On Wed, 24 Jul 2024 14:57:05 GMT, Archie Cobbs <aco...@openjdk.org> wrote:
>> `GZIPInputStream` supports reading data from multiple concatenated GZIP data >> streams since [JDK-4691425](https://bugs.openjdk.org/browse/JDK-4691425). In >> order to do this, after a GZIP trailer frame is read, it attempts to read a >> GZIP header frame and, if successful, proceeds onward to decompress the new >> stream. If the attempt to decode a GZIP header frame fails, or happens to >> trigger an `IOException`, it just ignores the trailing garbage and/or the >> `IOException` and returns EOF. >> >> There are several issues with this: >> >> 1. The behaviors of (a) supporting concatenated streams and (b) ignoring >> trailing garbage are not documented, much less precisely specified. >> 2. Ignoring trailing garbage is dubious because it could easily hide errors >> or other data corruption that an application would rather be notified about. >> Moreover, the API claims that a `ZipException` will be thrown when corrupt >> data is read, but obviously that doesn't happen in the trailing garbage >> scenario (so N concatenated streams where the last one has a corrupted >> header frame is indistinguishable from N-1 valid streams). >> 3. There's no way to create a `GZIPInputStream` that does _not_ support >> stream concatenation. >> >> On the other hand, `GZIPInputStream` is an old class with lots of existing >> usage, so it's important to preserve the existing behavior, warts and all >> (note: my the definition of "existing behavior" here includes the bug fix in >> [JDK-7036144](https://bugs.openjdk.org/browse/JDK-7036144)). >> >> So this patch adds a new constructor that takes two new parameters >> `allowConcatenation` and `allowTrailingGarbage`. The legacy behavior is >> enabled by setting both to true; otherwise, they do what they sound like. In >> particular, when `allowTrailingGarbage` is false, then the underlying input >> must contain exactly one (if `allowConcatenation` is false) or exactly N (if >> `allowConcatenation` is true) concatenated GZIP data streams, otherwise an >> exception is guaranteed. > > Archie Cobbs has updated the pull request with a new target base due to a > merge or a rebase. The pull request now contains 16 commits: > > - Merge branch 'master' into JDK-8322256 > - Wording tweak. > - Change concatenation policy config from booleans to new ConcatPolicy enum. > - Merge branch 'master' into JDK-8322256 > - Bump @since from 23 to 24. > - Merge branch 'master' into JDK-8322256 > - Relabel "trailing garbage" as "extra bytes" to sound less accusatory. > - Simplify code by eliminating an impossible case. > - Field name change and Javadoc wording tweaks. > - Merge branch 'master' into JDK-8322256 > - ... and 6 more: https://git.openjdk.org/jdk/compare/332df83e...72b60092 First thank you for your efforts and patience with this PR Archie. I am trying to better grasp the problem to be solved outside of better clarity surrounding how GZIPInputStream handles concatenated gzip files - I could see possibly providing an enum which indicates to stop decompressing after processing the first gzip file or to decompress until the end of input. - This would be similar to what the commons-compress GzipCompressorInputStream class does. - It is also what Eirik and Jai are suggesting I believe. - If support for processing multiple gzip files is enabled, which would be the default, then the existing behavior is not changed. - As I have mentioned previously, we should add more testing including taking a couple of concatenated examples created via the gzip tool (or equivalent) give how light our coverage is. I don't believe we want to do more than is needed given the age of the API and there is been minimal requests for improvements at this time. ------------- PR Comment: https://git.openjdk.org/jdk/pull/18385#issuecomment-2252783484
