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// Copyright 2014 The Chromium Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
#include "base/task/cancelable_task_tracker.h"
#include <stddef.h>
#include <utility>
#include "base/bind.h"
#include "base/callback_helpers.h"
#include "base/compiler_specific.h"
#include "base/location.h"
#include "base/memory/ref_counted.h"
#include "base/single_thread_task_runner.h"
#include "base/synchronization/cancellation_flag.h"
#include "base/task_runner.h"
#include "base/thread_task_runner_handle.h"
using base::Bind;
using base::CancellationFlag;
using base::Closure;
using base::hash_map;
using base::TaskRunner;
namespace {
void RunIfNotCanceled(const CancellationFlag* flag, const Closure& task) {
if (!flag->IsSet())
task.Run();
}
void RunIfNotCanceledThenUntrack(const CancellationFlag* flag,
const Closure& task,
const Closure& untrack) {
RunIfNotCanceled(flag, task);
untrack.Run();
}
bool IsCanceled(const CancellationFlag* flag,
base::ScopedClosureRunner* /* cleanup_runner */) {
return flag->IsSet();
}
void RunAndDeleteFlag(const Closure& closure, const CancellationFlag* flag) {
closure.Run();
delete flag;
}
void RunOrPostToTaskRunner(TaskRunner* task_runner, const Closure& closure) {
if (task_runner->RunsTasksOnCurrentThread())
closure.Run();
else
task_runner->PostTask(FROM_HERE, closure);
}
} // namespace
namespace base {
// static
const CancelableTaskTracker::TaskId CancelableTaskTracker::kBadTaskId = 0;
CancelableTaskTracker::CancelableTaskTracker()
: next_id_(1),weak_factory_(this) {}
CancelableTaskTracker::~CancelableTaskTracker() {
DCHECK(thread_checker_.CalledOnValidThread());
TryCancelAll();
}
CancelableTaskTracker::TaskId CancelableTaskTracker::PostTask(
TaskRunner* task_runner,
const tracked_objects::Location& from_here,
const Closure& task) {
DCHECK(thread_checker_.CalledOnValidThread());
return PostTaskAndReply(task_runner, from_here, task, Bind(&base::DoNothing));
}
CancelableTaskTracker::TaskId CancelableTaskTracker::PostTaskAndReply(
TaskRunner* task_runner,
const tracked_objects::Location& from_here,
const Closure& task,
const Closure& reply) {
DCHECK(thread_checker_.CalledOnValidThread());
// We need a MessageLoop to run reply.
DCHECK(base::ThreadTaskRunnerHandle::IsSet());
// Owned by reply callback below.
CancellationFlag* flag = new CancellationFlag();
TaskId id = next_id_;
next_id_++; // int64_t is big enough that we ignore the potential overflow.
const Closure& untrack_closure =
Bind(&CancelableTaskTracker::Untrack, weak_factory_.GetWeakPtr(), id);
bool success =
task_runner->PostTaskAndReply(from_here,
Bind(&RunIfNotCanceled, flag, task),
Bind(&RunIfNotCanceledThenUntrack,
base::Owned(flag),
reply,
untrack_closure));
if (!success)
return kBadTaskId;
Track(id, flag);
return id;
}
CancelableTaskTracker::TaskId CancelableTaskTracker::NewTrackedTaskId(
IsCanceledCallback* is_canceled_cb) {
DCHECK(thread_checker_.CalledOnValidThread());
DCHECK(base::ThreadTaskRunnerHandle::IsSet());
TaskId id = next_id_;
next_id_++; // int64_t is big enough that we ignore the potential overflow.
// Will be deleted by |untrack_and_delete_flag| after Untrack().
CancellationFlag* flag = new CancellationFlag();
Closure untrack_and_delete_flag = Bind(
&RunAndDeleteFlag,
Bind(&CancelableTaskTracker::Untrack, weak_factory_.GetWeakPtr(), id),
flag);
// Will always run |untrack_and_delete_flag| on current MessageLoop.
base::ScopedClosureRunner* untrack_and_delete_flag_runner =
new base::ScopedClosureRunner(Bind(&RunOrPostToTaskRunner,
base::ThreadTaskRunnerHandle::Get(),
untrack_and_delete_flag));
*is_canceled_cb =
Bind(&IsCanceled, flag, base::Owned(untrack_and_delete_flag_runner));
Track(id, flag);
return id;
}
void CancelableTaskTracker::TryCancel(TaskId id) {
DCHECK(thread_checker_.CalledOnValidThread());
hash_map<TaskId, CancellationFlag*>::const_iterator it = task_flags_.find(id);
if (it == task_flags_.end()) {
// Two possibilities:
//
// 1. The task has already been untracked.
// 2. The TaskId is bad or unknown.
//
// Since this function is best-effort, it's OK to ignore these.
return;
}
it->second->Set();
}
void CancelableTaskTracker::TryCancelAll() {
DCHECK(thread_checker_.CalledOnValidThread());
for (hash_map<TaskId, CancellationFlag*>::const_iterator it =
task_flags_.begin();
it != task_flags_.end();
++it) {
it->second->Set();
}
}
bool CancelableTaskTracker::HasTrackedTasks() const {
DCHECK(thread_checker_.CalledOnValidThread());
return !task_flags_.empty();
}
void CancelableTaskTracker::Track(TaskId id, CancellationFlag* flag) {
DCHECK(thread_checker_.CalledOnValidThread());
bool success = task_flags_.insert(std::make_pair(id, flag)).second;
DCHECK(success);
}
void CancelableTaskTracker::Untrack(TaskId id) {
DCHECK(thread_checker_.CalledOnValidThread());
size_t num = task_flags_.erase(id);
DCHECK_EQ(1u, num);
}
} // namespace base
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