stream_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 "pw_async2/dispatcher_base.h"
#include "pw_channel/channel.h"
#include "pw_multibuf/allocator.h"
#include "pw_multibuf/allocator_async.h"
#include "pw_multibuf/multibuf.h"
#include "pw_status/status.h"
#include "pw_stream/stream.h"
#include "pw_sync/interrupt_spin_lock.h"
#include "pw_sync/thread_notification.h"
#include "pw_thread/thread.h"
 
namespace pw::channel {
namespace internal {
 
class StreamChannelReadState {
 public:
  StreamChannelReadState() = default;
  StreamChannelReadState(const StreamChannelReadState&) = delete;
  StreamChannelReadState& operator=(const StreamChannelReadState&) = delete;
  StreamChannelReadState(StreamChannelReadState&&) = delete;
  StreamChannelReadState& operator=(StreamChannelReadState&&) = delete;
 
  bool HasBufferToFill();
 
  void ProvideBufferToFill(multibuf::MultiBuf&& buf);
 
  async2::Poll<Result<multibuf::MultiBuf>> PendFilledBuffer(
      async2::Context& cx);
 
  void ReadLoop(stream::Reader& reader);
 
 private:
  multibuf::OwnedChunk WaitForBufferToFillAndTakeFrontChunk();
  void ProvideFilledBuffer(multibuf::MultiBuf&& filled_buffer);
  void SetReadError(Status status);
 
  sync::ThreadNotification buffer_to_fill_available_;
  async2::Waker on_buffer_filled_;
  sync::InterruptSpinLock buffer_lock_;
  multibuf::MultiBuf buffer_to_fill_ PW_GUARDED_BY(buffer_lock_);
  multibuf::MultiBuf filled_buffer_ PW_GUARDED_BY(buffer_lock_);
  Status status_ PW_GUARDED_BY(buffer_lock_);
};
 
class StreamChannelWriteState {
 public:
  StreamChannelWriteState() = default;
  StreamChannelWriteState(const StreamChannelWriteState&) = delete;
  StreamChannelWriteState& operator=(const StreamChannelWriteState&) = delete;
  StreamChannelWriteState(StreamChannelWriteState&&) = delete;
  StreamChannelWriteState& operator=(StreamChannelWriteState&&) = delete;
 
  Status SendData(multibuf::MultiBuf&& buf);
 
  void WriteLoop(stream::Writer& writer);
 
 private:
  sync::ThreadNotification data_available_;
  sync::InterruptSpinLock buffer_lock_;
  multibuf::MultiBuf buffer_to_write_ PW_GUARDED_BY(buffer_lock_);
  Status status_;
};
 
}  // namespace internal
 
 
class StreamChannel final
    : public channel::Implement<channel::ByteReaderWriter> {
 public:
  StreamChannel(stream::Reader& reader,
                const thread::Options& read_thread_options,
                multibuf::MultiBufAllocator& read_allocator,
                stream::Writer& writer,
                const thread::Options& write_thread_option,
                multibuf::MultiBufAllocator& write_allocator);
 
  // Deprecated: prefer the two-allocator constructor in order to prevent reads
  // and writes blocking on waiting for buffer space from the other.
  StreamChannel(multibuf::MultiBufAllocator& allocator,
                stream::Reader& reader,
                const thread::Options& read_thread_options,
                stream::Writer& writer,
                const thread::Options& write_thread_options)
      : StreamChannel(reader,
                      read_thread_options,
                      allocator,
                      writer,
                      write_thread_options,
                      allocator) {}
 
  // StreamChannel is referenced from other threads and is therefore not movable
  // or copyable.
  StreamChannel(const StreamChannel&) = delete;
  StreamChannel& operator=(const StreamChannel&) = delete;
  StreamChannel(StreamChannel&&) = delete;
  StreamChannel& operator=(StreamChannel&&) = delete;
 
 private:
  // StreamChannel must live forever, as its state is referenced by other
  // threads.
  ~StreamChannel() final = default;
 
  // Even though the destructor is never called, classes with private
  // destructors must friend `pw::NoDestructor`.
  friend class pw::NoDestructor<StreamChannel>;
 
  Status ProvideBufferIfAvailable(async2::Context& cx);
 
  async2::Poll<Result<multibuf::MultiBuf>> DoPendRead(
      async2::Context& cx) override;
 
  async2::Poll<Status> DoPendReadyToWrite(async2::Context& cx) override;
 
  async2::Poll<std::optional<multibuf::MultiBuf>> DoPendAllocateWriteBuffer(
      async2::Context& cx, size_t min_bytes) override {
    write_allocation_future_.SetDesiredSize(min_bytes);
    return write_allocation_future_.Pend(cx);
  }
 
  Status DoStageWrite(multibuf::MultiBuf&& data) override;
 
  async2::Poll<Status> DoPendWrite(async2::Context&) override {
    return OkStatus();
  }
 
  async2::Poll<Status> DoPendClose(async2::Context&) override {
    return async2::Ready(OkStatus());
  }
 
  stream::Reader& reader_;
  stream::Writer& writer_;
  internal::StreamChannelReadState read_state_;
  internal::StreamChannelWriteState write_state_;
  multibuf::MultiBufAllocationFuture read_allocation_future_;
  multibuf::MultiBufAllocationFuture write_allocation_future_;
};
 
 
}  // namespace pw::channel