Use MIDIMessageQueue/IsValidWebMIDIData for MIDI byte stream validation

media/midi/midi_message_queue.h

Index: media/midi/midi_message_queue.h
diff --git a/media/midi/midi_message_queue.h b/media/midi/midi_message_queue.h
new file mode 100644
index 0000000000000000000000000000000000000000..e7b82d7d4a85e52e70ed260658cb36ab816ecaf5
--- /dev/null
+++ b/media/midi/midi_message_queue.h
@@ -0,0 +1,74 @@
+// 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_MESSAGE_QUEUE_H_
+#define MEDIA_MIDI_MIDI_MESSAGE_QUEUE_H_
+
+#include <deque>
+#include <vector>
+
+#include "base/basictypes.h"
+#include "media/base/media_export.h"
+
+namespace media {
+
+// A simple message splitter for possibly unsafe/corrupted MIDI data stream.
+// This class allows you to:
+// - maintain fragmented MIDI message.
+// - skip any invalid data sequence.
+// - reorder MIDI messages so that "System Real Time Message", which can be
+//   inserted at any point of the byte stream, is placed at the boundary of
+//   complete MIDI messages.
+// - (Optional) reconstruct complete MIDI messages from data stream where
+//   MIDI status byte is abbreviated (a.k.a. "running status").
+//
+// Example (pseudo message loop):
+//   MIDIMessageQueue queue(true);  // true to support "running status"
+//   while (true) {
+//     if (is_incoming_midi_data_available()) {
+//       std::vector<uint8> incoming_data;
+//       read_incoming_midi_data(&incoming_data)
+//       queue.Add(incoming_data);
+//     }
+//     while (true) {
+//       std::vector<uint8> next_message;
+//       queue.Get(&next_message);
+//       if (!next_message.empty())
+//         dispatch(next_message);
+//     }
+//   }
+class MEDIA_EXPORT MIDIMessageQueue {
+ public:
+  // Initializes the queue. Set true to |allow_running_status| to enable
+  // "MIDI running status" reconstruction.
+  explicit MIDIMessageQueue(bool allow_running_status);
+  ~MIDIMessageQueue();
+
+  // Enqueues |data| to the internal buffer.
+  void Add(const std::vector<uint8>& data);
+  // Enqueues |data| to the internal buffer. |data| must be valid until
+  // this method returns.

[scherkus (not reviewing), 2013/11/26 19:05:36]

nit: assuming this class is designed to be accessed on a single thread, you can
drop the "|data| must be valid until this method returns" bit

... otherwise it sounds as if data could somehow get changed by a different
thread while Add() is running (and why wouldn't this apply to the const-ref
std::vector version above?)

[yukawa, 2013/11/26 19:19:07]

Yes, it is definitely for single thread only. Remove the unnecessary bit to
unify the comment line to the previous one.

+  void Add(const uint8* data, size_t length);
+
+  // Fills the next complete MIDI message into |message|. If |message| is
+  // not empty, the data sequence falls into one of the following types of
+  // MIDI message.
+  // - Single "Channel Voice Message"    (w/o "System Real Time Messages")
+  // - Single "Channel Mode Message"     (w/o "System Real Time Messages")
+  // - Single "System Exclusive Message" (w/o "System Real Time Messages")
+  // - Single "System Common Message"    (w/o "System Real Time Messages")
+  // - Single "System Real Time message"
+  // |message| is empty if there is no complete MIDI message any more.
+  void Get(std::vector<uint8>* message);
+
+ private:
+  std::deque<uint8> queue_;
+  std::vector<uint8> next_message_;
+  const bool allow_running_status_;
+  DISALLOW_COPY_AND_ASSIGN(MIDIMessageQueue);
+};
+
+}  // namespace media
+
+#endif  // MEDIA_MIDI_MIDI_MESSAGE_QUEUE_H_