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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/callback_helpers.h"
#include "base/location.h"
#include "base/memory/ref_counted.h"
#include "base/synchronization/cancellation_flag.h"
#include "base/task_runner.h"
#include "base/threading/sequenced_task_runner_handle.h"
namespace base {
namespace {
void RunIfNotCanceled(const CancellationFlag* flag, OnceClosure task) {
if (!flag->IsSet())
std::move(task).Run();
}
void RunIfNotCanceledThenUntrack(const CancellationFlag* flag,
OnceClosure task,
OnceClosure untrack) {
RunIfNotCanceled(flag, std::move(task));
std::move(untrack).Run();
}
bool IsCanceled(const CancellationFlag* flag,
ScopedClosureRunner* cleanup_runner) {
return flag->IsSet();
}
void RunAndDeleteFlag(OnceClosure closure, const CancellationFlag* flag) {
std::move(closure).Run();
delete flag;
}
void RunOrPostToTaskRunner(TaskRunner* task_runner, OnceClosure closure) {
if (task_runner->RunsTasksOnCurrentThread())
std::move(closure).Run();
else
task_runner->PostTask(FROM_HERE, std::move(closure));
}
} // namespace
// static
const CancelableTaskTracker::TaskId CancelableTaskTracker::kBadTaskId = 0;
CancelableTaskTracker::CancelableTaskTracker()
: next_id_(1),weak_factory_(this) {}
CancelableTaskTracker::~CancelableTaskTracker() {
DCHECK(sequence_checker_.CalledOnValidSequence());
TryCancelAll();
}
CancelableTaskTracker::TaskId CancelableTaskTracker::PostTask(
TaskRunner* task_runner,
const tracked_objects::Location& from_here,
OnceClosure task) {
DCHECK(sequence_checker_.CalledOnValidSequence());
return PostTaskAndReply(task_runner, from_here, std::move(task),
BindOnce(&DoNothing));
}
CancelableTaskTracker::TaskId CancelableTaskTracker::PostTaskAndReply(
TaskRunner* task_runner,
const tracked_objects::Location& from_here,
OnceClosure task,
OnceClosure reply) {
DCHECK(sequence_checker_.CalledOnValidSequence());
// We need a SequencedTaskRunnerHandle to run |reply|.
DCHECK(SequencedTaskRunnerHandle::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.
OnceClosure untrack_closure =
BindOnce(&CancelableTaskTracker::Untrack, weak_factory_.GetWeakPtr(), id);
bool success = task_runner->PostTaskAndReply(
from_here, BindOnce(&RunIfNotCanceled, flag, std::move(task)),
BindOnce(&RunIfNotCanceledThenUntrack, Owned(flag), std::move(reply),
std::move(untrack_closure)));
if (!success)
return kBadTaskId;
Track(id, flag);
return id;
}
CancelableTaskTracker::TaskId CancelableTaskTracker::NewTrackedTaskId(
IsCanceledCallback* is_canceled_cb) {
DCHECK(sequence_checker_.CalledOnValidSequence());
DCHECK(SequencedTaskRunnerHandle::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();
OnceClosure untrack_and_delete_flag = BindOnce(
&RunAndDeleteFlag,
BindOnce(&CancelableTaskTracker::Untrack, weak_factory_.GetWeakPtr(), id),
flag);
// Will always run |untrack_and_delete_flag| on current sequence.
ScopedClosureRunner* untrack_and_delete_flag_runner =
new ScopedClosureRunner(Bind(
&RunOrPostToTaskRunner, RetainedRef(SequencedTaskRunnerHandle::Get()),
Passed(&untrack_and_delete_flag)));
*is_canceled_cb =
Bind(&IsCanceled, flag, Owned(untrack_and_delete_flag_runner));
Track(id, flag);
return id;
}
void CancelableTaskTracker::TryCancel(TaskId id) {
DCHECK(sequence_checker_.CalledOnValidSequence());
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->Set();
}
void CancelableTaskTracker::TryCancelAll() {
DCHECK(sequence_checker_.CalledOnValidSequence());
for (const auto& it : task_flags_)
it.second->Set();
}
bool CancelableTaskTracker::HasTrackedTasks() const {
DCHECK(sequence_checker_.CalledOnValidSequence());
return !task_flags_.empty();
}
void CancelableTaskTracker::Track(TaskId id, CancellationFlag* flag) {
DCHECK(sequence_checker_.CalledOnValidSequence());
bool success = task_flags_.insert(std::make_pair(id, flag)).second;
DCHECK(success);
}
void CancelableTaskTracker::Untrack(TaskId id) {
DCHECK(sequence_checker_.CalledOnValidSequence());
size_t num = task_flags_.erase(id);
DCHECK_EQ(1u, num);
}
} // namespace base
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