Integrated: 8286715: Generalize MemorySegment::ofBuffer

[Maurizio Cimadamore]

On Fri, 13 May 2022 12:33:10 GMT, Maurizio Cimadamore <mcimadamore at openjdk.org> wrote:

> This patch makes MemorySegment::ofBuffer more general, by allowing clients to pass *any* `Buffer` instance, not just `ByteBuffer`.
> This allows us to match expressiveness of JNI API, where JNI clients can obtain the address of any direct buffer instance, using the `GetDirectBufferAddress` function.
> 
> We thought about also providing a more general way to view a segment as a buffer (e.g. asIntBuffer) but doing that doesn't seem worth it: direct buffers can only created form `ByteBuffer`.
> So, to create a direct `IntBuffer`, clients have to first create a direct `ByteBuffer` then to view that buffer as an `IntBuffer`.
> 
> In other words, `IntBuffer` and friends are not first-class citizens in the `Buffer` API. As such it would not be possible to map many memory segments into an `IntBuffer`; in fact, the only segment we could safely map into an `IntBuffer` would be an _heap_ segment backed by an `int[]`. As such it doesn't seem worth adding a lot of API surface (in terms of additional overloads) for such a corner case.

This pull request has now been integrated.

Changeset: 89a1d055
Author:    Maurizio Cimadamore <mcimadamore at openjdk.org>
URL:       https://git.openjdk.java.net/jdk/commit/89a1d055d93ad57bcec7c1accb3f53b4c30f594d
Stats:     95 lines in 8 files changed: 55 ins; 1 del; 39 mod

8286715: Generalize MemorySegment::ofBuffer

Reviewed-by: jvernee

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

PR: https://git.openjdk.java.net/jdk/pull/8701