RFR: 8332003: Clarify javadoc for MemoryLayout::offsetHandle [v5]

[Paul Sandoz]

On Fri, 10 May 2024 16:10:29 GMT, Maurizio Cimadamore <mcimadamore at openjdk.org> wrote:

>> Consider this layout:
>> 
>> 
>> MemoryLayout SEQ = MemoryLayout.sequenceLayout(5,
>>              MemoryLayout.sequenceLayout(10, JAVA_INT));
>> 
>> 
>> And the corresponding offset handle:
>> 
>> 
>> MethodHandle offsetHandle = SEQ.offsetHandle(PathElement.sequenceLayout(), PathElement.sequenceLayout());
>> 
>> 
>> The resulting method handle takes two additional `long` indices. The implementation checks that the dynamically provided indices conform to the bound available at construction: that is, the first index must be < 5, while the second must be < 10. If this is not true, an `IndexOutOfBoundException` is thrown.
>> 
>> However, the javadoc for `MemoryLayout::byteOffsetHandle` doesn't claim anything in this direction. There are only some vague claims in the javadoc for `PathElement::sequenceElement()` and `PathElement::sequenceElement(long, long, long)` which make some claims on which indices are actually allowed, but the text seems more in the tone of a discussion, rather than actual normative text.
>> 
>> I've tweaked the javadoc for `MemoryLayout::byteOffsetHandle` to actually state that the indices will be checked against the "size" of the corresponding open path element (this is a new concept that I also have defined in the javadoc).
>> 
>> I also added a test for `byteOffsetHandle` as I don't think we had a test for that specifically (although this method is tested indirectly, via `MemoryLayout::varHandle`).
>
> Maurizio Cimadamore has updated the pull request incrementally with one additional commit since the last revision:
> 
>   Fix another index check

Marked as reviewed by psandoz (Reviewer).

-------------

PR Review: https://git.openjdk.org/jdk/pull/19158#pullrequestreview-2050771038