question: public long lengthBetween ( int start , int end ) { final int fileStart = mFileNoLookup . lookup ( start ) ; final int fileEnd = mFileNoLookup . lookup ( end ) ; final int startIndex = start - mFileNoLookup . startSeq ( fileStart ) ; final int endIndex = end - mFileNoLookup . startSeq ( fileEnd ) ; long retLength = - mPointers [ fileStart ] [ startIndex ] ; for ( int i = fileStart ; i < fileEnd ; i ++ ) { retLength += mPointers [ i ] [ mPointers [ i ] . length - 1 ] ; } retLength += mPointers [ fileEnd ] [ endIndex ] ; return retLength ; }
target:  return total length between given sequences