data: URIs in Ruby

Anne van Kesteren’s got a cute little demonstration of <canvas/>. I particularly like the idea of saving something to a data: URI; one of those cool little things about the Web that doesn’t get much attention.

I also like favicons, and not having to use a general-purpose image manipulation program to create them. Hence, a teeny-tiny Camping mount which will convert an image/png data: URI into a favicon (example). At its heart is a class for handling data: URIs that goes something like this:

module URI
  class Data < Generic
    attr_reader :mime_type, :data

    def read; data; end

    def initialize(scheme, userinfo, host, port, 
                   registry, path, opaque, query, fragment)
      super

      notdata, data = opaque.split(",", 2)
      match = URI.decode(notdata).match(/^(.*?)(;base64)?$/)

      @mime_type = match[1]
      if @mime_type.empty?
        @mime_type = "text/plain;charset=US-ASCII" 
      elsif @mime_type[0] == ?;
        @mime_type = "text/plain#{@mime_type}"
      end

      @data = unless match[2].nil?
        Base64.decode64(data)
      else
        URI.decode(data)
      end
    end 
  end
  @@schemes["DATA"] = Data
end

It’s not a complete implementation of RFC 2397; some legitimate URIs (eg. data:text/plain;charset=iso-8859-7,%be%fg%be) can’t be parsed without fiddling around with uri.rb’s internals.

(BTW, the favicon is much shrunken from Paintr’s canvas; you’ll have to go over your lines several times to get something you can see.)