Audio loop length - PositionableAudioSource

Hi - I cant seem to find an existing solution for this:

is there a function to set the loop length (start / end position) of a PositionableAudioSource / AudioFormatReaderSource ? I just need to be able to move the loop start & end positions to only loop selections of a file. I can figure out how to do this by comparing / moving read positions (to loop start / end variables) each time i getNextAudioBlock(), but I thought there might already be an implementation of this that would simplify my process?