src/base/scheduler.h

// Copyright 2010-2015, Google Inc.
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//
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// Scheduler is a timer, call registered callback at a given interval.
// Scheduler has following features.
//  1. Backoff when the registered callback returns false.
//    - When the backoff is occured, next try will be after 2 * interval msec.
//    - Interval will be doubled as long as callback returns false, but
//      will not exceed max_interval.
//  2. Randomised delayed start to reduce server traffic peak.
//
// usage:
// // start scheduled job
// Scheduler::AddJob(Scheduler::JobSetting(
//     "TimerName", 60*1000, 60*60*1000, 30*1000, 60*1000, &Callback, NULL));
// (NULL is the args for Callback)
// // stop job
// Scheduler::RemoveJob("TimerName");

#ifndef MOZC_BASE_SCHEDULER_H_
#define MOZC_BASE_SCHEDULER_H_

#include <string>

#include "base/port.h"
#include "base/util.h"

namespace mozc {
class Timer;

class Scheduler {
 public:
  // simple container class for the job setting to be scheduled.
  class JobSetting {
   public:
    typedef bool (*CallbackFunc)(void *);

    JobSetting(const string &name,
            uint32 default_interval,
            uint32 max_interval,
            uint32 delay_start,
            uint32 random_delay,
            CallbackFunc callback,
            void *data) :
        name_(name),
        default_interval_(default_interval),
        max_interval_(max_interval),
        delay_start_(delay_start),
        random_delay_(random_delay),
        callback_(callback),
        data_(data) {}

    ~JobSetting() {}

    string name() const { return name_; }
    uint32 default_interval() const { return default_interval_; }
    uint32 max_interval() const { return max_interval_; }
    uint32 delay_start() const { return delay_start_; }
    uint32 random_delay() const { return random_delay_; }
    CallbackFunc callback() const { return callback_; }
    void *data() const { return data_; }

   private:
    string name_;
    uint32 default_interval_;
    uint32 max_interval_;
    uint32 delay_start_;
    uint32 random_delay_;
    CallbackFunc callback_;
    void *data_;
  };

  // start scheduled job
  // return false if timer is already existed.
  // job will start after (delay_start + random_delay*rand()) msec
  static bool AddJob(const JobSetting &job_setting);

  // stop scheduled job specified by neme.
  static bool RemoveJob(const string &name);

  // stop all jobs
  static void RemoveAllJobs();

  // This function is provided for test.
  // The behavior of scheduler can be customized by replacing an underlying
  // helper class inside this.
  class SchedulerInterface;
  static void SetSchedulerHandler(SchedulerInterface *handler);

  // Interface of the helper class.
  // Default implementation is defined in the .cc file.
  class SchedulerInterface {
   public:
    virtual ~SchedulerInterface() {}
    virtual bool AddJob(const JobSetting &job_setting) = 0;
    virtual bool RemoveJob(const string &name) = 0;
    virtual void RemoveAllJobs() = 0;
  };

 private:
  // should never be allocated.
  DISALLOW_IMPLICIT_CONSTRUCTORS(Scheduler);
};
}  // namespace mozc
#endif  // MOZC_BASE_SCHEDULER_H_