Make TimerMgr an IOSource

- This allows the loop to check what the next timeout is and use that as the basis for the timeout of the poll
- This commit also removes the TimerMgr::Tag type, since it causes a name clash with other code in IOSource

src/Timer.h

@@ -2,10 +2,9 @@
 
 #pragma once
 
-#include <string>
-
 #include <string>
 #include "PriorityQueue.h"
+#include "iosource/IOSource.h"
 
 // If you add a timer here, adjust TimerNames in Timer.cc.
 enum TimerType : uint8_t {
@@ -48,10 +47,10 @@ class ODesc;
 
 class Timer : public PQ_Element {
 public:
-	Timer(double t, TimerType arg_type) : PQ_Element(t), type(arg_type) { }
+	Timer(double t, TimerType arg_type) : PQ_Element(t), type(arg_type) {}
 	~Timer() override { }
 
-	TimerType Type() const	{ return (TimerType) type; }
+	TimerType Type() const	{ return type; }
 
 	// t gives the dispatch time.  is_expire is true if the
 	// timer is being dispatched because we're expiring all
@@ -65,53 +64,73 @@ protected:
 	TimerType type;
 };
 
-class TimerMgr {
+class TimerMgr : public iosource::IOSource {
 public:
 	virtual ~TimerMgr();
 
 	virtual void Add(Timer* timer) = 0;
 
-	// Advance the clock to time t, expiring at most max_expire timers.
-	// Returns number of timers expired.
+	/**
+	 * Advance the clock to time t, expiring at most max_expire timers.
+	 *
+	 * @param t the new time.
+	 * @param max_expire the maximum number of timers to expire.
+	 * @return the number of timers expired.
+	 */
 	int Advance(double t, int max_expire);
 
-	// Returns the number of timers expired (so far) during the current
-	// or most recent advance.
+	/**
+	 * Returns the number of timers expired (so far) during the current
+	 * or most recent advance.
+	 */
 	int NumExpiredDuringCurrentAdvance()	{ return num_expired; }
 
-	// Expire all timers.
+	/**
+	 * Expire all timers.
+	 */
 	virtual void Expire() = 0;
 
-	// Cancel() is a method separate from Remove because
-	// (1) Remove is protected, but, more importantly, (2) in some
-	// timer schemes we have wound up separating timer cancelation
-	// from removing it from the manager's data structures, because
-	// the manager lacked an efficient way to find it.
+	/**
+	 * Removes a timer. Cancel() is a method separate from Remove()
+	 * because (1) Remove is protected, but, more importantly, (2)
+	 * in some timer schemes we have wound up separating timer
+	 * cancelation from removing it from the manager's data structures,
+	 * because the manager lacked an efficient way to find it.
+	 *
+	 * @param timer the timer to cancel
+	 */
 	void Cancel(Timer* timer)	{ Remove(timer); }
 
 	double Time() const		{ return t ? t : 1; }	// 1 > 0
 
- 	typedef std::string Tag;
- 	const Tag& GetTag() const 	{ return tag; }
+	const std::string& GetTag() const 	{ return tag; }
 
 	virtual int Size() const = 0;
 	virtual int PeakSize() const = 0;
 	virtual uint64_t CumulativeNum() const = 0;
 
 	double LastTimestamp() const	{ return last_timestamp; }
-	// Returns time of last advance in global network time.
+
+	/**
+	 * Returns time of last advance in global network time
+	 */
 	double LastAdvance() const	{ return last_advance; }
 
 	static unsigned int* CurrentTimers()	{ return current_timers; }
 
+	// IOSource API methods
+	virtual double GetNextTimeout() override { return -1; }
+	virtual void Process() override;
+	virtual const char* Tag() override { return fmt("TimerMgr %s", tag.c_str()); }
+
+	/**
+	 * Performs some extra initialization on a timer manager. This shouldn't
+	 * need to be called for managers other than the global one.
+	 */
+	void InitPostScript();
+
 protected:
-	explicit TimerMgr(const Tag& arg_tag)
- 		{
- 		t = 0.0;
- 		num_expired = 0;
- 		last_advance = last_timestamp = 0;
- 		tag = arg_tag;
- 		}
+	explicit TimerMgr(const std::string& arg_tag);
 
 	virtual int DoAdvance(double t, int max_expire) = 0;
 	virtual void Remove(Timer* timer) = 0;
@@ -119,7 +138,7 @@ protected:
 	double t;
 	double last_timestamp;
 	double last_advance;
-	Tag tag;
+	std::string tag;
 
 	int num_expired;
 
@@ -128,7 +147,7 @@ protected:
 
 class PQ_TimerMgr : public TimerMgr {
 public:
-	explicit PQ_TimerMgr(const Tag& arg_tag);
+	explicit PQ_TimerMgr(const std::string& arg_tag);
 	~PQ_TimerMgr() override;
 
 	void Add(Timer* timer) override;
@@ -137,6 +156,7 @@ public:
 	int Size() const override { return q->Size(); }
 	int PeakSize() const override { return q->PeakSize(); }
 	uint64_t CumulativeNum() const override { return q->CumulativeNum(); }
+	double GetNextTimeout() override;
 
 protected:
 	int DoAdvance(double t, int max_expire) override;