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// Copyright 2014 The Chromium Authors
// 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/functional/bind.h"
#include "base/functional/callback_helpers.h"
#include "base/location.h"
#include "base/memory/ref_counted.h"
#include "base/metrics/histogram_macros.h"
#include "base/task/sequenced_task_runner.h"
#include "base/task/task_runner.h"
namespace base {
namespace {
void RunOrPostToTaskRunner(scoped_refptr<SequencedTaskRunner> task_runner,
OnceClosure closure) {
if (task_runner->RunsTasksInCurrentSequence())
std::move(closure).Run();
else
task_runner->PostTask(FROM_HERE, std::move(closure));
}
} // namespace
// static
const CancelableTaskTracker::TaskId CancelableTaskTracker::kBadTaskId = 0;
CancelableTaskTracker::CancelableTaskTracker() {
weak_this_ = weak_factory_.GetWeakPtr();
}
CancelableTaskTracker::~CancelableTaskTracker() {
DCHECK_CALLED_ON_VALID_SEQUENCE(sequence_checker_);
TryCancelAll();
}
CancelableTaskTracker::TaskId CancelableTaskTracker::PostTask(
TaskRunner* task_runner,
const Location& from_here,
OnceClosure task) {
DCHECK_CALLED_ON_VALID_SEQUENCE(sequence_checker_);
CHECK(weak_this_);
return PostTaskAndReply(task_runner, from_here, std::move(task), DoNothing());
}
CancelableTaskTracker::TaskId CancelableTaskTracker::PostTaskAndReply(
TaskRunner* task_runner,
const Location& from_here,
OnceClosure task,
OnceClosure reply) {
DCHECK_CALLED_ON_VALID_SEQUENCE(sequence_checker_);
CHECK(weak_this_);
// We need a SequencedTaskRunner::CurrentDefaultHandle to run |reply|.
DCHECK(SequencedTaskRunner::HasCurrentDefault());
auto flag = MakeRefCounted<TaskCancellationFlag>();
TaskId id = next_id_;
next_id_++; // int64_t is big enough that we ignore the potential overflow.
// Unretained(this) is safe because |flag| will have been set to the
// "canceled" state after |this| is deleted.
OnceClosure untrack_closure =
BindOnce(&CancelableTaskTracker::Untrack, Unretained(this), id);
bool success = task_runner->PostTaskAndReply(
from_here, BindOnce(&RunIfNotCanceled, flag, std::move(task)),
BindOnce(&RunThenUntrackIfNotCanceled, flag, std::move(reply),
std::move(untrack_closure)));
if (!success)
return kBadTaskId;
Track(id, std::move(flag));
return id;
}
CancelableTaskTracker::TaskId CancelableTaskTracker::NewTrackedTaskId(
IsCanceledCallback* is_canceled_cb) {
DCHECK_CALLED_ON_VALID_SEQUENCE(sequence_checker_);
DCHECK(SequencedTaskRunner::HasCurrentDefault());
TaskId id = next_id_;
next_id_++; // int64_t is big enough that we ignore the potential overflow.
auto flag = MakeRefCounted<TaskCancellationFlag>();
// Unretained(this) is safe because |flag| will have been set to the
// "canceled" state after |this| is deleted.
OnceClosure untrack_closure =
BindOnce(&CancelableTaskTracker::Untrack, Unretained(this), id);
// Will always run |untrack_closure| on current sequence.
ScopedClosureRunner untrack_runner(
BindOnce(&RunOrPostToTaskRunner, SequencedTaskRunner::GetCurrentDefault(),
BindOnce(&RunIfNotCanceled, flag, std::move(untrack_closure))));
*is_canceled_cb = BindRepeating(&IsCanceled, flag, std::move(untrack_runner));
Track(id, std::move(flag));
return id;
}
void CancelableTaskTracker::TryCancel(TaskId id) {
DCHECK_CALLED_ON_VALID_SEQUENCE(sequence_checker_);
const auto 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->data.Set();
// Remove |id| from |task_flags_| immediately, since we have no further
// use for tracking it. This allows the reply closures (see
// PostTaskAndReply()) for cancelled tasks to be skipped, since they have
// no clean-up to perform.
task_flags_.erase(it);
}
void CancelableTaskTracker::TryCancelAll() {
DCHECK_CALLED_ON_VALID_SEQUENCE(sequence_checker_);
for (const auto& it : task_flags_)
it.second->data.Set();
task_flags_.clear();
}
bool CancelableTaskTracker::HasTrackedTasks() const {
DCHECK_CALLED_ON_VALID_SEQUENCE(sequence_checker_);
return !task_flags_.empty();
}
// static
void CancelableTaskTracker::RunIfNotCanceled(
const scoped_refptr<TaskCancellationFlag>& flag,
OnceClosure task) {
if (!flag->data.IsSet()) {
std::move(task).Run();
}
}
// static
void CancelableTaskTracker::RunThenUntrackIfNotCanceled(
const scoped_refptr<TaskCancellationFlag>& flag,
OnceClosure task,
OnceClosure untrack) {
RunIfNotCanceled(flag, std::move(task));
RunIfNotCanceled(flag, std::move(untrack));
}
// static
bool CancelableTaskTracker::IsCanceled(
const scoped_refptr<TaskCancellationFlag>& flag,
const ScopedClosureRunner& cleanup_runner) {
return flag->data.IsSet();
}
void CancelableTaskTracker::Track(TaskId id,
scoped_refptr<TaskCancellationFlag> flag) {
DCHECK_CALLED_ON_VALID_SEQUENCE(sequence_checker_);
CHECK(weak_this_);
bool success = task_flags_.insert(std::make_pair(id, std::move(flag))).second;
DCHECK(success);
}
void CancelableTaskTracker::Untrack(TaskId id) {
DCHECK_CALLED_ON_VALID_SEQUENCE(sequence_checker_);
CHECK(weak_this_);
size_t num = task_flags_.erase(id);
DCHECK_EQ(1u, num);
}
} // namespace base
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