RFR: 8329997: Add provisions for checking memory segment alignment constraints [v2]

[Per Minborg]

On Mon, 15 Apr 2024 10:05:44 GMT, Maurizio Cimadamore <mcimadamore at openjdk.org> wrote:

>> Per Minborg has updated the pull request incrementally with three additional commits since the last revision:
>> 
>>  - Update src/java.base/share/classes/jdk/internal/foreign/HeapMemorySegmentImpl.java
>>    
>>    Co-authored-by: Jorn Vernee <JornVernee at users.noreply.github.com>
>>  - Update src/java.base/share/classes/jdk/internal/foreign/NativeMemorySegmentImpl.java
>>    
>>    Co-authored-by: Jorn Vernee <JornVernee at users.noreply.github.com>
>>  - Update src/java.base/share/classes/java/lang/foreign/MemorySegment.java
>>    
>>    Co-authored-by: Maurizio Cimadamore <54672762+mcimadamore at users.noreply.github.com>
>
> src/java.base/share/classes/java/lang/foreign/MemorySegment.java line 408:
> 
>> 406:  * }
>> 407:  *
>> 408:  * In order to simplify determination of alignment, in the case of either native or heap
> 
> This can be expressed more directly as follows:
> 
> Clients can use the ... method to check if a memory segment supports the alignment constraint of a memory layout, as follows:
> 
> 
> I'd also advise against using a method in the snippet, as that looks like the method is part of the API. Perhaps something like this:
> 
> 
> MemoryLayout layout = ...
> MemorySegment segment = ...
> boolean isAligned = segment.maxByteAlignment() >= layout.byteAlignment()

The example was similar to an existing method shown in a snippet in the same class, but we could change it anyway.

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PR Review Comment: https://git.openjdk.org/jdk/pull/18779#discussion_r1565751189