RFR: 8343188: Investigate ways to simplify MemorySegment::ofBuffer [v2]

[Maurizio Cimadamore]

On Thu, 31 Oct 2024 07:10:29 GMT, Per Minborg <pminborg at openjdk.org> wrote:

>> src/java.base/share/classes/jdk/internal/foreign/AbstractMemorySegmentImpl.java line 541:
>> 
>>> 539: 
>>> 540:     @ForceInline
>>> 541:     private static AbstractMemorySegmentImpl arrayFreeSegment(Buffer b, long offset, long length) {
>> 
>> the names `arrayFreeSegment` and `arrayBackedSegments` seem a bit confusing. I'd suggest `ofDirectBuffer` and `ofHeapBuffer`
>
> I called them that initially but there is a subtle difference; there are heap buffers that are not backed by an array. The name arrayFreeSegment could better be arrayLessSegment.

Not sure I follow. The code asks if there's a backing array (accessing base). Then:
* if there is a base, it calls `arrayBackedSegment`
* otherwise it calls `arrayLessSegment`.

Now, `arrayBackedSegment` is only implemented for heap buffers. Direct buffers throws UOE.
And, inside `arrayLessSegment` we throw if we see a non-direct (=heap) buffer.

So... it seems to me that arrayBacked = heap and arrayLess = direct?

Do you refer to char buffers backed by Strings?

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PR Review Comment: https://git.openjdk.org/jdk/pull/21764#discussion_r1824221715