1 // Copyright 2013 The Chromium Authors. All rights reserved. 2 // Use of this source code is governed by a BSD-style license that can be 3 // found in the LICENSE file. 4 5 #ifndef MEDIA_BASE_CALLBACK_HOLDER_H_ 6 #define MEDIA_BASE_CALLBACK_HOLDER_H_ 7 8 #include "base/bind.h" 9 #include "base/callback.h" 10 #include "base/callback_helpers.h" 11 #include "media/base/bind_to_loop.h" 12 13 namespace media { 14 15 // A helper class that can hold a callback from being fired. 16 template <typename CB> class CallbackHolder { 17 public: CallbackHolder()18 CallbackHolder() : hold_(false) {} 19 ~CallbackHolder()20 ~CallbackHolder() { 21 // Make sure all callbacks are satisfied! 22 DCHECK(!hold_); 23 DCHECK(original_cb_.is_null()); 24 DCHECK(held_cb_.is_null()); 25 } 26 27 // Sets the callback to be potentially held. SetCallback(const CB & cb)28 void SetCallback(const CB& cb) { 29 DCHECK(original_cb_.is_null()); 30 DCHECK(held_cb_.is_null()); 31 original_cb_ = cb; 32 } 33 IsNull()34 bool IsNull() const { 35 return original_cb_.is_null() && held_cb_.is_null(); 36 } 37 38 // Holds the callback when Run() is called. HoldCallback()39 void HoldCallback() { hold_ = true; } 40 41 // Runs or holds the callback as specified by |hold_|. 42 // This method has overloaded versions to support different types of CB. RunOrHold()43 void RunOrHold() { 44 DCHECK(held_cb_.is_null()); 45 if (hold_) 46 held_cb_ = base::ResetAndReturn(&original_cb_); 47 else 48 base::ResetAndReturn(&original_cb_).Run(); 49 } 50 RunOrHold(A1 a1)51 template <typename A1> void RunOrHold(A1 a1) { 52 DCHECK(held_cb_.is_null()); 53 if (hold_) { 54 held_cb_ = base::Bind(base::ResetAndReturn(&original_cb_), 55 internal::TrampolineForward(a1)); 56 } else { 57 base::ResetAndReturn(&original_cb_).Run(a1); 58 } 59 } 60 RunOrHold(A1 a1,A2 a2)61 template <typename A1, typename A2> void RunOrHold(A1 a1, A2 a2) { 62 DCHECK(held_cb_.is_null()); 63 if (hold_) { 64 held_cb_ = base::Bind(base::ResetAndReturn(&original_cb_), 65 internal::TrampolineForward(a1), 66 internal::TrampolineForward(a2)); 67 } else { 68 base::ResetAndReturn(&original_cb_).Run(a1, a2); 69 } 70 } 71 72 // Releases and runs the held callback. RunHeldCallback()73 void RunHeldCallback() { 74 DCHECK(hold_); 75 DCHECK(!held_cb_.is_null()); 76 hold_ = false; 77 base::ResetAndReturn(&held_cb_).Run(); 78 } 79 80 private: 81 bool hold_; 82 CB original_cb_; 83 base::Closure held_cb_; 84 }; 85 86 } // namespace media 87 88 #endif // MEDIA_BASE_CALLBACK_HOLDER_H_ 89