1// Copyright 2013 The Chromium Authors. All rights reserved.
2// Use of this source code is governed by a BSD-style license that can be
3// found in the LICENSE file.
4
5#ifndef MEDIA_MIDI_MIDI_MESSAGE_QUEUE_H_
6#define MEDIA_MIDI_MIDI_MESSAGE_QUEUE_H_
7
8#include <deque>
9#include <vector>
10
11#include "base/basictypes.h"
12#include "media/base/media_export.h"
13
14namespace media {
15
16// A simple message splitter for possibly unsafe/corrupted MIDI data stream.
17// This class allows you to:
18// - maintain fragmented MIDI message.
19// - skip any invalid data sequence.
20// - reorder MIDI messages so that "System Real Time Message", which can be
21//   inserted at any point of the byte stream, is placed at the boundary of
22//   complete MIDI messages.
23// - (Optional) reconstruct complete MIDI messages from data stream where
24//   MIDI status byte is abbreviated (a.k.a. "running status").
25//
26// Example (pseudo message loop):
27//   MidiMessageQueue queue(true);  // true to support "running status"
28//   while (true) {
29//     if (is_incoming_midi_data_available()) {
30//       std::vector<uint8> incoming_data;
31//       read_incoming_midi_data(&incoming_data)
32//       queue.Add(incoming_data);
33//     }
34//     while (true) {
35//       std::vector<uint8> next_message;
36//       queue.Get(&next_message);
37//       if (!next_message.empty())
38//         dispatch(next_message);
39//     }
40//   }
41class MEDIA_EXPORT MidiMessageQueue {
42 public:
43  // Initializes the queue. Set true to |allow_running_status| to enable
44  // "MIDI running status" reconstruction.
45  explicit MidiMessageQueue(bool allow_running_status);
46  ~MidiMessageQueue();
47
48  // Enqueues |data| to the internal buffer.
49  void Add(const std::vector<uint8>& data);
50  void Add(const uint8* data, size_t length);
51
52  // Fills the next complete MIDI message into |message|. If |message| is
53  // not empty, the data sequence falls into one of the following types of
54  // MIDI message.
55  // - Single "Channel Voice Message"    (w/o "System Real Time Messages")
56  // - Single "Channel Mode Message"     (w/o "System Real Time Messages")
57  // - Single "System Exclusive Message" (w/o "System Real Time Messages")
58  // - Single "System Common Message"    (w/o "System Real Time Messages")
59  // - Single "System Real Time message"
60  // |message| is empty if there is no complete MIDI message any more.
61  void Get(std::vector<uint8>* message);
62
63 private:
64  std::deque<uint8> queue_;
65  std::vector<uint8> next_message_;
66  const bool allow_running_status_;
67  DISALLOW_COPY_AND_ASSIGN(MidiMessageQueue);
68};
69
70}  // namespace media
71
72#endif  // MEDIA_MIDI_MIDI_MESSAGE_QUEUE_H_
73