base/message_loop/message_pump_default.cc

   1 // Copyright (c) 2006-2008 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 "base/message_loop/message_pump_default.h"
   6
   7 #include <algorithm>
   8
   9 #include "base/logging.h"
  10 #include "base/threading/thread_restrictions.h"
  11
  12 #if defined(OS_MACOSX)
  13 #include "base/mac/scoped_nsautorelease_pool.h"
  14 #endif
  15
  16 namespace base {
  17
  18 MessagePumpDefault::MessagePumpDefault()
  19     : keep_running_(true),
  20       event_(false, false) {
  21 }
  22
  23 MessagePumpDefault::~MessagePumpDefault() {
  24 }
  25
  26 void MessagePumpDefault::Run(Delegate* delegate) {
  27   DCHECK(keep_running_) << "Quit must have been called outside of Run!";
  28
  29   for (;;) {
  30 #if defined(OS_MACOSX)
  31     mac::ScopedNSAutoreleasePool autorelease_pool;
  32 #endif
  33
  34     bool did_work = delegate->DoWork();
  35     if (!keep_running_)
  36       break;
  37
  38     did_work |= delegate->DoDelayedWork(&delayed_work_time_);
  39     if (!keep_running_)
  40       break;
  41
  42     if (did_work)
  43       continue;
  44
  45     did_work = delegate->DoIdleWork();
  46     if (!keep_running_)
  47       break;
  48
  49     if (did_work)
  50       continue;
  51
  52     ThreadRestrictions::ScopedAllowWait allow_wait;
  53     if (delayed_work_time_.is_null()) {
  54       event_.Wait();
  55     } else {
  56       TimeDelta delay = delayed_work_time_ - TimeTicks::Now();
  57 #if defined(OS_WIN)
  58       // If the delay is greater than zero and under 1 ms we need to round up to
  59       // 1 ms or else we will end up spinning until it counts down to zero
  60       // because sub-ms waits aren't supported on Windows.
  61       if (delay > TimeDelta())
  62         delay = std::max(delay, TimeDelta::FromMilliseconds(1));
  63 #endif
  64       if (delay > TimeDelta()) {
  65         event_.TimedWait(delay);
  66       } else {
  67         // It looks like delayed_work_time_ indicates a time in the past, so we
  68         // need to call DoDelayedWork now.
  69         delayed_work_time_ = TimeTicks();
  70       }
  71     }
  72     // Since event_ is auto-reset, we don't need to do anything special here
  73     // other than service each delegate method.
  74   }
  75
  76   keep_running_ = true;
  77 }
  78
  79 void MessagePumpDefault::Quit() {
  80   keep_running_ = false;
  81 }
  82
  83 void MessagePumpDefault::ScheduleWork() {
  84   // Since this can be called on any thread, we need to ensure that our Run
  85   // loop wakes up.
  86   event_.Signal();
  87 }
  88
  89 void MessagePumpDefault::ScheduleDelayedWork(
  90     const TimeTicks& delayed_work_time) {
  91   // We know that we can't be blocked on Wait right now since this method can
  92   // only be called on the same thread as Run, so we only need to update our
  93   // record of how long to sleep when we do sleep.
  94   delayed_work_time_ = delayed_work_time;
  95 }
  96
  97 }  // namespace base