# Transferer

The `Transferer` contract has the ability to move your tokens to our noncustodial `Vault`. It cannot transfer your tokens anywhere else.

Below is a function-by-function explanation of the code.

### Roles

```solidity
address immutable private vaultAddress; // set during construction
address immutable private transferEOASetter; // set during construction
mapping(address => bool) private _transferEOAs;
```

There are three roles (one dynamic, two immutable and set during construction) in this contract:

* `vaultAddress` is the address of the associated [Noncustodial Vault](/welcome-to-the-harpie-docs/tech-and-security/contracts/noncustodial-vault.md)
* `transferEOAs` are addresses that can call our [#transfer-functions](#transfer-functions "mention"). These addresses are controlled by our automated detection algorithm
* `transferEOASetter` is an address owned by Harpie that can set `_transferEOAs`

### Transfer Functions

```solidity
function transferERC721(
    address _ownerAddress, 
    address _erc721Address, 
    uint256 _erc721Id, 
    uint128 _fee
) public returns (bool)

function transferERC20(
    address _ownerAddress, 
    address _erc20Address, 
    uint128 _fee
) public returns (bool)

function batchTransferERC721(ERC721Details[] memory _details) public returns (bool)

function batchTransferERC20(ERC20Details[] memory _details) public returns (bool)
```

These functions transfer user assets into the `Vault` when we detect a malicious transaction. They're hardcoded to transfer tokens to the `vaultAddress` role, and cannot submit user tokens anywhere else. They are only callable by the `transferEOA` role.

* The `transfer` functions transfer a single user's assets (ERC20/ERC721) to the Vault.
* The `batchTransfer` functions are able to transfer multiple users' assets. We use these in case of large-scale attacks.

### Permission Functions

```solidity
function addTransferEOA(address _newTransferEOA) public

function removeTransferEOA(address _eoaToBeRemoved) public

function removeAbilityToSetNewTransferEOAs() public
```

These functions are only callable by the role `transferEOASetter`.

* `addTransferEEOA` and `removeTransferEOA` add and remove `transferEOAs`, the wallets that are able to call the [#transfer-functions](#transfer-functions "mention")
* `removeAbilityToSetNewTransferEOAs` is a permanent operation that prevents the addition of any new `transferEOAs`. After calling this flag, Harpie is no longer able to add new wallets to the `transferEOA` role, but will still able to remove them.


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