chrome/common/cancelable_task_tracker.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/cancelable_task_tracker.h"
   6
   7 #include <utility>
   8
   9 #include "base/bind.h"
  10 #include "base/callback_helpers.h"
  11 #include "base/compiler_specific.h"
  12 #include "base/location.h"
  13 #include "base/memory/ref_counted.h"
  14 #include "base/message_loop/message_loop_proxy.h"
  15 #include "base/synchronization/cancellation_flag.h"
  16 #include "base/task_runner.h"
  17
  18 using base::Bind;
  19 using base::CancellationFlag;
  20 using base::Closure;
  21 using base::hash_map;
  22 using base::TaskRunner;
  23
  24 namespace {
  25
  26 void RunIfNotCanceled(const CancellationFlag* flag, const Closure& task) {
  27   if (!flag->IsSet())
  28     task.Run();
  29 }
  30
  31 void RunIfNotCanceledThenUntrack(const CancellationFlag* flag,
  32                                  const Closure& task,
  33                                  const Closure& untrack) {
  34   RunIfNotCanceled(flag, task);
  35   untrack.Run();
  36 }
  37
  38 bool IsCanceled(const CancellationFlag* flag,
  39                 base::ScopedClosureRunner* cleanup_runner) {
  40   return flag->IsSet();
  41 }
  42
  43 void RunAndDeleteFlag(const Closure& closure, const CancellationFlag* flag) {
  44   closure.Run();
  45   delete flag;
  46 }
  47
  48 void RunOrPostToTaskRunner(TaskRunner* task_runner, const Closure& closure) {
  49   if (task_runner->RunsTasksOnCurrentThread())
  50     closure.Run();
  51   else
  52     task_runner->PostTask(FROM_HERE, closure);
  53 }
  54
  55 }  // namespace
  56
  57 // static
  58 const CancelableTaskTracker::TaskId CancelableTaskTracker::kBadTaskId = 0;
  59
  60 CancelableTaskTracker::CancelableTaskTracker()
  61     : weak_factory_(this),
  62       next_id_(1) {}
  63
  64 CancelableTaskTracker::~CancelableTaskTracker() {
  65   DCHECK(thread_checker_.CalledOnValidThread());
  66
  67   TryCancelAll();
  68 }
  69
  70 CancelableTaskTracker::TaskId CancelableTaskTracker::PostTask(
  71     TaskRunner* task_runner,
  72     const tracked_objects::Location& from_here,
  73     const Closure& task) {
  74   DCHECK(thread_checker_.CalledOnValidThread());
  75
  76   return PostTaskAndReply(task_runner, from_here, task, Bind(&base::DoNothing));
  77 }
  78
  79 CancelableTaskTracker::TaskId CancelableTaskTracker::PostTaskAndReply(
  80     TaskRunner* task_runner,
  81     const tracked_objects::Location& from_here,
  82     const Closure& task,
  83     const Closure& reply) {
  84   DCHECK(thread_checker_.CalledOnValidThread());
  85
  86   // We need a MessageLoop to run reply.
  87   DCHECK(base::MessageLoopProxy::current().get());
  88
  89   // Owned by reply callback below.
  90   CancellationFlag* flag = new CancellationFlag();
  91
  92   TaskId id = next_id_;
  93   next_id_++;  // int64 is big enough that we ignore the potential overflow.
  94
  95   const Closure& untrack_closure = Bind(
  96       &CancelableTaskTracker::Untrack, weak_factory_.GetWeakPtr(), id);
  97   bool success = task_runner->PostTaskAndReply(
  98       from_here,
  99       Bind(&RunIfNotCanceled, flag, task),
 100       Bind(&RunIfNotCanceledThenUntrack,
 101            base::Owned(flag), reply, untrack_closure));
 102
 103   if (!success)
 104     return kBadTaskId;
 105
 106   Track(id, flag);
 107   return id;
 108 }
 109
 110 CancelableTaskTracker::TaskId CancelableTaskTracker::NewTrackedTaskId(
 111     IsCanceledCallback* is_canceled_cb) {
 112   DCHECK(thread_checker_.CalledOnValidThread());
 113   DCHECK(base::MessageLoopProxy::current().get());
 114
 115   TaskId id = next_id_;
 116   next_id_++;  // int64 is big enough that we ignore the potential overflow.
 117
 118   // Will be deleted by |untrack_and_delete_flag| after Untrack().
 119   CancellationFlag* flag = new CancellationFlag();
 120
 121   Closure untrack_and_delete_flag = Bind(
 122       &RunAndDeleteFlag,
 123       Bind(&CancelableTaskTracker::Untrack, weak_factory_.GetWeakPtr(), id),
 124       flag);
 125
 126   // Will always run |untrack_and_delete_flag| on current MessageLoop.
 127   base::ScopedClosureRunner* untrack_and_delete_flag_runner =
 128       new base::ScopedClosureRunner(
 129           Bind(&RunOrPostToTaskRunner,
 130                base::MessageLoopProxy::current(),
 131                untrack_and_delete_flag));
 132
 133   *is_canceled_cb = Bind(
 134       &IsCanceled, flag, base::Owned(untrack_and_delete_flag_runner));
 135
 136   Track(id, flag);
 137   return id;
 138 }
 139
 140 void CancelableTaskTracker::TryCancel(TaskId id) {
 141   DCHECK(thread_checker_.CalledOnValidThread());
 142
 143   hash_map<TaskId, CancellationFlag*>::const_iterator it = task_flags_.find(id);
 144   if (it == task_flags_.end()) {
 145     // Two possibilities:
 146     //
 147     //   1. The task has already been untracked.
 148     //   2. The TaskId is bad or unknown.
 149     //
 150     // Since this function is best-effort, it's OK to ignore these.
 151     return;
 152   }
 153   it->second->Set();
 154 }
 155
 156 void CancelableTaskTracker::TryCancelAll() {
 157   DCHECK(thread_checker_.CalledOnValidThread());
 158
 159   for (hash_map<TaskId, CancellationFlag*>::const_iterator it =
 160            task_flags_.begin();
 161        it != task_flags_.end();
 162        ++it) {
 163     it->second->Set();
 164   }
 165 }
 166
 167 bool CancelableTaskTracker::HasTrackedTasks() const {
 168   DCHECK(thread_checker_.CalledOnValidThread());
 169   return !task_flags_.empty();
 170 }
 171
 172 void CancelableTaskTracker::Track(TaskId id, CancellationFlag* flag) {
 173   DCHECK(thread_checker_.CalledOnValidThread());
 174
 175   bool success = task_flags_.insert(std::make_pair(id, flag)).second;
 176   DCHECK(success);
 177 }
 178
 179 void CancelableTaskTracker::Untrack(TaskId id) {
 180   DCHECK(thread_checker_.CalledOnValidThread());
 181   size_t num = task_flags_.erase(id);
 182   DCHECK_EQ(1u, num);
 183 }