src/scheduler.h

   1 // Copyright (c) 2015 The Bitcoin Core developers
   2 // Distributed under the MIT software license, see the accompanying
   3 // file COPYING or http://www.opensource.org/licenses/mit-license.php.
   4
   5 #ifndef BITCOIN_SCHEDULER_H
   6 #define BITCOIN_SCHEDULER_H
   7
   8 //
   9 // NOTE:
  10 // boost::thread / boost::function / boost::chrono should be ported to
  11 // std::thread / std::function / std::chrono when we support C++11.
  12 //
  13 #include <boost/function.hpp>
  14 #include <boost/chrono/chrono.hpp>
  15 #include <boost/thread.hpp>
  16 #include <map>
  17
  18 //
  19 // Simple class for background tasks that should be run
  20 // periodically or once "after a while"
  21 //
  22 // Usage:
  23 //
  24 // CScheduler* s = new CScheduler();
  25 // s->scheduleFromNow(doSomething, 11); // Assuming a: void doSomething() { }
  26 // s->scheduleFromNow(boost::bind(Class::func, this, argument), 3);
  27 // boost::thread* t = new boost::thread(boost::bind(CScheduler::serviceQueue, s));
  28 //
  29 // ... then at program shutdown, clean up the thread running serviceQueue:
  30 // t->interrupt();
  31 // t->join();
  32 // delete t;
  33 // delete s; // Must be done after thread is interrupted/joined.
  34 //
  35
  36 class CScheduler
  37 {
  38 public:
  39     CScheduler();
  40     ~CScheduler();
  41
  42     typedef boost::function<void(void)> Function;
  43
  44     // Call func at/after time t
  45     void schedule(Function f, boost::chrono::system_clock::time_point t);
  46
  47     // Convenience method: call f once deltaSeconds from now
  48     void scheduleFromNow(Function f, int64_t deltaSeconds);
  49
  50     // Another convenience method: call f approximately
  51     // every deltaSeconds forever, starting deltaSeconds from now.
  52     // To be more precise: every time f is finished, it
  53     // is rescheduled to run deltaSeconds later. If you
  54     // need more accurate scheduling, don't use this method.
  55     void scheduleEvery(Function f, int64_t deltaSeconds);
  56
  57     // To keep things as simple as possible, there is no unschedule.
  58
  59     // Services the queue 'forever'. Should be run in a thread,
  60     // and interrupted using boost::interrupt_thread
  61     void serviceQueue();
  62
  63     // Tell any threads running serviceQueue to stop as soon as they're
  64     // done servicing whatever task they're currently servicing (drain=false)
  65     // or when there is no work left to be done (drain=true)
  66     void stop(bool drain=false);
  67
  68     // Returns number of tasks waiting to be serviced,
  69     // and first and last task times
  70     size_t getQueueInfo(boost::chrono::system_clock::time_point &first,
  71                         boost::chrono::system_clock::time_point &last) const;
  72
  73 private:
  74     std::multimap<boost::chrono::system_clock::time_point, Function> taskQueue;
  75     boost::condition_variable newTaskScheduled;
  76     mutable boost::mutex newTaskMutex;
  77     int nThreadsServicingQueue;
  78     bool stopRequested;
  79     bool stopWhenEmpty;
  80     bool shouldStop() { return stopRequested || (stopWhenEmpty && taskQueue.empty()); }
  81 };
  82
  83 #endif