add an explicit midi parser/chunker to CoreAudio

libs/backends/coreaudio/coreaudio_backend.h

@@ -445,6 +445,61 @@ class CoreAudioBackend : public AudioBackend {
 			return NULL;
 		}
 
+#define USE_MIDI_PARSER
+
+#ifdef USE_MIDI_PARSER
+
+	bool midi_process_byte (const uint8_t);
+
+	void midi_record_byte(uint8_t byte) {
+		if (_total_bytes < sizeof(_parser_buffer)) {
+			_parser_buffer[_total_bytes] = byte;
+		} else {
+			++_unbuffered_bytes;
+		}
+		++_total_bytes;
+	}
+
+	void midi_prepare_byte_event(const uint8_t byte) {
+		_parser_buffer[0] = byte;
+		_event.prepare(1);
+	}
+
+	bool midi_prepare_buffered_event() {
+		const bool result = _unbuffered_bytes == 0;
+		if (result) {
+			_event.prepare(_total_bytes);
+		}
+		_total_bytes = 0;
+		_unbuffered_bytes = 0;
+		if (_status_byte >= 0xf0) {
+			_expected_bytes = 0;
+			_status_byte = 0;
+		}
+		return result;
+	}
+
+	struct ParserEvent {
+		size_t _size;
+		bool _pending;
+		ParserEvent (const size_t size)
+			: _size(size)
+			, _pending(false) {}
+
+		void prepare(const size_t size) {
+			_size = size;
+			_pending = true;
+		}
+	} _event;
+
+	bool    _first_time;
+	size_t  _unbuffered_bytes;
+	size_t  _total_bytes;
+	size_t  _expected_bytes;
+	uint8_t _status_byte;
+	uint8_t _parser_buffer[1024];
+#endif
+
 }; // class CoreAudioBackend
 
 } // namespace