message_pipe_dispatcher.h

// Copyright 2015 The Chromium Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

#ifndef MOJO_CORE_MESSAGE_PIPE_DISPATCHER_H_
#define MOJO_CORE_MESSAGE_PIPE_DISPATCHER_H_

#include <stdint.h>

#include <memory>
#include <queue>

#include "base/memory/raw_ptr_exclusion.h"
#include "mojo/core/atomic_flag.h"
#include "mojo/core/dispatcher.h"
#include "mojo/core/ports/port_ref.h"
#include "mojo/core/watcher_set.h"
#include "third_party/abseil-cpp/absl/types/optional.h"

namespace mojo {
namespace core {

class NodeController;

class MessagePipeDispatcher : public Dispatcher {
 public:
  // Constructs a MessagePipeDispatcher permanently tied to a specific port.
  // |connected| must indicate the state of the port at construction time; if
  // the port is initialized with a peer, |connected| must be true. Otherwise it
  // must be false.
  //
  // A MessagePipeDispatcher may not be transferred while in a disconnected
  // state, and one can never return to a disconnected once connected.
  //
  // |pipe_id| is a unique identifier which can be used to track pipe endpoints
  // as they're passed around. |endpoint| is either 0 or 1 and again is only
  // used for tracking pipes (one side is always 0, the other is always 1.)
  MessagePipeDispatcher(NodeController* node_controller,
                        const ports::PortRef& port,
                        uint64_t pipe_id,
                        int endpoint);

  MessagePipeDispatcher(const MessagePipeDispatcher&) = delete;
  MessagePipeDispatcher& operator=(const MessagePipeDispatcher&) = delete;

  // Fuses this pipe with |other|. Returns |true| on success or |false| on
  // failure. Regardless of the return value, both dispatchers are closed by
  // this call.
  bool Fuse(MessagePipeDispatcher* other);

  // Dispatcher:
  Type GetType() const override;
  MojoResult Close() override;
  MojoResult WriteMessage(
      std::unique_ptr<ports::UserMessageEvent> message) override;
  MojoResult ReadMessage(
      std::unique_ptr<ports::UserMessageEvent>* message) override;
  MojoResult SetQuota(MojoQuotaType type, uint64_t limit) override;
  MojoResult QueryQuota(MojoQuotaType type,
                        uint64_t* limit,
                        uint64_t* usage) override;
  HandleSignalsState GetHandleSignalsState() const override;
  MojoResult AddWatcherRef(const scoped_refptr<WatcherDispatcher>& watcher,
                           uintptr_t context) override;
  MojoResult RemoveWatcherRef(WatcherDispatcher* watcher,
                              uintptr_t context) override;
  void StartSerialize(uint32_t* num_bytes,
                      uint32_t* num_ports,
                      uint32_t* num_handles) override;
  bool EndSerialize(void* destination,
                    ports::PortName* ports,
                    PlatformHandle* handles) override;
  bool BeginTransit() override;
  void CompleteTransitAndClose() override;
  void CancelTransit() override;

  static scoped_refptr<Dispatcher> Deserialize(const void* data,
                                               size_t num_bytes,
                                               const ports::PortName* ports,
                                               size_t num_ports,
                                               PlatformHandle* handles,
                                               size_t num_handles);

 private:
  class PortObserverThunk;
  friend class PortObserverThunk;

  ~MessagePipeDispatcher() override;

  MojoResult CloseNoLock();
  HandleSignalsState GetHandleSignalsStateNoLock() const;
  void OnPortStatusChanged();

  // These are safe to access from any thread without locking.
  // `node_controller_` is not a raw_ptr<...> for performance reasons (based on
  // analysis of sampling profiler data).
  RAW_PTR_EXCLUSION NodeController* const node_controller_;
  const ports::PortRef port_;
  const uint64_t pipe_id_;
  const int endpoint_;

  // Guards access to all the fields below.
  mutable base::Lock signal_lock_;

  // This is not the same is |port_transferred_|. It's only held true between
  // BeginTransit() and Complete/CancelTransit().
  AtomicFlag in_transit_;

  mutable MojoHandleSignals last_known_satisfied_signals_ = 0;
  bool port_transferred_ = false;
  AtomicFlag port_closed_;
  WatcherSet watchers_;
  absl::optional<uint64_t> receive_queue_length_limit_;
  absl::optional<uint64_t> receive_queue_memory_size_limit_;
  absl::optional<uint64_t> unread_message_count_limit_;
};

}  // namespace core
}  // namespace mojo

#endif  // MOJO_CORE_MESSAGE_PIPE_DISPATCHER_H_