PermissionMath Code Style Findings

PMH-01C: Optimization of Permission Encoding

Type	Severity	Location
Gas Optimization		PermissionMath.sol:L21, L27

Description:

The PermissionMath::encode function is relatively inefficient as it will construct the encoded result of multiple permissions using a uint192 data type redundantly.

As a uint192 cast is performed on each bitwise shift operation of a _permission, the code will redundantly clear the upper 64 bits of the bitwise shift result under the hood as it performs a cast to the uint192 data type.

Example:

Copy
20function encode(INFTPermissions.Permission[] memory _permissions) internal pure returns (NFTPermissions.EncodedPermissions) {
21  uint192 _encodedResult;
22  for (uint256 i = 0; i < _permissions.length;) {
23    uint8 _permission = INFTPermissions.Permission.unwrap(_permissions[i]);
24    if (_permission >= 192) {
25      revert InvalidPermission(_permission);
26    }
27    _encodedResult |= uint192(1 << _permission);
28    unchecked {
29      i++;
30    }
31  }
32  return NFTPermissions.EncodedPermissions.wrap(_encodedResult);
33}

Recommendation:

Given that the code already ensures the _permission value unwrapped is strictly less-than 192, we advise the _encodedResult to be set as a uint256 value and each bitwise shift to be utilized as-is.

As a last step, the wrapping operation should pass in the _encodedResult cast to a uint192 value which is guaranteed to be a safe cast. These changes will result in an observable optimization of the function's gas cost.

Alleviation:

All statements in the code have been updated per our recommendation, ensuring that the encoding function exposed by PermissionMath is as optimal as possible.