ViewCodec

A Codec whose decode returns a borrowed view into the source buffer instead of a self-contained value — the explicit opt-in that lets a @RemainingBytes @UseCodec(C) val: T field carry a non-Payload type (including ReadBuffer itself).

The buffer-codec lockdown forbids raw buffer types in @ProtocolMessage fields by default because they leak ownership ambiguity (who frees, when, aliased?). Implementing ViewCodec is the ownership answer, and it is a contract the implementor must honor and document:

• decode returns a view whose lifetime is tied to the buffer it was decoded from (e.g. buffer.readBytes(buffer.remaining())). The consumer must read, copy, or otherwise consume the view before the source buffer is recycled — the contract zero-copy streaming protocols (HTTP/3 DATA/HEADERS payloads, QPACK field sections) already place on their frame readers. Nothing is allocated and nothing needs freeing beyond the source buffer's own lifecycle.

• encode must be non-consuming (restore the view's position after copying) so a value can be size-checked and re-encoded.

When the decoded value must outlive the source buffer, this is the wrong tool — use a Payload-marked type over an OwnedBytesHandle (consumer-owned copy) instead.