ERC20PermitUpgradeable

Inherits: Initializable, ERC20Upgradeable, IERC20Permit, EIP712Upgradeable, NoncesUpgradeable

Implementation of the ERC-20 Permit extension allowing approvals to be made via signatures, as defined in https://eips.ethereum.org/EIPS/eip-2612[ERC-2612]. Adds the permit method, which can be used to change an account's ERC-20 allowance (see {IERC20-allowance}) by presenting a message signed by the account. By not relying on {IERC20-approve}, the token holder account doesn't need to send a transaction, and thus is not required to hold Ether at all.

State Variables

PERMIT_TYPEHASH

bytes32 private constant PERMIT_TYPEHASH =
    keccak256("Permit(address owner,address spender,uint256 value,uint256 nonce,uint256 deadline)");

Functions

__ERC20Permit_init

Initializes the {EIP712} domain separator using the name parameter, and setting version to "1". It's a good idea to use the same name that is defined as the ERC-20 token name.

function __ERC20Permit_init(string memory name) internal onlyInitializing;

__ERC20Permit_init_unchained

function __ERC20Permit_init_unchained(string memory) internal onlyInitializing;

permit

*Sets value as the allowance of spender over owner's tokens, given owner's signed approval. IMPORTANT: The same issues {IERC20-approve} has related to transaction ordering also apply here. Emits an {Approval} event. Requirements:

• spender cannot be the zero address.
• deadline must be a timestamp in the future.
• v, r and s must be a valid secp256k1 signature from owner over the EIP712-formatted function arguments.
• the signature must use owner's current nonce (see {nonces}). For more information on the signature format, see the https://eips.ethereum.org/EIPS/eip-2612#specification[relevant EIP section]. CAUTION: See Security Considerations above.*

function permit(address owner, address spender, uint256 value, uint256 deadline, uint8 v, bytes32 r, bytes32 s)
    public
    virtual;

nonces

Returns the current nonce for owner. This value must be included whenever a signature is generated for {permit}. Every successful call to {permit} increases owner's nonce by one. This prevents a signature from being used multiple times.

function nonces(address owner) public view virtual override(IERC20Permit, NoncesUpgradeable) returns (uint256);

DOMAIN_SEPARATOR

Returns the domain separator used in the encoding of the signature for {permit}, as defined by {EIP712}.

function DOMAIN_SEPARATOR() external view virtual returns (bytes32);

Errors

ERC2612ExpiredSignature

Permit deadline has expired.

error ERC2612ExpiredSignature(uint256 deadline);

ERC2612InvalidSigner

Mismatched signature.

error ERC2612InvalidSigner(address signer, address owner);