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SwapFlashLoan

Swap - A StableSwap implementation in solidity.
This contract is responsible for custody of closely pegged assets (eg. group of stablecoins) and automatic market making system. Users become an LP (Liquidity Provider) by depositing their tokens in desired ratios for an exchange of the pool token that represents their share of the pool. Users can burn pool tokens and withdraw their share of token(s). Each time a swap between the pooled tokens happens, a set fee incurs which effectively gets distributed to the LPs. In case of emergencies, admin can pause additional deposits, swaps, or single-asset withdraws - which stops the ratio of the tokens in the pool from changing. Users can always withdraw their tokens via multi-asset withdraws.
Most of the logic is stored as a library SwapUtils for the sake of reducing contract's deployment size.

Methods

MAX_BPS

function MAX_BPS() external view returns (uint256)

Returns

Name
Type
Description
_0
uint256
undefined

addLiquidity

function addLiquidity(uint256[] amounts, uint256 minToMint, uint256 deadline) external nonpayable returns (uint256)
Add liquidity to the pool with the given amounts of tokens

Parameters

Name
Type
Description
amounts
uint256[]
the amounts of each token to add, in their native precision
minToMint
uint256
the minimum LP tokens adding this amount of liquidity should mint, otherwise revert. Handy for front-running mitigation
deadline
uint256
latest timestamp to accept this transaction

Returns

Name
Type
Description
_0
uint256
amount of LP token user minted and received

calculateRemoveLiquidity

function calculateRemoveLiquidity(uint256 amount) external view returns (uint256[])
A simple method to calculate amount of each underlying tokens that is returned upon burning given amount of LP tokens

Parameters

Name
Type
Description
amount
uint256
the amount of LP tokens that would be burned on withdrawal

Returns

Name
Type
Description
_0
uint256[]
array of token balances that the user will receive

calculateRemoveLiquidityOneToken

function calculateRemoveLiquidityOneToken(uint256 tokenAmount, uint8 tokenIndex) external view returns (uint256 availableTokenAmount)
Calculate the amount of underlying token available to withdraw when withdrawing via only single token

Parameters

Name
Type
Description
tokenAmount
uint256
the amount of LP token to burn
tokenIndex
uint8
index of which token will be withdrawn

Returns

Name
Type
Description
availableTokenAmount
uint256
calculated amount of underlying token available to withdraw

calculateSwap

function calculateSwap(uint8 tokenIndexFrom, uint8 tokenIndexTo, uint256 dx) external view returns (uint256)
Calculate amount of tokens you receive on swap

Parameters

Name
Type
Description
tokenIndexFrom
uint8
the token the user wants to sell
tokenIndexTo
uint8
the token the user wants to buy
dx
uint256
the amount of tokens the user wants to sell. If the token charges a fee on transfers, use the amount that gets transferred after the fee.

Returns

Name
Type
Description
_0
uint256
amount of tokens the user will receive

calculateTokenAmount

function calculateTokenAmount(uint256[] amounts, bool deposit) external view returns (uint256)
A simple method to calculate prices from deposits or withdrawals, excluding fees but including slippage. This is helpful as an input into the various "min" parameters on calls to fight front-running
This shouldn't be used outside frontends for user estimates.

Parameters

Name
Type
Description
amounts
uint256[]
an array of token amounts to deposit or withdrawal, corresponding to pooledTokens. The amount should be in each pooled token's native precision. If a token charges a fee on transfers, use the amount that gets transferred after the fee.
deposit
bool
whether this is a deposit or a withdrawal

Returns

Name
Type
Description
_0
uint256
token amount the user will receive

flashLoan

function flashLoan(address receiver, contract IERC20 token, uint256 amount, bytes params) external nonpayable
Borrow the specified token from this pool for this transaction only. This function will call IFlashLoanReceiver(receiver).executeOperation and the receiver must return the full amount of the token and the associated fee by the end of the callback transaction. If the conditions are not met, this call is reverted.

Parameters

Name
Type
Description
receiver
address
the address of the receiver of the token. This address must implement the IFlashLoanReceiver interface and the callback function executeOperation.
token
contract IERC20
the protocol fee in bps to be applied on the total flash loan fee
amount
uint256
the total amount to borrow in this transaction
params
bytes
optional data to pass along to the callback function

flashLoanFeeBPS

function flashLoanFeeBPS() external view returns (uint256)

Returns

Name
Type
Description
_0
uint256
undefined

getA

function getA() external view returns (uint256)
Return A, the amplification coefficient * n * (n - 1)
See the StableSwap paper for details

Returns

Name
Type
Description
_0
uint256
A parameter

getAPrecise

function getAPrecise() external view returns (uint256)
Return A in its raw precision form
See the StableSwap paper for details

Returns

Name
Type
Description
_0
uint256
A parameter in its raw precision form

getAdminBalance

function getAdminBalance(uint256 index) external view returns (uint256)
This function reads the accumulated amount of admin fees of the token with given index

Parameters

Name
Type
Description
index
uint256
Index of the pooled token

Returns

Name
Type
Description
_0
uint256
admin's token balance in the token's precision

getToken

function getToken(uint8 index) external view returns (contract IERC20)
Return address of the pooled token at given index. Reverts if tokenIndex is out of range.

Parameters

Name
Type
Description
index
uint8
the index of the token

Returns

Name
Type
Description
_0
contract IERC20
address of the token at given index

getTokenBalance

function getTokenBalance(uint8 index) external view returns (uint256)
Return current balance of the pooled token at given index

Parameters

Name
Type
Description
index
uint8
the index of the token

Returns

Name
Type
Description
_0
uint256
current balance of the pooled token at given index with token's native precision

getTokenIndex

function getTokenIndex(address tokenAddress) external view returns (uint8)
Return the index of the given token address. Reverts if no matching token is found.

Parameters

Name
Type
Description
tokenAddress
address
address of the token

Returns

Name
Type
Description
_0
uint8
the index of the given token address

getVirtualPrice

function getVirtualPrice() external view returns (uint256)
Get the virtual price, to help calculate profit

Returns

Name
Type
Description
_0
uint256
the virtual price, scaled to the POOL_PRECISION_DECIMALS

initialize

function initialize(contract IERC20[] _pooledTokens, uint8[] decimals, string lpTokenName, string lpTokenSymbol, uint256 _a, uint256 _fee, uint256 _adminFee, address lpTokenTargetAddress) external nonpayable
Initializes this Swap contract with the given parameters. This will also clone a LPToken contract that represents users' LP positions. The owner of LPToken will be this contract - which means only this contract is allowed to mint/burn tokens.

Parameters

Name
Type
Description
_pooledTokens
contract IERC20[]
an array of ERC20s this pool will accept
decimals
uint8[]
the decimals to use for each pooled token, eg 8 for WBTC. Cannot be larger than POOL_PRECISION_DECIMALS
lpTokenName
string
the long-form name of the token to be deployed
lpTokenSymbol
string
the short symbol for the token to be deployed
_a
uint256
the amplification coefficient * n * (n - 1). See the StableSwap paper for details
_fee
uint256
default swap fee to be initialized with
_adminFee
uint256
default adminFee to be initialized with
lpTokenTargetAddress
address
the address of an existing LPToken contract to use as a target

owner

function owner() external view returns (address)
Returns the address of the current owner.

Returns

Name
Type
Description
_0
address
undefined

pause

function pause() external nonpayable
Pause the contract. Revert if already paused.

paused

function paused() external view returns (bool)
Returns true if the contract is paused, and false otherwise.

Returns

Name
Type
Description
_0
bool
undefined

protocolFeeShareBPS

function protocolFeeShareBPS() external view returns (uint256)

Returns

Name
Type
Description
_0
uint256
undefined

rampA

function rampA(uint256 futureA, uint256 futureTime) external nonpayable
Start ramping up or down A parameter towards given futureA and futureTime Checks if the change is too rapid, and commits the new A value only when it falls under the limit range.

Parameters

Name
Type
Description
futureA
uint256
the new A to ramp towards
futureTime
uint256
timestamp when the new A should be reached

removeLiquidity

function removeLiquidity(uint256 amount, uint256[] minAmounts, uint256 deadline) external nonpayable returns (uint256[])
Burn LP tokens to remove liquidity from the pool. Withdraw fee that decays linearly over period of 4 weeks since last deposit will apply.
Liquidity can always be removed, even when the pool is paused.

Parameters

Name
Type
Description
amount
uint256
the amount of LP tokens to burn
minAmounts
uint256[]
the minimum amounts of each token in the pool acceptable for this burn. Useful as a front-running mitigation
deadline
uint256
latest timestamp to accept this transaction

Returns

Name
Type
Description
_0
uint256[]
amounts of tokens user received

removeLiquidityImbalance

function removeLiquidityImbalance(uint256[] amounts, uint256 maxBurnAmount, uint256 deadline) external nonpayable returns (uint256)
Remove liquidity from the pool, weighted differently than the pool's current balances. Withdraw fee that decays linearly over period of 4 weeks since last deposit will apply.

Parameters

Name
Type
Description
amounts
uint256[]
how much of each token to withdraw
maxBurnAmount
uint256
the max LP token provider is willing to pay to remove liquidity. Useful as a front-running mitigation.
deadline
uint256
latest timestamp to accept this transaction

Returns

Name
Type
Description
_0
uint256
amount of LP tokens burned

removeLiquidityOneToken

function removeLiquidityOneToken(uint256 tokenAmount, uint8 tokenIndex, uint256 minAmount, uint256 deadline) external nonpayable returns (uint256)
Remove liquidity from the pool all in one token. Withdraw fee that decays linearly over period of 4 weeks since last deposit will apply.

Parameters

Name
Type
Description
tokenAmount
uint256
the amount of the token you want to receive
tokenIndex
uint8
the index of the token you want to receive
minAmount
uint256
the minimum amount to withdraw, otherwise revert
deadline
uint256
latest timestamp to accept this transaction

Returns

Name
Type
Description
_0
uint256
amount of chosen token user received

renounceOwnership

function renounceOwnership() external nonpayable
Leaves the contract without owner. It will not be possible to call onlyOwner functions anymore. Can only be called by the current owner. NOTE: Renouncing ownership will leave the contract without an owner, thereby removing any functionality that is only available to the owner.

setAdminFee

function setAdminFee(uint256 newAdminFee) external nonpayable
Update the admin fee. Admin fee takes portion of the swap fee.

Parameters

Name
Type
Description
newAdminFee
uint256
new admin fee to be applied on future transactions

setFlashLoanFees

function setFlashLoanFees(uint256 newFlashLoanFeeBPS, uint256 newProtocolFeeShareBPS) external nonpayable
Updates the flash loan fee parameters. This function can only be called by the owner.

Parameters

Name
Type
Description
newFlashLoanFeeBPS
uint256
the total fee in bps to be applied on future flash loans
newProtocolFeeShareBPS
uint256
the protocol fee in bps to be applied on the total flash loan fee

setSwapFee

function setSwapFee(uint256 newSwapFee) external nonpayable
Update the swap fee to be applied on swaps

Parameters

Name
Type
Description
newSwapFee
uint256
new swap fee to be applied on future transactions

stopRampA

function stopRampA() external nonpayable
Stop ramping A immediately. Reverts if ramp A is already stopped.

swap

function swap(uint8 tokenIndexFrom, uint8 tokenIndexTo, uint256 dx, uint256 minDy, uint256 deadline) external nonpayable returns (uint256)
Swap two tokens using this pool

Parameters

Name
Type
Description
tokenIndexFrom
uint8
the token the user wants to swap from
tokenIndexTo
uint8
the token the user wants to swap to
dx
uint256
the amount of tokens the user wants to swap from
minDy
uint256
the min amount the user would like to receive, or revert.
deadline
uint256
latest timestamp to accept this transaction

Returns

Name
Type
Description
_0
uint256
undefined

swapStorage

function swapStorage() external view returns (uint256 initialA, uint256 futureA, uint256 initialATime, uint256 futureATime, uint256 swapFee, uint256 adminFee, contract LPToken lpToken)

Returns

Name
Type
Description
initialA
uint256
undefined
futureA
uint256
undefined
initialATime
uint256
undefined
futureATime
uint256
undefined
swapFee
uint256
undefined
adminFee
uint256
undefined
lpToken
contract LPToken
undefined

transferOwnership

function transferOwnership(address newOwner) external nonpayable
Transfers ownership of the contract to a new account (newOwner). Can only be called by the current owner.

Parameters

Name
Type
Description
newOwner
address
undefined

unpause

function unpause() external nonpayable
Unpause the contract. Revert if already unpaused.

withdrawAdminFees

function withdrawAdminFees() external nonpayable
Withdraw all admin fees to the contract owner

Events

AddLiquidity

event AddLiquidity(address indexed provider, uint256[] tokenAmounts, uint256[] fees, uint256 invariant, uint256 lpTokenSupply)