On Tue, 7 Feb 2023 14:39:31 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: > > Update StringLatin1.trim for consistency src/java.base/share/classes/java/lang/String.java line 4546: > 4544: // To avoid surprises due to data races (which would either > truncate or throw an exception) > 4545: // we should check that length <= val.length up front > 4546: checkOffset(length, val.length); I agree a check is needed here but I assume using checkOffset means that SB::toString could fail with SIOOBE. I wonder if Math.min(length, val.length) would be better here. ------------- PR: https://git.openjdk.org/jdk/pull/12453
