chrome/common/worker_thread_ticker.cc

   1 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
   2 // Use of this source code is governed by a BSD-style license that can be
   3 // found in the LICENSE file.
   4
   5 #include "chrome/common/worker_thread_ticker.h"
   6
   7 #include <algorithm>
   8
   9 #include "base/bind.h"
  10 #include "base/bind_helpers.h"
  11 #include "base/location.h"
  12 #include "base/logging.h"
  13 #include "base/single_thread_task_runner.h"
  14 #include "base/threading/thread.h"
  15
  16 WorkerThreadTicker::WorkerThreadTicker(int tick_interval)
  17     : timer_thread_("worker_thread_ticker"),
  18       is_running_(false),
  19       tick_interval_(base::TimeDelta::FromMilliseconds(tick_interval)) {
  20 }
  21
  22 WorkerThreadTicker::~WorkerThreadTicker() {
  23   Stop();
  24 }
  25
  26 bool WorkerThreadTicker::RegisterTickHandler(Callback *tick_handler) {
  27   DCHECK(tick_handler);
  28   base::AutoLock lock(lock_);
  29   // You cannot change the list of handlers when the timer is running.
  30   // You need to call Stop first.
  31   if (IsRunning())
  32     return false;
  33   tick_handler_list_.push_back(tick_handler);
  34   return true;
  35 }
  36
  37 bool WorkerThreadTicker::UnregisterTickHandler(Callback *tick_handler) {
  38   DCHECK(tick_handler);
  39   base::AutoLock lock(lock_);
  40   // You cannot change the list of handlers when the timer is running.
  41   // You need to call Stop first.
  42   if (IsRunning()) {
  43     return false;
  44   }
  45   TickHandlerListType::iterator index = std::remove(tick_handler_list_.begin(),
  46                                                     tick_handler_list_.end(),
  47                                                     tick_handler);
  48   if (index == tick_handler_list_.end()) {
  49     return false;
  50   }
  51   tick_handler_list_.erase(index, tick_handler_list_.end());
  52   return true;
  53 }
  54
  55 bool WorkerThreadTicker::Start() {
  56   // Do this in a lock because we don't want 2 threads to
  57   // call Start at the same time
  58   base::AutoLock lock(lock_);
  59   if (IsRunning())
  60     return false;
  61   if (!timer_thread_.Start())
  62     return false;
  63   is_running_ = true;
  64   ScheduleTimerTask();
  65   return true;
  66 }
  67
  68 bool WorkerThreadTicker::Stop() {
  69   // Do this in a lock because we don't want 2 threads to
  70   // call Stop at the same time
  71   base::AutoLock lock(lock_);
  72   if (!IsRunning())
  73     return false;
  74   is_running_ = false;
  75   timer_thread_.Stop();
  76   return true;
  77 }
  78
  79 void WorkerThreadTicker::ScheduleTimerTask() {
  80   timer_thread_.task_runner()->PostDelayedTask(
  81       FROM_HERE,
  82       base::Bind(&WorkerThreadTicker::TimerTask, base::Unretained(this)),
  83       tick_interval_);
  84 }
  85
  86 void WorkerThreadTicker::TimerTask() {
  87   // When the ticker is running, the handler list CANNOT be modified.
  88   // So we can do the enumeration safely without a lock
  89   const TickHandlerListType& handlers = tick_handler_list_;
  90   for (TickHandlerListType::const_iterator i = handlers.begin();
  91        i != handlers.end(); ++i) {
  92     (*i)->OnTick();
  93   }
  94
  95   ScheduleTimerTask();
  96 }
  97