> This change generalizes `String#bytesCompatible` and > `String#copyToSegmentRaw` to support UTF-16, see this comment in the existing > code: > > https://github.com/openjdk/jdk/blob/479d43dc63674e9d7e6b543a899e76e070a632fc/src/java.base/share/classes/java/lang/String.java#L2135-L2137 > > Those APIs are used to avoid copies in `SegmentAllocator#allocateFrom` and > `MemorySegment#copy` when `String` data is compatible with the destination > charset. This is possible for UTF-16 when the platform and target charset > endianness match (UTF-16LE on little endian platforms, or UTF-16BE on big > endian) and when the UTF-16 string contains no unpaired surrogates (which > require copying the data and handling replacement characters). > > * Test coverage has been added in > `test/jdk/java/foreign/TestStringEncoding.java`, and existing coverage was > generalized to exercise multi-byte charsets like UTF-16. > * UTF-16 constants were added in `sun.nio.cs` to allow reference comparisons > of charsets, similar to existing handling of other charsets. > * An allocation-free fast path was added to `encodedLength` for UTF-16. > > (This is partly related to [this panama-dev@ > thread](https://mail.openjdk.org/archives/list/[email protected]/thread/YSPX3TBXZTZEFZNXWDYOZCWLUQPC62P6/). > UTF-16 is a less widely used charset for data outside the JVM, which is why > the existing `bytesCompatible` / `copyToSegmentRaw` fast paths focused on > UTF-8. Having fast paths for UTF-16 is interesting inside the JVM because of > UTF-16's treatment in the String APIs, it's the only option for zero-copy > String operations on non-latin1 Strings.) > > --------- > - [x] I confirm that I make this contribution in accordance with the [OpenJDK > Interim AI Policy](https://openjdk.org/legal/ai).
Liam Miller-Cushon has updated the pull request incrementally with two additional commits since the last revision: - Add OutOfMemoryError checks for UTF-16 encodedLength fast paths - Copyright years ------------- Changes: - all: https://git.openjdk.org/jdk/pull/32268/files - new: https://git.openjdk.org/jdk/pull/32268/files/fbec7c40..37d2581a Webrevs: - full: https://webrevs.openjdk.org/?repo=jdk&pr=32268&range=01 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=32268&range=00-01 Stats: 59 lines in 10 files changed: 48 ins; 0 del; 11 mod Patch: https://git.openjdk.org/jdk/pull/32268.diff Fetch: git fetch https://git.openjdk.org/jdk.git pull/32268/head:pull/32268 PR: https://git.openjdk.org/jdk/pull/32268
