gistfile1.rb

class ResponsePadder
  def initialize (app, minlength, pad=' ', &condition)
    @app = app
    @minlength = minlength
    @pad = pad
    @condition = condition
  end
  
  def call (env)
    response = @app.call(env)
    if @condition.call(response)
      @body = response[2]
      response[2] = self
    end
    response
  end
  
  def each
    length = 0
    @body.each do |part|
      length += part.length
      yield part
    end
    
    yield @pad * (@minlength-length) unless length >= @minlength
  end
end