor, address root, bytes memory depositData) = abi.decode(syncData, (address, address, bytes));
            
            return (SyncType.Deposit, depositor, root, depositData);
        }
        
        return (SyncType.Unsupported, address(0), address(0), "");
    }
    
    function decodeERC20Deposit(bytes calldata depositData) external pure returns(uint256) {
        return abi.decode(depositData, (uint256));
    }
    
    function decodeERC721SingleDeposit(bytes calldata depositData) external pure returns(uint256) {
        return abi.decode(depositData, (uint256));
    }
    
    function decodeERC721BatchDeposit(bytes calldata depositData) external pure returns(uint256[] memory) {
        return abi.decode(depositData, (uint256[]));
    }
    
    function decodeERC1155BatchDeposit(bytes calldata depositData) external pure returns(uint256[] memory, uint256[] memory, bytes memory) {
        return abi.decode(depositData, (uint256[], uint256[], bytes));
    }
}

Introduction

👆 contract is written for using it in combination with Matic Network's The Graph deployment, so that, caught StateSync event's data field can be decoded & put in The Graph.

It's capable of decoding both general Deposit & TokenMapping state syncs.

Usage

• If you've StateSync data, you can call decodeStateSyncData to unwrap first two folds.

• In response, if your first field ∈ {0, 1}, we've successfully decoded data

  • 0 -> Deposit
    • depositor => Address performing deposit on Ethereum
    • root => Token which is being deposited
    • depositData => ABI encoded deposit data i.e. might contain token amount ( for Ether, ERC20 ), token id(s) ( for ERC721 ), token id(s) & amount ( for ERC1155 )
  • 1 -> Token Mapping
    • root => Root chain token address of token mapping
    • child => Child chain token address of token mapping

• For decoding depositData, obtained from 👆, respective decoder function can be used depending upon what kind of token, you're dealing with.

Deployment Details

Source verified version of Decoder is deployed on

• Goerli
• Ethereum Mainnet