question: private long checkFileHeader ( BufferedFileDataInput bfdi ) throws ReplicatorException , InterruptedException { int magic = 0 ; short major = 0 ; short minor = 0 ; try { bfdi . waitAvailable ( HEADER_LENGTH , HEADER_WAIT_MILLIS ) ; magic = bfdi . readInt ( ) ; major = bfdi . readShort ( ) ; minor = bfdi . readShort ( ) ; baseSeqno = bfdi . readLong ( ) ; } catch ( IOException e ) { throw new THLException ( "Failed to read file header from  " + file . getAbsolutePath ( ) , e ) ; } if ( magic != MAGIC_NUMBER ) throw new THLException ( "Could not open file " + file . getAbsolutePath ( ) + " : invalid magic number" ) ; if ( major != MAJOR_VERSION ) throw new THLException ( "Could not open file " + file . getAbsolutePath ( ) + " : incompatible major version" ) ; if ( minor != MINOR_VERSION ) logger . warn ( "Minor version mismatch : file " + file . getAbsolutePath ( ) + " using format " + major + "." + minor + " - Tungsten running version " + MAJOR_VERSION + "." + MINOR_VERSION ) ; return baseSeqno ; }
target:  Read the file header and return the log sequence number stored in the file header.