On Tue, 19 Sep 2023 14:30:18 GMT, 温绍锦 <d...@openjdk.org> wrote:
>> In the improvement of @cl4es PR #15591, the advantages of non-lookup-table
>> were discussed.
>>
>> But if the input is byte[], using lookup table can improve performance.
>>
>> For HexFormat#formatHex(Appendable, byte[]) and HexFormat#formatHex(byte[]),
>> If the length of byte[] is larger, the performance of table lookup will be
>> improved more obviously.
>
> 温绍锦 has updated the pull request incrementally with one additional commit
> since the last revision:
>
> fix typo
HexFormat.DIGITS now uses 256-length byte[], which can be changed to
128-length. This is a small change. Should it be changed in the current PR?
public final class HexFormat {
private static final byte[] DIGITS = {
-1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
-1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
-1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
0, 1, 2, 3, 4, 5, 6, 7, 8, 9, -1, -1, -1, -1, -1, -1,
-1, 10, 11, 12, 13, 14, 15, -1, -1, -1, -1, -1, -1, -1, -1, -1,
-1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
-1, 10, 11, 12, 13, 14, 15, -1, -1, -1, -1, -1, -1, -1, -1, -1,
-1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1
// remove 128 - 255
};
public static boolean isHexDigit(int ch) {
// unsigned right shift 8 change to 7
return ((ch >>> 7) == 0 && DIGITS[ch] >= 0);
}
public static int fromHexDigit(int ch) {
int value;
// unsigned right shift 8 change to 7
if ((ch >>> 7) == 0 && (value = DIGITS[ch]) >= 0)
...
}
}
-------------
PR Comment: https://git.openjdk.org/jdk/pull/15768#issuecomment-1736630070
