Comptroller Functions

Enter Markets

Enter into a list of markets - it is not an error to enter the same market more than once. In order to supply collateral or borrow in a market, it must be entered first.

Comptroller

function enterMarkets(address[] calldata bTokens) returns (uint[] memory)

• msg.sender: The account which shall enter the given markets.

• bTokens: The addresses of the bToken markets to enter.

• RETURN: For each market, returns an error code indicating whether or not it was entered. Each is 0 on success, otherwise an Error code.

Solidity

Comptroller troll = Comptroller(0xABCD...);
BToken[] memory bTokens = new BToken[](2);
bTokens[0] = BBrc20(0x3FDA...);
bTokens[1] = BBtt(0x3FDB...);
uint[] memory errors = troll.enterMarkets(bTokens);

Web3 1.0

const troll = Comptroller.at(0xABCD...);
const bTokens = [BBrc20.at(0x3FDA...), BBtt.at(0x3FDB...)];
const errors = await troll.methods.enterMarkets(bTokens).send({from: ...});

Exit Market

Exit a market - it is not an error to exit a market that is not currently entered. Exited markets will not count towards account liquidity calculations.

Comptroller

function exitMarket(address bToken) returns (uint)

• msg.sender: The account which shall exit the given market.

• bTokens: The addresses of the bToken market to exit.

• RETURN: 0 on success, otherwise an Error code.

Solidity

Comptroller troll = Comptroller(0xABCD...);
uint error = troll.exitMarket(BToken(0x3FDA...));

Web3 1.0

const troll = Comptroller.at(0xABCD...);
const errors = await troll.methods.exitMarket(BBtt.at(0x3FDB...)).send({from: ...});

Get Assets In

Get the list of markets an account is currently entered into. In order to supply collateral or borrow in a market, it must be entered first. Entered markets count towards account liquidity calculations.

Comptroller

function getAssetsIn(address account) view returns (address[] memory)

• account: The account whose list of entered markets shall be queried.

• RETURN: The address of each market which is currently entered into.

Solidity

Comptroller troll = Comptroller(0xABCD...);
address[] memory markets = troll.getAssetsIn(0xMyAccount);

Web3 1.0

const troll = Comptroller.at(0xABCD...);
const markets = await troll.methods.getAssetsIn(bTokens).call();

Collateral Factor

A bToken's collateral factor can range from 0-90%, and represents the proportionate increase in liquidity (borrow limit) that an account receives by minting the bToken. Generally, large or liquid assets have high collateral factors, while small or illiquid assets have low collateral factors. If an asset has a 0% collateral factor, it can't be used as collateral (or seized in liquidation), though it can still be borrowed.

Collateral factors can be increased (or decreased) through Bitlend Governance, as market conditions change.

Comptroller

function markets(address bTokenAddress) view returns (bool, uint, bool)

• bTokenAddress: The address of the bToken to check if listed and get the collateral factor for.

• RETURN: Tuple of values (isListed, collateralFactorMantissa, isComped); isListed represents whether the comptroller recognizes this bToken; collateralFactorMantissa, scaled by 1e18, is multiplied by a supply balance to determine how much value can be borrowed. The isComped boolean indicates whether or not suppliers and borrowers are distributed BLEND tokens.

Solidity

Comptroller troll = Comptroller(0xABCD...);
(bool isListed, uint collateralFactorMantissa, bool isComped) = troll.markets(0x3FDA...);

Web3 1.0

const troll = Comptroller.at(0xABCD...);
const result = await troll.methods.markets(0x3FDA...).call();
const {0: isListed, 1: collateralFactorMantissa, 2: isComped} = result;

Get Account Liquidity

Account Liquidity represents the USD value borrowable by a user before it reaches liquidation. Users with a shortfall (negative liquidity) are subject to liquidation, and can’t withdraw or borrow assets until Account Liquidity is positive again.

For each market the user has entered into, their supplied balance is multiplied by the market’s collateral factor, and summed; borrow balances are then subtracted, to equal Account Liquidity. Borrowing an asset reduces Account Liquidity for each USD borrowed; withdrawing an asset reduces Account Liquidity by the asset’s collateral factor times each USD withdrawn.

Because the Bitlend Protocol exclusively uses unsigned integers, Account Liquidity returns either a surplus or shortfall.

Comptroller

function getAccountLiquidity(address account) view returns (uint, uint, uint)

• account: The account whose liquidity shall be calculated.

• RETURN: Tuple of values (error, liquidity, shortfall). The error shall be 0 on success, otherwise an error code. A non-zero liquidity value indicates the account has available account liquidity. A non-zero shortfall value indicates the account is currently below his/her collateral requirement and is subject to liquidation. At most, one of liquidity or shortfall shall be non-zero.

Solidity

Comptroller troll = Comptroller(0xABCD...);
(uint error, uint liquidity, uint shortfall) = troll.getAccountLiquidity(msg.caller);
require(error == 0, "join the Discord");
require(shortfall == 0, "account underwater");
require(liquidity > 0, "account has excess collateral");

Web3 1.0

const troll = Comptroller.at(0xABCD...);
const result = await troll.methods.getAccountLiquidity(0xBorrower).call();
const {0: error, 1: liquidity, 2: shortfall} = result;

Close Factor

The percent, ranging from 0% to 100%, of a liquidatable account's borrow that can be repaid in a single liquidate transaction. If a user has multiple borrowed assets, the closeFactor applies to any single borrowed asset, not the aggregated value of a user’s outstanding borrowing.

Comptroller

function closeFactorMantissa() view returns (uint)

• RETURN: The closeFactor, scaled by 1e18, is multiplied by an outstanding borrow balance to determine how much could be closed.

Solidity

Comptroller troll = Comptroller(0xABCD...);
uint closeFactor = troll.closeFactorMantissa();

Web3 1.0

const troll = Comptroller.at(0xABCD...);
const closeFactor = await troll.methods.closeFactorMantissa().call();

Liquidation Incentive

The additional collateral given to liquidators as an incentive to perform liquidation of underwater accounts. A portion of this is given to the collateral bToken reserves as determined by the seize share. The seize share is assumed to be 0 if the bToken does not have a protocolSeizeShareMantissa constant. For example, if the liquidation incentive is 1.08, and the collateral's seize share is 1.028, liquidators receive an extra 5.2% of the borrower's collateral for every unit they close, and the remaining 2.8% is added to the bToken's reserves.

Comptroller

function liquidationIncentiveMantissa() view returns (uint)

• RETURN: The liquidationIncentive, scaled by 1e18, is multiplied by the closed borrow amount from the liquidator to determine how much collateral can be seized.

Solidity

Comptroller troll = Comptroller(0xABCD...);
uint closeFactor = troll.liquidationIncentiveMantissa();

Web3 1.0

const troll = Comptroller.at(0xABCD...);
const closeFactor = await troll.methods.liquidationIncentiveMantissa().call();

Key Events

Event	Description
MarketEntered(BToken bToken, address account)	Emitted upon a successful Enter Market.
MarketExited(BToken bToken, address account)	Emitted upon a successful Exit Market.

Error Codes

Code	Name	Description
0	NO_ERROR	Not a failure.
1	UNAUTHORIZED	The sender is not authorized to perform this action.
2	COMPTROLLER_MISMATCH	Liquidation cannot be performed in markets with different comptrollers.
3	INSUFFICIENT_SHORTFALL	The account does not have sufficient shortfall to perform this action.
4	INSUFFICIENT_LIQUIDITY	The account does not have sufficient liquidity to perform this action.
5	INVALID_CLOSE_FACTOR	The close factor is not valid.
6	INVALID_COLLATERAL_FACTOR	The collateral factor is not valid.
7	INVALID_LIQUIDATION_INCENTIVE	The liquidation incentive is invalid.
8	MARKET_NOT_ENTERED	The market has not been entered by the account.
9	MARKET_NOT_LISTED	The market is not currently listed by the comptroller.
10	MARKET_ALREADY_LISTED	An admin tried to list the same market more than once.
11	MATH_ERROR	A math calculation error occurred.
12	NONZERO_BORROW_BALANCE	The action cannot be performed since the account carries a borrow balance.
13	PRICE_ERROR	The comptroller could not obtain a required price of an asset.
14	REJECTION	The comptroller rejects the action requested by the market.
15	SNAPSHOT_ERROR	The comptroller could not get the account borrows and exchange rate from the market.
16	TOO_MANY_ASSETS	Attempted to enter more markets than are currently supported.
17	TOO_MUCH_REPAY	Attempted to repay more than is allowed by the protocol.

Failure Info

Code	Name
0	ACCEPT_ADMIN_PENDING_ADMIN_CHECK
1	ACCEPT_PENDING_IMPLEMENTATION_ADDRESS_CHECK
2	EXIT_MARKET_BALANCE_OWED
3	EXIT_MARKET_REJECTION
4	SET_CLOSE_FACTOR_OWNER_CHECK
5	SET_CLOSE_FACTOR_VALIDATION
6	SET_COLLATERAL_FACTOR_OWNER_CHECK
7	SET_COLLATERAL_FACTOR_NO_EXISTS
8	SET_COLLATERAL_FACTOR_VALIDATION
9	SET_COLLATERAL_FACTOR_WITHOUT_PRICE
10	SET_IMPLEMENTATION_OWNER_CHECK
11	SET_LIQUIDATION_INCENTIVE_OWNER_CHECK
12	SET_LIQUIDATION_INCENTIVE_VALIDATION
13	SET_MAX_ASSETS_OWNER_CHECK
14	SET_PENDING_ADMIN_OWNER_CHECK
15	SET_PENDING_IMPLEMENTATION_OWNER_CHECK
16	SET_PRICE_ORACLE_OWNER_CHECK
17	SUPPORT_MARKET_EXISTS
18	SUPPORT_MARKET_OWNER_CHECK

BLEND Distribution Speeds

BLEND Speed

The "BLEND speed" unique to each market is an unsigned integer that specifies the amount of BLEND that is distributed, per block, to suppliers and borrowers in each market. This number can be changed for individual markets by calling the _setCompSpeed method through a successful Bitlend Governance proposal. The following is the formula for calculating the rate that BLEND is distributed to each supported market.

utility = bTokenTotalBorrows * assetPrice
utilityFraction = utility / sumOfAllCOMPedMarketUtilities
marketCompSpeed = compRate * utilityFractionjavas

BLEND Distributed Per Block (All Markets)

The Comptroller contract’s compRate is an unsigned integer that indicates the rate at which the protocol distributes BLEND to markets’ suppliers or borrowers, every Ethereum block. The value is the amount of BLEND (in wei), per block, allocated for the markets. Note that not every market has BLEND distributed to its participants (see Market Metadata). The compRate indicates how much BLEND goes to the suppliers or borrowers, so doubling this number shows how much BLEND goes to all suppliers and borrowers combined. The code examples implement reading the amount of BLEND distributed, per Ethereum block, to all markets.

Comptroller

uint public compRate;

Solidity

Comptroller troll = Comptroller(0xABCD...);
// BLEND issued per block to suppliers OR borrowers * (1 * 10 ^ 18)
uint compRate = troll.compRate();
// Approximate BLEND issued per day to suppliers OR borrowers * (1 * 10 ^ 18)
uint compRatePerDay = compRate * 4 * 60 * 24;
// Approximate BLEND issued per day to suppliers AND borrowers * (1 * 10 ^ 18)
uint compRatePerDayTotal = compRatePerDay * 2;

Web3 1.2.6

const comptroller = new web3.eth.Contract(comptrollerAbi, comptrollerAddress);
let compRate = await comptroller.methods.compRate().call();
compRate = compRate / 1e18;
// BLEND issued to suppliers OR borrowers
const compRatePerDay = compRate * 4 * 60 * 24;
// BLEND issued to suppliers AND borrowers
const compRatePerDayTotal = compRatePerDay * 2;javasc

BLEND Distributed Per Block (Single Market)

The Comptroller contract has a mapping called compSpeeds. It maps bToken addresses to an integer of each market’s BLEND distribution per Ethereum block. The integer indicates the rate at which the protocol distributes BLEND to markets’ suppliers or borrowers. The value is the amount of BLEND (in wei), per block, allocated for the market. Note that not every market has BLEND distributed to its participants (see Market Metadata). The speed indicates how much BLEND goes to the suppliers or the borrowers, so doubling this number shows how much BLEND goes to market suppliers and borrowers combined. The code examples implement reading the amount of BLEND distributed, per Ethereum block, to a single market.

Comptroller

mapping(address => uint) public compSpeeds;

Solidity

Comptroller troll = Comptroller(0x123...);
address bToken = 0xabc...;
// BLEND issued per block to suppliers OR borrowers * (1 * 10 ^ 18)
uint compSpeed = troll.compSpeeds(bToken);
// Approximate BLEND issued per day to suppliers OR borrowers * (1 * 10 ^ 18)
uint compSpeedPerDay = compSpeed * 4 * 60 * 24;
// Approximate BLEND issued per day to suppliers AND borrowers * (1 * 10 ^ 18)
uint compSpeedPerDayTotal = compSpeedPerDay * 2;

Web3 1.2.6

const bTokenAddress = '0xabc...';
const comptroller = new web3.eth.Contract(comptrollerAbi, comptrollerAddress);
let compSpeed = await comptroller.methods.compSpeeds(bTokenAddress).call();
compSpeed = compSpeed / 1e18;
// BLEND issued to suppliers OR borrowers
const compSpeedPerDay = compSpeed * 4 * 60 * 24;
// BLEND issued to suppliers AND borrowers
const compSpeedPerDayTotal = compSpeedPerDay * 2;

Claim BLEND

Every Bitlend user accrues BLEND for each block they are supplying to or borrowing from the protocol. Users may call the Comptroller's claimComp method at any time to transfer BLEND accrued to their address.

Comptroller

// Claim all the BLEND accrued by holder in all markets
function claimComp(address holder) public
// Claim all the BLEND accrued by holder in specific markets
function claimComp(address holder, BToken[] memory bTokens) public
// Claim all the BLEND accrued by specific holders in specific markets for their supplies and/or borrows
function claimComp(address[] memory holders, BToken[] memory bTokens, bool borrowers, bool suppliers) public

Solidity

Comptroller troll = Comptroller(0xABCD...);
troll.claimComp(0x1234...);

Web3 1.2.6

const comptroller = new web3.eth.Contract(comptrollerAbi, comptrollerAddress);
await comptroller.methods.claimComp("0x1234...").send({ from: sender });

Market Metadata

The Comptroller contract has an array called getAllMarkets that contains the addresses of each bToken contract. Each address in the getAllMarkets array can be used to fetch a metadata struct in the Comptroller’s markets constant. See the Comptroller Storage contract for the Market struct definition.

Comptroller

BToken[] public getAllMarkets;

Solidity

Comptroller troll = Comptroller(0xABCD...);
BToken bTokens[] = troll.getAllMarkets();

Web3 1.2.6

const comptroller = new web3.eth.Contract(comptrollerAbi, comptrollerAddress);
const bTokens = await comptroller.methods.getAllMarkets().call();
const bToken = bTokens[0]; // address of a bToken