Web MIDI API back-end (work-in-progress)

media/midi/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 <set>
+
+#include "base/basictypes.h"
+#include "base/synchronization/lock.h"
+#include "media/base/media_export.h"
+#include "media/midi/midi_port_info.h"
+
+namespace media {
+
+// A MIDIManagerClient registers with the MIDIManager to receive MIDI data.
+// See MIDIManager::RequestAccess() and MIDIManager::ReleaseAccess()
+// for details.
+class MEDIA_EXPORT MIDIManagerClient {
+ public:
+   virtual ~MIDIManagerClient() {}
+
+  // 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(int port_index,
+                               const uint8* data,
+                               size_t length,
+                               double timestamp) = 0;
+};
+
+// Manages access to all MIDI hardware.
+class MEDIA_EXPORT MIDIManager {
+ public:
+  enum AccessType {
+    kNoSystemExclusive,
+    kSystemExclusive
+  };
+
+  static MIDIManager* Create();
+
+  MIDIManager();
+  virtual ~MIDIManager();
+
+  // A client calls RequestAccess() to receive and send MIDI data.
+  // If access is approved, the MIDI system is lazily initialized
+  // and the client is registered to receive MIDI data.
+  // Returns |true| if access is approved.
+  bool RequestAccess(MIDIManagerClient* client, int access);
+
+  // A client calls ReleaseAccess() to stop receiving MIDI data.
+  void ReleaseAccess(MIDIManagerClient* client);
+
+  // SendMIDIData() sends one or more messages at the given time.
+  // |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.
+  virtual void SendMIDIData(int port_index,
+                            const uint8* data,
+                            size_t length,
+                            double timestamp) = 0;
+
+  // input_ports() is a list of MIDI ports for receiving MIDI data.
+  // Each individual port in this list can be identified by its
+  // integer index into this list.
+  const MIDIPortInfoList& input_ports() { return input_ports_; }
+
+  // output_ports() is a list of MIDI ports for sending MIDI data.
+  // Each individual port in this list can be identified by its
+  // integer index into this list.
+  const MIDIPortInfoList& output_ports() { return output_ports_; }
+
+ protected:
+  // Initializes the MIDI system, returning |true| on success.
+  virtual bool Initialize() = 0;
+
+  void AddInputPort(const MIDIPortInfo& info);
+  void AddOutputPort(const MIDIPortInfo& info);
+
+  // Dispatches to all clients.
+  void ReceiveMIDIData(
+      int port_index,
+      const uint8* data,
+      size_t length,
+      double timestamp);
+
+  bool initialized_;
+
+  // Keeps track of all clients who wish to receive MIDI data.
+  typedef std::set<MIDIManagerClient*> ClientList;
+  ClientList clients_;
+
+  // Protects access to our clients.
+  base::Lock clients_lock_;
+
+  MIDIPortInfoList input_ports_;
+  MIDIPortInfoList output_ports_;
+
+  DISALLOW_COPY_AND_ASSIGN(MIDIManager);
+};
+
+}  // namespace media
+
+#endif  // MEDIA_MIDI_MIDI_MANAGER_H_