# File lib/roauth.rb, line 75
    def signature(oauth, uri, params, http_method = :get)
      uri = URI.parse(uri)
      uri.query = nil
      uri = uri.to_s

      sig_base = http_method.to_s.upcase + "&" + escape(uri) + "&" + escape(normalize(params))
      digest   = SIGNATURE_METHODS[oauth[:signature_method]]
      secret   = "#{escape(oauth[:consumer_secret])}&#{escape(oauth[:token_secret])}"

      Base64.encode64(OpenSSL::HMAC.digest(digest, secret, sig_base)).chomp.gsub(/\n/, "")
    end