// keccak256("Permit(address owner,address spender,uint256 value,uint256 nonce,uint256 deadline)"); bytes32 public constant PERMIT_TYPEHASH = 0x6e71edae12b1b97f4d1f60370fef10105fa2faae0126114a169c64845d6126c9;

请问uniswap代码中PERMIT_TYPEHASH的详细计算方法