anchor.diff:  import sys
   import tempfile
   import resource
  +import signal
   
   # Limit maximum CPU time
   # The Postscript output format can sometimes take hours
  
positive.code: # Process the request
  if idletime < 0.2:
    # Abort if the CPU idle time on the machine is too low
    print "Status: 503 Service Unavailable"
    output_error("The server is too busy at the moment. Please wait a few minutes before trying again.")
  <% @blocks["user_agents"].each do |user_agent| -%>
  elif os.environ['HTTP_USER_AGENT'] == '<%= user_agent %>':
    # Block scraper
    print "Status: 503 Service Unavailable"
    output_error("The server is too busy at the moment. Please wait a few minutes before trying again.")
  <% end -%>
  elif not form.has_key("bbox"):
    # No bounding box specified
  
negative.code:       # Zoom the map to the bounding box
        map.zoom_to_box(bbox)
  
        # Fork so that we can handle crashes rendering the map
        pid = os.fork()
  
        # Render the map
        if pid == 0:
          if form.getvalue("format") == "png":
            image = mapnik.Image(map.width, map.height)
            mapnik.render(map, image)
            png = image.tostring("png")
            output_headers("image/png", "map.png", len(png))
            sys.stdout.write(png)
          elif form.getvalue("format") == "jpeg":
            image = mapnik.Image(map.width, map.height)
            mapnik.render(map, image)
            jpeg = image.tostring("jpeg")
            output_headers("image/jpeg", "map.jpg", len(jpeg))
            sys.stdout.write(jpeg)
          elif form.getvalue("format") == "svg":
            file = tempfile.NamedTemporaryFile(prefix = "export")
            surface = cairo.SVGSurface(file.name, map.width, map.height)
            mapnik.render(map, surface)
            surface.finish()
            output_headers("image/svg+xml", "map.svg", file_size(file))
            output_file(file)
          elif form.getvalue("format") == "pdf":
            file = tempfile.NamedTemporaryFile(prefix = "export")
            surface = cairo.PDFSurface(file.name, map.width, map.height)
            mapnik.render(map, surface)
            surface.finish()
            output_headers("application/pdf", "map.pdf", file_size(file))
            output_file(file)
          elif form.getvalue("format") == "ps":
            file = tempfile.NamedTemporaryFile(prefix = "export")
            surface = cairo.PSSurface(file.name, map.width, map.height)
            mapnik.render(map, surface)
            surface.finish()
            output_headers("application/postscript", "map.ps", file_size(file))
            output_file(file)
          else:
            output_error("Unknown format '%s'" % form.getvalue("format"))
        else:
          pid, status = os.waitpid(pid, 0)
          if status & 0xff == signal.SIGXCPU:
            output_error("CPU time limit exceeded", "509 Resource Limit Exceeded")
          elif status & 0xff == signal.SIGSEGV:
            output_error("Memory limit exceeded", "509 Resource Limit Exceeded")
          elif status != 0:
            output_error("Internal server error", "500 Internal Server Error")
  