lib tunes: Add string input method

src/lib/tunes/tunes.cpp

@@ -140,6 +140,17 @@ int Tunes::parse_cmd(struct tune_control_s &tune_control, unsigned &frequency, u
 	return continue_sequnece;
 }
 
+int Tunes::parse_string(const char *string, unsigned &frequency, unsigned &duration, unsigned &silence)
+{
+	// set tune string the first time
+	if (_tune == nullptr) {
+		_tune = string;
+		_next = _tune;
+	}
+
+	return next_note(frequency, duration, silence);
+}
+
 unsigned Tunes::note_to_frequency(unsigned note)
 {
 	// compute the frequency (Hz)

src/lib/tunes/tunes.h

@@ -54,6 +54,7 @@ public:
 	Tunes(unsigned tempo, unsigned octave, unsigned note_length, NoteMode mode);
 	~Tunes() = default;
 	int parse_cmd(tune_control_s &tune_control, unsigned &frequency, unsigned &duration, unsigned &silence);
+	int parse_string(const char *string, unsigned &frequency, unsigned &duration, unsigned &silence);
 
 private:
 	static const unsigned	_tune_max = 1024 * 8; // be reasonable about user tunes