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AllowanceTransfer

Overview​

The main functionalities of this contract include:

  • approve: Used when token permissions are set without signature validation.
  • permit: Used when token permissions are set with signature validation.
  • transferFrom: Used to transfer tokens when appropriate permissions are granted.

Functions​

approve​

Function Signature

function approve(address token, address spender, uint160 amount, uint48 expiration) external

Parameters

  • token: Address of the token to approve.
  • spender: Address of the spender to approve.
  • amount: Approved amount of the token. type(uint160).max denotes an unlimited allowance.
  • expiration: Timestamp when the approval expires. 0 expires the permissions at block.timestamp.

Single permit​

Function Signature

function permit(address owner, PermitSingle memory permitSingle, bytes calldata signature) external;

Parameters

  • owner: Address of the token's owner.
  • permitSingle: Structure containing permit data.
  • signature: Signature over the permit data.

Batched permit​

Function Signature

function permit(address owner, PermitBatch memory permitBatch, bytes calldata signature) external;

Parameters

  • owner: Address of the token's owner.
  • permitBatch: Structure containing permit data for multiple token allowances.
  • signature: Signature over the permit data.

Single transferFrom​

Function Signature

function transferFrom(address from, address to, uint160 amount, address token) external;

Parameters

  • from: Address to transfer the token from.
  • to: Address of the recipient.
  • amount: Amount of the token to transfer.
  • token: Address of the token to be transferred.

Batched transferFrom​

Function Signature

function transferFrom(AllowanceTransferDetails[] calldata transferDetails) external;

Parameters

  • transferDetails: Details of token transfers, including owner, recipient, amount, and token address.

Nonce Schema​

Nonces are used to prevent replay attacks of signatures. They are incremented per owner, per token, and per spender, ensuring that two different permits signed at the same time with the same nonces won't cancel each other out.

Security Considerations​

Integrating contracts need to perform valid safety checks on the caller and provide correct addresses for the from argument in transfer calls. Additionally, all amounts on the AllowanceTransfer contract are of type uint160, so integrating contracts must safely downcast if necessary.