> This PR proposes adding a new overload to `MemorySegment::getString` that > takes a known byte length of the content. > > This was previously proposed in https://github.com/openjdk/jdk/pull/20725, > but the outcome of [JDK-8333843](https://bugs.openjdk.org/browse/JDK-8333843) > was to update `MemorySegment#getString` to suggest > > > byte[] bytes = new byte[length]; > MemorySegment.copy(segment, JAVA_BYTE, offset, bytes, 0, length); > return new String(bytes, charset); > > > However this is less efficient than what the implementation of getString does > after [JDK-8362893](https://bugs.openjdk.org/browse/JDK-8362893), it now uses > `JavaLangAccess::uncheckedNewStringNoRepl` to avoid the copy. > > See also discussion in [this panama-dev@ > thread](https://mail.openjdk.org/pipermail/panama-dev/2025-November/021193.html), > and mcimadamore's document [Pulling the (foreign) > string](https://cr.openjdk.org/~mcimadamore/panama/strings_ffm.html) > > Benchmark results: > > > Benchmark (size) Mode Cnt Score Error > Units > ToJavaStringTest.jni_readString 5 avgt 30 55.339 ± 0.401 > ns/op > ToJavaStringTest.jni_readString 20 avgt 30 59.887 ± 0.295 > ns/op > ToJavaStringTest.jni_readString 100 avgt 30 84.288 ± 0.419 > ns/op > ToJavaStringTest.jni_readString 200 avgt 30 119.275 ± 0.496 > ns/op > ToJavaStringTest.jni_readString 451 avgt 30 193.106 ± 1.528 > ns/op > ToJavaStringTest.panama_copyLength 5 avgt 30 7.348 ± 0.048 > ns/op > ToJavaStringTest.panama_copyLength 20 avgt 30 7.440 ± 0.125 > ns/op > ToJavaStringTest.panama_copyLength 100 avgt 30 11.766 ± 0.058 > ns/op > ToJavaStringTest.panama_copyLength 200 avgt 30 16.096 ± 0.089 > ns/op > ToJavaStringTest.panama_copyLength 451 avgt 30 25.844 ± 0.054 > ns/op > ToJavaStringTest.panama_readString 5 avgt 30 5.857 ± 0.046 > ns/op > ToJavaStringTest.panama_readString 20 avgt 30 7.750 ± 0.046 > ns/op > ToJavaStringTest.panama_readString 100 avgt 30 14.109 ± 0.187 > ns/op > ToJavaStringTest.panama_readString 200 avgt 30 18.035 ± 0.130 > ns/op > ToJavaStringTest.panama_readString 451 avgt 30 35.896 ± 0.227 > ns/op > ToJavaStringTest.panama_readStringLength 5 avgt 30 4.565 ± 0.038 > ns/op > ToJavaStringTest.panama_readStringLength 20 avgt 30 4.654 ± 0.040 > ns/op > ToJavaStringTest.panama_readString...
Liam Miller-Cushon has updated the pull request incrementally with two additional commits since the last revision: - Updates from panama-dev thread - . ------------- Changes: - all: https://git.openjdk.org/jdk/pull/28043/files - new: https://git.openjdk.org/jdk/pull/28043/files/b729b551..3f6ee815 Webrevs: - full: https://webrevs.openjdk.org/?repo=jdk&pr=28043&range=05 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=28043&range=04-05 Stats: 278 lines in 9 files changed: 228 ins; 15 del; 35 mod Patch: https://git.openjdk.org/jdk/pull/28043.diff Fetch: git fetch https://git.openjdk.org/jdk.git pull/28043/head:pull/28043 PR: https://git.openjdk.org/jdk/pull/28043
