RFR: 8296024: Usage of DIrectBuffer::address should be guarded [v12]

[Per Minborg]

On Wed, 23 Nov 2022 16:14:52 GMT, Maurizio Cimadamore <mcimadamore at openjdk.org> wrote:

>> Per Minborg has updated the pull request incrementally with one additional commit since the last revision:
>> 
>>   Cleanup
>
> src/java.base/share/classes/jdk/internal/access/JavaNioAccess.java line 125:
> 
>> 123:      * @see #releaseScope(Buffer, MemorySessionImpl)
>> 124:      */
>> 125:     MemorySessionImpl acquireScopeOrNull(Buffer buffer);
> 
> I think this looks better - but naming-wise it's still a bit problematic. This method really acquires the underlying session, not a scope. And also, here we have `OrNull`, but the already existing `acquireSession` also has a similar semantics w.r.t. null.
> 
> I suggest to rename:
> 
> * `acquireSession` -> `acquireSessionAsRunnable`
> * `acquireScopeOrNull` -> `acquireSession`
> * `releaseScope` -> `releaseSession`
> 
> Also, once we have `acquire/releaseSession`, it is not clear to me that we still need `acquireSessionAsRunnable` in the JavaNIOAccess class - it seems like you can create the Runnable where it's required (probably IOUtil), simply by using straight acquire/release.

The name "scope" was used in anticipation of the new proposed Java 20 naming. But I can change it back to session again. We could always rename later.

> src/java.base/share/classes/jdk/internal/access/JavaNioAccess.java line 164:
> 
>> 162:     int pageSize();
>> 163: 
>> 164:     sealed interface ScopeAcquisition extends AutoCloseable {
> 
> Is this still needed?

Well spotted.

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PR: https://git.openjdk.org/jdk/pull/11260