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Fee.sol

The contract fetches real-time price feed from Chainlink Oracles and converts the gas fee amount to an equivalent token price.

admin

mapping(address => bool) admins;
Key-value pair map that keeps track of the contract admin.

Parameter Type
key address input addresses
value bool True: the address is an admin, False: otherwise

priceContracts

mapping(bytes => address) public priceContracts;
Key-value pair map that stores the address of a Chainlink pricefeed oracle contract.

Parameter Type
key bytes The input price feed index, with the format: <network>-<token>-eth. For example, to query the USDC/ETH price from the Mainnet, enter main-usdc-eth
value address The Chainlink oracle address

tokensMap

mapping(address => bytes) public tokensMap;
Key-value pair mapping tokens to their contract addresses.

Parameter Type
key address The ERC20 token address
value bytes The input price feed index, as defined in priceContracts

constructor()

constructor() public;
Assigns the deployer as a default admin, and pre-assigns the following price feed:

  • main-usdc-eth
  • main-uni-eth
  • kovan-usdc-eth

onlyAdmin()

modifier onlyAdmin();
Verifies msg.sender is a contract admin.

modifyAdmin()

function modifyAdmin(address input, bool isAdmin) public onlyAdmin();
Adds or removes admin privilege to or from the input address.

Parameter Type
input address The input address to be given or revoked admin privilege
isAdmin bool true: assigns admin, false: revokes admin

addPriceFeed()

function addPriceFeed(
    string memory priceIndex, 
    address feed, 
    address token
) public onlyAdmin();
Adds a new price feed, then maps to the token address. It can only be invoked by an admin. To find more oracle addresses, check out the Chainlink docs.

Parameter Type
priceIndex string The input price feed index, as defined in priceContracts
feed address The address of the Chainlink price feed
token address The ERC20 token address

gasPrice()

function getPrice(address token) public view returns (int256);
Gets the real time price data from Chainlink in 18 decimals.

Parameter Type
token address The ERC20 Token address

calculateGasInTokens()

function calculateGasInTokens(
    address token, 
    uint256 gas, 
    uint256 weiPerToken
) public view returns (uint256)
Returns the amount of tokens equivalent to the gas fee.

Parameter Type
token address The ERC20 token address
gas uint256 The gas fee
weiPerToken uint256 The Wei amount per token