module Enumerable
  class Reader
    def initialize(enumerable)
      @enumerable = enumerable
      @buffer = "".b
    end

    def read(nsize, buffer = nil)
      @iterator ||= @enumerable.enum_for(:each)
      (buffer ||= @buffer).clear
      if @rest
        buffer << @rest
        @rest.clear
      end
      while buffer.bytesize < nsize
        begin
          buffer << @iterator.next.force_encoding(Encoding::BINARY)
        rescue StopIteration
          return if buffer.empty?
          break
        end
      end
      @rest = buffer.slice!(nsize..-1)
      buffer
    end
  end

  def to_reader
    Reader.new(self)
  end
end