// whether the slot was found in the table already (TRUE => found).
func (sc *slotCanonicalizer) lookup(ls LocalSlot) (SlKeyIdx, bool) {
	split := noSlot
	if ls.SplitOf != nil {
		split, _ = sc.lookup(*ls.SplitOf)
	}
	k := slotKey{
		name: ls.N, offset: ls.Off, width: ls.Type.Size(),
		splitOf: split, splitOffset: ls.SplitOffset,
	}
	if idx, ok := sc.slmap[k]; ok {
		return idx, true
	}
	rv := SlKeyIdx(len(sc.slkeys))

	encodedResource := req.URL.RawPath
	encodedQuery := req.URL.RawQuery
	if encodedResource == "" {
		splits := strings.SplitN(req.URL.Path, "?", 2)
		encodedResource = splits[0]
		if len(splits) == 2 {
			encodedQuery = splits[1]
		}
	}

	unescapedQueries, err := unescapeQueries(encodedQuery)
	if err != nil {
		return err
	}