[foreign-jextract] RFR: Add MemoryLayout::byteOffset

[Ty Young]

On 5/11/20 3:36 AM, Chris Hegarty wrote:
> Hi,
>
> As part of feedback on the Foreign Memory API (when experimenting with
> its usage internally in the JDK), a small number of potential usability
> enhancements could be made to the API. This is the first such.
>
> This change:
>   1) renames MemoryLayout::offset to MemoryLayout::bitOffset, and
>   2) adds MemoryLayout::byteOffset
>
> This allows for easier interoperation with MemoryAddress, which deals
> with offsets and lengths in terms of bytes (rather than bits), e.g.
>     addr.addOffset(layout.byteOffset(groupElement("foo")))
>
> This brings a nice symmetry to the API; there is a trio of bit-wise
> methods: bitAlignment, bitOffset, bitSize, and their matching byte-wise
> counterparts; byteAlignment, byteOffset, byteSize.


This reminds me something I meant to bring up awhile ago: it would be 
nice to have a counterpart method "ofPaddingBytes" and pre-defined 
layouts like "PAD_BYTE_1" to the existing Bit based versions.


Could those be added too?


>
> -------------
>
> Commit messages:
>   - fix typo in javadoc example
>   - Initial MemoryLayout::byteOffset and test changes
>
> Changes: https://git.openjdk.java.net/panama-foreign/pull/157/files
>   Webrev: https://webrevs.openjdk.java.net/panama-foreign/157/webrev.00
>    Stats: 131 lines in 2 files changed: 103 ins; 1 del; 27 mod
>    Patch: https://git.openjdk.java.net/panama-foreign/pull/157.diff
>    Fetch: git fetch https://git.openjdk.java.net/panama-foreign pull/157/head:pull/157
>
> PR: https://git.openjdk.java.net/panama-foreign/pull/157