stBTC

stBTC

This contract implements the ERC-4626 tokenized vault standard. By staking tBTC, users acquire a liquid staking token called stBTC, commonly referred to as "shares". Users have the flexibility to redeem stBTC, enabling them to withdraw their deposited tBTC along with the accrued yield.

ERC-4626 is a standard to optimize and unify the technical parameters of yield-bearing vaults. This contract facilitates the minting and burning of shares (stBTC), which are represented as standard ERC20 tokens, providing a seamless exchange with tBTC tokens.

dispatcher

contract IDispatcher dispatcher

Dispatcher contract that routes tBTC from stBTC to a given allocation contract and back.

treasury

address treasury

Address of the treasury wallet, where fees should be transferred to.

minimumDepositAmount

uint256 minimumDepositAmount

Minimum amount for a single deposit operation. The value should be set low enough so the deposits routed through Bitcoin Depositor contract won't be rejected. It means that minimumDepositAmount should be lower than tBTC protocol's depositDustThreshold reduced by all the minting fees taken before depositing in the Acre contract.

entryFeeBasisPoints

uint256 entryFeeBasisPoints

Entry fee basis points applied to entry fee calculation.

exitFeeBasisPoints

uint256 exitFeeBasisPoints

Exit fee basis points applied to exit fee calculation.

TreasuryUpdated

event TreasuryUpdated(address oldTreasury, address newTreasury)

Emitted when the treasury wallet address is updated.

Parameters

Name	Type	Description
oldTreasury	address	Address of the old treasury wallet.
newTreasury	address	Address of the new treasury wallet.

MinimumDepositAmountUpdated

event MinimumDepositAmountUpdated(uint256 minimumDepositAmount)

Emitted when deposit parameters are updated.

Parameters

Name	Type	Description
minimumDepositAmount	uint256	New value of the minimum deposit amount.

DispatcherUpdated

event DispatcherUpdated(address oldDispatcher, address newDispatcher)

Emitted when the dispatcher contract is updated.

Parameters

Name	Type	Description
oldDispatcher	address	Address of the old dispatcher contract.
newDispatcher	address	Address of the new dispatcher contract.

EntryFeeBasisPointsUpdated

event EntryFeeBasisPointsUpdated(uint256 entryFeeBasisPoints)

Emitted when the entry fee basis points are updated.

Parameters

Name	Type	Description
entryFeeBasisPoints	uint256	New value of the fee basis points.

ExitFeeBasisPointsUpdated

event ExitFeeBasisPointsUpdated(uint256 exitFeeBasisPoints)

Emitted when the exit fee basis points are updated.

Parameters

Name	Type	Description
exitFeeBasisPoints	uint256	New value of the fee basis points.

LessThanMinDeposit

error LessThanMinDeposit(uint256 amount, uint256 min)

Reverts if the amount is less than the minimum deposit amount.

Parameters

Name	Type	Description
amount	uint256	Amount to check.
min	uint256	Minimum amount to check 'amount' against.

DisallowedAddress

error DisallowedAddress()

Reverts if the address is disallowed.

ExceedsMaxFeeBasisPoints

error ExceedsMaxFeeBasisPoints()

Reverts if the fee basis points exceed the maximum value.

SameTreasury

error SameTreasury()

Reverts if the treasury address is the same.

SameDispatcher

error SameDispatcher()

Reverts if the dispatcher address is the same.

constructor

constructor() public

initialize

function initialize(contract IERC20 asset, address _treasury) public

updateTreasury

function updateTreasury(address newTreasury) external

Updates treasury wallet address.

Parameters

Name	Type	Description
newTreasury	address	New treasury wallet address.

updateMinimumDepositAmount

function updateMinimumDepositAmount(uint256 newMinimumDepositAmount) external

Updates minimum deposit amount.

Parameters

Name	Type	Description
newMinimumDepositAmount	uint256	New value of the minimum deposit amount. It is the minimum amount for a single deposit operation.

updateDispatcher

function updateDispatcher(contract IDispatcher newDispatcher) external

Updates the dispatcher contract and gives it an unlimited allowance to transfer deposited tBTC.

Parameters

Name	Type	Description
newDispatcher	contract IDispatcher	Address of the new dispatcher contract.

updateEntryFeeBasisPoints

function updateEntryFeeBasisPoints(uint256 newEntryFeeBasisPoints) external

Update the entry fee basis points.

Parameters

Name	Type	Description
newEntryFeeBasisPoints	uint256	New value of the fee basis points.

updateExitFeeBasisPoints

function updateExitFeeBasisPoints(uint256 newExitFeeBasisPoints) external

Update the exit fee basis points.

Parameters

Name	Type	Description
newExitFeeBasisPoints	uint256	New value of the fee basis points.

approveAndCall

function approveAndCall(address spender, uint256 value, bytes extraData) external returns (bool)

Calls receiveApproval function on spender previously approving the spender to withdraw from the caller multiple times, up to the value amount. If this function is called again, it overwrites the current allowance with value. Reverts if the approval reverted or if receiveApproval call on the spender reverted.

If the value is set to type(uint256).max then transferFrom and burnFrom will not reduce an allowance.

Parameters

Name	Type	Description
spender	address	The address which will spend the funds.
value	uint256	The amount of tokens to be spent.
extraData	bytes	Additional data.

Return Values

Name	Type	Description
[0]	bool	True if both approval and receiveApproval calls succeeded.

deposit

function deposit(uint256 assets, address receiver) public returns (uint256)

Mints shares to receiver by depositing exactly amount of tBTC tokens.

Takes into account a deposit parameter, minimum deposit amount, which determines the minimum amount for a single deposit operation. The amount of the assets has to be pre-approved in the tBTC contract.

Parameters

Name	Type	Description
assets	uint256	Approved amount of tBTC tokens to deposit. This includes treasury fees for staking tBTC.
receiver	address	The address to which the shares will be minted.

Return Values

Name	Type	Description
[0]	uint256	Minted shares adjusted for the fees taken by the treasury.

mint

function mint(uint256 shares, address receiver) public returns (uint256 assets)

Mints shares to receiver by depositing tBTC tokens.

Takes into account a deposit parameter, minimum deposit amount, which determines the minimum amount for a single deposit operation. The amount of the assets has to be pre-approved in the tBTC contract. The msg.sender is required to grant approval for the transfer of a certain amount of tBTC, and in addition, approval for the associated fee. Specifically, the total amount to be approved (amountToApprove) should be equal to the sum of the deposited amount and the fee. To determine the total assets amount necessary for approval corresponding to a given share amount, use the previewMint function.

Parameters

Name	Type	Description
shares	uint256	Amount of shares to mint.
receiver	address	The address to which the shares will be minted.

Return Values

Name	Type	Description
assets	uint256	Used assets to mint shares.

withdraw

function withdraw(uint256 assets, address receiver, address owner) public returns (uint256)

Withdraws assets from the vault and transfers them to the receiver.

Withdraw unallocated assets first and and if not enough, then pull the assets from the dispatcher.

Parameters

Name	Type	Description
assets	uint256	Amount of assets to withdraw.
receiver	address	The address to which the assets will be transferred.
owner	address	The address of the owner of the shares.

redeem

function redeem(uint256 shares, address receiver, address owner) public returns (uint256)

Redeems shares for assets and transfers them to the receiver.

Redeem unallocated assets first and and if not enough, then pull the assets from the dispatcher.

Parameters

Name	Type	Description
shares	uint256	Amount of shares to redeem.
receiver	address	The address to which the assets will be transferred.
owner	address	The address of the owner of the shares.

totalAssets

function totalAssets() public view returns (uint256)

Returns the total amount of assets held by the vault across all allocations and this contract.

maxDeposit

function maxDeposit(address) public view returns (uint256)

Returns the maximum amount of the underlying asset that can be deposited into the Vault for the receiver, through a deposit call. If the Vault is paused, returns 0.

maxMint

function maxMint(address) public view returns (uint256)

Returns the maximum amount of the Vault shares that can be minted for the receiver, through a mint call. If the Vault is paused, returns 0.

maxWithdraw

function maxWithdraw(address owner) public view returns (uint256)

Returns the maximum amount of the underlying asset that can be withdrawn from the owner balance in the Vault, through a withdraw call. If the Vault is paused, returns 0.

maxRedeem

function maxRedeem(address owner) public view returns (uint256)

Returns the maximum amount of Vault shares that can be redeemed from the owner balance in the Vault, through a redeem call. If the Vault is paused, returns 0.

assetsBalanceOf

function assetsBalanceOf(address account) public view returns (uint256)

Returns the number of assets that corresponds to the amount of shares held by the specified account.

This function is used to convert shares to assets position for the given account. It does not take fees into account.

Parameters

Name	Type	Description
account	address	The owner of the shares.

Return Values

Name	Type	Description
[0]	uint256	The amount of assets.

_entryFeeBasisPoints

function _entryFeeBasisPoints() internal view returns (uint256)

Return Values

Name	Type	Description
[0]	uint256	Returns entry fee basis point used in deposits.

_exitFeeBasisPoints

function _exitFeeBasisPoints() internal view returns (uint256)

Return Values

Name	Type	Description
[0]	uint256	Returns exit fee basis point used in withdrawals.

_feeRecipient

function _feeRecipient() internal view returns (address)

Returns the address of the treasury wallet, where fees should be transferred to.