blob: b4dbb2d3dbeb1ea4d2d7a04037bd592f630bdfde [file] [log] [blame]
// Copyright (c) 2015 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 <memory>
#include "base/bind.h"
#include "base/location.h"
#include "base/memory/scoped_vector.h"
#include "base/single_thread_task_runner.h"
#include "base/threading/thread_task_runner_handle.h"
// This is a helper utility for base::Bind()ing callbacks to the current
// MessageLoop. The typical use is when |a| (of class |A|) wants to hand a
// callback such as base::Bind(&A::AMethod, a) to |b|, but needs to ensure that
// when |b| executes the callback, it does so on |a|'s current MessageLoop.
// Typical usage: request to be called back on the current thread:
// other->StartAsyncProcessAndCallMeBack(
// media::BindToCurrentLoop(base::Bind(&MyClass::MyMethod, this)));
// Note that like base::Bind(), BindToCurrentLoop() can't bind non-constant
// references, and that *unlike* base::Bind(), BindToCurrentLoop() makes copies
// of its arguments, and thus can't be used with arrays.
namespace media {
// Mimic base::internal::CallbackForward, replacing std::move(p) with
// base::Passed(&p) to account for the extra layer of indirection.
namespace internal {
template <typename T>
T& TrampolineForward(T& t) { return t; }
template <typename T, typename R>
base::internal::PassedWrapper<std::unique_ptr<T, R>> TrampolineForward(
std::unique_ptr<T, R>& p) {
return base::Passed(&p);
template <typename T>
base::internal::PassedWrapper<ScopedVector<T> > TrampolineForward(
ScopedVector<T>& p) { return base::Passed(&p); }
// First, tell the compiler TrampolineHelper is a struct template with one
// type parameter. Then define specializations where the type is a function
// returning void and taking zero or more arguments.
template <typename Sig> struct TrampolineHelper;
template <>
struct TrampolineHelper<void()> {
static void Run(
const scoped_refptr<base::SingleThreadTaskRunner>& task_runner,
const base::Closure& cb) {
task_runner->PostTask(FROM_HERE, cb);
template <typename... Args>
struct TrampolineHelper<void(Args...)> {
static void Run(
const scoped_refptr<base::SingleThreadTaskRunner>& task_runner,
const base::Callback<void(Args...)>& cb,
Args... args) {
base::Bind(cb, TrampolineForward(args)...));
} // namespace internal
template<typename T>
static base::Callback<T> BindToCurrentLoop(
const base::Callback<T>& cb) {
return base::Bind(&internal::TrampolineHelper<T>::Run,
base::ThreadTaskRunnerHandle::Get(), cb);
} // namespace media