7036144: GZIPInputStream readTrailer uses faulty available() test for end-of-stream

[toddjonker]

This is a clean backport of d3f3011, originally authored by @archiecobbs and reviewed by @jaikiran

I believe this should be covered by CSR https://bugs.openjdk.org/browse/JDK-8340729 though (as noted there) the description and issue metadata differ regarding JDK21.

Testing:

• New regression test fails without the fix, passes with it
• linux-x86_64-server-release: headless tiers 1-3

---

Progress

• Change must not contain extraneous whitespace
• Change requires a CSR request matching fixVersion 21.0.9 to be approved (needs to be created)
• Commit message must refer to an issue
• JDK-7036144 needs maintainer approval

Issue

• JDK-7036144: GZIPInputStream readTrailer uses faulty available() test for end-of-stream (Bug - P4 - Requested)

Reviewing

Using git

Checkout this PR locally:
$ git fetch https://git.openjdk.org/jdk21u-dev.git pull/1897/head:pull/1897
$ git checkout pull/1897

Update a local copy of the PR:
$ git checkout pull/1897
$ git pull https://git.openjdk.org/jdk21u-dev.git pull/1897/head

Using Skara CLI tools

Checkout this PR locally:
$ git pr checkout 1897

View PR using the GUI difftool:
$ git pr show -t 1897

Using diff file

Download this PR as a diff file:
https://git.openjdk.org/jdk21u-dev/pull/1897.diff

[bridgekeeper]

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[openjdk]

❗ This change is not yet ready to be integrated.
See the Progress checklist in the description for automated requirements.

[openjdk]

This backport pull request has now been updated with issue from the original commit.

[openjdk]

At least one of the issues associated with this backport has a resolved CSR for a different version. As this means that this backport may also need a CSR, the csr label is being added to this pull request to signal this potential requirement. The command /csr unneeded can be used to remove the label in case a CSR is not needed.