   
   # ##Instance Methods
 
+  # Determine the number of characters following a header or data unit
+  excessBytes: (length) =>
+    return (@BLOCKLENGTH - (length % @BLOCKLENGTH)) % @BLOCKLENGTH
+
   # Extracts a single header without interpreting each line.
   # Interpretation is slow for large headers.
   readHeader: ->

      break if @eof
  
  # ##Class Methods

  # Determine the number of characters following a header or data unit
  @excessBytes: (length) ->
    return (File.BLOCKLENGTH - (length % File.BLOCKLENGTH)) % File.BLOCKLENGTH

  @extendDataView: (view) ->
    

        DU = Image
    data = new DU(header, @view, @offset)
    
    excess = @excessBytes(data.length)
    
    # Forward to the next HDU
    @offset += data.length + excess
