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eTokens
Each asset supported by the Eco DeFi Protocol is integrated through a eToken contract, which is an EIP-20 compliant representation of balances supplied to the protocol. By minting eTokens, users (1) earn interest through the eToken's exchange rate, which increases in value relative to the underlying asset, and (2) gain the ability to use eTokens as collateral.
eTokens are the primary means of interacting with the Eco DeFi Protocol; when a user mints, redeems, borrows, repays a borrow, liquidates a borrow, or transfers eTokens, he/she will do so using the eToken contract.
There are currently two types of eTokens: EBEP20 and EBNB. Though both types expose the EIP-20 interface, EBEP20 wraps an underlying BEP-20 asset, while BNB simply wraps Ether itself. As such, the core functions which involve transferring an asset into the protocol have slightly different interfaces depending on the type, each of which is shown below.
The redeem function converts a specified quantity of eTokens into the underlying asset, and returns them to the user. The amount of underlying tokens received is equal to the quantity of eTokens redeemed, multiplied by the current Exchange Rate. The amount redeemed must be less than the user's Account Liquidity and the market's available liquidity
function redeem(uint redeemTokens) returns (uint)
msg.sender: The account to which redeemed funds shall be transferredredeemTokens: The number of eTokens to be redeemedRETURN: 0 on success, otherwise an Error code
Solidity
Web3 1.0
EToken eToken = EToken (0x3FDB...);
require(eToken.redeem(7) == 0, "something went wrong");
const eToken = EBEP20.at(0x3FDA...);
eToken.methods.redeemUnderlying(10).send({from: ...});
The redeem underlying function converts eTokens into a specified quantity of the underlying asset, and returns them to the user. The amount of eTokens redeemed is equal to the quantity of underlying tokens received, divided by the current Exchange Rate. The amount redeemed must be less than the user's account liquidity and the market's available liquidity.
function redeemUnderlying(uint redeemAmount) returns (uint)
- msg.sender: The account to which redeemed funds shall be transferred
- redeemAmount: The amount of underlying to be redeemed
- RETURN: 0 on success, otherwise an Error code
Solidity
Web3 1.0
EToken eToken = EToken (0x3FDB...);
require(eToken.redeemUnderlying(50) == 0, "something went wrong");
const eToken = EBEP20.at(0x3FDA...);
eToken.methods.redeemUnderlying(10).send({from: ...});
The borrow function transfers an asset from the protocol to the user, and creates a borrow balance which begins accumulating interest based on the Borrow Rate for the asset. The amount borrowed must be less than the user's Account Liquidity and the market's available liquidity.
To borrow EBNB, the borrower must be 'payable' (solidity).
function borrow(uint borrowAmount) returns (uint)
- msg.sender: The account to which borrowed funds shall be transferred.
- borrowAmount : The amount of the underlying asset to be borrowed.
- RETURN: 0 on success, otherwise an Error code
Solidity
Second Tab
EToken eToken = EToken (0x3FDB...);
require(eToken.borrow(100) == 0, "got collateral?");
const eToken = EBEP20.at(0x3FDB...);
await eToken.methods.borrow(50).send({from: 0xMyAccount});
The repay function transfers an asset into the protocol, reducing the user's borrow balance.
function repayBorrow(uint repayAmount) returns (uint)
- msg.sender: The account which borrowed the asset, and shall repay the borrow.
- repayAmount: The amount of the underlying borrowed asset to be repaid. A value of -1 (i.e. 2256 - 1) can be used to repay the full amount.
- RETURN: 0 on success, otherwise an Error code Before repaying an asset, users must first approve the eToken to access their token balance.
function repayBorrow() payable
- msg.valuepayable: The amount of BNB to be repaid, in wei.
- msg.sender: The account which borrowed the asset, and shall repay the borrow.
- RETURN: No return, reverts on error.
Solidity
Second Tab
EToken eToken = EToken (0x3FDB...);
require(eToken.repayBorrow.value(100)() == 0, "transfer approved?");
const eToken = EBEP20.at(0x3FDA...);
eToken.methods.repayBorrow(10000).send({from: ...});
The repay function transfers an asset into the protocol, reducing the target user's borrow balance.
function repayBorrowBehalf(address borrower, uint repayAmount) returns (uint)
- msg.sender: The account which shall repay the borrow.
- borrower: The account which borrowed the asset to be repaid.
- repayAmount: The amount of the underlying borrowed asset to be repaid. A value of -1 (i.e. 2256 - 1) can be used to repay the full amount.
- RETURN: 0 on success, otherwise an Error code Before repaying an asset, users must first approve the eToken to access their token balance.
function repayBorrowBehalf(address borrower) payable
- msg.valuepayable: The amount of bnb to be repaid, in wei.
- msg.sender: The account which shall repay the borrow.
- borrower: The account which borrowed the asset to be repaid.
- RETURN: No return, reverts on error.
Solidity
Second Tab
EToken eToken = EToken(0x3FDB...);
require(eToken.repayBorrowBehalf.value(100)(0xBorrower) == 0, "transfer approved?");
const eToken = EBEP20.at(0x3FDA...);
await eToken.methods.repayBorrowBehalf(0xBorrower, 10000).send({from: 0xPayer});
Transfer is BEP20 method that allows accounts to send tokens to other BNB addresses. eToken transfer will fail if the account has entered that eToken market and the transfer would have put the account into a state of negative liquidity.
function transfer(address recipient, uint256 amount) returns (bool)
- recipient: The transfer recipient address.
- amount: The amount of eTokens to transfer.
- RETURN: Returns a boolean value indicating whether or not the operation succeeded.
Solidity
Web3 1.0
EToken eToken = EToken(0x3FDB...);
eToken.transfer(0xABCD..., 100000000000);
const eToken = EBEP20.at(0x3FDA...);
await eToken.methods.transfer(0xABCD..., 100000000000).send({from: 0xSender});
A user who has negative account liquidity is subject to liquidation by other users of the protocol to return his/her account liquidity back to positive (i.e. above the collateral requirement). When a liquidation occurs, a liquidator may repay some or all of an outstanding borrow on behalf of a borrower and in return receive a discounted amount of collateral held by the borrower; this discount is defined as the liquidation incentive.
A liquidator may close up to a certain fixed percentage (i.e. close factor) of any individual outstanding borrow of the underwater account. When collateral is seized, the liquidator transferes eTokens, which may redeem the same as if they had supplied the asset themselves. Users must approve each eToken contract before calling liquidate (i.e. on the borrowed asset which they are repaying), as they are transferring funds into the contract.
function liquidateBorrow(address borrower, uint amount, address collateral) returns (uint)
- msg.sender: The account which shall liquidate the borrower by repaying their debt and seizing their collateral.
- borrower: The account with negative account liquidity that shall be liquidated.
- repayAmount: The amount of the borrowed asset to be repaid and converted into collateral, specified in units of the underlying borrowed asset.
- eTokenCollateral: The address of the eToken currently held as collateral by a borrower, that the liquidator shall seize.
- RETURN: 0 on success, otherwise an Error code Before supplying an asset, users must first approve the eToken to access their token balance.
function liquidateBorrow(address borrower, address eTokenCollateral) payable
- msg.valuepayable: The amount of ether to be repaid and converted into collateral, in wei.
- msg.sender: The account which shall liquidate the borrower by repaying their debt and seizing their collateral.
- borrower: The account with negative account liquidity that shall be liquidated.
- eTokenCollateral: The address of the eToken currently held as collateral by a borrower, that the liquidator shall seize.
- RETURN: No return, reverts on error.
Solidity
Web3 1.0
EToken eToken = EToken(0x3FDB...);
EBEP20 eTokenCollateral = EBEP20(0x3FDA...);
require(eToken.liquidateBorrow.value(100)(0xBorrower, eTokenCollateral) == 0, "borrower underwater??");
const eToken = EBEP20.at(0x3FDA...);
const eTokenCollateral = EBNB.at(0x3FDB...);
await eToken.methods.liquidateBorrow(0xBorrower, 33, eTokenCollateral).send({from: 0xLiquidator});
Event | Description |
Mint(address minter, uint mintAmount, uint mintTokens) | Emitted upon a successful Mint. |
Redeem(address redeemer, uint redeemAmount, uint redeemTokens) | Emitted upon a successful Redeem. |
Borrow(address borrower, uint borrowAmount, uint accountBorrows, uint totalBorrows) | Emitted upon a successful Borrow. |
RepayBorrow(address payer, address borrower, uint repayAmount, uint accountBorrows, uint totalBorrows) | Emitted upon a successful Repay Borrow. |
LiquidateBorrow(address liquidator, address borrower, uint repayAmount, address cTokenCollateral, uint seizeTokens) | Emitted upon a successful Liquidate Borrow. |
Name | Description |
NO_ERROR | Not a failure. |
UNAUTHORIZED | The sender is not authorized to perform this action. |
BAD_INPUT | An invalid argument was supplied by the caller. |
ESGTROLLER_REJECTION | The action would violate the esgtroller policy. |
ESGTROLLER_CALCULATION_ERROR | An internal calculation has failed in the esgtroller. |
INTEREST_RATE_MODEL_ERROR | The interest rate model returned an invalid value. |
INVALID_ACCOUNT_PAIR | The specified combination of accounts is invalid. |
INVALID_CLOSE_AMOUNT_REQUESTED | The amount to liquidate is invalid. |
INVALID_COLLATERAL_FACTOR | The collateral factor is invalid. |
MATH_ERROR | A math calculation error occurred. |
MARKET_NOT_FRESH | Interest has not been properly accrued. |
MARKET_NOT_LISTED | The market is not currently listed by its esgtroller. |
TOKEN_INSUFFICIENT_ALLOWANCE | BEP-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. |
TOKEN_INSUFFICIENT_BALANCE | Caller does not have sufficient balance in the BEP-20 contract to complete the desired action. |
TOKEN_INSUFFICIENT_CASH | The market does not have a sufficient cash balance to complete the transaction. You may attempt this transaction again later. |
TOKEN_TRANSFER_IN_FAILED | Failure in BEP-20 when transfering token into the market. |
TOKEN_TRANSFER_OUT_FAILED | Failure in BEP-20 when transfering token out of the market. |
Name |
ACCEPT_ADMIN_PENDING_ADMIN_CHECK |
ACCRUE_INTEREST_ACCUMULATED_INTEREST_CALCULATION_FAILED |
ACCRUE_INTEREST_BORROW_RATE_CALCULATION_FAILED |
ACCRUE_INTEREST_NEW_BORROW_INDEX_CALCULATION_FAILED |
ACCRUE_INTEREST_NEW_TOTAL_BORROWS_CALCULATION_FAILED |
ACCRUE_INTEREST_NEW_TOTAL_RESERVES_CALCULATION_FAILED |
ACCRUE_INTEREST_SIMPLE_INTEREST_FACTOR_CALCULATION_FAILED |
BORROW_ACCUMULATED_BALANCE_CALCULATION_FAILED |
BORROW_ACCRUE_INTEREST_FAILED |
BORROW_CASH_NOT_AVAILABLE |
BORROW_FRESHNESS_CHECK |
BORROW_NEW_TOTAL_BALANCE_CALCULATION_FAILED |
BORROW_NEW_ACCOUNT_BORROW_BALANCE_CALCULATION_FAILED |
BORROW_MARKET_NOT_LISTED |
BORROW_ETROLLER_REJECTION |
LIQUIDATE_ACCRUE_BORROW_INTEREST_FAILED |
LIQUIDATE_ACCRUE_COLLATERAL_INTEREST_FAILED |
LIQUIDATE_COLLATERAL_FRESHNESS_CHECK |
LIQUIDATE_ESGTROLLER_REJECTION |
LIQUIDATE_E SGTROLLER_CALCULATE_AMOUNT_SEIZE_FAILED |
LIQUIDATE_CLOSE_AMOUNT_IS_UINT_MAX |
LIQUIDATE_CLOSE_AMOUNT_IS_ZERO |
LIQUIDATE_FRESHNESS_CHECK |
LIQUIDATE_LIQUIDATOR_IS_BORROWER |
LIQUIDATE_REPAY_BORROW_FRESH_FAILED |
LIQUIDATE_SEIZE_BALANCE_INCREMENT_FAILED |
LIQUIDATE_SEIZE_BALANCE_DECREMENT_FAILED |
LIQUIDATE_SEIZE_ESGTROLLER_REJECTION |
LIQUIDATE_SEIZE_LIQUIDATOR_IS_BORROWER |
LIQUIDATE_SEIZE_TOO_MUCH |
MINT_ACCRUE_INTEREST_FAILED |
MINT_ESGTROLLER_REJECTION |
MINT_EXCHANGE_CALCULATION_FAILED |
MINT_EXCHANGE_RATE_READ_FAILED |
MINT_FRESHNESS_CHECK |
MINT_NEW_ACCOUNT_BALANCE_CALCULATION_FAILED |
MINT_NEW_TOTAL_SUPPLY_CALCULATION_FAILED |
MINT_TRANSFER_IN_FAILED |
MINT_TRANSFER_IN_NOT_POSSIBLE |
REDEEM_ACCRUE_INTEREST_FAILED |
REDEEM_ESGTROLLER_REJECTION |
REDEEM_EXCHANGE_TOKENS_CALCULATION_FAILED |
REDEEM_EXCHANGE_AMOUNT_CALCULATION_FAILED |
REDEEM_EXCHANGE_RATE_READ_FAILED |
REDEEM_FRESHNESS_CHECK |
REDEEM_NEW_ACCOUNT_BALANCE_CALCULATION_FAILED |
REDEEM_NEW_TOTAL_SUPPLY_CALCULATION_FAILED |
REDEEM_TRANSFER_OUT_NOT_POSSIBLE |
REDUCE_RESERVES_ACCRUE_INTEREST_FAILED |
REDUCE_RESERVES_ADMIN_CHECK |
REDUCE_RESERVES_CASH_NOT_AVAILABLE |
REDUCE_RESERVES_FRESH_CHECK |
REDUCE_RESERVES_VALIDATION |
REPAY_BEHALF_ACCRUE_INTEREST_FAILED |
REPAY_BORROW_ACCRUE_INTEREST_FAILED |
REPAY_BORROW_ACCUMULATED_BALANCE_CALCULATION_FAILED |
REPAY_BORROW_ESGTROLLER_REJECTION |
REPAY_BORROW_FRESHNESS_CHECK |
REPAY_BORROW_NEW_ACCOUNT_BORROW_BALANCE_CALCULATION_FAILED |
REPAY_BORROW_NEW_TOTAL_BALANCE_CALCULATION_FAILED |
REPAY_BORROW_TRANSFER_IN_NOT_POSSIBLE |
SET_COLLATERAL_FACTOR_OWNER_CHECK |
SET_COLLATERAL_FACTOR_VALIDATION |
SET_ESGTROLLER_OWNER_CHECK |
SET_INTEREST_RATE_MODEL_ACCRUE_INTEREST_FAILED |
SET_INTEREST_RATE_MODEL_FRESH_CHECK |
SET_INTEREST_RATE_MODEL_OWNER_CHECK |
SET_MAX_ASSETS_OWNER_CHECK |
SET_ORACLE_MARKET_NOT_LISTED |
SET_PENDING_ADMIN_OWNER_CHECK |
SET_RESERVE_FACTOR_ACCRUE_INTEREST_FAILED |
SET_RESERVE_FACTOR_ADMIN_CHECK |
SET_RESERVE_FACTOR_FRESH_CHECK |
SET_RESERVE_FACTOR_BOUNDS_CHECK |
TRANSFER_ESGTROLLER_REJECTION |
TRANSFER_NOT_ALLOWED |
TRANSFER_NOT_ENOUGH |
TRANSFER_TOO_MUCH |
Each eToken is convertible into an ever increasing quantity of the underlying asset, as interest accrues in the market. The exchange rate between a eToken and the underlying asset is equal to:
exchangeRate = (getCash() + totalBorrows() - totalReserves()) / totalSupply()
function exchangeRateCurrent() returns (uint)
- RETURN: The current exchange rate as an unsigned integer, scaled by 1 * 10^(18 - 8 + Underlying Token Decimals).
Solidity
Web3 1.0
EBEP20 eToken = EToken(0x3FDA...);
uint exchangeRateMantissa = eToken.exchangeRateCurrent();
const eToken = EToken.at(0x3FDB...);
const exchangeRate = (await eToken.methods.exchangeRateCurrent().call()) / 1e18;
Tip: note the use of call vs. send to invoke the function from off-chain without incurring gas costs.
Cash is the amount of underlying balance owned by this eToken contract. One may query the total amount of cash currently available to this market.
function getCash() returns (uint)
- RETURN: The quantity of underlying asset owned by the contract.
Solidity
Web3 1.0
EBEP20 eToken = EToken(0x3FDA...);
uint cash = eToken.getCash();
const eToken = EToken.at(0x3FDB...);
const cash = (await eToken.methods.getCash().call());
Total Borrows is the amount of underlying currently loaned out by the market, and the amount upon which interest is accumulated to suppliers of the market.
function totalBorrowsCurrent() returns (uint)
- RETURN: The total amount of borrowed underlying, with interest.
Solidity
Web3 1.0
EBEP20 eToken = EToken(0x3FDA...);
uint borrows = eToken.totalBorrowsCurrent();
const eToken = EToken.at(0x3FDB...);
const borrows = (await eToken.methods.totalBorrowsCurrent().call());
A user who borrows assets from the protocol is subject to accumulated interest based on the current borrow rate. Interest is accumulated every block and integrations may use this function to obtain the current value of a user's borrow balance with interest.
function borrowBalanceCurrent(address account) returns (uint)
- account: The account which borrowed the assets.
- RETURN: The user's current borrow balance (with interest) in units of the underlying asset
Solidity
Web3 1.0
EBEP20 eToken = EToken(0x3FDA...);
uint borrows = eToken.borrowBalanceCurrent(msg.caller);
const eToken = EToken.at(0x3FDB...);
const borrows = await eToken.methods.borrowBalanceCurrent(account).call();
At any point in time one may query the contract to get the current borrow rate per block.
function borrowRatePerBlock() returns (uint)
- RETURN: The current borrow rate as an unsigned integer, scaled by 1e18.
Solidity
Web3 1.0
EBEP20 eToken = EToken(0x3FDA...);
uint borrowRateMantissa = eToken.borrowRatePerBlock();
const eToken = EToken.at(0x3FDB...);
const borrowRate = (await eToken.methods.borrowRatePerBlock().call()) / 1e18;
Total Supply is the number of tokens currently in circulation in this eToken market. It is part of the EIP-20 interface of the eToken contract.
function totalSupply() returns (uint)
- RETURN: The total number of tokens in circulation for the market.
Solidity
Web3 1.0
EBEP20 eToken = EToken(0x3FDA...);
uint tokens = eToken.totalSupply();
const eToken = EToken.at(0x3FDB...);
const tokens = (await eToken.methods.totalSupply().call());
The user's underlying balance, representing their assets in the protocol, is equal to the user's eToken balance multiplied by the Exchange Rate.
function balanceOfUnderlying(address account) returns (uint)
- account: The account to get the underlying balance.
- RETURN: The amount of underlying currently owned by the account.
Solidity
Web3 1.0
EBEP20 eToken = EToken(0x3FDA...);
uint tokens = eToken.balanceOfUnderlying(msg.caller);
const eToken = EToken.at(0x3FDB...);
const tokens = await eToken.methods.balanceOfUnderlying(account).call();
At any point in time one may query the contract to get the current supply rate per block. The supply rate is derived from the borrow rate, reserve factor and the amount of total borrows.
function supplyRatePerBlock() returns (uint)
- RETURN: The current supply rate as an unsigned integer, scaled by 1e18.
Solidity
Web3 1.0
EBEP20 eToken = EToken(0x3FDA...);
uint supplyRateMantissa = eToken.supplyRatePerBlock();
const eToken = EToken.at(0x3FDB...);
const supplyRate = (await eToken.methods.supplyRatePerBlock().call()) / 1e18;
Reserves are an accounting entry in each eToken contract that represents a portion of historical interest set aside as cash which can be withdrawn or transferred through the protocol's governance. A small portion of borrower interest accrues into the protocol, determined by the reserve factor.
function totalReserves() returns (uint)
- RETURN: The total amount of reserves held in the market.
Solidity
Web3 1.0
EBEP20 eToken = EToken(0x3FDA...);
uint reserves = eToken.totalReserves();
const eToken = EToken.at(0x3FDB...);
const reserves = (await eToken.methods.totalReserves().call());
The reserve factor defines the portion of borrower interest that is converted into reserves.
function reserveFactorMantissa() returns (uint)
- RETURN: The current reserve factor as an unsigned integer, scaled by 1e18.
Solidity
Web3 1.0
EBEP20 eToken = EToken(0x3FDA...);
uint reserveFactorMantissa = eToken.reserveFactorMantissa();
const eToken = EToken.at(0x3FDB...);
const reserveFactor = (await eToken.methods.reserveFactorMantissa().call()) / 1e18;
Last modified 1yr ago