| // Copyright 2013 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. |
| |
| #ifndef MEDIA_BASE_CALLBACK_HOLDER_H_ |
| #define MEDIA_BASE_CALLBACK_HOLDER_H_ |
| |
| #include "base/bind.h" |
| #include "base/callback.h" |
| #include "base/callback_helpers.h" |
| |
| namespace media { |
| |
| // A helper class that can hold a callback from being fired. |
| template <typename CB> class CallbackHolder { |
| public: |
| CallbackHolder() : hold_(false) {} |
| |
| ~CallbackHolder() { |
| DCHECK(original_cb_.is_null()); |
| DCHECK(held_cb_.is_null()); |
| } |
| |
| // Sets the callback to be potentially held. |
| void SetCallback(const CB& cb) { |
| DCHECK(original_cb_.is_null()); |
| DCHECK(held_cb_.is_null()); |
| original_cb_ = cb; |
| } |
| |
| bool IsNull() const { |
| return original_cb_.is_null() && held_cb_.is_null(); |
| } |
| |
| // Holds the callback when Run() is called. |
| void HoldCallback() { hold_ = true; } |
| |
| // Runs or holds the callback as specified by |hold_|. |
| void RunOrHold() { |
| DCHECK(held_cb_.is_null()); |
| if (hold_) |
| held_cb_ = base::ResetAndReturn(&original_cb_); |
| else |
| base::ResetAndReturn(&original_cb_).Run(); |
| } |
| |
| template <typename... Args> |
| void RunOrHold(Args&&... args) { |
| DCHECK(held_cb_.is_null()); |
| if (hold_) { |
| held_cb_ = base::BindOnce(base::ResetAndReturn(&original_cb_), |
| std::forward<Args>(args)...); |
| } else { |
| base::ResetAndReturn(&original_cb_).Run(std::forward<Args>(args)...); |
| } |
| } |
| |
| // Releases and runs the held callback. |
| void RunHeldCallback() { |
| DCHECK(hold_); |
| DCHECK(!held_cb_.is_null()); |
| hold_ = false; |
| base::ResetAndReturn(&held_cb_).Run(); |
| } |
| |
| private: |
| bool hold_; |
| CB original_cb_; |
| base::OnceClosure held_cb_; |
| }; |
| |
| } // namespace media |
| |
| #endif // MEDIA_BASE_CALLBACK_HOLDER_H_ |