Caviar contest - millersplanet's results

[GAS] Redundant built-in safe arithmetics

Instances (4) : SafeERC20Namer.sol#13,22,33,39

Avoid unnecessary built-in safe arithmetics. In the following for loops, each increment is performed with bound-checks when they are entirely redundant :

SafeERC20Namer.sol#13:

for (uint256 j = 0; j < 32; j++) {
	bytes1 char = x[j];
	if (char != 0) {
		bytesString[charCount] = char;
		charCount++;
	}
}

SafeERC20Namer.sol#22:

for (uint256 j = 0; j < charCount; j++) {
        (...)
}

SafeERC20Namer.sol#33:

for (uint256 i = 32; i < 64; i++) {
        (...)
}

SafeERC20Namer.sol#39:

for (uint256 i = 0; i < charCount; i++) {
        (...)
}

Due to the inherent constraints of Solidity and the declaration of the variables, i and j are guaranteed to fit within a uint256 variable, meaning that performing a safe incrementation on each loop for the i and j variables are redundant and costly.

To optimize such code blocks, it's recommended to place the code implementation of the bytes32ToString and the parseStringData functions inside an unchecked code block, saving, for example, around 8000 gas in a 13 character string conversion:

SafeERC20Namer.sol#10-27:

function bytes32ToString(bytes32 x) private pure returns (string memory) {
	unchecked {
		bytes memory bytesString = new bytes(32);
			uint256 charCount = 0;
			for (uint256 j = 0; j < 32; j++) {
				bytes1 char = x[j];
				if (char != 0) {
					bytesString[charCount] = char;
					charCount++;
				}
			}
			bytes memory bytesStringTrimmed = new bytes(charCount);
			for (uint256 j = 0; j < charCount; j++) {
				bytesStringTrimmed[j] = bytesString[j];
			}
		return string(bytesStringTrimmed);
	}
}

SafeERC20Namer.sol#30-44:

function parseStringData(bytes memory b) private pure returns (string memory) {
	unchecked {
		uint256 charCount = 0;
		// first parse the charCount out of the data
		for (uint256 i = 32; i < 64; i++) {
			charCount <<= 8;
			charCount += uint8(b[i]);
		}

		bytes memory bytesStringTrimmed = new bytes(charCount);
		for (uint256 i = 0; i < charCount; i++) {
			bytesStringTrimmed[i] = b[i + 64];
		}
		return string(bytesStringTrimmed);
	}
}