question: private LocusInfo createNextUncoveredLocusInfo ( final Locus stopBeforeLocus ) { while ( lastReferenceSequence <= stopBeforeLocus . getSequenceIndex ( ) && lastReferenceSequence <= referenceSequenceMask . getMaxSequenceIndex ( ) ) { if ( lastReferenceSequence == stopBeforeLocus . getSequenceIndex ( ) && lastPosition + 1 >= stopBeforeLocus . getPosition ( ) ) { return null ; } final int nextbit = referenceSequenceMask . nextPosition ( lastReferenceSequence , lastPosition ) ; if ( nextbit == - 1 ) { if ( lastReferenceSequence == stopBeforeLocus . getSequenceIndex ( ) ) { lastPosition = stopBeforeLocus . getPosition ( ) ; return null ; } lastReferenceSequence ++ ; lastPosition = 0 ; } else if ( lastReferenceSequence < stopBeforeLocus . getSequenceIndex ( ) || nextbit < stopBeforeLocus . getPosition ( ) ) { lastPosition = nextbit ; return new LocusInfo ( getReferenceSequence ( lastReferenceSequence ) , lastPosition ) ; } else if ( nextbit >= stopBeforeLocus . getPosition ( ) ) { return null ; } } return null ; }
target:  Create the next relevant zero-coverage LocusInfo