private String getSegmentFileName(long currentId, long previousId) {
        return PbdSegmentName.createName(m_nonce, currentId, previousId, false);
    }
private String getSegmentFileName ( long currentId , long previousId ) { return PbdSegmentName . createName ( m_nonce , currentId , previousId , false ) ; }
Return a segment file name from m_nonce and current + previous segment ids.

@see parseFiles for file name structure
@param currentId   current segment id
@param previousId  previous segment id
@return  segment file name