diff --git a/src/util/signal-signal.hpp b/src/util/signal-signal.hpp
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+++ b/src/util/signal-signal.hpp
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+/* -*- Mode:C++; c-file-style:"gnu"; indent-tabs-mode:nil; -*- */
+/**
+ * Copyright (c) 2013-2014 Regents of the University of California.
+ *
+ * This file is part of ndn-cxx library (NDN C++ library with eXperimental eXtensions).
+ *
+ * ndn-cxx library is free software: you can redistribute it and/or modify it under the
+ * terms of the GNU Lesser General Public License as published by the Free Software
+ * Foundation, either version 3 of the License, or (at your option) any later version.
+ *
+ * ndn-cxx library 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 Lesser General Public License for more details.
+ *
+ * You should have received copies of the GNU General Public License and GNU Lesser
+ * General Public License along with ndn-cxx, e.g., in COPYING.md file.  If not, see
+ * <http://www.gnu.org/licenses/>.
+ *
+ * See AUTHORS.md for complete list of ndn-cxx authors and contributors.
+ */
+
+#ifndef NDN_UTIL_SIGNAL_SIGNAL_HPP
+#define NDN_UTIL_SIGNAL_SIGNAL_HPP
+
+#include "signal-connection.hpp"
+#include <list>
+
+namespace ndn {
+namespace util {
+namespace signal {
+
+/** \brief provides a lightweight signal / event system
+ *
+ *  To declare a signal:
+ *    public:
+ *      Signal<Owner, T1, T2> signalName;
+ *  To connect to a signal:
+ *    owner->signalName.connect(f);
+ *    Multiple functions can connect to the same signal.
+ *  To emit a signal from owner:
+ *    this->signalName(arg1, arg2);
+ *
+ *  \tparam Owner the signal owner class; only this class can emit the signal
+ *  \tparam TArgs types of signal arguments
+ *  \sa signal-emit.hpp allows owner's derived classes to emit signals
+ */
+template<typename Owner, typename ...TArgs>
+class Signal : noncopyable
+{
+public: // API for anyone
+  /** \brief represents a function that can connect to the signal
+   */
+  typedef function<void(const TArgs&...)> Handler;
+
+  Signal();
+
+  /** \brief connects a handler to the signal
+   *  \note If invoked from a handler, the new handler won't receive the current emitted signal.
+   */
+  Connection
+  connect(const Handler& handler);
+
+private: // API for owner
+  /** \retval true if there is no connection
+   */
+  bool
+  isEmpty() const;
+
+  /** \brief emits a signal
+   *  \param args arguments passed to all handlers
+   *  \warning Emitting the signal from a handler is undefined behavior.
+   *  \note If a handler throws, the exception will be propagated to the caller
+   *        who emits this signal, and some handlers may not be executed.
+   */
+  void
+  operator()(const TArgs&...args);
+
+  // make Owner a friend of Signal<Owner, ...> so that API for owner can be called
+#if NDN_CXX_HAVE_CXX_FRIEND_TYPENAME
+  friend Owner;
+#elif NDN_CXX_HAVE_CXX_FRIEND_TYPENAME_WRAPPER
+  template<typename T>
+  struct TypeWrapper
+  {
+    typedef T Type;
+  }; // http://stackoverflow.com/a/5608542/3729203
+  friend class TypeWrapper<Owner>::Type;
+#else
+#  error "cannot declare Owner as friend"
+#endif
+
+private: // internal implementation
+  typedef Signal<Owner, TArgs...> Self;
+  struct Slot;
+
+  /** \brief stores slots
+   *  \note std::list is used because iterators must not be invalidated
+   *        when other slots are added or removed
+   */
+  typedef std::list<Slot> SlotList;
+
+  /** \brief stores a handler function, and a function to disconnect this handler
+   */
+  struct Slot
+  {
+    /** \brief the handler function who will receive emitted signals
+     */
+    Handler handler;
+
+    /** \brief the disconnect function which will disconnect this handler
+     *
+     *  This is .disconnect method bound with the iterator to this slot.
+     *
+     *  This is the only shared_ptr to this function object.
+     *  Connection class has a weak_ptr which references the same function object.
+     *  When the slot is removed or the signal is destructed, this function object would be
+     *  destructed, and the related Connections cannot disconnect this slot again.
+     */
+    shared_ptr<function<void()>> disconnect;
+  };
+
+  /** \brief stores slots
+   */
+  SlotList m_slots;
+
+  /** \brief is a signal handler executing?
+   */
+  bool m_isExecuting;
+
+  /** \brief iterator to current executing slot
+   *  \note This field is meaningful when isExecuting==true
+   */
+  typename SlotList::iterator m_currentSlot;
+
+  /** \brief disconnects the handler in a slot
+   */
+  void
+  disconnect(typename SlotList::iterator it);
+};
+
+template<typename Owner, typename ...TArgs>
+Signal<Owner, TArgs...>::Signal()
+  : m_isExecuting(false)
+{
+}
+
+template<typename Owner, typename ...TArgs>
+inline Connection
+Signal<Owner, TArgs...>::connect(const Handler& handler)
+{
+  typename SlotList::iterator it = m_slots.insert(m_slots.end(), {handler, nullptr});
+  it->disconnect = make_shared<function<void()>>(bind(&Self::disconnect, this, it));
+
+  return signal::Connection(weak_ptr<function<void()>>(it->disconnect));
+}
+
+template<typename Owner, typename ...TArgs>
+inline void
+Signal<Owner, TArgs...>::disconnect(typename SlotList::iterator it)
+{
+  // it could be const_iterator, but gcc 4.6 doesn't support std::list::erase(const_iterator)
+
+  if (m_isExecuting) {
+    // during signal emission, only the currently executing handler can be disconnected
+    BOOST_ASSERT_MSG(it == m_currentSlot,
+                     "cannot disconnect another handler from a handler");
+    m_currentSlot = m_slots.end(); // prevent disconnect twice
+  }
+  m_slots.erase(it);
+}
+
+template<typename Owner, typename ...TArgs>
+inline bool
+Signal<Owner, TArgs...>::isEmpty() const
+{
+  return !m_isExecuting && m_slots.empty();
+}
+
+template<typename Owner, typename ...TArgs>
+inline void
+Signal<Owner, TArgs...>::operator()(const TArgs&... args)
+{
+  BOOST_ASSERT_MSG(!m_isExecuting, "cannot emit signal from a handler");
+  if (m_slots.empty()) {
+    return;
+  }
+  m_isExecuting = true;
+
+  typename SlotList::iterator it = m_slots.begin();
+  typename SlotList::iterator last = m_slots.end();
+  --last;
+
+  try {
+    bool isLast = false;
+    while (!isLast) {
+      m_currentSlot = it;
+      isLast = it == last;
+      ++it;
+
+      m_currentSlot->handler(args...);
+    }
+  }
+  catch (...) {
+    m_isExecuting = false;
+    throw;
+  }
+  m_isExecuting = false;
+}
+
+} // namespace signal
+
+// expose as ndn::util::Signal
+using signal::Signal;
+
+} // namespace util
+} // namespace ndn
+
+#endif // NDN_UTIL_SIGNAL_SIGNAL_HPP