On Wed, 18 Oct 2023 03:43:15 GMT, Jorn Vernee <jver...@openjdk.org> wrote:
> > I'm unclear why it is "better". It seems more obscure to me. > > Ok. I think it's better because it doesn't require creating a maximum size > sequence layout in order to then make a var handle out of, which is a bit of > a hack IMO. One that was required in the previous version of the API. Not sure which "previous" that was, but in JDK 21 I did not need to specify a size. The need to do that was something that came in as of JDK 22 and I thought it a bit of a backwards step perhaps motivated to help devs understand the sizes involved but given the arithmetic involved in general I am not sure it was justified. > > This kind of use-case, where the size of the sequence is not known > statically, is one of the reasons why we added the extra base offset > parameter to the var handles. The previous API dealt with that just fine. And equivalently as far as I can tell. The base offset parameter may have other uses but I need its relevance to this explained to me, > Another way of writing this would be to use the base var handle, with its > extra leading offset parameter, and then pass e.g. `i * > PositionLayout.byteSize()` as the offset at every call site (where `i` is the > array index). The two extra combination steps essentially create a var handle > with that behavior baked in. OK, but now you have a VarHandle intended for use on a SequenceLayout (ie array) of Struct and are disguising it for some reason that isn't (sufficiently?) obvious at an API level and definitely isn't obvious at a performance level. Is there some fundamental reason why the 21 API could not internally be reduced to the same ? ------------- PR Review Comment: https://git.openjdk.org/jdk/pull/15476#discussion_r1363167938
