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[utils] RegEx is slow (can we make faster hex functions?) #10208
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[-]RegEx is slow[/-][+]RegEx is slow (can we make faster hex functions?)[/+]on Jul 8, 2025 I got into some further optimizations:
function isHexAddressCaseInsensitiveFast(str) { if (typeof str !== "string" || str.length !== 42) return false; if (str[0] !== '0' || str[1] !== 'x') return false; for (let i = 2; i < 42; i++) { // transform the character code for case-insensitivity const charCode = str.charCodeAt(i) & 0xDF; // after transformation, '0'-'9' are in the range 16-25 const numberRange = (charCode - 16) | (25 - charCode); // after transformation, 'a'-'f' are in the range 65-70 ('A'-'F'), `A`-`F` remains unchanged const letterRange = (charCode - 65) | (70 - charCode); // identifies if the charCode is OUTSIDE of both valid ranges. if (((numberRange & letterRange) & 0x80000000) !== 0) { return false; } } return true; }for a 50% spread of 1000000 valid/invalid mix-cased strings the runtimes are:
isHexAddressCaseInsensitive: 238.701ms (uses `HEX_CHECKSUM_ADDRESS_REGEX`) isHexAddressCaseInsensitiveFast: 50.609msOk, I'm going to stop now. Use bitwise responsibly. :-)
@davidmurdoch I thought your view was that these changes to the hex functions were in the end micro-optimizations? Do you think it's still worth it to optimize them further?
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[-]RegEx is slow (can we make faster hex functions?)[/-][+][utils] RegEx is slow (can we make faster hex functions?)[/+]on Sep 11, 2026
Noticed a recent attempt at speeding up some functions by switching to RegEx. But RegExes are usually slower than iterating over strings.
For example, this function:
https://github.com/MetaMask/utils/blob/1bea7f378c37117260912af1921556bc57110d20/src/hex.ts#L60
Is probably about 4-5x slower than something like this:
(don't take my word for it. this should be tested further)