util: scheduler::ScopedEventId to automatically cancel scheduled events upon destruction

Change-Id: I3254983ab27480143c778baa28de7eb0409b26ce
Refs: #2442
diff --git a/src/util/scheduler-scoped-event-id.cpp b/src/util/scheduler-scoped-event-id.cpp
new file mode 100644
index 0000000..c69af3b
--- /dev/null
+++ b/src/util/scheduler-scoped-event-id.cpp
@@ -0,0 +1,69 @@
+/* -*- Mode:C++; c-file-style:"gnu"; indent-tabs-mode:nil; -*- */
+/**
+ * Copyright (c) 2013-2015 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.
+ */
+
+#include "scheduler-scoped-event-id.hpp"
+
+namespace ndn {
+namespace util {
+namespace scheduler {
+
+ScopedEventId::ScopedEventId(Scheduler& scheduler)
+  : m_scheduler(&scheduler)
+{
+}
+
+ScopedEventId::ScopedEventId(ScopedEventId&& other)
+  : m_scheduler(other.m_scheduler)
+  , m_event(other.m_event)
+{
+  other.release();
+}
+
+ScopedEventId&
+ScopedEventId::operator=(const EventId& event)
+{
+  if (m_event != event) {
+    m_scheduler->cancelEvent(m_event);
+    m_event = event;
+  }
+  return *this;
+}
+
+ScopedEventId::~ScopedEventId()
+{
+  m_scheduler->cancelEvent(m_event);
+}
+
+void
+ScopedEventId::cancel()
+{
+  m_scheduler->cancelEvent(m_event);
+}
+
+void
+ScopedEventId::release()
+{
+  m_event.reset();
+}
+
+} // namespace scheduler
+} // namespace util
+} // namespace ndn
diff --git a/src/util/scheduler-scoped-event-id.hpp b/src/util/scheduler-scoped-event-id.hpp
new file mode 100644
index 0000000..89cab89
--- /dev/null
+++ b/src/util/scheduler-scoped-event-id.hpp
@@ -0,0 +1,82 @@
+/* -*- Mode:C++; c-file-style:"gnu"; indent-tabs-mode:nil; -*- */
+/**
+ * Copyright (c) 2013-2015 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_SCHEDULER_SCOPED_EVENT_ID_HPP
+#define NDN_UTIL_SCHEDULER_SCOPED_EVENT_ID_HPP
+
+#include "scheduler.hpp"
+
+namespace ndn {
+namespace util {
+namespace scheduler {
+
+/** \brief Event that is automatically cancelled upon destruction
+ */
+class ScopedEventId : noncopyable
+{
+public:
+  /** \brief Construct ScopedEventId tied to the specified scheduler
+   *  \param scheduler Scheduler to which the event is tied.  Behavior is undefined if
+   *                   scheduler is destructed before an uncanceled ScopedEventId.
+   */
+  explicit
+  ScopedEventId(Scheduler& scheduler);
+
+  /** \brief move constructor
+   */
+  ScopedEventId(ScopedEventId&& other);
+
+  /** \brief assigns an event
+   *
+   *  If a different event has been assigned to this instance previously,
+   *  that event will be cancelled immediately.
+   *
+   *  \note The caller should ensure that ScopedEventId is tied to a correct scheduler.
+   *        Behavior is undefined when assigning event scheduled in another scheduler instance.
+   */
+  ScopedEventId&
+  operator=(const EventId& event);
+
+  /** \brief cancels the event
+   */
+  ~ScopedEventId();
+
+  /** \brief cancels the event manually
+   */
+  void
+  cancel();
+
+  /** \brief releases the event so that it won't be canceled
+   *         when this ScopedEventId is destructed
+   */
+  void
+  release();
+
+private:
+  Scheduler* m_scheduler; // pointer to allow move semantics
+  EventId m_event;
+};
+
+} // namespace scheduler
+} // namespace util
+} // namespace ndn
+
+#endif // NDN_UTIL_SCHEDULER_SCOPED_EVENT_ID_HPP
diff --git a/src/util/scheduler.cpp b/src/util/scheduler.cpp
index 998728f..c2f5564 100644
--- a/src/util/scheduler.cpp
+++ b/src/util/scheduler.cpp
@@ -1,6 +1,6 @@
 /* -*- Mode:C++; c-file-style:"gnu"; indent-tabs-mode:nil; -*- */
 /**
- * Copyright (c) 2013-2014 Regents of the University of California.
+ * Copyright (c) 2013-2015 Regents of the University of California.
  *
  * This file is part of ndn-cxx library (NDN C++ library with eXperimental eXtensions).
  *
@@ -24,6 +24,8 @@
 #include "scheduler.hpp"
 
 namespace ndn {
+namespace util {
+namespace scheduler {
 
 struct EventIdImpl
 {
@@ -195,4 +197,6 @@
 }
 
 
+} // namespace scheduler
+} // namespace util
 } // namespace ndn
diff --git a/src/util/scheduler.hpp b/src/util/scheduler.hpp
index 4287556..8948860 100644
--- a/src/util/scheduler.hpp
+++ b/src/util/scheduler.hpp
@@ -1,6 +1,6 @@
 /* -*- Mode:C++; c-file-style:"gnu"; indent-tabs-mode:nil; -*- */
 /**
- * Copyright (c) 2013-2014 Regents of the University of California.
+ * Copyright (c) 2013-2015 Regents of the University of California.
  *
  * This file is part of ndn-cxx library (NDN C++ library with eXperimental eXtensions).
  *
@@ -28,6 +28,8 @@
 #include <set>
 
 namespace ndn {
+namespace util {
+namespace scheduler {
 
 struct EventIdImpl; ///< \brief Private storage of information about the event
 /**
@@ -105,6 +107,16 @@
   bool m_isEventExecuting;
 };
 
+} // namespace scheduler
+
+using util::scheduler::Scheduler;
+
+} // namespace util
+
+// for backwards compatibility
+using util::scheduler::Scheduler;
+using util::scheduler::EventId;
+
 } // namespace ndn
 
 #endif // NDN_UTIL_SCHEDULER_HPP