question: static Tuple < Map < String , String > , Long > readLegacyChecksums ( Directory directory ) throws IOException { synchronized ( directory ) { long lastFound = - 1 ; for ( String name : directory . listAll ( ) ) { if ( ! isChecksum ( name ) ) { continue ; } long current = Long . parseLong ( name . substring ( CHECKSUMS_PREFIX . length ( ) ) ) ; if ( current > lastFound ) { lastFound = current ; } } if ( lastFound > - 1 ) { try ( IndexInput indexInput = directory . openInput ( CHECKSUMS_PREFIX + lastFound , IOContext . READONCE ) ) { indexInput . readInt ( ) ; return new Tuple ( indexInput . readStringStringMap ( ) , lastFound ) ; } } return new Tuple ( new HashMap < > ( ) , - 1l ) ; } }
target:  Reads legacy checksum files found in the directory. <p/> Files are expected to start with _checksums- prefix followed by long file version. Only file with the highest version is read, all other files are ignored.