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// Copyright 2025 The Chromium Authors
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
#ifndef THIRD_PARTY_BLINK_RENDERER_PLATFORM_WTF_BIND_POST_TASK_H_
#define THIRD_PARTY_BLINK_RENDERER_PLATFORM_WTF_BIND_POST_TASK_H_
#include <memory>
#include <utility>
#include "base/functional/callback.h"
#include "base/location.h"
#include "base/task/sequenced_task_runner.h"
#include "third_party/blink/renderer/platform/wtf/cross_thread_copier_std.h"
#include "third_party/blink/renderer/platform/wtf/cross_thread_functional.h"
#include "third_party/blink/renderer/platform/wtf/functional.h"
// See base::BindPostTask() for docs, this is the WTF cross-thread version.
namespace WTF {
namespace internal {
// Based on base::internal::BindPostTaskTrampoline with modifications for
// CrossThreadFunction/CrossThreadOnceFunction. CrossThreadOnceFunction works
// identically to the base version, but CrossThreadFunction is not copyable or
// convertible to a CrossThreadOnceFunction, so a task must be posted to run it
// instead of directly passing it to `task_runner`. Safety is guaranteed by
// ensuring CrossThreadBindPostTaskTrampoline is destructed on `task_runner`.
template <typename CallbackType>
class CrossThreadBindPostTaskTrampoline {
public:
CrossThreadBindPostTaskTrampoline(
scoped_refptr<base::SequencedTaskRunner> task_runner,
const base::Location& location,
CallbackType callback)
: task_runner_(std::move(task_runner)),
location_(location),
callback_(std::move(callback)) {
DCHECK(task_runner_);
CHECK(callback_);
}
~CrossThreadBindPostTaskTrampoline() {
DCHECK(task_runner_->RunsTasksInCurrentSequence());
}
CrossThreadBindPostTaskTrampoline(
const CrossThreadBindPostTaskTrampoline& other) = delete;
CrossThreadBindPostTaskTrampoline& operator=(
const CrossThreadBindPostTaskTrampoline& other) = delete;
template <typename... Args>
void RunOnce(Args... args) {
task_runner_->PostTask(
location_, ConvertToBaseOnceCallback(CrossThreadBindOnce(
std::move(callback_), std::forward<Args>(args)...)));
}
template <typename... Args>
void RunRepeating(Args... args) {
// Safe since the destruction of `this` is posted to `task_runner_`.
task_runner_->PostTask(
location_,
ConvertToBaseOnceCallback(CrossThreadBindOnce(
&RunOnTaskRunner<Args...>, CrossThreadUnretained(&callback_),
std::forward<Args>(args)...)));
}
private:
template <typename... Args>
static void RunOnTaskRunner(CallbackType* callback, Args... args) {
callback->Run(std::forward<Args>(args)...);
}
const scoped_refptr<base::SequencedTaskRunner> task_runner_;
const base::Location location_;
CallbackType callback_;
};
} // namespace internal
template <typename ReturnType, typename... Args>
requires std::is_void_v<ReturnType>
CrossThreadOnceFunction<void(Args...)> BindPostTask(
scoped_refptr<base::SequencedTaskRunner> task_runner,
CrossThreadOnceFunction<ReturnType(Args...)> callback,
const base::Location& location = FROM_HERE) {
using Helper = internal::CrossThreadBindPostTaskTrampoline<
CrossThreadOnceFunction<void(Args...)>>;
std::unique_ptr<Helper, base::OnTaskRunnerDeleter> helper(
new Helper(task_runner, location, std::move(callback)),
base::OnTaskRunnerDeleter(task_runner));
return CrossThreadBindOnce(&Helper::template RunOnce<Args...>,
std::move(helper));
}
template <typename ReturnType, typename... Args>
requires std::is_void_v<ReturnType>
CrossThreadFunction<void(Args...)> BindPostTask(
scoped_refptr<base::SequencedTaskRunner> task_runner,
CrossThreadFunction<ReturnType(Args...)> callback,
const base::Location& location = FROM_HERE) {
using Helper = internal::CrossThreadBindPostTaskTrampoline<
CrossThreadFunction<void(Args...)>>;
std::unique_ptr<Helper, base::OnTaskRunnerDeleter> helper(
new Helper(task_runner, location, std::move(callback)),
base::OnTaskRunnerDeleter(task_runner));
return CrossThreadBindRepeating(&Helper::template RunRepeating<Args...>,
std::move(helper));
}
} // namespace WTF
#endif // THIRD_PARTY_BLINK_RENDERER_PLATFORM_WTF_BIND_POST_TASK_H_
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