Please consider this PR which makes `ZipFileInflaterInputStream` release its `Inflater` instance back to the pool when observing that the stream has been fully consumed.
This is motivated by the following observations: * After a `ZipFileInflaterInputStream` has reached the end of stream, its `Inflater` instance no longer does useful work. * Obtaining an input stream via `ZipFile::getInputStream` without properly closing it is probably common. Obtaining it without fully consuming it is probably more rare. (Something like `classLoader.getInputStream(entry).readAllBytes()` is probably common) * While GC will eventually release the `Inflater` when the `Cleaner` closes the stream, this will only happen at some later point in time. In the meantime, `ZipFile::getInputStream` may produce many new `Inflater` instances. These will all be released to the pool once GC eventually catches up. * Once an `Inflater` is released to to pool, it will stay there for the lifetime of the `ZipFile` * The lifetime of a `ZipFile` may often be as long as the application (consider class loaders). This PR suggests the following changes: * Rename the existing field `ZipFileInflaterInputStream.eof` to `compressedEof`. (This tracks the EOF of the filtered input stream) * Add a new field `ZipFileInflaterInputStream.eof` to track the EOF of uncompressed data. * Override `ZipFileInflaterInputStream.read(byte[] b, int off, int len)` to detect the EOF of uncompressed data and release the `Inflater` instance back to the pool when it is no longer needed. * To protect the `Inflater` instance from being used after being released and reset, the following updates are needed: * `ZipFileInflaterInputStream.read` must check if EOF has been reached but that the stream has not yet been closed. In this case, EOF should be returned. * Similarly, `ZipFileInflaterInputStream.available` needs an update to return 0 if EOF has been detected. The PR adds a test `ReleaseInflaterOnEOF` which verifies that all fully consumed input streams are backed by the same `Inflater` instance. This PR was inspired by JDK-7031076 and this discussion: https://mail.openjdk.org/pipermail/core-libs-dev/2011-March/006341.html ------------- Commit messages: - Add comment justifying the override of InputStream.read - Use correct copyright year for a new test - Make sure the ZipFile is closed using TwR - Call transferTo on the correct stream instance - Make ZipFileInflaterInputStream release its Inflater to the pool when observing that the stream is fully consumed (EOF) Changes: https://git.openjdk.org/jdk/pull/21157/files Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=21157&range=00 Issue: https://bugs.openjdk.org/browse/JDK-8340814 Stats: 139 lines in 2 files changed: 135 ins; 0 del; 4 mod Patch: https://git.openjdk.org/jdk/pull/21157.diff Fetch: git fetch https://git.openjdk.org/jdk.git pull/21157/head:pull/21157 PR: https://git.openjdk.org/jdk/pull/21157
