question: public int computeId ( BitSet activeMatches , IReadBlock readBlock ) { if ( name2id != null ) { final String name = readBlock . getReadName ( ) ; final Integer id = name2id . get ( name ) ; if ( id != null && id > 0 ) return id ; } if ( activeMatches . cardinality ( ) == 0 ) return IdMapper . NOHITS_ID ; for ( int i = activeMatches . nextSetBit ( 0 ) ; i != - 1 ; i = activeMatches . nextSetBit ( i + 1 ) ) { IMatchBlock match = readBlock . getMatchBlock ( i ) ; int id = match . getId ( cName ) ; if ( id > 0 ) return id ; } return IdMapper . UNASSIGNED_ID ; }
target:  computes the id for a read from its matches matches