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pragma solidity ^0.5.0;
import "./PriceOracle.sol";
import "./SafeMath.sol";
import "./StringUtils.sol";
import "openzeppelin-solidity/contracts/ownership/Ownable.sol";
interface DSValue {
function read() external view returns (bytes32);
// StablePriceOracle sets a price in USD, based on an oracle.
contract StablePriceOracle is Ownable, PriceOracle {
using SafeMath for *;
using StringUtils for *;
// Oracle address
DSValue usdOracle;
// Rent in attodollars (1e-18) per second
uint[] public rentPrices;
event OracleChanged(address oracle);
event RentPriceChanged(uint[] prices);
constructor(DSValue _usdOracle, uint[] memory _rentPrices) public {
* @dev Sets the price oracle address
* @param _usdOracle The address of the price oracle to use.
function setOracle(DSValue _usdOracle) public onlyOwner {
usdOracle = _usdOracle;
emit OracleChanged(address(_usdOracle));
* @dev Sets rent prices.
* @param _rentPrices The price array. Each element corresponds to a specific
* name length; names longer than the length of the array
* default to the price of the last element.
function setPrices(uint[] memory _rentPrices) public onlyOwner {
rentPrices = _rentPrices;
emit RentPriceChanged(_rentPrices);
* @dev Returns the price to register or renew a name.
* @param name The name being registered or renewed.
* @param duration How long the name is being registered or extended for, in seconds.
* @return The price of this renewal or registration, in wei.
function price(string calldata name, uint /*expires*/, uint duration) view external returns(uint) {
uint len = name.strlen();
if(len > rentPrices.length) {
len = rentPrices.length;
require(len > 0);
uint priceUSD = rentPrices[len - 1].mul(duration);
// Price of one ether in attodollars
uint ethPrice = uint(;
// priceUSD and ethPrice are both fixed-point values with 18dp, so we
// multiply the numerator by 1e18 before dividing.
return priceUSD.mul(1e18).div(ethPrice);
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