compose MemorySegments

[Chris Vest]

In Netty we have a handler called ByteToMessageDecoder which I think
implements Douglas's use case.
Bytes come in, in chunks determined by IO, get collected, and then leave in
chunks of one whole message per chunk, whatever that means for the
implemented protocol in question.
Our ByteToMessageDecoder can use the CompositeByteBuf as Douglas described,
when collecting the incoming bytes.
However, the extra indirections on every memory access, introduced by the
CompositeByteBuf, turns out to be expensive in practice, so we actually use
copying by default.
The ByteToMessageDecoder can be configured to operate in either mode.

Cheers,
Chris

On Fri, 11 Jun 2021 at 13:09, Maurizio Cimadamore <
maurizio.cimadamore at oracle.com> wrote:

> One thing I saw which is very similar to what you want is this:
>
> https://netty.io/4.0/api/io/netty/buffer/CompositeByteBuf.html
>
> Perhaps Chris Vest or some other folks in Netty can comment more on that
> API. Netty is also doing some exploratory work to validate use of memory
> segments within Netty itself [1].
>
> Maurizio
>
> [1] - https://github.com/netty/netty-incubator-buffer-api
>
> On 11/06/2021 00:41, Douglas Surber wrote:
> > As I understand them, no a mapped MemorySegment wouldn't work. The data
> is not in a file. It is in byte[]s. My code has to look at the bits as it
> gets them from the network to deal with metadata. Based on that it copies
> the data bits from the network buffer into byte[]s with no additional
> processing.
> >
> > Douglas
> >
> > On Jun 10, 2021, at 4:24 PM, panama-dev-request at openjdk.java.net<mailto:
> panama-dev-request at openjdk.java.net> wrote:
> >
> > Would a mapped MemorySegment work for you?
> >
>