On Tue, 19 Sep 2023 09:25:36 GMT, Chen Liang <li...@openjdk.org> wrote:
>> 温绍锦 has updated the pull request incrementally with one additional commit >> since the last revision: >> >> "-" -> "& ~" > > 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``` ------------- PR Review Comment: https://git.openjdk.org/jdk/pull/15768#discussion_r1329846187
