# Extract and set `content_length` from header.
	private fun parse_content_length(head: String) do
		var hlines = head.split("\r\n")
		for hline in hlines do
			var hparts = hline.split(": ")
			if hparts.first == "Content-Length" then
				content_length = hparts[1].to_i
			end
		end
	end