event/Loop: use boost::intrusive::multiset to store TimeoutMonitors

By using an "intrusive" data structure, we can easily eliminate
struct TimerRecord.

src/event/Loop.cxx

@@ -19,7 +19,6 @@
 
 #include "config.h"
 #include "Loop.hxx"
-#include "TimeoutMonitor.hxx"
 #include "SocketMonitor.hxx"
 #include "IdleMonitor.hxx"
 #include "DeferredMonitor.hxx"
@@ -27,18 +26,6 @@
 
 #include <algorithm>
 
-inline std::chrono::steady_clock::time_point
-EventLoop::TimerRecord::GetDue() const noexcept
-{
-	return timer.due;
-}
-
-inline bool
-EventLoop::TimerRecord::operator<(const TimerRecord &other) const noexcept
-{
-	return timer.due < other.timer.due;
-}
-
 EventLoop::EventLoop(ThreadId _thread)
 	:SocketMonitor(*this), thread(_thread)
 {
@@ -106,7 +93,7 @@ EventLoop::AddTimer(TimeoutMonitor &t, std::chrono::steady_clock::duration d)
 	assert(IsInside());
 
 	t.due = now + d;
-	timers.insert(TimerRecord(t));
+	timers.insert(t);
 	again = true;
 }
 
@@ -115,12 +102,7 @@ EventLoop::CancelTimer(TimeoutMonitor &t)
 {
 	assert(IsInside());
 
-	for (auto i = timers.begin(), end = timers.end(); i != end; ++i) {
-		if (&i->timer == &t) {
-			timers.erase(i);
-			return;
-		}
-	}
+	timers.erase(timers.iterator_to(t));
 }
 
 /**
@@ -163,11 +145,11 @@ EventLoop::Run()
 				break;
 			}
 
-			timeout = i->GetDue() - now;
+			TimeoutMonitor &m = *i;
+			timeout = m.due - now;
 			if (timeout > timeout.zero())
 				break;
 
-			TimeoutMonitor &m = i->timer;
 			timers.erase(i);
 
 			m.Run();

src/event/Loop.hxx

@@ -28,6 +28,9 @@
 #include "thread/Mutex.hxx"
 #include "WakeFD.hxx"
 #include "SocketMonitor.hxx"
+#include "TimeoutMonitor.hxx"
+
+#include <boost/intrusive/set.hpp>
 
 #include <chrono>
 #include <list>
@@ -50,22 +53,23 @@ class DeferredMonitor;
  */
 class EventLoop final : SocketMonitor
 {
-	struct TimerRecord {
-		TimeoutMonitor &timer;
-
-		explicit constexpr TimerRecord(TimeoutMonitor &_timer)
-			:timer(_timer) {}
-
-		gcc_pure
-		std::chrono::steady_clock::time_point GetDue() const noexcept;
-
-		gcc_pure
-		bool operator<(const TimerRecord &other) const noexcept;
-	};
-
 	WakeFD wake_fd;
 
-	std::multiset<TimerRecord> timers;
+	struct TimerCompare {
+		constexpr bool operator()(const TimeoutMonitor &a,
+					  const TimeoutMonitor &b) const {
+			return a.due < b.due;
+		}
+	};
+
+	typedef boost::intrusive::multiset<TimeoutMonitor,
+					   boost::intrusive::member_hook<TimeoutMonitor,
+									 TimeoutMonitor::TimerSetHook,
+									 &TimeoutMonitor::timer_set_hook>,
+					   boost::intrusive::compare<TimerCompare>,
+					   boost::intrusive::constant_time_size<false>> TimerSet;
+	TimerSet timers;
+
 	std::list<IdleMonitor *> idle;
 
 	Mutex mutex;

src/event/TimeoutMonitor.cxx

@@ -24,10 +24,8 @@
 void
 TimeoutMonitor::Cancel()
 {
-	if (IsActive()) {
-		active = false;
+	if (IsActive())
 		loop.CancelTimer(*this);
-	}
 }
 
 void
@@ -35,13 +33,5 @@ TimeoutMonitor::Schedule(std::chrono::steady_clock::duration d)
 {
 	Cancel();
 
-	active = true;
 	loop.AddTimer(*this, d);
 }
-
-void
-TimeoutMonitor::Run()
-{
-	active = false;
-	OnTimeout();
-}

src/event/TimeoutMonitor.hxx

@@ -22,6 +22,8 @@
 
 #include "check.h"
 
+#include <boost/intrusive/set_hook.hpp>
+
 #include <chrono>
 
 class EventLoop;
@@ -37,6 +39,9 @@ class EventLoop;
 class TimeoutMonitor {
 	friend class EventLoop;
 
+	typedef boost::intrusive::set_member_hook<> TimerSetHook;
+	TimerSetHook timer_set_hook;
+
 	EventLoop &loop;
 
 	/**
@@ -45,11 +50,9 @@ class TimeoutMonitor {
 	 */
 	std::chrono::steady_clock::time_point due;
 
-	bool active;
-
 public:
 	TimeoutMonitor(EventLoop &_loop)
-		:loop(_loop), active(false) {
+		:loop(_loop) {
 	}
 
 	~TimeoutMonitor() {
@@ -61,7 +64,7 @@ public:
 	}
 
 	bool IsActive() const {
-		return active;
+		return timer_set_hook.is_linked();
 	}
 
 	void Schedule(std::chrono::steady_clock::duration d);
@@ -71,7 +74,9 @@ protected:
 	virtual void OnTimeout() = 0;
 
 private:
-	void Run();
+	void Run() {
+		OnTimeout();
+	}
 };
 
 #endif /* MAIN_NOTIFY_H */