API

FraxlendPairCore

An abstract contract which contains the core logic and storage for the FraxlendPair

constructor

constructor(bytes _configData, bytes _immutables, uint256 _maxLTV, uint256 _liquidationFee, uint256 _maturityDate, uint256 _penaltyRate, bool _isBorrowerWhitelistActive, bool _isLenderWhitelistActive) internal

The constructor function is called on deployment

Param	Type	Description
_configData	bytes	abi.encode(address _asset, address _collateral, address _oracleMultiply, address _oracleDivide, uint256 _oracleNormalization, address _rateContract, bytes memory _rateInitData)
_immutables	bytes
_maxLTV	uint256	The Maximum Loan-To-Value for a borrower to be considered solvent (1e5 precision)
_liquidationFee	uint256	The fee paid to liquidators given as a % of the repayment (1e5 precision)
_maturityDate	uint256	The maturityDate date of the Pair
_penaltyRate	uint256	The interest rate after maturity date
_isBorrowerWhitelistActive	bool	Enables borrower whitelist
_isLenderWhitelistActive	bool	Enables lender whitelist

initialize

function initialize(string _name, address[] _approvedBorrowers, address[] _approvedLenders, bytes _rateInitCallData) external

The initialize function is called immediately after deployment

This function can only be called by the deployer

Param	Type	Description
_name	string	The name of the contract
_approvedBorrowers	address[]	An array of approved borrower addresses
_approvedLenders	address[]	An array of approved lender addresses
_rateInitCallData	bytes	The configuration data for the Rate Calculator contract

_totalAssetAvailable

function _totalAssetAvailable(struct VaultAccount _totalAsset, struct VaultAccount _totalBorrow) internal pure returns (uint256)

The _totalAssetAvailable function returns the total balance of Asset Tokens in the contract

Param	Type	Description
_totalAsset	struct VaultAccount	VaultAccount struct which stores total amount and shares for assets
_totalBorrow	struct VaultAccount	VaultAccount struct which stores total amount and shares for borrows

Return	Type	Description
[0]	uint256	The balance of Asset Tokens held by contract

_isSolvent

function _isSolvent(address _borrower, uint256 _exchangeRate) internal view returns (bool)

The _isSolvent function determines if a given borrower is solvent given an exchange rate

Param	Type	Description
_borrower	address	The borrower address to check
_exchangeRate	uint256	The exchange rate, i.e. the amount of collateral to buy 1e18 asset

Return	Type	Description
[0]	bool	Whether borrower is solvent

_isPastMaturity

function _isPastMaturity() internal view returns (bool)

The _isPastMaturity function determines if the current block timestamp is past the maturityDate date

Return	Type	Description
[0]	bool	Whether or not the debt is past maturity

isSolvent

modifier isSolvent(address _borrower)

Checks for solvency AFTER executing contract code

Param	Type	Description
_borrower	address	The borrower whose solvency we will check

approvedBorrower

modifier approvedBorrower()

Checks if msg.sender is an approved Borrower

approvedLender

modifier approvedLender(address _receiver)

Checks if msg.sender and _receiver are both an approved Lender

Param	Type	Description
_receiver	address	An additional receiver address to check

isNotPastMaturity

modifier isNotPastMaturity()

Ensure function is not called when passed maturity

AddInterest

event AddInterest(uint256 _interestEarned, uint256 _rate, uint256 _deltaTime, uint256 _feesAmount, uint256 _feesShare)

The AddInterest event is emitted when interest is accrued by borrowers

Param	Type	Description
_interestEarned	uint256	The total interest accrued by all borrowers
_rate	uint256	The interest rate used to calculate accrued interest
_deltaTime	uint256	The time elapsed since last interest accrual
_feesAmount	uint256	The amount of fees paid to protocol
_feesShare	uint256	The amount of shares distributed to protocol

UpdateRate

event UpdateRate(uint256 _ratePerSec, uint256 _deltaTime, uint256 _utilizationRate, uint256 _newRatePerSec)

The UpdateRate event is emitted when the interest rate is updated

Param	Type	Description
_ratePerSec	uint256	The old interest rate (per second)
_deltaTime	uint256	The time elapsed since last update
_utilizationRate	uint256	The utilization of assets in the Pair
_newRatePerSec	uint256	The new interest rate (per second)

addInterest

function addInterest() external returns (uint256 _interestEarned, uint256 _feesAmount, uint256 _feesShare, uint64 _newRate)

The addInterest function is a public implementation of _addInterest and allows 3rd parties to trigger interest accrual

Return	Type	Description
_interestEarned	uint256	The amount of interest accrued by all borrowers
_feesAmount	uint256
_feesShare	uint256
_newRate	uint64

_addInterest

function _addInterest() internal returns (uint256 _interestEarned, uint256 _feesAmount, uint256 _feesShare, uint64 _newRate)

The _addInterest function is invoked prior to every external function and is used to accrue interest and update interest rate

Can only called once per block

Return	Type	Description
_interestEarned	uint256	The amount of interest accrued by all borrowers
_feesAmount	uint256
_feesShare	uint256
_newRate	uint64

UpdateExchangeRate

event UpdateExchangeRate(uint256 _rate)

The UpdateExchangeRate event is emitted when the Collateral:Asset exchange rate is updated

Param	Type	Description
_rate	uint256	The new rate given as the amount of Collateral Token to buy 1e18 Asset Token

updateExchangeRate

function updateExchangeRate() external returns (uint256 _exchangeRate)

The updateExchangeRate function is the external implementation of _updateExchangeRate.

This function is invoked at most once per block as these queries can be expensive

Return	Type	Description
_exchangeRate	uint256	The new exchange rate

_updateExchangeRate

function _updateExchangeRate() internal returns (uint256 _exchangeRate)

The _updateExchangeRate function retrieves the latest exchange rate. i.e how much collateral to buy 1e18 asset.

This function is invoked at most once per block as these queries can be expensive

Return	Type	Description
_exchangeRate	uint256	The new exchange rate

_deposit

function _deposit(struct VaultAccount _totalAsset, uint128 _amount, uint128 _shares, address _receiver) internal

The _deposit function is the internal implementation for lending assets

Caller must invoke ERC20.approve on the Asset Token contract prior to calling function

Param	Type	Description
_totalAsset	struct VaultAccount	An in memory VaultAccount struct representing the total amounts and shares for the Asset Token
_amount	uint128	The amount of Asset Token to be transferred
_shares	uint128	The amount of Asset Shares (fTokens) to be minted
_receiver	address	The address to receive the Asset Shares (fTokens)

deposit

function deposit(uint256 _amount, address _receiver) external returns (uint256 _sharesReceived)

The deposit function allows a user to Lend Assets by specifying the amount of Asset Tokens to lend

Caller must invoke ERC20.approve on the Asset Token contract prior to calling function

Param	Type	Description
_amount	uint256	The amount of Asset Token to transfer to Pair
_receiver	address	The address to receive the Asset Shares (fTokens)

Return	Type	Description
_sharesReceived	uint256	The number of fTokens received for the deposit

mint

function mint(uint256 _shares, address _receiver) external returns (uint256 _amountReceived)

The mint function allows a user to Lend assets by specifying the number of Assets Shares (fTokens) to mint

Caller must invoke ERC20.approve on the Asset Token contract prior to calling function

Param	Type	Description
_shares	uint256	The number of Asset Shares (fTokens) that a user wants to mint
_receiver	address	The address to receive the Asset Shares (fTokens)

Return	Type	Description
_amountReceived	uint256	The amount of Asset Tokens transferred to the Pair

_redeem

function _redeem(struct VaultAccount _totalAsset, uint128 _amountToReturn, uint128 _shares, address _receiver, address _owner) internal

The _redeem function is an internal implementation which allows a Lender to pull their Asset Tokens out of the Pair

Caller must invoke ERC20.approve on the Asset Token contract prior to calling function

Param	Type	Description
_totalAsset	struct VaultAccount	An in-memory VaultAccount struct which holds the total amount of Asset Tokens and the total number of Asset Shares (fTokens)
_amountToReturn	uint128	The number of Asset Tokens to return
_shares	uint128	The number of Asset Shares (fTokens) to burn
_receiver	address	The address to which the Asset Tokens will be transferred
_owner	address	The owner of the Asset Shares (fTokens)

redeem

function redeem(uint256 _shares, address _receiver, address _owner) external returns (uint256 _amountToReturn)

The redeem function allows the caller to redeem their Asset Shares for Asset Tokens

Param	Type	Description
_shares	uint256	The number of Asset Shares (fTokens) to burn for Asset Tokens
_receiver	address	The address to which the Asset Tokens will be transferred
_owner	address	The owner of the Asset Shares (fTokens)

Return	Type	Description
_amountToReturn	uint256	The amount of Asset Tokens to be transferred

withdraw

function withdraw(uint256 _amount, address _receiver, address _owner) external returns (uint256 _shares)

The withdraw function allows a user to redeem their Asset Shares for a specified amount of Asset Tokens

Param	Type	Description
_amount	uint256	The amount of Asset Tokens to be transferred in exchange for burning Asset Shares
_receiver	address	The address to which the Asset Tokens will be transferred
_owner	address	The owner of the Asset Shares (fTokens)

Return	Type	Description
_shares	uint256	The number of Asset Shares (fTokens) burned

BorrowAsset

event BorrowAsset(address _borrower, address _receiver, uint256 _borrowAmount, uint256 _sharesAdded)

The BorrowAsset event is emitted when a borrower increases their position

Param	Type	Description
_borrower	address	The borrower whose account was debited
_receiver	address	The address to which the Asset Tokens were transferred
_borrowAmount	uint256	The amount of Asset Tokens transferred
_sharesAdded	uint256	The number of Borrow Shares the borrower was debited

_borrowAsset

function _borrowAsset(uint128 _borrowAmount, address _receiver) internal returns (uint256 _sharesAdded)

The _borrowAsset function is the internal implementation for borrowing assets

Param	Type	Description
_borrowAmount	uint128	The amount of the Asset Token to borrow
_receiver	address	The address to receive the Asset Tokens

Return	Type	Description
_sharesAdded	uint256	The amount of borrow shares the msg.sender will be debited

borrowAsset

function borrowAsset(uint256 _borrowAmount, uint256 _collateralAmount, address _receiver) external returns (uint256 _shares)

The borrowAsset function allows a user to open/increase a borrow position

Borrower must call ERC20.approve on the Collateral Token contract if applicable

Param	Type	Description
_borrowAmount	uint256	The amount of Asset Token to borrow
_collateralAmount	uint256	The amount of Collateral Token to transfer to Pair
_receiver	address	The address which will receive the Asset Tokens

Return	Type	Description
_shares	uint256	The number of borrow Shares the msg.sender will be debited

_addCollateral

function _addCollateral(address _sender, uint256 _collateralAmount, address _borrower) internal

The _addCollateral function is an internal implementation for adding collateral to a borrowers position

Param	Type	Description
_sender	address	The source of funds for the new collateral
_collateralAmount	uint256	The amount of Collateral Token to be transferred
_borrower	address	The borrower account for which the collateral should be credited

addCollateral

function addCollateral(uint256 _collateralAmount, address _borrower) external

The addCollateral function allows the caller to add Collateral Token to a borrowers position

msg.sender must call ERC20.approve() on the Collateral Token contract prior to invocation

Param	Type	Description
_collateralAmount	uint256	The amount of Collateral Token to be added to borrower's position
_borrower	address	The account to be credited

RemoveCollateral

event RemoveCollateral(address _sender, uint256 _collateralAmount, address _receiver, address _borrower)

The RemoveCollateral event is emitted when collateral is removed from a borrower's position

Param	Type	Description
_sender	address	The account from which funds are transferred
_collateralAmount	uint256	The amount of Collateral Token to be transferred
_receiver	address	The address to which Collateral Tokens will be transferred
_borrower	address

_removeCollateral

function _removeCollateral(uint256 _collateralAmount, address _receiver, address _borrower) internal

The _removeCollateral function is the internal implementation for removing collateral from a borrower's position

Param	Type	Description
_collateralAmount	uint256	The amount of Collateral Token to remove from the borrower's position
_receiver	address	The address to receive the Collateral Token transferred
_borrower	address	The borrower whose account will be debited the Collateral amount

removeCollateral

function removeCollateral(uint256 _collateralAmount, address _receiver) external

The removeCollateral function is used to remove collateral from msg.sender's borrow position

msg.sender must be solvent after invocation or transaction will revert

Param	Type	Description
_collateralAmount	uint256	The amount of Collateral Token to transfer
_receiver	address	The address to receive the transferred funds

RepayAsset

event RepayAsset(address _sender, address _borrower, uint256 _amountToRepay, uint256 _shares)

The RepayAsset event is emitted whenever a debt position is repaid

Param	Type	Description
_sender	address	The msg.sender of the transaction
_borrower	address	The borrower whose account will be credited
_amountToRepay	uint256	The amount of Asset token to be transferred
_shares	uint256	The amount of Borrow Shares which will be debited from the borrower after repayment

_repayAsset

function _repayAsset(struct VaultAccount _totalBorrow, uint128 _amountToRepay, uint128 _shares, address _payer, address _borrower) internal

The _repayAsset function is the internal implementation for repaying a borrow position

The payer must have called ERC20.approve() on the Asset Token contract prior to invocation

Param	Type	Description
_totalBorrow	struct VaultAccount	An in memory copy of the totalBorrow VaultAccount struct
_amountToRepay	uint128	The amount of Asset Token to transfer
_shares	uint128	The number of Borrow Shares the sender is repaying
_payer	address	The address from which funds will be transferred
_borrower	address	The borrower account which will be credited

repayAsset

function repayAsset(uint256 _shares, address _borrower) external returns (uint256 _amountToRepay)

The repayAsset function allows the caller to pay down the debt for a given borrower.

Caller must first invoke ERC20.approve() for the Asset Token contract

Param	Type	Description
_shares	uint256	The number of Borrow Shares which will be repaid by the call
_borrower	address	The account for which the debt will be reduced

Return	Type	Description
_amountToRepay	uint256	The amount of Asset Tokens which were transferred in order to repay the Borrow Shares

Liquidate

event Liquidate(address _borrower, uint256 _collateralForLiquidator, uint256 _shares)

The Liquidate event is emitted when a liquidation occurs

Param	Type	Description
_borrower	address	The borrower account for which the liquidation occured
_collateralForLiquidator	uint256	The amount of Collateral Token transferred to the liquidator
_shares	uint256	The number of Borrow Shares the liquidator repaid on behalf of the borrower

liquidate

function liquidate(uint256 _shares, address _borrower) external returns (uint256 _collateralForLiquidator)

The liquidate function allows a third party to repay a borrower's debt if they have become insolvent

Caller must invoke ERC20.approve on the Asset Token contract prior to calling Liquidate()

Param	Type	Description
_shares	uint256	The number of Borrow Shares repaid by the liquidator
_borrower	address	The account for which the repayment is credited and from whom collateral will be taken

Return	Type	Description
_collateralForLiquidator	uint256	The amount of Collateral Token transferred to the liquidator

LeveragedPosition

event LeveragedPosition(address _borrower, address _swapperAddress, uint256 _borrowAmount, uint256 _borrowShares, uint256 _initialCollateralAmount, uint256 _amountCollateralOut)

The LeveragedPosition event is emitted when a borrower takes out a new leveraged position

Param	Type	Description
_borrower	address	The account for which the debt is debited
_swapperAddress	address	The address of the swapper which conforms the FraxSwap interface
_borrowAmount	uint256	The amount of Asset Token to be borrowed to be borrowed
_borrowShares	uint256	The number of Borrow Shares the borrower is credited
_initialCollateralAmount	uint256	The amount of initial Collateral Tokens supplied by the borrower
_amountCollateralOut	uint256	The amount of Collateral Token which was received for the Asset Tokens

leveragedPosition

function leveragedPosition(address _swapperAddress, uint256 _borrowAmount, uint256 _initialCollateralAmount, uint256 _amountCollateralOutMin, address[] _path) external returns (uint256 _totalCollateralBalance)

The leveragedPosition function allows a user to enter a leveraged borrow position with minimal upfront Collateral

Caller must invoke ERC20.approve() on the Collateral Token contract prior to calling function

Param	Type	Description
_swapperAddress	address	The address of the whitelisted swapper to use to swap borrowed Asset Tokens for Collateral Tokens
_borrowAmount	uint256	The amount of Asset Tokens borrowed
_initialCollateralAmount	uint256	The initial amount of Collateral Tokens supplied by the borrower
_amountCollateralOutMin	uint256	The minimum amount of Collateral Tokens to be received in exchange for the borrowed Asset Tokens
_path	address[]	An array containing the addresses of ERC20 tokens to swap. Adheres to UniV2 style path params.

Return	Type	Description
_totalCollateralBalance	uint256	The total amount of Collateral Tokens added to a users account (initial + swap)

RepayAssetWithCollateral

event RepayAssetWithCollateral(address _borrower, address _swapperAddress, uint256 _collateralToSwap, uint256 _amountAssetOut, uint256 _sharesRepaid)

The RepayAssetWithCollateral event is emitted whenever repayAssetWithCollateral() is invoked

Param	Type	Description
_borrower	address	The borrower account for which the repayment is taking place
_swapperAddress	address	The address of the whitelisted swapper to use for token swaps
_collateralToSwap	uint256	The amount of Collateral Token to swap and use for repayment
_amountAssetOut	uint256	The amount of Asset Token which was repaid
_sharesRepaid	uint256	The number of Borrow Shares which were repaid

repayAssetWithCollateral

function repayAssetWithCollateral(address _swapperAddress, uint256 _collateralToSwap, uint256 _amountAssetOutMin, address[] _path) external returns (uint256 _amountAssetOut)

The repayAssetWithCollateral function allows a borrower to repay their debt using existing collateral in contract

Param	Type	Description
_swapperAddress	address	The address of the whitelisted swapper to use for token swaps
_collateralToSwap	uint256	The amount of Collateral Tokens to swap for Asset Tokens
_amountAssetOutMin	uint256	The minimum amount of Asset Tokens to receive during the swap
_path	address[]	An array containing the addresses of ERC20 tokens to swap. Adheres to UniV2 style path params.

Return	Type	Description
_amountAssetOut	uint256	The amount of Asset Tokens received for the Collateral Tokens, the amount the borrowers account was credited