On Tue, 7 Feb 2023 15:25:05 GMT, Claes Redestad <redes...@openjdk.org> wrote:
>> This adds a local, specialized `copyBytes` method to `String` that avoids >> certain redundant range checks and clamping that JIT has issues removing >> fully. >> >> This has a small but statistically significant effect on `String` >> microbenchmarks, eg.: >> >> Baseline >> >> Benchmark (size) Mode Cnt >> Score Error Units >> StringConstructor.newStringFromArray 7 avgt 15 >> 16.817 ± 0.369 ns/op >> StringConstructor.newStringFromArrayWithCharset 7 avgt 15 >> 16.866 ± 0.449 ns/op >> StringConstructor.newStringFromArrayWithCharsetName 7 avgt 15 >> 22.198 ± 0.396 ns/op >> >> >> Patch: >> >> Benchmark (size) Mode Cnt >> Score Error Units >> StringConstructor.newStringFromArray 7 avgt 15 >> 15.477 ± 0.342 ns/op >> StringConstructor.newStringFromArrayWithCharset 7 avgt 15 >> 15.557 ± 0.352 ns/op >> StringConstructor.newStringFromArrayWithCharsetName 7 avgt 15 >> 21.272 ± 0.398 ns/op >> >> >> Care has to be taken to ensure preconditions have been checked when using >> `checkBytes`. In the case of `String(AbstractStringBuilder)` there's a >> possible pre-existing issue where the constructor might either throw an >> exception or truncate the buffer if the builder byte array and length is not >> in agreement (theoretically possible if you clear/remove and call >> `trimToSize()` concurrently). Adding an explicit check here seem to be the >> right thing to do regardless of this RFE. > > Claes Redestad has updated the pull request incrementally with one additional > commit since the last revision: > > copyrights Marked as reviewed by smarks (Reviewer). src/java.base/share/classes/java/lang/StringLatin1.java line 763: > 761: return ""; > 762: } > 763: return new String(String.copyBytes(val, index, len), LATIN1); It might be worthwhile putting a comment at the top of this method saying that the caller is required to bounds-check the arguments. It's called from several other classes in this package, so it would be good to document this package-internal contract. I checked the callers and they seem fine. ------------- PR: https://git.openjdk.org/jdk/pull/12453
