Feeder Pools
Feeder Pools are 50/50 AMMs, usually consisting of one mAsset and another mAsset-like asset. Feeder Pools are an extension of the mStable ecosystem and allow for more assets to swap and mint.
Main Contracts
Peripheral Contracts
Feeder Pool tokens follow the ERC20 standard. The non-standard decreaseAllowance and increaseAllowance functions have been added to mitigate the well-known issues around setting allowances. These are based on the OpenZeppelin ERC20 implementation.
ERC-20 Functions
totalSupply()
function totalSupply () external returns (uint256)
Returns the amount of tokens in existence.
balanceOf()
function balanceOf () external returns (uint256)
Returns the amount of tokens owned by account.
transfer()
function transfer () external returns (bool)
Moves amount tokens from the caller's account to recipient.
Returns a boolean value indicating whether the operation succeeded.
Emits a {Transfer} event.
allowance()
function allowance () external returns (uint256)
Returns the remaining number of tokens thatspenderwill be allowed to spend on behalf ofownerthrough {transferFrom}. This is zero by default.
This value changes when {approve} or {transferFrom} are called.
approve()
function approve () external returns (bool)
Sets amount as the allowance of spender over the caller's tokens.
Returns a boolean value indicating whether the operation succeeded.
IMPORTANT: Beware that changing an allowance with this method brings the risk that someone may use both the old and the new allowance by unfortunate transaction ordering. One possible solution to mitigate this race condition is to first reduce the spender's allowance to 0 and set the desired value afterwards: https://github.com/ethereum/EIPs/issues/20#issuecomment-263524729
Emits an {Approval} event.
transferFrom()
function transferFrom () external returns (bool)
Moves amount tokens from sender to recipient using the allowance mechanism. amount is then deducted from the caller's allowance.
Returns a boolean value indicating whether the operation succeeded.
Emits a {Transfer} event.
increaseAllowance()
function increaseAllowance () public returns (bool)
Atomically increases the allowance granted to spender by the caller.
This is an alternative to {approve} that can be used as a mitigation for problems described in {IERC20-approve}.
Emits an {Approval} event indicating the updated allowance.
Requirements:
spendercannot be the zero address.
decreaseAllowance()
function decreaseAllowance () public returns (bool)
Atomically decreases the allowance granted to spender by the caller.
This is an alternative to {approve} that can be used as a mitigation for problems described in {IERC20-approve}.
Emits an {Approval} event indicating the updated allowance.
Requirements:
spendercannot be the zero address.spendermust have allowance for the caller of at leastsubtractedValue.
Feeder Pool Functions
mint()
function mint (address _input, uint256 _inputQuantity, uint256 _minOutputQuantity, address _recipient) external returns (uint256 mintOutput)
Mint fpTokens with a single bAsset. This contract must have approval to spend the senders bAsset. Supports either fAsset, mAsset or mpAsset as input - with mpAssets used to mint mAsset before depositing.
Parameter | Type | Description |
| address | Address of the bAsset to deposit. |
| uint256 | Quantity in input token units. |
| uint256 | Minimum fpToken quantity to be minted. This protects against slippage. |
| address | Receipient of the newly minted fpTokens |
mintMulti()
function mintMulti (address[] _inputs, uint256[] _inputQuantities, uint256 _minOutputQuantity, address _recipient) external returns (uint256 mintOutput)
Mint fpTokens with multiple bAssets. This contract must have approval to spend the senders bAssets. Supports only fAsset or mAsset as inputs.
Parameter | Type | Description |
| address[] | Address of the bAssets to deposit. |
| uint256[] | Quantity in input token units. |
| uint256 | Minimum fpToken quantity to be minted. This protects against slippage. |
| address | Receipient of the newly minted fpTokens |
getMintOutput()
function getMintOutput (address _input, uint256 _inputQuantity) external returns (uint256 mintOutput)
Get the projected output of a given mint.
Parameter | Type | Description |
| address | Address of the bAsset to deposit |
| uint256 | Quantity in bAsset units |
getMintMultiOutput()
function getMintMultiOutput (address[] _inputs, uint256[] _inputQuantities) external returns (uint256 mintOutput)
Get the projected output of a given mint
Parameter | Type | Description |
| address[] | Non-duplicate address array of addresses to bAssets to deposit for the minted mAsset tokens. |
| uint256[] | Quantity of each bAsset to deposit for the minted fpToken. |
swap()
function swap (address _input, address _output, uint256 _inputQuantity, uint256 _minOutputQuantity, address _recipient) external returns (uint256 swapOutput)
Swaps two assets - either internally between fAsset<>mAsset, or between fAsset<>mpAsset by first routing through the mAsset pool.
Parameter | Type | Description |
| address | Address of bAsset to deposit |
| address | Address of bAsset to withdraw |
| uint256 | Units of input bAsset to swap in |
| uint256 | Minimum quantity of the swap output asset. This protects against slippage |
| address | Address to transfer output asset to |
getSwapOutput()
function getSwapOutput (address _input, address _output, uint256 _inputQuantity) external returns (uint256 swapOutput)
Determines both if a trade is valid, and the expected fee or output. Swap is valid if it does not result in the input asset exceeding its maximum weight.
Parameter | Type | Description |
| address | Address of bAsset to deposit |
| address | Address of bAsset to receive |
| uint256 | Units of input bAsset to swap |
redeem()
function redeem (address _output, uint256 _fpTokenQuantity, uint256 _minOutputQuantity, address _recipient) external returns (uint256 outputQuantity)
Burns a specified quantity of the senders fpToken in return for a bAsset. The output amount is derived from the invariant. Supports redemption into either the fAsset, mAsset or assets in the mAsset basket.
Parameter | Type | Description |
| address | Address of the bAsset to withdraw |
| uint256 | Quantity of LP Token to burn |
| uint256 | Minimum bAsset quantity to receive for the burnt fpToken. This protects against slippage. |
| address | Address to transfer the withdrawn bAssets to. |
redeemProportionately()
function redeemProportionately (uint256 _inputQuantity, uint256[] _minOutputQuantities, address _recipient) external returns (uint256[] outputQuantities)
Credits a recipient with a proportionate amount of bAssets, relative to current vault balance levels and desired fpToken quantity. Burns the fpToken as payment. Only fAsset & mAsset are supported in this path.
Parameter | Type | Description |
| uint256 | Quantity of fpToken to redeem |
| uint256[] | Min units of output to receive |
| address | Address to credit the withdrawn bAssets |
redeemExactBassets()
function redeemExactBassets (address[] _outputs, uint256[] _outputQuantities, uint256 _maxInputQuantity, address _recipient) external returns (uint256 fpTokenQuantity)
Credits a recipient with a certain quantity of selected bAssets, in exchange for burning the relative fpToken quantity from the sender. Only fAsset & mAsset (0,1) are supported in this path.
Parameter | Type | Description |
| address[] | Addresses of the bAssets to receive |
| uint256[] | Units of the bAssets to receive |
| uint256 | Maximum fpToken quantity to burn for the received bAssets. This protects against slippage. |
| address | Address to receive the withdrawn bAssets |
getRedeemOutput()
function getRedeemOutput (address _output, uint256 _fpTokenQuantity) external returns (uint256 bAssetOutput)
Gets the estimated output from a given redeem
Parameter | Type | Description |
| address | Address of the bAsset to receive |
| uint256 | Quantity of fpToken to redeem |
getRedeemExactBassetsOutput()
function getRedeemExactBassetsOutput (address[] _outputs, uint256[] _outputQuantities) external returns (uint256 fpTokenQuantity)
Gets the estimated output from a given redeem
Parameter | Type | Description |
| address[] | Addresses of the bAsset to receive |
| uint256[] | Quantities of bAsset to redeem |
getPrice()
function getPrice () public returns (uint256 price, uint256 k)
Gets the price of the fpToken, and invariant value k
getConfig()
function getConfig () external returns (struct FeederConfig config)
Gets all config needed for general InvariantValidator calls
getBasset()
function getBasset (address _bAsset) external returns (struct BassetPersonal personal, struct BassetData vaultData)
Get data for a specific bAsset, if it exists
Parameter | Type | Description |
| address | Address of bAsset |
getBassets()
function getBassets () external returns (struct BassetPersonal[], struct BassetData[] vaultData)
Get data for a all bAssets in basket
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