ndnpeek: replace --link-file with --fwhint

refs #4207, #5187

Change-Id: I8213e971520d3edab631634a03bf7950d265dc11
diff --git a/core/program-options-ext.cpp b/core/program-options-ext.cpp
new file mode 100644
index 0000000..5667aab
--- /dev/null
+++ b/core/program-options-ext.cpp
@@ -0,0 +1,45 @@
+/* -*- Mode:C++; c-file-style:"gnu"; indent-tabs-mode:nil; -*- */
+/*
+ * Copyright (c) 2014-2022,  Regents of the University of California,
+ *                           Arizona Board of Regents,
+ *                           Colorado State University,
+ *                           University Pierre & Marie Curie, Sorbonne University,
+ *                           Washington University in St. Louis,
+ *                           Beijing Institute of Technology,
+ *                           The University of Memphis.
+ *
+ * This file is part of ndn-tools (Named Data Networking Essential Tools).
+ * See AUTHORS.md for complete list of ndn-tools authors and contributors.
+ *
+ * ndn-tools is free software: you can redistribute it and/or modify it under the terms
+ * of the GNU General Public License as published by the Free Software Foundation,
+ * either version 3 of the License, or (at your option) any later version.
+ *
+ * ndn-tools is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY;
+ * without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR
+ * PURPOSE.  See the GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License along with
+ * ndn-tools, e.g., in COPYING.md file.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#include "core/program-options-ext.hpp"
+
+namespace ndn {
+
+void
+validate(boost::any& v, const std::vector<std::string>& values, Name*, int)
+{
+  using namespace boost::program_options;
+
+  validators::check_first_occurrence(v);
+  const std::string& s = validators::get_single_string(values);
+
+  try {
+    v = Name(s);
+  } catch (const Name::Error&) {
+    throw invalid_option_value(s);
+  }
+}
+
+} // namespace ndn