decoder/wildmidi: move code to wildmidi_output()

src/decoder/plugins/WildmidiDecoderPlugin.cxx

@@ -65,6 +65,17 @@ wildmidi_finish(void)
 	WildMidi_Shutdown();
 }
 
+static DecoderCommand
+wildmidi_output(Decoder &decoder, midi *wm)
+{
+	char buffer[4096];
+	int length = WildMidi_GetOutput(wm, buffer, sizeof(buffer));
+	if (length <= 0)
+		return DecoderCommand::STOP;
+
+	return decoder_data(decoder, nullptr, buffer, length, 0);
+}
+
 static void
 wildmidi_file_decode(Decoder &decoder, Path path_fs)
 {
@@ -94,18 +105,11 @@ wildmidi_file_decode(Decoder &decoder, Path path_fs)
 
 	DecoderCommand cmd;
 	do {
-		char buffer[4096];
-		int len;
-
 		info = WildMidi_GetInfo(wm);
 		if (info == nullptr)
 			break;
 
-		len = WildMidi_GetOutput(wm, buffer, sizeof(buffer));
-		if (len <= 0)
-			break;
-
-		cmd = decoder_data(decoder, nullptr, buffer, len, 0);
+		cmd = wildmidi_output(decoder, wm);
 
 		if (cmd == DecoderCommand::SEEK) {
 			unsigned long seek_where =