midi_manager.h

// Copyright (c) 2013 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 MEDIA_MIDI_MIDI_MANAGER_H_
#define MEDIA_MIDI_MIDI_MANAGER_H_

#include <stddef.h>
#include <stdint.h>

#include <set>
#include <vector>

#include "base/macros.h"
#include "base/memory/ref_counted.h"
#include "base/synchronization/lock.h"
#include "base/time/time.h"
#include "media/midi/midi_export.h"
#include "media/midi/midi_port_info.h"
#include "media/midi/midi_service.mojom.h"

namespace base {
class SingleThreadTaskRunner;
}  // namespace base

namespace midi {

class MidiService;

// A MidiManagerClient registers with the MidiManager to receive MIDI data.
// See MidiManager::RequestAccess() and MidiManager::ReleaseAccess()
// for details.
// TODO(toyoshim): Consider to have a MidiServiceClient interface.
class MIDI_EXPORT MidiManagerClient {
 public:
  virtual ~MidiManagerClient() {}

  // AddInputPort() and AddOutputPort() are called before CompleteStartSession()
  // is called to notify existing MIDI ports, and also called after that to
  // notify new MIDI ports are added.
  virtual void AddInputPort(const MidiPortInfo& info) = 0;
  virtual void AddOutputPort(const MidiPortInfo& info) = 0;

  // SetInputPortState() and SetOutputPortState() are called to notify a known
  // device gets disconnected, or connected again.
  virtual void SetInputPortState(uint32_t port_index,
                                 mojom::PortState state) = 0;
  virtual void SetOutputPortState(uint32_t port_index,
                                  mojom::PortState state) = 0;

  // CompleteStartSession() is called when platform dependent preparation is
  // finished.
  virtual void CompleteStartSession(mojom::Result result) = 0;

  // ReceiveMidiData() is called when MIDI data has been received from the
  // MIDI system.
  // |port_index| represents the specific input port from input_ports().
  // |data| represents a series of bytes encoding one or more MIDI messages.
  // |length| is the number of bytes in |data|.
  // |timestamp| is the time the data was received, in seconds.
  virtual void ReceiveMidiData(uint32_t port_index,
                               const uint8_t* data,
                               size_t length,
                               double timestamp) = 0;

  // AccumulateMidiBytesSent() is called to acknowledge when bytes have
  // successfully been sent to the hardware.
  // This happens as a result of the client having previously called
  // MidiManager::DispatchSendMidiData().
  virtual void AccumulateMidiBytesSent(size_t n) = 0;

  // Detach() is called when MidiManager is going to shutdown immediately.
  // Client should not touch MidiManager instance after Detach() is called.
  virtual void Detach() = 0;
};

// Manages access to all MIDI hardware.
// *** Note ***: If dynamic instantiation feature is enabled, all MidiManager
// methods will be called on Chrome_IOThread. See comments on Shutdown() too.
class MIDI_EXPORT MidiManager {
 public:
  static const size_t kMaxPendingClientCount = 128;

  explicit MidiManager(MidiService* service);
  virtual ~MidiManager();

  // The constructor and the destructor will be called on the CrBrowserMain
  // thread.
  static MidiManager* Create(MidiService* service);

  // Called on the CrBrowserMain thread to notify the Chrome_IOThread will stop
  // and the instance will be destructed on the CrBrowserMain thread soon.
  // *** Note ***: If dynamic instantiation feature is enabled, MidiService
  // calls this on Chrome_IOThread and ShutdownOnSessionThread() will be called
  // synchronously so that MidiService can destruct MidiManager synchronously.
  void Shutdown();

  // A client calls StartSession() to receive and send MIDI data.
  // If the session is ready to start, the MIDI system is lazily initialized
  // and the client is registered to receive MIDI data.
  // CompleteStartSession() is called with mojom::Result::OK if the session is
  // started. Otherwise CompleteStartSession() is called with a proper
  // mojom::Result code.
  // StartSession() and EndSession() can be called on the Chrome_IOThread.
  // CompleteStartSession() will be invoked on the same Chrome_IOThread.
  void StartSession(MidiManagerClient* client);

  // A client calls EndSession() to stop receiving MIDI data.
  void EndSession(MidiManagerClient* client);

  // Invoke AccumulateMidiBytesSent() for |client| safely. If the session was
  // already closed, do nothing.
  void AccumulateMidiBytesSent(MidiManagerClient* client, size_t n);

  // DispatchSendMidiData() is called when MIDI data should be sent to the MIDI
  // system.
  // This method is supposed to return immediately and should not block.
  // |port_index| represents the specific output port from output_ports().
  // |data| represents a series of bytes encoding one or more MIDI messages.
  // |length| is the number of bytes in |data|.
  // |timestamp| is the time to send the data, in seconds. A value of 0
  // means send "now" or as soon as possible.
  // The default implementation is for unsupported platforms.
  virtual void DispatchSendMidiData(MidiManagerClient* client,
                                    uint32_t port_index,
                                    const std::vector<uint8_t>& data,
                                    double timestamp);

 protected:
  friend class MidiManagerUsb;

  // Initializes the platform dependent MIDI system. MidiManager class has a
  // default implementation that synchronously calls CompleteInitialization()
  // with mojom::Result::NOT_SUPPORTED on the caller thread. A derived class for
  // a specific platform should override this method correctly.
  // This method is called on Chrome_IOThread thread inside StartSession().
  // Platform dependent initialization can be processed synchronously or
  // asynchronously. When the initialization is completed,
  // CompleteInitialization() should be called with |result|.
  // |result| should be mojom::Result::OK on success, otherwise a proper
  // mojom::Result.
  virtual void StartInitialization();

  // Finalizes the platform dependent MIDI system. Called on Chrome_IOThread
  // thread and the thread will stop immediately after this call.
  // Platform dependent resources that were allocated on the Chrome_IOThread
  // should be disposed inside this method.
  virtual void Finalize() {}

  // Called from a platform dependent implementation of StartInitialization().
  // It invokes CompleteInitializationInternal() on the thread that calls
  // StartSession() and distributes |result| to MIDIManagerClient objects in
  // |pending_clients_|.
  void CompleteInitialization(mojom::Result result);

  void AddInputPort(const MidiPortInfo& info);
  void AddOutputPort(const MidiPortInfo& info);
  void SetInputPortState(uint32_t port_index, mojom::PortState state);
  void SetOutputPortState(uint32_t port_index, mojom::PortState state);

  // Dispatches to all clients.
  // TODO(toyoshim): Fix the mac implementation to use
  // |ReceiveMidiData(..., base::TimeTicks)|.
  void ReceiveMidiData(uint32_t port_index,
                       const uint8_t* data,
                       size_t length,
                       double timestamp);

  void ReceiveMidiData(uint32_t port_index,
                       const uint8_t* data,
                       size_t length,
                       base::TimeTicks time) {
    ReceiveMidiData(port_index, data, length,
                    (time - base::TimeTicks()).InSecondsF());
  }

  size_t clients_size_for_testing() const { return clients_.size(); }
  size_t pending_clients_size_for_testing() const {
    return pending_clients_.size();
  }

  const MidiPortInfoList& input_ports() const { return input_ports_; }
  const MidiPortInfoList& output_ports() const { return output_ports_; }
  MidiService* service() { return service_; }

 private:
  enum class InitializationState {
    NOT_STARTED,
    STARTED,
    COMPLETED,
  };

  void CompleteInitializationInternal(mojom::Result result);
  void AddInitialPorts(MidiManagerClient* client);
  void ShutdownOnSessionThread();

  // Keeps track of all clients who wish to receive MIDI data.
  typedef std::set<MidiManagerClient*> ClientSet;
  ClientSet clients_;

  // Keeps track of all clients who are waiting for CompleteStartSession().
  ClientSet pending_clients_;

  // Keeps a SingleThreadTaskRunner of the thread that calls StartSession in
  // order to invoke CompleteStartSession() on the thread.
  scoped_refptr<base::SingleThreadTaskRunner> session_thread_runner_;

  // Tracks platform dependent initialization state.
  InitializationState initialization_state_;

  // Keeps false until Finalize() is called.
  bool finalized_;

  // Keeps the platform dependent initialization result if initialization is
  // completed. Otherwise keeps mojom::Result::NOT_INITIALIZED.
  mojom::Result result_;

  // Keeps all MidiPortInfo.
  MidiPortInfoList input_ports_;
  MidiPortInfoList output_ports_;

  // Protects access to |clients_|, |pending_clients_|,
  // |session_thread_runner_|, |initialization_state_|, |finalize_|, |result_|,
  // |input_ports_| and |output_ports_|.
  base::Lock lock_;

  // MidiService outlives MidiManager.
  MidiService* const service_;

  DISALLOW_COPY_AND_ASSIGN(MidiManager);
};

}  // namespace midi

#endif  // MEDIA_MIDI_MIDI_MANAGER_H_