SBM

Introduction

The JustLend DAO Supply and Borrow Market (SBM) is a decentralized liquidity pool where users can participate as suppliers, borrowers or liquidators. Suppliers provide liquidity to a market and can earn interest on the assets provided, where borrowers are able to borrow in a collateralize assets way.

The SBM contract is the main user-facing contract. Most user interactions with the JustLend DAO Protocol occur via the Ctoken contract. It exposes the liquidity management methods that can be invoked using either Solidity or Web3 libraries.

Ctoken.sol allows users to:

• Supply

• Borrow

• Withdraw

• Repay

• Liquidation

The source code is available on Github.

Query Interface

ExchangeRate

Calling this method accrues interest and returns the up-to-date exchange rate.

function exchangeRateCurrent() public nonReentrant returns (uint)

• Parameter description: N/A

• Returns: calculated exchange rate scaled by 1e18.

---

Get Cash

Calling this method gets the total amount of underlying balance currently available to this market.

function getCash() public view returns (uint)

• Parameter description: N/A

• Returns: The quantity of underlying assets owned by this contract.

---

Total Borrows

Calling this method gets the sum of the currently loaned-outs and the accrued interests.

function totalBorrowsCurrent() external nonReentrant returns (uint)

• Parameter description: N/A

• Returns: The total borrows with interest.

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Borrow Balance

Calling this method accrues interest to the updated borrowIndex and then calculates the account's borrow balance using the updated borrowIndex.

function borrowBalanceCurrent(address account) external nonReentrant returns (uint)

• Parameter description:

  • account: the address whose balance should be calculated after updating borrowIndex.

• Returns: The calculated balance.

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Borrow Rate

Calling this method gets the current per-block borrow interest rate for this jToken.

function borrowRatePerBlock() external view returns (uint)

• Parameter description: N/A

• Returns: The borrow interest rate per block, scaled by 1e18.

---

Total Supply

Calling this method gets the total number of tokens in circulation.

function totalSupply() external view returns (uint256)

• Parameter description: N/A

• Returns: The supply of tokens.

---

Underlying Balance

Calling this method gets the underlying balance of the owner.

function balanceOfUnderlying(address owner) external returns (uint)

• Parameter description:

  • owner: the address of the account.

• Returns: The amount of underlying owned by owner.

---

Supply Rate

Calling this method gets the current per-block supply interest rate for this jToken.

function supplyRatePerBlock() external view returns (uint)

• Parameter description: N/A

• Returns: the supply interest rate per block, scaled by 1e18.

---

Total Reserves

Calling this method gets the reserves. Reserve represents a portion of historical interest set aside as cash which can be withdrawn or transferred through the protocol's governance.

function totalReserves() returns (uint)

• Parameter description: N/A

• Returns: the total amount of reserves.

---

Reserve Factor

Calling this method gets the current reserve factor.

function reserveFactorMantissa() returns (uint)

• Parameter description: N/A

• Returns: The current reserve factor.

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Liquidation Incentive

By calling the liquidationIncentiveMantissa function of the Unitroller contract, liquidation incentives can be inquired. Liquidators will be given a proportion of the borrower's collateral as an incentive, which is defined as liquidation incentive. This is to encourage liquidators to perform liquidation of underwater accounts.

function liquidationIncentiveMantissa() view returns (uint)

• Parameter description: N/A

• Returns: N/A

---

Get Account Liquidity

By calling the getAccountLiquidity function of the Unitroller contract, account information can be accessed through an account's address to determine whether the account should be liquidated or not.

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

• Parameter description:

  • account: user address.

• Returns:

  • error: error code, 0 means success.

  • liquidity: liquidity.

  • shortfall: When the value is bigger than 0, the current account does not meet the market requirement for collateralization and needs to be liquidated.

Note: There should be at most one non-zero value between liquidity and shortfall.

---

Wtite Interface

Borrow

Calling this method borrows assets from JustLend DAO protocol to the sender's owner address.

function borrow(uint borrowAmount) external returns (uint)

• Parameter description:

  • borrowAmount: the amount of the underlying asset to borrow.

• Returns: None, reverts on error.

📅 Event

Borrow(address borrower, uint borrowAmount, uint accountBorrows, uint totalBorrows, uint borrowIndex)

• Emits when user successfully borrow.

  • borrower: address of borrow assets account;

  • borrowAmount: the amount of borrowed assets;

  • accountBorrows: the account borrow the assets;

  • totalBorrows: total borrow assets form the account;

  • borrowIndex: the index of this borrow order.

---

repayBorrow

Calling this method repays their own borrow.

function repayBorrow(uint amount) external payable

• Parameter description:

  • amount: the amount of the asset to repay.

• Returns: None, reverts on error.

📅 Event

RepayBorrow(address payer, address borrower, uint repayAmount, uint accountBorrows, uint totalBorrows, uint borrowIndex)

• Emits when user successfully repay borrow.

  • payer: operate repay borrow;

  • borrower: address of borrow assets account;

  • repayAmount: the amount of repaid assets;

  • accountBorrows: the account borrow the assets;

  • totalBorrows: total borrow assets form the account;

  • borrowIndex: the index of this borrow order.

---

repayBorrowBehalf

Calling this method repays a borrow belonging to borrower.

function repayBorrowBehalf(address borrower) external payable

• Parameter description:

  • borrower: the account with the debt being payed off.

  • msg.value: the amount to repay.

• Returns: None, reverts on error.

---

Mint

Calling this method supplies assets into the market and receives jTokens in exchange.

function mint() external payable

• Parameter description:

  • msg.value: the amount of TRX to supply.

• Returns: None, reverts on error.

📅 Event

Mint(address minter, uint mintAmount, uint mintTokens)

• Emits when user successfully mint.

  • minter: operate supply assets into the market;

  • mintAmount: the amount of supplied assets;

  • mintTokens: the tokens need to mint.

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Redeem

Calling this method redeems jTokens in exchange for the underlying asset and accrues interest whether or not the operation succeeds.

function redeem(uint redeemTokens) external returns (uint)

• Parameter description:

  • redeemTokens: the number of jTokens to redeem into underlying.

• Returns: 0 for success, reverts on error.

📅 Event

Redeem(address redeemer, uint redeemAmount, uint redeemTokens)

• Emits when user successfully redeem.

  • redeemer: operate redeem jTokens;

  • redeemAmount: the amount of redeem assets;

  • redeemTokens: the tokens need to redeem.

---

RedeemUnderlying

Calling this method redeems jTokens in exchange for a specified amount of underlying asset.

function redeemUnderlying(uint redeemAmount) external returns (uint)

• Parameter description:

  • redeemAmount: the amount of underlying to redeem.

• Returns: 0 for success, reverts on error.

---

Transfer

Calling this method transfers a specified amount of jtokens to the destination. This action will fail if the account's liquidity become negative due to the transfer.

function transfer(address dst, uint256 amount) external nonReentrant returns (bool)

• Parameter description:

  • dst: the receiver's address.

  • amount: amount of token to be transferred.

• Returns: A boolean value indicating whether or not the transfer succeeded.

---

Liquidate Borrow（jTrc20）

By calling liquidateBorrow function of the corresponding jTrc20 contract (e.g. jUSDT), accounts whose liquidity does not meet the market requirement for collateralization will be liquidated by other users to restore the account liquidity to a normal level (i.e. higher than the market requirement for collateralization). In the event of liquidation, liquidators may repay part or 50% of the loan for the borrower. Liquidators will be given a proportion of the borrower's collateral as an incentive.

function liquidateBorrow(address borrower, uint repayAmount, address jTokenCollateral) returns (uint)

• Parameter description:

  • borrower: address of a liquidated account.

  • repayAmount: amount of token to be repaid in the event of liquidation (measured in the borrowed asset).

  • jTokenCollateral: address of the jTOKEN contract to set aside the collateralized asset of a borrower.

• Returns: None, reverts on error.

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Liquidate Borrow（jTRX）

By calling the liquidateBorrow function of the jTRX contract, accounts whose liquidity does not meet the market requirement for collateralization will be liquidated by other users to restore the account liquidity to a normal level (i.e., higher than the market requirement for collateralization). In the event of liquidation, liquidators may repay part or 50% of the loan for the borrower. Liquidators will be given a proportion of the borrower's collateral as an incentive.

function liquidateBorrow(address borrower, address jTokenCollateral) payable

• Parameter description:

  • borrower: address of a liquidated account.

  • jTokenCollateral: address of the jTRX contract to set aside the collateralized asset of a borrower.

  • msg.value: amount of TRX to be repaid in the event of liquidation (measured in SUN).

• Returns: No return. If any error occurs, the transaction will be reverted.

📅 Event

LiquidateBorrow(address liquidator, address borrower, uint repayAmount, address cTokenCollateral, uint seizeTokens)

• Emits when user successfully liquidate borrow order.

  • liquidator: operate liquidation;

  • borrower: address of a liquidated account;

  • repayAmount: the amount of repaid assets;

  • cTokenCollateral: address of the jTRX contract to set aside the collateralized asset of a borrower.

  • seizeTokens: the tokens need to be liquidated.

---

Error Code And Failure info

Error Codes

Code	Name	Description
0	NO_ERROR	Not a failure.
1	UNAUTHORIZED	The sender is not authorized to perform this action.
2	BAD_INPUT	An invalid argument was supplied by the caller.
3	COMPTROLLER_REJECTION	The action would violate the comptroller policy.
4	COMPTROLLER_CALCULATION_ERROR	An internal calculation has failed in the comptroller.
5	INTEREST_RATE_MODEL_ERROR	The interest rate model returned an invalid value.
6	INVALID_ACCOUNT_PAIR	The specified combination of accounts is invalid.
7	INVALID_CLOSE_AMOUNT_REQUESTED	The amount to liquidate is invalid.
8	INVALID_COLLATERAL_FACTOR	The collateral factor is invalid.
9	MATH_ERROR	A math calculation error occurred.
10	MARKET_NOT_FRESH	Interest has not been properly accrued.
11	MARKET_NOT_LISTED	The market is not currently listed by its comptroller.
12	TOKEN_INSUFFICIENT_ALLOWANCE	ERC-20 contract must allow Money Market contract to call transferFrom. The current allowance is either 0 or less than the requested supply, repayBorrow or liquidate amount.
13	TOKEN_INSUFFICIENT_BALANCE	Caller does not have sufficient balance in the ERC-20 contract to complete the desired action.
14	TOKEN_INSUFFICIENT_CASH	The market does not have a sufficient cash balance to complete the transaction. You may attempt this transaction again later.
15	TOKEN_TRANSFER_IN_FAILED	Failure in ERC-20 when transfering token into the market.
16	TOKEN_TRANSFER_OUT_FAILED	Failure in ERC-20 when transfering token out of the market.

Failure Info

Code	Name
0	ACCEPT_ADMIN_PENDING_ADMIN_CHECK
1	ACCRUE_INTEREST_ACCUMULATED_INTEREST_CALCULATION_FAILED
2	ACCRUE_INTEREST_BORROW_RATE_CALCULATION_FAILED
3	ACCRUE_INTEREST_NEW_BORROW_INDEX_CALCULATION_FAILED
4	ACCRUE_INTEREST_NEW_TOTAL_BORROWS_CALCULATION_FAILED
5	ACCRUE_INTEREST_NEW_TOTAL_RESERVES_CALCULATION_FAILED
6	ACCRUE_INTEREST_SIMPLE_INTEREST_FACTOR_CALCULATION_FAILED
7	BORROW_ACCUMULATED_BALANCE_CALCULATION_FAILED
8	BORROW_ACCRUE_INTEREST_FAILED
9	BORROW_CASH_NOT_AVAILABLE
10	BORROW_FRESHNESS_CHECK
11	BORROW_NEW_TOTAL_BALANCE_CALCULATION_FAILED
12	BORROW_NEW_ACCOUNT_BORROW_BALANCE_CALCULATION_FAILED
13	BORROW_MARKET_NOT_LISTED
14	BORROW_COMPTROLLER_REJECTION
15	LIQUIDATE_ACCRUE_BORROW_INTEREST_FAILED
16	LIQUIDATE_ACCRUE_COLLATERAL_INTEREST_FAILED
17	LIQUIDATE_COLLATERAL_FRESHNESS_CHECK
18	LIQUIDATE_COMPTROLLER_REJECTION
19	LIQUIDATE_COMPTROLLER_CALCULATE_AMOUNT_SEIZE_FAILED
20	LIQUIDATE_CLOSE_AMOUNT_IS_UINT_MAX
21	LIQUIDATE_CLOSE_AMOUNT_IS_ZERO
22	LIQUIDATE_FRESHNESS_CHECK
23	LIQUIDATE_LIQUIDATOR_IS_BORROWER
24	LIQUIDATE_REPAY_BORROW_FRESH_FAILED
25	LIQUIDATE_SEIZE_BALANCE_INCREMENT_FAILED
26	LIQUIDATE_SEIZE_BALANCE_DECREMENT_FAILED
27	LIQUIDATE_SEIZE_COMPTROLLER_REJECTION
28	LIQUIDATE_SEIZE_LIQUIDATOR_IS_BORROWER
29	LIQUIDATE_SEIZE_TOO_MUCH
30	MINT_ACCRUE_INTEREST_FAILED
31	MINT_COMPTROLLER_REJECTION
32	MINT_EXCHANGE_CALCULATION_FAILED
33	MINT_EXCHANGE_RATE_READ_FAILED
34	MINT_FRESHNESS_CHECK
35	MINT_NEW_ACCOUNT_BALANCE_CALCULATION_FAILED
36	MINT_NEW_TOTAL_SUPPLY_CALCULATION_FAILED
37	MINT_TRANSFER_IN_FAILED
38	MINT_TRANSFER_IN_NOT_POSSIBLE
39	REDEEM_ACCRUE_INTEREST_FAILED
40	REDEEM_COMPTROLLER_REJECTION
41	REDEEM_EXCHANGE_TOKENS_CALCULATION_FAILED
42	REDEEM_EXCHANGE_AMOUNT_CALCULATION_FAILED
43	REDEEM_EXCHANGE_RATE_READ_FAILED
44	REDEEM_FRESHNESS_CHECK
45	REDEEM_NEW_ACCOUNT_BALANCE_CALCULATION_FAILED
46	REDEEM_NEW_TOTAL_SUPPLY_CALCULATION_FAILED
47	REDEEM_TRANSFER_OUT_NOT_POSSIBLE
48	REDUCE_RESERVES_ACCRUE_INTEREST_FAILED
49	REDUCE_RESERVES_ADMIN_CHECK
50	REDUCE_RESERVES_CASH_NOT_AVAILABLE
51	REDUCE_RESERVES_FRESH_CHECK
52	REDUCE_RESERVES_VALIDATION
53	REPAY_BEHALF_ACCRUE_INTEREST_FAILED
54	REPAY_BORROW_ACCRUE_INTEREST_FAILED
55	REPAY_BORROW_ACCUMULATED_BALANCE_CALCULATION_FAILED
56	REPAY_BORROW_COMPTROLLER_REJECTION
57	REPAY_BORROW_FRESHNESS_CHECK
58	REPAY_BORROW_NEW_ACCOUNT_BORROW_BALANCE_CALCULATION_FAILED
59	REPAY_BORROW_NEW_TOTAL_BALANCE_CALCULATION_FAILED
60	REPAY_BORROW_TRANSFER_IN_NOT_POSSIBLE
61	SET_COLLATERAL_FACTOR_OWNER_CHECK
62	SET_COLLATERAL_FACTOR_VALIDATION
63	SET_COMPTROLLER_OWNER_CHECK
64	SET_INTEREST_RATE_MODEL_ACCRUE_INTEREST_FAILED
65	SET_INTEREST_RATE_MODEL_FRESH_CHECK
66	SET_INTEREST_RATE_MODEL_OWNER_CHECK
67	SET_MAX_ASSETS_OWNER_CHECK
68	SET_ORACLE_MARKET_NOT_LISTED
69	SET_PENDING_ADMIN_OWNER_CHECK
70	SET_RESERVE_FACTOR_ACCRUE_INTEREST_FAILED
71	SET_RESERVE_FACTOR_ADMIN_CHECK
72	SET_RESERVE_FACTOR_FRESH_CHECK
73	SET_RESERVE_FACTOR_BOUNDS_CHECK
74	TRANSFER_COMPTROLLER_REJECTION
75	TRANSFER_NOT_ALLOWED
76	TRANSFER_NOT_ENOUGH
77	TRANSFER_TOO_MUCH