RFR: 8292758: put support for UNSIGNED5 format into its own header file [v2]

[Dean Long]

On Fri, 2 Sep 2022 00:04:17 GMT, John R Rose <jrose at openjdk.org> wrote:

>> Refactor code from inside of CompressedStream into its own unit.
>> 
>> This code is likely to be used in future refactorings, such as JDK-8292818 (replace 96-bit representation for field metadata with variable-sized streams).
>> 
>> Add gtests.
>
> John R Rose 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 two additional commits since the last revision:
> 
>  - Merge branch 'master' of https://git.openjdk.org/jdk into compressed-stream
>  - 8292758: put support for UNSIGNED5 format into its own header file

I'm concerned about the "excluded bytes" change.  It appears to change the encoding, which would mean that SA would not be able to read streams from earlier JVMs, which may or may not be a concern.  I suggest splitting this up into the straight-forward refactor (without the excluded bytes change), then adding excluded bytes as a follow-up.

-------------

Changes requested by dlong (Reviewer).

PR: https://git.openjdk.org/jdk/pull/10067