# Bank ## Bank Bank is a central component tracking Bitcoin balances. Balances can be transferred between balance owners, and balance owners can approve their balances to be spent by others. Balances in the Bank are updated for depositors who deposited their Bitcoin into the Bridge and only the Bridge can increase balances. Bank is a governable contract and the Governance can upgrade the Bridge address. ### bridge ```solidity address bridge ``` ### balanceOf ```solidity mapping(address => uint256) balanceOf ``` The balance of the given account in the Bank. Zero by default. ### allowance ```solidity mapping(address => mapping(address => uint256)) allowance ``` The remaining amount of balance a spender will be allowed to transfer on behalf of an owner using `transferBalanceFrom`. Zero by default. ### nonces ```solidity mapping(address => uint256) nonces ``` Returns the current nonce for an EIP2612 permission for the provided balance owner to protect against replay attacks. Used to construct an EIP2612 signature provided to the `permit` function. ### cachedChainId ```solidity uint256 cachedChainId ``` ### cachedDomainSeparator ```solidity bytes32 cachedDomainSeparator ``` ### PERMIT\_TYPEHASH ```solidity bytes32 PERMIT_TYPEHASH ``` Returns an EIP2612 Permit message hash. Used to construct an EIP2612 signature provided to the `permit` function. ### BalanceTransferred ```solidity event BalanceTransferred(address from, address to, uint256 amount) ``` ### BalanceApproved ```solidity event BalanceApproved(address owner, address spender, uint256 amount) ``` ### BalanceIncreased ```solidity event BalanceIncreased(address owner, uint256 amount) ``` ### BalanceDecreased ```solidity event BalanceDecreased(address owner, uint256 amount) ``` ### BridgeUpdated ```solidity event BridgeUpdated(address newBridge) ``` ### onlyBridge ```solidity modifier onlyBridge() ``` ### constructor ```solidity constructor() public ``` ### updateBridge ```solidity function updateBridge(address _bridge) external ``` Allows the Governance to upgrade the Bridge address. The function does not implement any governance delay and does not check the status of the Bridge. The Governance implementation needs to ensure all requirements for the upgrade are satisfied before executing this function. Requirements: * The new Bridge address must not be zero. #### Parameters | Name | Type | Description | | -------- | ------- | ----------------------- | | \_bridge | address | The new Bridge address. | ### transferBalance ```solidity function transferBalance(address recipient, uint256 amount) external ``` Moves the given `amount` of balance from the caller to `recipient`. Requirements: * `recipient` cannot be the zero address, * the caller must have a balance of at least `amount`. #### Parameters | Name | Type | Description | | --------- | ------- | -------------------------------------- | | recipient | address | The recipient of the balance. | | amount | uint256 | The amount of the balance transferred. | ### approveBalance ```solidity function approveBalance(address spender, uint256 amount) external ``` Sets `amount` as the allowance of `spender` over the caller's balance. Does not allow updating an existing allowance to a value that is non-zero to avoid someone using both the old and the new allowance by unfortunate transaction ordering. To update an allowance to a non-zero value please set it to zero first or use `increaseBalanceAllowance` or `decreaseBalanceAllowance` for an atomic update. If the `amount` is set to `type(uint256).max`, `transferBalanceFrom` will not reduce an allowance. #### Parameters | Name | Type | Description | | ------- | ------- | ------------------------------------------------------ | | spender | address | The address that will be allowed to spend the balance. | | amount | uint256 | The amount the spender is allowed to spend. | ### approveBalanceAndCall ```solidity function approveBalanceAndCall(address spender, uint256 amount, bytes extraData) external ``` Sets the `amount` as an allowance of a smart contract `spender` over the caller's balance and calls the `spender` via `receiveBalanceApproval`. If the `amount` is set to `type(uint256).max`, the potential `transferBalanceFrom` executed in `receiveBalanceApproval` of `spender` will not reduce an allowance. Beware that changing an allowance with this function brings the risk that `spender` may use both the old and the new allowance by unfortunate transaction ordering. Please use `increaseBalanceAllowance` and `decreaseBalanceAllowance` to eliminate the risk. #### Parameters | Name | Type | Description | | --------- | ------- | ------------------------------------------------------------------------------ | | spender | address | The smart contract that will be allowed to spend the balance. | | amount | uint256 | The amount the spender contract is allowed to spend. | | extraData | bytes | Extra data passed to the `spender` contract via `receiveBalanceApproval` call. | ### increaseBalanceAllowance ```solidity function increaseBalanceAllowance(address spender, uint256 addedValue) external ``` Atomically increases the caller's balance allowance granted to `spender` by the given `addedValue`. #### Parameters | Name | Type | Description | | ---------- | ------- | --------------------------------------------------------- | | spender | address | The spender address for which the allowance is increased. | | addedValue | uint256 | The amount by which the allowance is increased. | ### decreaseBalanceAllowance ```solidity function decreaseBalanceAllowance(address spender, uint256 subtractedValue) external ``` Atomically decreases the caller's balance allowance granted to `spender` by the given `subtractedValue`. Requirements: * `spender` must not be the zero address, * the current allowance for `spender` must not be lower than the `subtractedValue`. #### Parameters | Name | Type | Description | | --------------- | ------- | --------------------------------------------------------- | | spender | address | The spender address for which the allowance is decreased. | | subtractedValue | uint256 | The amount by which the allowance is decreased. | ### transferBalanceFrom ```solidity function transferBalanceFrom(address spender, address recipient, uint256 amount) external ``` Moves `amount` of balance from `spender` to `recipient` using the allowance mechanism. `amount` is then deducted from the caller's allowance unless the allowance was made for `type(uint256).max`. Requirements: * `recipient` cannot be the zero address, * `spender` must have a balance of at least `amount`, * the caller must have an allowance for `spender`'s balance of at least `amount`. #### Parameters | Name | Type | Description | | --------- | ------- | -------------------------------------------------- | | spender | address | The address from which the balance is transferred. | | recipient | address | The address to which the balance is transferred. | | amount | uint256 | The amount of balance that is transferred. | ### permit ```solidity function permit(address owner, address spender, uint256 amount, uint256 deadline, uint8 v, bytes32 r, bytes32 s) external ``` An EIP2612 approval made with secp256k1 signature. Users can authorize a transfer of their balance with a signature conforming to the EIP712 standard, rather than an on-chain transaction from their address. Anyone can submit this signature on the user's behalf by calling the `permit` function, paying gas fees, and possibly performing other actions in the same transaction. The deadline argument can be set to `type(uint256).max to create permits that effectively never expire. If the` amount`is set to`type(uint256).max`then`transferBalanceFrom`will not reduce an allowance. Beware that changing an allowance with this function brings the risk that someone may use both the old and the new allowance by unfortunate transaction ordering. Please use`increaseBalanceAllowance`and`decreaseBalanceAllowance\` to eliminate the risk. #### Parameters | Name | Type | Description | | -------- | ------- | ------------------------------------------------------ | | owner | address | The balance owner who signed the permission. | | spender | address | The address that will be allowed to spend the balance. | | amount | uint256 | The amount the spender is allowed to spend. | | deadline | uint256 | The UNIX time until which the permit is valid. | | v | uint8 | V part of the permit signature. | | r | bytes32 | R part of the permit signature. | | s | bytes32 | S part of the permit signature. | ### increaseBalances ```solidity function increaseBalances(address[] recipients, uint256[] amounts) external ``` Increases balances of the provided `recipients` by the provided `amounts`. Can only be called by the Bridge. Requirements: * length of `recipients` and `amounts` must be the same, * none of `recipients` addresses must point to the Bank. #### Parameters | Name | Type | Description | | ---------- | ---------- | ---------------------------------------- | | recipients | address\[] | Balance increase recipients. | | amounts | uint256\[] | Amounts by which balances are increased. | ### increaseBalance ```solidity function increaseBalance(address recipient, uint256 amount) external ``` Increases balance of the provided `recipient` by the provided `amount`. Can only be called by the Bridge. Requirements: * `recipient` address must not point to the Bank. #### Parameters | Name | Type | Description | | --------- | ------- | ----------------------------------------- | | recipient | address | Balance increase recipient. | | amount | uint256 | Amount by which the balance is increased. | ### increaseBalanceAndCall ```solidity function increaseBalanceAndCall(address vault, address[] recipients, uint256[] amounts) external ``` Increases the given smart contract `vault`'s balance and notifies the `vault` contract about it. Can be called only by the Bridge. Requirements: * `vault` must implement `IVault` interface, * length of `recipients` and `amounts` must be the same. #### Parameters | Name | Type | Description | | ---------- | ---------- | ---------------------------------------- | | vault | address | Address of `IVault` recipient contract. | | recipients | address\[] | Balance increase recipients. | | amounts | uint256\[] | Amounts by which balances are increased. | ### decreaseBalance ```solidity function decreaseBalance(uint256 amount) external ``` Decreases caller's balance by the provided `amount`. There is no way to restore the balance so do not call this function unless you really know what you are doing! Requirements: * The caller must have a balance of at least `amount`. #### Parameters | Name | Type | Description | | ------ | ------- | --------------------------------------------- | | amount | uint256 | The amount by which the balance is decreased. | ### DOMAIN\_SEPARATOR ```solidity function DOMAIN_SEPARATOR() public view returns (bytes32) ``` Returns hash of EIP712 Domain struct with `TBTC Bank` as a signing domain and Bank contract as a verifying contract. Used to construct an EIP2612 signature provided to the `permit` function. ### \_increaseBalance ```solidity function _increaseBalance(address recipient, uint256 amount) internal ``` --- # Agent Instructions: Querying This Documentation If you need additional information that is not directly available in this page, you can query the documentation dynamically by asking a question. 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