Dispatch separate MIDIMessageEvents for multiple messages in the received data buffer.

Source/modules/webmidi/MIDIInput.cpp

 /*
  * Copyright (C) 2013 Google Inc. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions are
  * met:
  *
  *     * Redistributions of source code must retain the above copyright
  * notice, this list of conditions and the following disclaimer.
  *     * Redistributions in binary form must reproduce the above
@@ skipping 31 matching lines @@
 MIDIInput::MIDIInput(ScriptExecutionContext* context, const String& id, const String& manufacturer, const String& name, const String& version)
     : MIDIPort(context, id, manufacturer, name, MIDIPortTypeInput, version)
 {
     ScriptWrappable::init(this);
 }
 
 void MIDIInput::didReceiveMIDIData(unsigned portIndex, const unsigned char* data, size_t length, double timeStamp)
 {
     ASSERT(isMainThread());
 
-    RefPtr<Uint8Array> array = Uint8Array::create(length);
-    array->setRange(data, length, 0);
+    // The received MIDI data may contain one or more messages.
+    // The Web MIDI API requires that a separate event be dispatched for each message,
+    // so we walk through the data and dispatch one at a time.
+    size_t i = 0;
+    while (i < length) {
+        unsigned char status = data[i];
+        unsigned char strippedStatus = status & 0xf0;
 
-    dispatchEvent(MIDIMessageEvent::create(timeStamp, array));
+        // FIXME: support System Exclusive.
+        if (strippedStatus >= 0xf0)
+            break;
+
+        // All non System Exclusive messages have a total size of 3 except for Program Change and Channel Pressure.
+        size_t totalMessageSize = (strippedStatus == 0xc0 || strippedStatus == 0xd0) ? 2 : 3;
+
+        if (i + totalMessageSize <= length) {
+            RefPtr<Uint8Array> array = Uint8Array::create(totalMessageSize);
+            array->setRange(data + i, totalMessageSize, 0);
+
+            dispatchEvent(MIDIMessageEvent::create(timeStamp, array));
+        }
+
+        i += totalMessageSize;
+    }
 }
 
 } // namespace WebCore