question: private void positionAtCentralDirectory ( ) throws IOException { boolean found = false ; long off = archive . length ( ) - MIN_EOCD_SIZE ; if ( off >= 0 ) { archive . seek ( off ) ; byte [ ] sig = JBZipOutputStream . EOCD_SIG ; int curr = archive . read ( ) ; while ( curr != - 1 ) { if ( curr == sig [ POS_0 ] ) { curr = archive . read ( ) ; if ( curr == sig [ POS_1 ] ) { curr = archive . read ( ) ; if ( curr == sig [ POS_2 ] ) { curr = archive . read ( ) ; if ( curr == sig [ POS_3 ] ) { found = true ; break ; } } } } archive . seek ( -- off ) ; curr = archive . read ( ) ; } } if ( ! found ) { throw new ZipException ( "archive is not a ZIP archive" ) ; } archive . seek ( off + CFD_LOCATOR_OFFSET ) ; byte [ ] cfdOffset = new byte [ WORD ] ; archive . readFully ( cfdOffset ) ; currentcfdfoffset = ZipLong . getValue ( cfdOffset ) ; archive . seek ( currentcfdfoffset ) ; }
target:  Searches for the &quot;End of central dir record&quot;, parses it and positions the stream at the first central directory record.