[jdk17] RFR: 8269246: Scoped ByteBuffer vector access

[Maurizio Cimadamore]

On Wed, 23 Jun 2021 19:10:41 GMT, Paul Sandoz <psandoz at openjdk.org> wrote:

> The Foreign Memory API supports viewing a `MemorySegment` as a `ByteBuffer`, an instance of which can then be passed to the vector load/store access methods.
> 
> Such `ByteBuffer` access requires accesses are scoped (a method annotated with `ScopedMemoryAccess.Scoped`) and the `ByteBuffer`'s scope (instance of `ScopedMemoryAccess.Scope`) checked for validity. Thereby ensuring exceptional failure if the underlying segment is shared and is closed. 
> 
> All Vector tests pass on linux-x64, linux-aarch64, macosx-x64, and windows-x64.

Changes look good - thanks for taking the time to centralize the various vector operations inside ScopedMemoryAccess.

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Marked as reviewed by mcimadamore (Reviewer).

PR: https://git.openjdk.java.net/jdk17/pull/129