prepare_cache_control!

# File actionpack/lib/action_dispatch/http/cache.rb, line 74
        def prepare_cache_control!
          @cache_control = {}
          @etag = self[ETAG]

          if cache_control = self[CACHE_CONTROL]
            cache_control.split(/,\s*/).each do |segment|
              first, last = segment.split("=")
              @cache_control[first.to_sym] = last || true
            end
          end
        end