Please review this PR which proposes to change the input buffer size of `ZipFileInflaterInputStream` to be based on the _compressed_ size of a ZIP entry instead of the _uncompressed_ size. This saves allocation since buffers will no longer be oversized:
* The `size` parameter passed to the `ZipFileInflaterInputStream` constructor is passed on to the superclass `InflaterInputStream` where it determines the size of the input buffer. This buffer is used to read compressed data and pass it on to the `Inflater`. * `ZipFile:getInputStream` currently looks at the _uncompressed_ size when determining the input buffer size. It should instead use the _compressed_ size, since this buffer is used for compressed, not uncompressed data. * The current implementation somewhat mysteriously adds 2 to the uncompressed size. My guess is that this is to allow fitting a two-byte DEFLATE header for empty files (where the uncompressed size is 0 and the compressed size is 2). * There is a check for `size <= 0`. This condition is unreachable in the current code and in the PR as well, since the compressed size will always be `>= 2`. I propose we remove this check. Performance: A benchmark which measures the cost of opening and closing input streams using `ZipFile::getInputStream` shows a modest improvement of ~5%, consistent with less allocation of unused buffer space. Testing: No tests are added in this PR. The `noreg-cleanup` label is added in JBS. GHA testing is currently pending. ------------- Commit messages: - Use compressed size instead of uncompressed size when determining the ZipFileInflaterInputStream input buffer size Changes: https://git.openjdk.org/jdk/pull/21379/files Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=21379&range=00 Issue: https://bugs.openjdk.org/browse/JDK-8341597 Stats: 4 lines in 1 file changed: 0 ins; 3 del; 1 mod Patch: https://git.openjdk.org/jdk/pull/21379.diff Fetch: git fetch https://git.openjdk.org/jdk.git pull/21379/head:pull/21379 PR: https://git.openjdk.org/jdk/pull/21379
