RFR: 8360025: (se) Convert kqueue Selector Implementation to use FFM APIs [v4]

[Per Minborg]

On Thu, 28 Aug 2025 13:24:30 GMT, Alan Bateman <alanb at openjdk.org> wrote:

>> Darragh Clarke 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 12 additional commits since the last revision:
>> 
>>  - fixed copyright header
>>  - merged master into branch
>>  - moved repeating code into own method
>>  - implementing feedback, adding missing errno checks, cleanup
>>  - feedback
>>  - general cleanup
>>  - small refactoring
>>  - Performance
>>  - implementing feedback
>>  - removed unrelated change
>>  - ... and 2 more: https://git.openjdk.org/jdk/compare/c00c2dcb...cc5f558a
>
> src/java.base/macosx/classes/sun/nio/ch/KQueue.java line 91:
> 
>> 89:      */
>> 90:     static MemorySegment getEvent(MemorySegment memoryHandle, int i) {
>> 91:         return kevent.asSlice(memoryHandle, i);
> 
> Previous work eliminated allocating from the performance critical usages, might have to check the implications of asSlice here.

We could use indices/offsets directly in the methods that receive the slices from this method.

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PR Review Comment: https://git.openjdk.org/jdk/pull/25546#discussion_r2310386763