question: public synchronized int readFromFile ( JDBCSequentialFile file , ByteBuffer bytes ) throws SQLException { connection . setAutoCommit ( false ) ; readLargeObject . setInt ( 1 , file . getId ( ) ) ; int readLength = 0 ; try ( ResultSet rs = readLargeObject . executeQuery ( ) ) { if ( rs . next ( ) ) { Blob blob = rs . getBlob ( 1 ) ; readLength = ( int ) calculateReadLength ( blob . length ( ) , bytes . remaining ( ) , file . position ( ) ) ; byte [ ] data = blob . getBytes ( file . position ( ) + 1 , readLength ) ; bytes . put ( data ) ; } connection . commit ( ) ; return readLength ; } catch ( Throwable e ) { connection . rollback ( ) ; throw e ; } }
target:  Reads data from the file (at file.readPosition) into the byteBuffer.