loopback_channel.h

// Copyright 2024 The Pigweed Authors
//
// Licensed under the Apache License, Version 2.0 (the "License"); you may not
// use this file except in compliance with the License. You may obtain a copy of
// the License at
//
//     https://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
// WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
// License for the specific language governing permissions and limitations under
// the License.
#pragma once
 
#include <cstdint>
#include <optional>
 
#include "pw_async2/dispatcher.h"
#include "pw_async2/poll.h"
#include "pw_channel/channel.h"
#include "pw_multibuf/allocator.h"
#include "pw_multibuf/allocator_async.h"
#include "pw_multibuf/multibuf.h"
 
namespace pw::channel {
 
 
// Channel implementation which will read its own writes.
template <DataType kType>
class LoopbackChannel;
 
using LoopbackDatagramChannel = LoopbackChannel<DataType::kDatagram>;
 
using LoopbackByteChannel = LoopbackChannel<DataType::kByte>;
 
 
template <>
class LoopbackChannel<DataType::kDatagram>
    : public Implement<ReliableDatagramReaderWriter> {
 public:
  LoopbackChannel(multibuf::MultiBufAllocator& write_allocator)
      : write_alloc_future_(write_allocator) {}
  LoopbackChannel(const LoopbackChannel&) = delete;
  LoopbackChannel& operator=(const LoopbackChannel&) = delete;
 
  LoopbackChannel(LoopbackChannel&&) = default;
  LoopbackChannel& operator=(LoopbackChannel&&) = default;
 
 private:
  async2::Poll<Result<multibuf::MultiBuf>> DoPendRead(
      async2::Context& cx) override;
 
  async2::Poll<Status> DoPendReadyToWrite(async2::Context& cx) final;
 
  async2::Poll<std::optional<multibuf::MultiBuf>> DoPendAllocateWriteBuffer(
      async2::Context& cx, size_t min_bytes) final {
    write_alloc_future_.SetDesiredSize(min_bytes);
    return write_alloc_future_.Pend(cx);
  }
 
  Status DoStageWrite(multibuf::MultiBuf&& data) final;
 
  async2::Poll<Status> DoPendWrite(async2::Context&) final;
 
  async2::Poll<Status> DoPendClose(async2::Context&) final;
 
  multibuf::MultiBufAllocationFuture write_alloc_future_;
  std::optional<multibuf::MultiBuf> queue_;
 
  async2::Waker waker_;
};
 
template <>
class LoopbackChannel<DataType::kByte>
    : public Implement<ReliableByteReaderWriter> {
 public:
  LoopbackChannel(multibuf::MultiBufAllocator& write_allocator)
      : write_alloc_future_(write_allocator) {}
  LoopbackChannel(const LoopbackChannel&) = delete;
  LoopbackChannel& operator=(const LoopbackChannel&) = delete;
 
  LoopbackChannel(LoopbackChannel&&) = default;
  LoopbackChannel& operator=(LoopbackChannel&&) = default;
 
 private:
  async2::Poll<Result<multibuf::MultiBuf>> DoPendRead(
      async2::Context& cx) override;
 
  async2::Poll<Status> DoPendReadyToWrite(async2::Context&) final {
    return async2::Ready(OkStatus());
  }
 
  async2::Poll<std::optional<multibuf::MultiBuf>> DoPendAllocateWriteBuffer(
      async2::Context& cx, size_t min_bytes) final {
    write_alloc_future_.SetDesiredSize(min_bytes);
    return write_alloc_future_.Pend(cx);
  }
 
  Status DoStageWrite(multibuf::MultiBuf&& data) final;
 
  async2::Poll<Status> DoPendWrite(async2::Context&) final;
 
  async2::Poll<Status> DoPendClose(async2::Context&) final;
 
  multibuf::MultiBufAllocationFuture write_alloc_future_;
  multibuf::MultiBuf queue_;
 
  async2::Waker read_waker_;
};
 
}  // namespace pw::channel