A ruby rewrite of dpkg-scanpackages. It's faster, has no dependencies, and you can embed it into your Rails/Sinatra app!

dpkg-scanpackages.rb

#!/usr/bin/env ruby
require "digest/md5"

module DPKG
  def self.control(deb_package_path)
    return `ar p #{deb_package_path} control.tar.gz | tar -xzO`
  end
  
  class ScanPackages
    def self.scan(path)
      packages = Dir.entries(path).select{ |filename| filename =~ /.*\.deb/ }
      
      controls = []

      packages.each do |filename|
        filepath = (path.length > 0 && path[-1] == "/" ? path : path+"/")+filename
        control = DPKG.control(filepath)
        control << "MD5sum: #{Digest::MD5.file(filepath)}\n"
        control << "Size: #{File.size(filepath)}\n"
        control << "Filename: #{filepath}\n"
        controls << control
      end
      
      return controls.join("\n")
    end    
  end
end