On Fri, 27 Jun 2025 01:04:32 GMT, Shaojin Wen <s...@openjdk.org> wrote:
>> In BufferedReader.readLine and other similar scenarios, we need to use >> StringBuilder.append(char[]) to build the string. >> >> For these scenarios, we can Unsafe.copyMemory instead of the character copy >> of the char-by-char loop to improve the speed. >> >> @RogerRiggs completed the optimization when the encoder is LATIN1 in PR >> #24967. This PR continues to complete the optimization when the encoder is >> UTF16. > > Shaojin Wen has updated the pull request incrementally with one additional > commit since the last revision: > > Update src/java.base/share/classes/java/lang/StringUTF16.java > > Co-authored-by: Chen Liang <li...@openjdk.org> src/java.base/share/classes/java/lang/StringUTF16.java line 1490: > 1488: val, > 1489: Unsafe.ARRAY_BYTE_BASE_OFFSET + ((long) index << 1), > 1490: (long) (end - off) << 1); The documentation of `copyMemory()` is not super-clear about endianness. But it seems to imply that in this case it behaves as if it were to copy `short`s, so endianness seems to be preserved. The invocation of `copyMemory()` here implicitly assumes that `ARRAY_CHAR_INDEX_SCALE` and `ARRAY_BYTE_INDEX_SCALE` are 2 and 1, resp., which seems quite reasonable but not written in the stone. ------------- PR Review Comment: https://git.openjdk.org/jdk/pull/24773#discussion_r2228500325
