# File lib/zip/zip_input_stream.rb, line 49
    def initialize(filename, offset = 0, io = nil)
      super()
      if (io.nil?) 
        @archiveIO = ::File.open(filename, "rb")
        @archiveIO.seek(offset, IO::SEEK_SET)
      else
        @archiveIO = io
      end
      @decompressor = NullDecompressor.instance
      @currentEntry = nil
    end