On Tue, 21 Dec 2021 12:50:36 GMT, Roland Westrelin <rol...@openjdk.org> wrote:
>> @dean-long actually the issue reproduces with Java 17 where >> `checkBoundsOffCount` was implemented in a more straight forward manner: >> >> >> static void checkBoundsOffCount(int offset, int count, int length) { >> if (offset < 0 || count < 0 || offset > length - count) { >> throw new StringIndexOutOfBoundsException( >> "offset " + offset + ", count " + count + ", length " + length); >> } >> } >> >> >> >> Here's a >> [gist](https://gist.github.com/amirhadadi/9505c3f5d9ad68cad2fbfd1b9e01f0b8) >> with a benchmark you can run. This benchmark compares safe and unsafe reads >> from the byte array (In this gist I didn't modify the code to add the >> offset >= 0 condition). >> >> Here are the results: >> >> >> OpenJDK 17.0.1+12 >> OSX with 2.9 GHz Quad-Core Intel Core i7 >> >> >> >> Benchmark Mode Cnt Score Error Units >> StringBenchmark.safeDecoding avgt 20 120.312 ± 11.674 ns/op >> StringBenchmark.unsafeDecoding avgt 20 72.628 ± 0.479 ns/op > > @amirhadadi unsafeDecode() is buggy I think. Offsets in the array when read > with unsafe should be computed as `offset * unsafe.ARRAY_BYTE_INDEX_SCALE + > unsafe.ARRAY_BYTE_BASE_OFFSET`. @rwestrel thanks for the correction! Here are the updated results: Benchmark Mode Cnt Score Error Units StringBenchmark.safeDecoding avgt 20 113.849 ± 1.609 ns/op StringBenchmark.unsafeDecoding avgt 20 85.272 ± 1.462 ns/op ------------- PR: https://git.openjdk.java.net/jdk/pull/6812