Gas Optimizations

[code423n4]

Caching the length in for loops

This reduce gas cost as show here https://forum.openzeppelin.com/t/a-collection-of-gas-optimisation-tricks/19966/5

1. if it is a storage array, this is an extra sload operation (100 additional extra gas (EIP-2929 2) for each iteration except for the first),
2. if it is a memory array, this is an extra mload operation (3 additional gas for each iteration except for the first),
3. if it is a calldata array, this is an extra calldataload operation (3 additional gas for each iteration except for the first)

https://github.com/code-423n4/2022-06-nested/blob/b4a153c943d54755711a2f7b80cbbf3a5bb49d76/contracts/NestedFactory.sol#L121-L130

    function addOperator(bytes32 operator) external override onlyOwner {
        require(operator != bytes32(""), "NF: INVALID_OPERATOR_NAME");
        bytes32[] memory operatorsCache = operators;
        for (uint256 i = 0; i < operatorsCache.length; i++) {
            require(operatorsCache[i] != operator, "NF: EXISTENT_OPERATOR");
        }
        operators.push(operator);
        rebuildCache();
        emit OperatorAdded(operator);
    }

Can be optimized to

    function addOperator(bytes32 operator) external override onlyOwner {
        require(operator != bytes32(""), "NF: INVALID_OPERATOR_NAME");
        bytes32[] memory operatorsCache = operators;
        uint256 operatorsCacheLength = operatorsCache.length;
        for (uint256 i = 0; i < operatorsCacheLength; i++) {
            require(operatorsCache[i] != operator, "NF: EXISTENT_OPERATOR");
        }
        operators.push(operator);
        rebuildCache();
        emit OperatorAdded(operator);
    }

The increment in for loop postcondition can be made unchecked

This reduce gas cost as show here https://forum.openzeppelin.com/t/a-collection-of-gas-optimisation-tricks/19966/5

Gas savings: roughly speaking this can save 30-40 gas per loop iteration. For lengthy loops, this can be significant!

Apply this to all part in your code with for loops. For example

https://github.com/code-423n4/2022-06-nested/blob/b4a153c943d54755711a2f7b80cbbf3a5bb49d76/contracts/NestedFactory.sol#L196-L199

        for (uint256 i = 0; i < batchedOrdersLength; i++) {
            (uint256 fees, IERC20 tokenSold) = _submitInOrders(nftId, _batchedOrders[i], false);
            _transferFeeWithRoyalty(fees, tokenSold, nftId);
        }

Can be optimized to

        for (uint256 i = 0; i < batchedOrdersLength; ) {
            (uint256 fees, IERC20 tokenSold) = _submitInOrders(nftId, _batchedOrders[i], false);
            _transferFeeWithRoyalty(fees, tokenSold, nftId);

            unchecked { i++; }
        }

Consider using custom errors instead of revert strings

This reduce gas cost as show here https://forum.openzeppelin.com/t/a-collection-of-gas-optimisation-tricks/19966/5

Solidity 0.8.4 introduced custom errors. They are more gas efficient than revert strings, when it comes to deployment cost as well as runtime cost when the revert condition is met. Use custom errors instead of revert strings for gas savings.

Any require statement in your code can be replaced with custom error for example:

require(batchedOrdersLength != 0, "NF: INVALID_MULTI_ORDERS");

Can be replaced with

// declare error before contract declaration
error InvalidMultiOrders();

if (batchedOrdersLength == 0) revert InvalidMultiOrders();

[maximebrugel]

Consider using custom errors instead of revert strings (Duplicated)

#6 (see comment)

[Yashiru]

Caching the length in for loops (Duplicated)

Duplicated of #2 at For loop optimizaion

The increment in for loop postcondition can be made unchecked (Duplicated)

Duplicated of #2 at For loop optimizaion