util: move signal-*.* into util/signal/ directory
refs #3940
Change-Id: I36e3420846959f39bb51a3ce7ef7f03e7c2c22aa
diff --git a/src/util/signal/signal.hpp b/src/util/signal/signal.hpp
new file mode 100644
index 0000000..9b502ab
--- /dev/null
+++ b/src/util/signal/signal.hpp
@@ -0,0 +1,268 @@
+/* -*- Mode:C++; c-file-style:"gnu"; indent-tabs-mode:nil; -*- */
+/*
+ * Copyright (c) 2013-2017 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 "connection.hpp"
+#include <list>
+
+namespace ndn {
+namespace util {
+namespace signal {
+
+class DummyExtraArg;
+
+/** \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();
+
+ ~Signal();
+
+ /** \brief connects a handler to the signal
+ * \note If invoked from a handler, the new handler won't receive the current emitted signal.
+ * \warning The handler is permitted to disconnect itself, but it must ensure its validity.
+ */
+ Connection
+ connect(const Handler& handler);
+
+ /** \brief connects a single-shot handler to the signal
+ *
+ * After the handler is executed once, it is automatically disconnected.
+ */
+ Connection
+ connectSingleShot(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.
+ * \warning Destructing the Signal object during signal emission 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);
+
+ /** \brief (implementation detail) emits a signal
+ * \note This overload is used by signal-emit.hpp.
+ */
+ void
+ operator()(const TArgs&... args, const DummyExtraArg&);
+
+ // make Owner a friend of Signal<Owner, ...> so that API for owner can be called
+ friend Owner;
+
+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
+ *
+ * In practice this is the Signal::disconnect method bound to an iterator
+ * pointing at 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 erased or the signal is destructed, this function object is
+ * 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>
+Signal<Owner, TArgs...>::~Signal()
+{
+ BOOST_ASSERT(!m_isExecuting);
+}
+
+template<typename Owner, typename ...TArgs>
+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>
+Connection
+Signal<Owner, TArgs...>::connectSingleShot(const Handler& handler)
+{
+ typename SlotList::iterator it = m_slots.insert(m_slots.end(), {nullptr, nullptr});
+ it->disconnect = make_shared<function<void()>>(bind(&Self::disconnect, this, it));
+ signal::Connection conn(weak_ptr<function<void()>>(it->disconnect));
+
+ it->handler = [conn, handler] (const TArgs&... args) mutable {
+ handler(args...);
+ conn.disconnect();
+ };
+
+ return conn;
+}
+
+template<typename Owner, typename ...TArgs>
+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");
+
+ // this serves to indicate that the current slot needs to be erased from the list
+ // after it finishes executing; we cannot do it here because of bug #2333
+ m_currentSlot = m_slots.end();
+
+ // expire all weak_ptrs, to prevent double disconnections
+ it->disconnect.reset();
+ }
+ else {
+ m_slots.erase(it);
+ }
+}
+
+template<typename Owner, typename ...TArgs>
+bool
+Signal<Owner, TArgs...>::isEmpty() const
+{
+ return !m_isExecuting && m_slots.empty();
+}
+
+template<typename Owner, typename ...TArgs>
+void
+Signal<Owner, TArgs...>::operator()(const TArgs&... args)
+{
+ BOOST_ASSERT_MSG(!m_isExecuting, "cannot emit signal from a handler");
+
+ if (m_slots.empty()) {
+ return;
+ }
+
+ auto it = m_slots.begin();
+ auto last = std::prev(m_slots.end());
+ m_isExecuting = true;
+
+ try {
+ bool isLast = false;
+ while (!isLast) {
+ m_currentSlot = it;
+ isLast = it == last;
+
+ m_currentSlot->handler(args...);
+
+ if (m_currentSlot == m_slots.end())
+ it = m_slots.erase(it);
+ else
+ ++it;
+ }
+ }
+ catch (...) {
+ m_isExecuting = false;
+ throw;
+ }
+
+ m_isExecuting = false;
+}
+
+template<typename Owner, typename ...TArgs>
+void
+Signal<Owner, TArgs...>::operator()(const TArgs&... args, const DummyExtraArg&)
+{
+ this->operator()(args...);
+}
+
+} // namespace signal
+
+// expose as ndn::util::Signal
+using signal::Signal;
+
+} // namespace util
+} // namespace ndn
+
+#endif // NDN_UTIL_SIGNAL_SIGNAL_HPP