file := r.Form.Get("file")
	if len(file) == 0 {
		writeErrorResponseJSON(ctx, w, errorCodes.ToAPIErr(ErrInvalidRequest), r.URL)
		return
	}

	file = filepath.ToSlash(file)
	// Reject attempts to traverse parent or absolute paths.
	if hasBadPathComponent(volume) || hasBadPathComponent(file) {
		writeErrorResponse(r.Context(), w, errorCodes.ToAPIErr(ErrInvalidResourceName), r.URL)
		return
	}

     * be read without locking. Next fields of nodes are immutable (final). All list additions are
     * performed at the front of each bin. This makes it easy to check changes, and also fast to
     * traverse. When nodes would otherwise be changed, new nodes are created to replace them. This
     * works well for hash tables since the bin lists tend to be short. (The average length is less
     * than two.)
     *