On Tue, 19 Sep 2023 09:34:56 GMT, Claes Redestad <redes...@openjdk.org> wrote:
>> src/java.base/share/classes/jdk/internal/util/HexDigits.java line 103: >> >>> 101: short v = DIGITS[i & 0xff]; >>> 102: return ucase >>> 103: ? (short) (v - ((v & 0b0100_0000_0100_0000) >> 1)) // >>> really: v - ((v >= 'a' && v <= 'f') ? 32 : 0) >> >> I think this logic is somewhat complicated that explaining directly is >> better: >> `0b0100_0000_0100_0000` is a selector that selects letters (1 << 6), >> uppercase or not, and shifting it right by 1 bit incidentally becomes a bit >> offset between cases (1 << 5). >> >> I think you can keep the original `& ~` which is clearer (as `-` will not >> work had the differences not be aligned bit-wise). But you should explain >> what `>> 1` does which is a major hurdle to understanding this function. > > If we changed DIGITS to be encoded with the uppercase digits then the > expression could be simplified to > ```return ucase ? v : (short) (v | 0b0010_0000_0010_0000); // or 0x2020``` Some performance-focused scenarios, such as UUID.toString, use lowercase, so I think DIGITS should be lowercase. ------------- PR Review Comment: https://git.openjdk.org/jdk/pull/15768#discussion_r1329908384
