Web MIDI: running status should be reset on receiving a system message

media/midi/midi_message_queue.cc

 // Copyright 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.
 
 #include "media/midi/midi_message_queue.h"
 
 #include <algorithm>
 
 #include "base/logging.h"
 #include "media/midi/midi_message_util.h"
 
 namespace media {
 namespace {
 
 const uint8 kSysEx = 0xf0;
 const uint8 kEndOfSysEx = 0xf7;
 
 bool IsDataByte(uint8 data) {
   return (data & 0x80) == 0;
 }
 
 bool IsFirstStatusByte(uint8 data) {
   return !IsDataByte(data) && data != kEndOfSysEx;
 }
 
 bool IsSystemRealTimeMessage(uint8 data) {
   return 0xf8 <= data;
 }
 
+bool IsSystemMessage(uint8 data) {
+  return 0xf0 <= data;
+}
+
 }  // namespace
 
 MidiMessageQueue::MidiMessageQueue(bool allow_running_status)
     : allow_running_status_(allow_running_status) {}
 
 MidiMessageQueue::~MidiMessageQueue() {}
 
 void MidiMessageQueue::Add(const std::vector<uint8>& data) {
   queue_.insert(queue_.end(), data.begin(), data.end());
 }
@@ skipping 57 matching lines @@
     }
 
     DCHECK(IsDataByte(next));
     DCHECK_NE(kSysEx, status_byte);
     const size_t target_len = GetMidiMessageLength(status_byte);
     if (next_message_.size() < target_len)
       continue;
     if (next_message_.size() == target_len) {
       std::swap(*message, next_message_);
       next_message_.clear();
-      if (allow_running_status_) {
+      if (allow_running_status_ && !IsSystemMessage(status_byte)) {
         // Speculatively keep the status byte in case of running status. If this
         // assumption is not true, |next_message_| will be cleared anyway.
+        // Note that system common messages should reset the running status.
         next_message_.push_back(status_byte);
       }
       return;
     }
 
     NOTREACHED();
   }
 }
 
 }  // namespace media