# Get `self` as a single string for HTTP POST
	#
	# Require: `curl.is_ok`
	private fun to_url_encoded(curl: Curl): String
	do
		assert curl.is_ok

		var lines = new Array[String]
		for k, v in self do
			if k.length == 0 then continue

			k = curl.native.escape(k)
			v = curl.native.escape(v)
			lines.add "{k}={v}"
		end
		return lines.join("&")
	end