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
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
Web3 1.0
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
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
Web3 1.0
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
account
: The account whose list of entered markets shall be queried.RETURN
: The address of each market which is currently entered into.
Solidity
Web3 1.0
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
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
Web3 1.0
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
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
Web3 1.0
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
RETURN
: The closeFactor, scaled by 1e18, is multiplied by an outstanding borrow balance to determine how much could be closed.
Solidity
Web3 1.0
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
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
Web3 1.0
Key Events
Event | Description |
---|---|
| Emitted upon a successful Enter Market. |
| Emitted upon a successful Exit Market. |
Error Codes
Code | Name | Description |
---|---|---|
0 |
| Not a failure. |
1 |
| The sender is not authorized to perform this action. |
2 |
| Liquidation cannot be performed in markets with different comptrollers. |
3 |
| The account does not have sufficient shortfall to perform this action. |
4 |
| The account does not have sufficient liquidity to perform this action. |
5 |
| The close factor is not valid. |
6 |
| The collateral factor is not valid. |
7 |
| The liquidation incentive is invalid. |
8 |
| The market has not been entered by the account. |
9 |
| The market is not currently listed by the comptroller. |
10 |
| An admin tried to list the same market more than once. |
11 |
| A math calculation error occurred. |
12 |
| The action cannot be performed since the account carries a borrow balance. |
13 |
| The comptroller could not obtain a required price of an asset. |
14 |
| The comptroller rejects the action requested by the market. |
15 |
| The comptroller could not get the account borrows and exchange rate from the market. |
16 |
| Attempted to enter more markets than are currently supported. |
17 |
| Attempted to repay more than is allowed by the protocol. |
Failure Info
Code | Name |
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0 |
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2 |
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18 |
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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.
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
Solidity
Web3 1.2.6
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
Solidity
Web3 1.2.6
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
Solidity
Web3 1.2.6
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
Solidity
Web3 1.2.6
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