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      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 
     14 namespace 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 //   }
     41 class 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