pragma solidity >0.6.11; // SPDX-License-Identifier: GPL-3.0-or-later contract TokenUniqueSymbolIndex { // EIP 173 address public owner; address newOwner; mapping(address => bool) writers; mapping ( bytes32 => uint256 ) public registry; address[] tokens; event OwnershipTransferred(address indexed previousOwner, address indexed newOwner); // EIP173 event AddressAdded(address indexed addedAccount, uint256 indexed accountIndex); // AccountsIndex constructor() { owner = msg.sender; tokens.push(address(0)); } // Implements AccountsIndex function entry(uint256 _idx) public view returns ( address ) { return tokens[_idx + 1]; } // Implements RegistryClient function addressOf(bytes32 _key) public view returns ( address ) { uint256 idx; idx = registry[_key]; return tokens[idx]; } function register(address _token) public returns (bool) { require(writers[msg.sender]); bytes memory token_symbol; bytes32 token_symbol_key; uint256 idx; (bool _ok, bytes memory _r) = _token.call(abi.encodeWithSignature('symbol()')); require(_ok); token_symbol = abi.decode(_r, (bytes)); token_symbol_key = sha256(token_symbol); idx = registry[token_symbol_key]; require(idx == 0); registry[token_symbol_key] = tokens.length; tokens.push(_token); emit AddressAdded(_token, tokens.length - 1); return true; } // Implements AccountsIndex function add(address _token) public returns (bool) { return register(_token); } // Implements AccountsIndex function entryCount() public view returns ( uint256 ) { return tokens.length - 1; } // Implements EIP173 function transferOwnership(address _newOwner) public returns (bool) { require(msg.sender == owner); newOwner = _newOwner; return true; } // Implements OwnedAccepter function acceptOwnership() public returns (bool) { address oldOwner; require(msg.sender == newOwner); oldOwner = owner; owner = newOwner; newOwner = address(0); emit OwnershipTransferred(oldOwner, owner); return true; } // Implements Writer function addWriter(address _writer) public returns (bool) { require(owner == msg.sender); writers[_writer] = true; return true; } // Implements Writer function deleteWriter(address _writer) public returns (bool) { require(owner == msg.sender); delete writers[_writer]; return true; } // Implements EIP165 function supportsInterface(bytes4 _sum) public pure returns (bool) { if (_sum == 0xcbdb05c7) { // AccountsIndex return true; } if (_sum == 0xbb34534c) { // RegistryClient return true; } if (_sum == 0x01ffc9a7) { // EIP165 return true; } if (_sum == 0x9493f8b2) { // EIP173 return true; } if (_sum == 0x37a47be4) { // OwnedAccepter return true; } if (_sum == 0x80c84bd6) { // Writer return true; } return false; } }