Gas Optimizations

[code423n4]

GAS

1.

Title: Caching _tokens[i] can save gas

Occurrences: https://github.com/code-423n4/2022-06-nibbl/blob/main/contracts/Basket.sol#L71-L73 https://github.com/code-423n4/2022-06-nibbl/blob/main/contracts/Basket.sol#L44-L45

Instead of calling array value by assign its key every call, we can cache it for gas saving Change to:

        for (uint256 i = 0; i < _tokens.length; i++) {
        address _token = _tokens[i];
        uint _tokenId = _tokenIds[i]
            uint256 _balance = IERC1155(_token).balanceOf(address(this),  _tokenId);
            IERC1155(_token).safeTransferFrom(address(this), _to, _tokenId, _balance, "0");
            emit WithdrawERC1155(_token, _tokenId, _balance, _to);
        }

By doing this way we can save 48 gas per call

2.

Title: Prefix increment and unchecked for i

Occurrences: https://github.com/code-423n4/2022-06-nibbl/blob/main/contracts/Basket.sol#L43 https://github.com/code-423n4/2022-06-nibbl/blob/main/contracts/Basket.sol#L70 https://github.com/code-423n4/2022-06-nibbl/blob/main/contracts/Basket.sol#L93

Best practice for doing increment is using prefix increment and unchecked for i var inside for():

Change to:

        for (uint256 i = 0; i < _tokens.length;) {
            IERC721(_tokens[i]).safeTransferFrom(address(this), _to, _tokenId[i]);
            emit WithdrawERC721(_tokens[i], _tokenId[i], _to);
        unchecked{++i;}
        }

3.

Title: Using calldata to store argument variable:

Occurrences: https://github.com/code-423n4/2022-06-nibbl/blob/main/contracts/Basket.sol#L41 https://github.com/code-423n4/2022-06-nibbl/blob/main/contracts/Basket.sol#L68

We can store _tokens and _tokenIds read only parameter with calldata instead of using memory.

Recommended mitigation step

Change to:

    function withdrawMultipleERC721(address[] calldata _tokens, uint256[] calldata _tokenId, address _to) external override {

4.

Title: Using < operator instead of <=

https://github.com/code-423n4/2022-06-nibbl/blob/main/contracts/NibblVault.sol#L147

By using < operator to validate we can save 3 gas per call. The 1 second difference can be ignore

5.

Title: Using delete statement to set to default value

https://github.com/code-423n4/2022-06-nibbl/blob/main/contracts/NibblVault.sol#L477

Using delete statement to set value to 0 can save 8 gas per execution

Recommended mitigation step

delete feeAccruedCurator;