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// Copyright 2022 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_HEAP_CROSS_THREAD_HANDLE_H_
#define THIRD_PARTY_BLINK_RENDERER_PLATFORM_HEAP_CROSS_THREAD_HANDLE_H_
#include "third_party/blink/renderer/platform/heap/cross_thread_handle_internal.h"
namespace blink {
// A handle object that may be used to hold a garbage collection object from a
// different thread than the object was created on. The handle supports
// thread-safe copy/move/destruction. The underlying object may only be used
// from the creation thread.
//
// Example posting to a static method that forwards back to an instance method
// on the main thread:
// ```
// class PingPong final : public GarbageCollected<PingPong> {
// public:
// void Ping() {
// DCHECK(IsMainThread());
// worker_pool::PostTask(FROM_HERE,
// CrossThreadBindOnce(&PingPong::PongOnBackground,
// MakeCrossThreadHandle(this),
// std::move(task_runner_)));
// }
//
// private:
// const scoped_refptr<base::SingleThreadTaskRunner> task_runner_ =
// GetTaskRunner();
//
// void DoneOnMainThread() { DCHECK(IsMainThread()); }
//
// static void PongOnBackground(
// CrossThreadHandle<PingPong> ping_pong,
// scoped_refptr<base::SingleThreadTaskRunner> task_runner) {
// DCHECK(!IsMainThread());
// PostCrossThreadTask(
// *task_runner, FROM_HERE,
// CrossThreadBindOnce(&PingPong::DoneOnMainThread,
// MakeUnwrappingCrossThreadWeakHandle(
// std::move(ping_pong))));
// }
// };
// ```
template <typename T>
using CrossThreadHandle = internal::
BasicCrossThreadHandle<T, internal::StrongCrossThreadHandleWeaknessPolicy>;
// Utility function creating a `CrossThreadHandle` tracking the current source
// location position in debugging configurations.
template <typename T>
CrossThreadHandle<T> MakeCrossThreadHandle(
T* value,
const CrossThreadHandleLocation& loc =
CROSS_THREAD_HANDLE_LOCATION_FROM_HERE) {
return CrossThreadHandle<T>(value);
}
// A weak handle object with similar restrictions as `CrossThreadHandle`.
// The object is only held alive weakly, meaning that the object may be
// reclaimed by the garbage collector. As a consequence, any value retrieved
// from this handle must be checked against nullptr.
template <typename T>
using CrossThreadWeakHandle = internal::
BasicCrossThreadHandle<T, internal::WeakCrossThreadHandleWeaknessPolicy>;
// Utility function creating a `CrossThreadWeakHandle` tracking the current
// source location position in debugging configurations.
template <typename T>
CrossThreadWeakHandle<T> MakeCrossThreadWeakHandle(
T* value,
const CrossThreadHandleLocation& loc =
CROSS_THREAD_HANDLE_LOCATION_FROM_HERE) {
return CrossThreadWeakHandle<T>(value);
}
// A version of `CrossThreadHandle` that automatically unwraps into `T*` on
// invocation of a bound function. This is useful for binding against regular
// instance methods of a type.
template <typename T>
using UnwrappingCrossThreadHandle = internal::BasicUnwrappingCrossThreadHandle<
T,
internal::StrongCrossThreadHandleWeaknessPolicy>;
// Utility function creating an `UnwrappingCrossThreadHandle`.
template <typename T>
UnwrappingCrossThreadHandle<T> MakeUnwrappingCrossThreadHandle(
T* value,
const CrossThreadHandleLocation& loc =
CROSS_THREAD_HANDLE_LOCATION_FROM_HERE) {
return UnwrappingCrossThreadHandle<T>(value, loc);
}
// Utility function creating an `UnwrappingCrossThreadHandle`.
template <typename T>
UnwrappingCrossThreadHandle<T> MakeUnwrappingCrossThreadHandle(
const CrossThreadHandle<T>& handle) {
return UnwrappingCrossThreadHandle<T>(handle);
}
// Utility function creating an `UnwrappingCrossThreadHandle`.
template <typename T>
UnwrappingCrossThreadHandle<T> MakeUnwrappingCrossThreadHandle(
CrossThreadHandle<T>&& handle) {
return UnwrappingCrossThreadHandle<T>(std::move(handle));
}
// A version of `CrossThreadWeakHandle` that automatically unwraps into `T*`
// on invocation of a bound function. This is useful for binding against regular
// instance methods of a type.
template <typename T>
using UnwrappingCrossThreadWeakHandle =
internal::BasicUnwrappingCrossThreadHandle<
T,
internal::WeakCrossThreadHandleWeaknessPolicy>;
// Utility function creating an `UnwrappingCrossThreadHandle`.
template <typename T>
UnwrappingCrossThreadWeakHandle<T> MakeUnwrappingCrossThreadWeakHandle(
T* value,
const CrossThreadHandleLocation& loc =
CROSS_THREAD_HANDLE_LOCATION_FROM_HERE) {
return UnwrappingCrossThreadWeakHandle<T>(value, loc);
}
// Utility function creating an `UnwrappingCrossThreadHandle`.
template <typename T>
UnwrappingCrossThreadWeakHandle<T> MakeUnwrappingCrossThreadWeakHandle(
const CrossThreadWeakHandle<T>& handle) {
return UnwrappingCrossThreadWeakHandle<T>(handle);
}
// Utility function creating an `UnwrappingCrossThreadHandle`.
template <typename T>
UnwrappingCrossThreadWeakHandle<T> MakeUnwrappingCrossThreadWeakHandle(
CrossThreadWeakHandle<T>&& handle) {
return UnwrappingCrossThreadWeakHandle<T>(std::move(handle));
}
} // namespace blink
#endif // THIRD_PARTY_BLINK_RENDERER_PLATFORM_HEAP_CROSS_THREAD_HANDLE_H_
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