On Wed, 19 Mar 2025 14:37:33 GMT, Jaikiran Pai <j...@openjdk.org> wrote:
>> Can I please get a review of this change which proposes to fix an issue >> `java.util.zip.ZipFile` which would cause failures when multiple instances >> of `ZipFile` using non-UTF8 `Charset` were operating against the same >> underlying ZIP file? This addresses >> https://bugs.openjdk.org/browse/JDK-8347712. >> >> ZIP file specification allows for ZIP entries to mark a `UTF-8` flag to >> indicate that the entry name and comment are encoded using UTF8. A >> `java.util.zip.ZipFile` can be constructed by passing it a `Charset`. This >> `Charset` (which defaults to UTF-8) gets used for decoding entry names and >> comments for non-UTF8 entries. >> >> The internal implementation of `ZipFile` uses a `ZipCoder` (backed by >> `java.nio.charset.CharsetEncoder/CharsetDecoder` instance) for the given >> `Charset`. Except for UTF8 `ZipCoder`, other `ZipCoder`s are not thread safe. >> >> The internal implementation of `ZipFile` maintains a cache of >> `ZipFile$Source`. A `Source` corresponds to the underlying ZIP file and >> during construction, uses a `ZipCoder` for parsing the ZIP entries and once >> constructed holds on to the parsed ZIP structure. Multiple instances of a >> `ZipFile` which all correspond to the same ZIP file on the filesystem, share >> a single instance of `Source` (after the `Source` has been constructed and >> cached). Although `ZipFile` instances aren't expected to be thread-safe, the >> fact that multiple different instances of `ZipFile` could be sharing the >> same instance of `Source` in concurrent threads, mandates that the `Source` >> must be thread-safe. >> >> In Java 15, we did a performance optimization through >> https://bugs.openjdk.org/browse/JDK-8243469. As part of that change, we >> started holding on to the `ZipCoder` instance (corresponding to the >> `Charset` provided during `ZipFile` construction) in the `Source`. This >> stored `ZipCoder` was then used for `ZipFile` operations when working with >> the ZIP entries. As noted previously, any non-UTF8 `ZipCoder` is not >> thread-safe and as a result, any usages of `ZipCoder` in the `Source` makes >> `Source` not thread-safe too. That effectively violates the requirement that >> `Source` must be thread-safe to allow for its usage in multiple different >> `ZipFile` instances concurrently. This then causes `ZipFile` usages to fail >> in unexpected ways like the one shown in the linked >> https://bugs.openjdk.org/browse/JDK-8347712. >> >> The commit in this PR addresses the issue by not maintaining `ZipCoder` as a >> instance field of `Source`. Instead the `ZipCoder` is now mainta... > > Jaikiran Pai has updated the pull request with a new target base due to a > merge or a rebase. The incremental webrev excludes the unrelated changes > brought in by the merge/rebase. The pull request contains nine additional > commits since the last revision: > > - Eirik's suggestion - update test method comment > - rename entryNameCharset to charset in the test > - Eirik's suggestion - update test to even call ZipFile.getEntry() > - Eirik's inputs - replace useUTF8Coder() with zipCoderFor() > - merge latest from master branch > - add code comment > - rename field > - tiny typo fix in newly introduced documentation > - 8347712: IllegalStateException on multithreaded ZipFile access with > non-UTF8 charset src/java.base/share/classes/java/util/zip/ZipCoder.java line 47: > 45: * and can be used concurrently by multiple threads. All other {@code > ZipCoder} instances > 46: * are not thread-safe and external synchronization is required by > callers, if those > 47: * instances are to be used concurrently by multiple threads. I think you can trim this down to just say that the UTF-8 ZipCoder is thread safe, ZipCoder for other charsets require synchronization. ------------- PR Review Comment: https://git.openjdk.org/jdk/pull/23986#discussion_r2008822662
