Swap

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

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tokenIndex	uint8	index of which token will be withdrawn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

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

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

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)

Parameters

Name	Type	Description
provider indexed	address	undefined
tokenAmounts	uint256[]	undefined
fees	uint256[]	undefined
invariant	uint256	undefined
lpTokenSupply	uint256	undefined

NewAdminFee

event NewAdminFee(uint256 newAdminFee)

Parameters

Name	Type	Description
newAdminFee	uint256	undefined

NewSwapFee

event NewSwapFee(uint256 newSwapFee)

Parameters

Name	Type	Description
newSwapFee	uint256	undefined

OwnershipTransferred

event OwnershipTransferred(address indexed previousOwner, address indexed newOwner)

Parameters

Name	Type	Description
previousOwner indexed	address	undefined
newOwner indexed	address	undefined

Paused

event Paused(address account)

Parameters

Name	Type	Description
account	address	undefined

RampA

event RampA(uint256 oldA, uint256 newA, uint256 initialTime, uint256 futureTime)

Parameters

Name	Type	Description
oldA	uint256	undefined
newA	uint256	undefined
initialTime	uint256	undefined
futureTime	uint256	undefined

RemoveLiquidity

event RemoveLiquidity(address indexed provider, uint256[] tokenAmounts, uint256 lpTokenSupply)

Parameters

Name	Type	Description
provider indexed	address	undefined
tokenAmounts	uint256[]	undefined
lpTokenSupply	uint256	undefined

RemoveLiquidityImbalance

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

Parameters

Name	Type	Description
provider indexed	address	undefined
tokenAmounts	uint256[]	undefined
fees	uint256[]	undefined
invariant	uint256	undefined
lpTokenSupply	uint256	undefined

RemoveLiquidityOne

event RemoveLiquidityOne(address indexed provider, uint256 lpTokenAmount, uint256 lpTokenSupply, uint256 boughtId, uint256 tokensBought)

Parameters

Name	Type	Description
provider indexed	address	undefined
lpTokenAmount	uint256	undefined
lpTokenSupply	uint256	undefined
boughtId	uint256	undefined
tokensBought	uint256	undefined

StopRampA

event StopRampA(uint256 currentA, uint256 time)

Parameters

Name	Type	Description
currentA	uint256	undefined
time	uint256	undefined

TokenSwap

event TokenSwap(address indexed buyer, uint256 tokensSold, uint256 tokensBought, uint128 soldId, uint128 boughtId)

Parameters

Name	Type	Description
buyer indexed	address	undefined
tokensSold	uint256	undefined
tokensBought	uint256	undefined
soldId	uint128	undefined
boughtId	uint128	undefined

Unpaused

event Unpaused(address account)

Parameters

Name	Type	Description
account	address	undefined