[AsyncStremaing] Introduce a MultiProducerSingleConsumerChannel and a duplex#425
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[AsyncStremaing] Introduce a MultiProducerSingleConsumerChannel and a duplex#425FranzBusch wants to merge 4 commits into
MultiProducerSingleConsumerChannel and a duplex#425FranzBusch wants to merge 4 commits into
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## Motivation Real transports deliver structured data alongside end-of-stream and need to fuse the last write with the close. HTTP trailers and gRPC status are the obvious cases. Neither can be expressed by an empty-buffer terminator, and both lose H2/H3/QUIC's DATA+END_STREAM coalescing without a fused call. ## Modification Adds `FinalElement: ~Copyable = Void` as a primary associated type on all four protocols. `AsyncReader` delivers it via a `consuming FinalElement?` closure parameter; `CallerAsyncReader` returns it. Both writers gain a consuming `finish` carrying the last chunk and the payload in one call. `forEachBuffer`, `collect`, and the `pipe` variants thread the payload through. `collect` becomes consuming and gains a `Void`-final overload returning just the result. Adds an "Alternatives considered" entry covering what would break without this: HTTP body, gRPC, and fused close on H2/H3/QUIC. ## Result The four protocols can back HTTP body, gRPC streaming, and similar shapes without giving up the fused close. Default `Void` keeps simple conformers unchanged; `Never` marks infinite streams. Custom and `~Copyable` payloads work end to end.
## Motivation It is quite common to have one type of writer and wanting to adapt to the other type of writer. ## Modifications This PR adds two adapters into either direction between the writers to make conversion seamless. ## Result It is easy to go from one type of writer to the other type.
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Motivation
When working with async reader and writer one often needs "root" readers and writers. A multi producer single consumer channel can provide the foundation for such a reader and writer pair. Furthermore, developers often want a connected duplex pair of readers and writers for testing or in-memory purposes.
Modifications
This PR brings over the existing
MultiProducerSingleConsumerAsyncChannelwith adaptions to handle reader and writer like interfaces and leverage unstable types such asUniqueDeque. Furthermore, this PR also brings aDuplexStreamthat sets up two connected pairs of MPSC channels.I intentionally copied and modified the MPSC implementation since I don't want to carry
#ifconditionals in an existing used implementation. Once we stabilize this module we can evaluate how to best proceed.Result
Makes it easier for developers to work with readers and writers. In particular, makes testing a lot easier.