PriceOracle

PriceOracleV2 aggregates price data from connected price feeds and uses it to value collateral assets to, e.g., compute Credit Account health.

Feeds must be USD-denominated and have 8 decimals.

Each priceFeed (data source) has 3 key parameters:

Price feeds by token type

Chainlink price feed

PriceOracleV2 supports Chainlink price feeds that implement AggregatorV3Interface. By default, all results from Chainlink feeds goes through a correctness check, which reverts if the result is incorrect or stale:

 
function _checkAnswer(
        uint80 roundID,
        int256 price,
        uint256 updatedAt,
        uint80 answeredInRound
    ) internal pure {
        if (price <= 0) revert ZeroPriceException(); // F:[PO-5]
        if (answeredInRound < roundID || updatedAt == 0)
            revert ChainPriceStaleException(); // F:[PO-5]
    }
 

LP price feeds

LP price feeds usually return a function computed from ordinary token price feeds, as well as some additional data, depending on the protocol.

An abstract contract LPPriceFeed serves as a base for all LP price feeds and contains logic for bound control for results. In some cases, values used for LP price feed calculation (e.g., Yearn pricePerShare) may be manipulatable, and the bounds ensure that short-term manipulation does not affect Gearbox.

NFT and address dependent pricefeeds

Unlike fungible tokens, NFTs, such as Uniswap V3 LP positions, do not have a single uniform price. There is no reliable way to compute the actual value of NFTs on an account from balance alone.

Passing the credit account's address allows the price feed to determine the NFTs a CA has, and correctly compute their value.

ZeroPriceFeed

ZeroPriceFeed returns zero at all times. Only one ZeroPriceFeed contract is deployed on each network and serves all tokens for which there are no Chainlink feeds, or those feeds are unreliable.

Methods

ConvertToUSD

Converts an asset amount into USD (decimals = 8). Reverts if priceFeed doesn't exist.

function convertToUSD(
    address creditAccount,
    uint256 amount,
    address token
) external view returns (uint256);

ConvertFromUSD

Converts an amount of USD (decimals = 8) into an asset.

function convertFromUSD(
    address creditAccount,
    uint256 amount,
    address token
) external view returns (uint256);

getPrice

Returns price of a single token unit in USD (decimals = 8).

function getPrice(address creditAccount, address token)
    external
    view
    returns (uint256 price);

convert

Convers an amount of one asset to an equivalent amount of another asset.

function convert(
    address creditAccount,
    uint256 amount,
    address tokenFrom,
    address tokenTo
) external view returns (uint256)

priceFeedsWithFlags

Returns a price feed with all relevant parameters for a token. Reverts if there is no price feed for the passed token.

function priceFeedsWithFlags(address token)
    public
    view
    returns (
        address priceFeed,
        bool skipCheck,
        uint256 decimals
    );