graphviz-web.rb の抜粋（Sinatra Application）

graphviz-web.rb

  post '/graphviz' do
    data = params[:data]
    if data.respond_to?(:has_key?) && data.has_key?(:tempfile) && data[:tempfile].respond_to?(:read)
      data = data[:tempfile].read
    end
    format = params[:format]
    layout = params[:layout]
    hash = Digest::SHA1.hexdigest(data)
    src_file, img_file, err_file = *filenames(hash, layout, format)
    if ! validate_layout(layout)
      return json :result => 'failed', :message => "Invalid layout \"#{layout}\". Available formats: #{settings.layouts.join(', ')}"
    end
    if ! validate_format(format)
      return json :result => 'failed', :message => "Invalid format \"#{format}\". Available formats: #{settings.formats.join(', ')}"
    end
    if !File.exist?(src_file) || !File.exist?(img_file)
      File.open(src_file, 'w') { |fh| fh << data }
    end
    if !File.exist?(img_file)
      cmd = "#{layout} -o #{img_file} -T #{format} #{src_file} 2> #{err_file} && rm #{err_file}"
      system(cmd)
    end
    if File.exist?(err_file)
      json :result => 'failed', :message => 'Command execution failed.', :message_detail => File.read(err_file)
    else
      json :result => 'ok', :hash => hash, :image_url => url("/graphviz/#{layout}/#{hash}.#{format}"), :image_view_url => url("/graphviz/#{layout}/#{hash}.#{format}.html")
    end
  end