Gas Optimizations

[code423n4]

1. ++i costs less gas than i++, especially when it's used in for-loops (--i/i-- too)

Line14:	for(len = 0; i < bytelength; len++) {

https://github.com/code-423n4/2022-07-ens/blob/ff6e59b9415d0ead7daf31c2ed06e86d9061ae22/contracts/ethregistrar/StringUtils.sol#L14

LineL93: for(uint i = 0; i < input.length; i++) {

https://github.com/code-423n4/2022-07-ens/blob/ff6e59b9415d0ead7daf31c2ed06e86d9061ae22/contracts/dnssec-oracle/DNSSECImpl.sol#L93

L266: for(uint i = 0; i < len; i++) {

https://github.com/code-423n4/2022-07-ens/blob/ff6e59b9415d0ead7daf31c2ed06e86d9061ae22/contracts/dnssec-oracle/BytesUtils.sol#L266

L313: for(uint256 idx = off; idx < off + len; idx++) {

https://github.com/code-423n4/2022-07-ens/blob/ff6e59b9415d0ead7daf31c2ed06e86d9061ae22/contracts/dnssec-oracle/BytesUtils.sol#L313

2. array.length should not be looked up in every loop of a for-loop

            for(uint i = 0; i < data.length + 31; i += 32) {
                uint word;
                assembly {
                    word := mload(add(add(data, 32), i))
                }
                if(i + 32 > data.length) {
                    uint unused = 256 - (data.length - i) * 8;

https://github.com/code-423n4/2022-07-ens/blob/main/contracts/dnssec-oracle/RRUtils.sol#L310-L316

            assert(idx < self.length);

https://github.com/code-423n4/2022-07-ens/blob/ff6e59b9415d0ead7daf31c2ed06e86d9061ae22/contracts/dnssec-oracle/RRUtils.sol#L22

        for(uint i = 0; i < input.length; i++) {

https://github.com/code-423n4/2022-07-ens/blob/ff6e59b9415d0ead7daf31c2ed06e86d9061ae22/contracts/dnssec-oracle/DNSSECImpl.sol#L93

3. x += y costs more gas than x = x + y for state variables

L207: function memcpy(uint dest, uint src, uint len) private pure {
        // Copy word-length chunks while possible
        for (; len >= 32; len -= 32) {
            assembly {
                mstore(dest, mload(src))
            }
            dest += 32;
            src += 32;

https://github.com/code-423n4/2022-07-ens/blob/main/contracts/dnssec-oracle/BytesUtils.sol#L207-L214