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