CScheduler class for lightweight task scheduling

Simple class to manage a task queue that is serviced by one or
more threads.

src/scheduler.h

@@ -0,0 +1,70 @@
+// Copyright (c) 2015 The Bitcoin Core developers
+// Distributed under the MIT software license, see the accompanying
+// file COPYING or http://www.opensource.org/licenses/mit-license.php.
+
+#ifndef BITCOIN_SCHEDULER_H
+#define BITCOIN_SCHEDULER_H
+
+//
+// NOTE:
+// boost::thread / boost::function / boost::chrono should be ported to
+// std::thread / std::function / std::chrono when we support C++11.
+//
+#include <boost/function.hpp>
+#include <boost/chrono/chrono.hpp>
+#include <boost/thread.hpp>
+#include <map>
+
+//
+// Simple class for background tasks that should be run
+// periodically or once "after a while"
+//
+// Usage:
+//
+// CScheduler* s = new CScheduler();
+// s->scheduleFromNow(doSomething, 11); // Assuming a: void doSomething() { }
+// s->scheduleFromNow(boost::bind(Class::func, this, argument), 3);
+// boost::thread* t = new boost::thread(boost::bind(CScheduler::serviceQueue, s));
+//
+// ... then at program shutdown, clean up the thread running serviceQueue:
+// t->interrupt();
+// t->join();
+// delete t;
+// delete s; // Must be done after thread is interrupted/joined.
+//
+
+class CScheduler
+{
+public:
+    CScheduler();
+    ~CScheduler();
+
+    typedef boost::function<void(void)> Function;
+
+    // Call func at/after time t
+    void schedule(Function f, boost::chrono::system_clock::time_point t);
+
+    // Convenience method: call f once deltaSeconds from now
+    void scheduleFromNow(Function f, int64_t deltaSeconds);
+
+    // Another convenience method: call f approximately
+    // every deltaSeconds forever, starting deltaSeconds from now.
+    // To be more precise: every time f is finished, it
+    // is rescheduled to run deltaSeconds later. If you
+    // need more accurate scheduling, don't use this method.
+    void scheduleEvery(Function f, int64_t deltaSeconds);
+
+    // To keep things as simple as possible, there is no unschedule.
+
+    // Services the queue 'forever'. Should be run in a thread,
+    // and interrupted using boost::interrupt_thread
+    void serviceQueue();
+
+private:
+    std::multimap<boost::chrono::system_clock::time_point, Function> taskQueue;
+    boost::condition_variable newTaskScheduled;
+    boost::mutex newTaskMutex;
+    int nThreadsServicingQueue;
+};
+
+#endif