id = c.Next()
	c.StartRequest(id)
	err = c.PrintfLine(format, args...)
	c.EndRequest(id)
	if err != nil {
		return 0, err
	}
	return id, nil
}

// TrimString returns s without leading and trailing ASCII space.
func TrimString(s string) string {
	for len(s) > 0 && isASCIISpace(s[0]) {
		s = s[1:]
	}
	for len(s) > 0 && isASCIISpace(s[len(s)-1]) {
		s = s[:len(s)-1]
	}
	return s
}

	if trailers, ok := rw.snapHeader["Trailer"]; ok {
		res.Trailer = make(http.Header, len(trailers))
		for _, k := range trailers {
			for _, k := range strings.Split(k, ",") {
				k = http.CanonicalHeaderKey(textproto.TrimString(k))
				if !httpguts.ValidTrailerHeader(k) {
					// Ignore since forbidden by RFC 7230, section 4.1.2.
					continue
				}
				vv, ok := rw.HeaderMap[k]
				if !ok {
					continue
				}

	case '`', '~':
		f := t.string()
		n := 0
		for i := 0; ; i++ {
			if !t.trim(c) {
				if i >= 3 {
					break
				}
				return false
			}
			n++
		}
		txt := mdUnescaper.Replace(t.trimString())
		if c == '`' && strings.Contains(txt, "`") {
			return false
		}
		txt = trimSpaceTab(txt)
		*info = txt

		*fence = f[:n]
		*s = line{}
		return true
	}
	return false
}

			// way to provide the error back to the server
			// handler, so just drop invalid headers instead.
			continue
		}
		for _, v := range kv.values {
			v = headerNewlineToSpace.Replace(v)
			v = textproto.TrimString(v)
			for _, s := range []string{kv.key, ": ", v, "\r\n"} {
				if _, err := ws.WriteString(s); err != nil {
					headerSorterPool.Put(sorter)
					return err
				}
			}