func (hg hostGenerator) permission(key, value string, forTCP bool) (*rbacpb.Permission, error) {
	if forTCP {
		return nil, fmt.Errorf("%q is HTTP only", key)
	}

	return permissionHeader(matcher.HostMatcher(hostHeader, value)), nil
}

func (hostGenerator) principal(key, value string, forTCP bool, _ bool) (*rbacpb.Principal, error) {
	return nil, fmt.Errorf("unimplemented")
}

type pathGenerator struct{}

            final String preHeader = "--< ";
            final String postHeader = " >--";

            final int headerLen = preHeader.length() + projectKey.length() + postHeader.length();

            String prefix = chars('-', Math.max(0, (lineLength - headerLen) / 2)) + preHeader;

            String suffix =
                    postHeader + chars('-', Math.max(0, lineLength - headerLen - prefix.length() + preHeader.length()));