[foreign-memaccess+abi] RFR: 8300785: Add way to select group element paths by index

[Maurizio Cimadamore]

On Fri, 20 Jan 2023 15:53:49 GMT, Jorn Vernee <jvernee at openjdk.org> wrote:

>> This patch adds a new factory to MemoryLayout.PathElement, namely, to create a group element path from a long index, rather than a name. While named struct/union fields are common, there are cases where being able to access elements by index is important, such when doing a full (recursive) scan of the contents of a struct.
>
> test/jdk/java/foreign/TestLayoutPaths.java line 113:
> 
>> 111:         g.byteOffset(groupElement(-1));
>> 112:     }
>> 113: 
> 
> Maybe you could add another test case that tests an index that is too large. e.g. `2` for a struct with 1 element.

Good point - it was my intention but got distracted :-)

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PR: https://git.openjdk.org/panama-foreign/pull/773