Stableswap

This section contains a full API reference of all public functions & events related to Connext's stableswap contracts.

Events

TokenSwap

event TokenSwap(bytes32 key, address buyer, uint256 tokensSold, uint256 tokensBought, uint128 soldId, uint128 boughtId)

AddLiquidity

event AddLiquidity(bytes32 key, address provider, uint256[] tokenAmounts, uint256[] fees, uint256 invariant, uint256 lpTokenSupply)

RemoveLiquidity

event RemoveLiquidity(bytes32 key, address provider, uint256[] tokenAmounts, uint256 lpTokenSupply)

RemoveLiquidityOne

event RemoveLiquidityOne(bytes32 key, address provider, uint256 lpTokenAmount, uint256 lpTokenSupply, uint256 boughtId, uint256 tokensBought)

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Getters

getSwapStorage

function getSwapStorage(bytes32 key) external view returns (struct SwapUtils.Swap)

Return Stable swap storage

Parameters

Name	Type	Description
key	bytes32	Hash of the canonical id + domain

Return Values

Name	Type	Description
[0]	struct SwapUtils.Swap	SwapUtils.Swap

getSwapLPToken

function getSwapLPToken(bytes32 key) external view returns (address)

Return LP token for canonical Id

Parameters

Name	Type	Description
key	bytes32	Hash of the canonical id + domain

Return Values

Name	Type	Description
[0]	address	LPToken

getSwapA

function getSwapA(bytes32 key) external view returns (uint256)

Return A, the amplification coefficient _ n _ (n - 1)

See the StableSwap paper for details

Parameters

Name	Type	Description
key	bytes32	Hash of the canonical id + domain

Return Values

Name	Type	Description
[0]	uint256	A parameter

getSwapAPrecise

function getSwapAPrecise(bytes32 key) external view returns (uint256)

Return A in its raw precision form

See the StableSwap paper for details

Parameters

Name	Type	Description
key	bytes32	Hash of the canonical id + domain

Return Values

Name	Type	Description
[0]	uint256	A parameter in its raw precision form

getSwapToken

function getSwapToken(bytes32 key, uint8 index) public view returns (contract IERC20)

Return address of the pooled token at given index. Reverts if tokenIndex is out of range.

Parameters

Name	Type	Description
key	bytes32	Hash of the canonical id + domain
index	uint8	the index of the token

Return Values

Name	Type	Description
[0]	contract IERC20	address of the token at given index

getSwapTokenIndex

function getSwapTokenIndex(bytes32 key, address tokenAddress) public view returns (uint8)

Return the index of the given token address. Reverts if no matching token is found.

Parameters

Name	Type	Description
key	bytes32	Hash of the canonical id + domain
tokenAddress	address	address of the token

Return Values

Name	Type	Description
[0]	uint8	the index of the given token address

getSwapTokenBalance

function getSwapTokenBalance(bytes32 key, uint8 index) external view returns (uint256)

Return current balance of the pooled token at given index

Parameters

Name	Type	Description
key	bytes32	Hash of the canonical id + domain
index	uint8	the index of the token

Return Values

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

getSwapVirtualPrice

function getSwapVirtualPrice(bytes32 key) external view returns (uint256)

Get the virtual price, to help calculate profit

Parameters

Name	Type	Description
key	bytes32	Hash of the canonical id + domain

Return Values

Name	Type	Description
[0]	uint256	the virtual price, scaled to the POOL_PRECISION_DECIMALS

calculateSwap

function calculateSwap(bytes32 key, uint8 tokenIndexFrom, uint8 tokenIndexTo, uint256 dx) external view returns (uint256)

Calculate amount of tokens you receive on swap

Parameters

Name	Type	Description
key	bytes32	Hash of the canonical id + domain
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.

Return Values

Name	Type	Description
[0]	uint256	amount of tokens the user will receive

calculateSwapTokenAmount

function calculateSwapTokenAmount(bytes32 key, 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
key	bytes32	Hash of the canonical id + domain
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

Return Values

Name	Type	Description
[0]	uint256	token amount the user will receive

calculateRemoveSwapLiquidity

function calculateRemoveSwapLiquidity(bytes32 key, 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
key	bytes32	Hash of the canonical id + domain
amount	uint256	the amount of LP tokens that would be burned on withdrawal

Return Values

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

calculateRemoveSwapLiquidityOneToken

function calculateRemoveSwapLiquidityOneToken(bytes32 key, 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
key	bytes32	Hash of the canonical id + domain
tokenAmount	uint256	the amount of LP token to burn
tokenIndex	uint8	index of which token will be withdrawn

Return Values

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

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Functions

swap

function swap(bytes32 key, uint8 tokenIndexFrom, uint8 tokenIndexTo, uint256 dx, uint256 minDy, uint256 deadline) external returns (uint256)

Swap two tokens using this pool

Parameters

Name	Type	Description
key	bytes32	Hash of the canonical id + domain
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

swapExact

function swapExact(bytes32 key, uint256 amountIn, address assetIn, address assetOut, uint256 minAmountOut, uint256 deadline) external returns (uint256)

Swap two tokens using this pool

Parameters

Name	Type	Description
key	bytes32	Hash of the canonical id + domain
amountIn	uint256	the amount of tokens the user wants to swap from
assetIn	address	the token the user wants to swap from
assetOut	address	the token the user wants to swap to
minAmountOut	uint256
deadline	uint256

swapExactOut

function swapExactOut(bytes32 key, uint256 amountOut, address assetIn, address assetOut, uint256 maxAmountIn, uint256 deadline) external returns (uint256)

Swap two tokens using this pool

Parameters

Name	Type	Description
key	bytes32	Hash of the canonical id + domain
amountOut	uint256	the amount of tokens the user wants to swap to
assetIn	address	the token the user wants to swap from
assetOut	address	the token the user wants to swap to
maxAmountIn	uint256
deadline	uint256

addSwapLiquidity

function addSwapLiquidity(bytes32 key, uint256[] amounts, uint256 minToMint, uint256 deadline) external returns (uint256)

Add liquidity to the pool with the given amounts of tokens

Parameters

Name	Type	Description
key	bytes32	Hash of the canonical id + domain
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

Return Values

Name	Type	Description
[0]	uint256	amount of LP token user minted and received

removeSwapLiquidity

function removeSwapLiquidity(bytes32 key, uint256 amount, uint256[] minAmounts, uint256 deadline) external 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
key	bytes32	Hash of the canonical id + domain
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

Return Values

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

removeSwapLiquidityOneToken

function removeSwapLiquidityOneToken(bytes32 key, uint256 tokenAmount, uint8 tokenIndex, uint256 minAmount, uint256 deadline) external 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
key	bytes32	Hash of the canonical id + domain
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

Return Values

Name	Type	Description
[0]	uint256	amount of chosen token user received