[foreign-memaccess+abi] RFR: 8310362: Improve composability of handle derived from layouts [v2]

[Jorn Vernee]

On Thu, 22 Jun 2023 21:01:50 GMT, Maurizio Cimadamore <mcimadamore at openjdk.org> wrote:

>> Jorn Vernee has updated the pull request incrementally with five additional commits since the last revision:
>> 
>>  - missing changes
>>  - rework offset computation doc
>>  - address most review comments
>>  - add collectCoordinates void filter review changes
>>  - include root layout check review changes
>
> src/java.base/share/classes/java/lang/foreign/MemoryLayout.java line 343:
> 
>> 341:      */
>> 342:     @ForceInline
>> 343:     default long scale(long offset, long index) {
> 
> was thinking... do we want the output of this method to ever be negative? (since it's used as an offset to a segment). Also, should we check for overflows with multiplyExact?

I initially consider negative inputs, I wasn't sure, but thought they might be useful in some cases, so I left them in.

multiplyExact/addExtact seems like a good idea to use.

> src/java.base/share/classes/java/lang/foreign/MemoryLayout.java line 387:
> 
>> 385:      * <ul>
>> 386:      *     <li>its return type is {@code long};</li>
>> 387:      *     <li>it has at least one {@code long} leading parameter representing the base offset;</li>
> 
> should be "it has one" e.g. not "at least one" right?

I put at least one as a hint there might be more (dynamic) coordinates. But maybe it's not important. I'll simplify

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PR Review Comment: https://git.openjdk.org/panama-foreign/pull/840#discussion_r1239068812
PR Review Comment: https://git.openjdk.org/panama-foreign/pull/840#discussion_r1239067606