new(arg, encoding=nil)
  public
  
    
    
Constructor @param arg must be a String, and
should be a valid XML document @param encoding if
non-null, sets the encoding of the source to this value, overriding all
encoding detection
   
  
    Show source    
    
      
    def initialize(arg, encoding=nil)
      @orig = @buffer = arg
      if encoding
        self.encoding = encoding
      else
        self.encoding = check_encoding( @buffer )
      end
      @line = 0
    end