1 files changed, 68 insertions, 0 deletions
diff --git a/third_party/libwebrtc/api/notifier.h b/third_party/libwebrtc/api/notifier.h
new file mode 100644
index 0000000000..fc2480e00a
--- /dev/null
+++ b/third_party/libwebrtc/api/notifier.h
@@ -0,0 +1,68 @@
+/*
+ *  Copyright 2011 The WebRTC project authors. All Rights Reserved.
+ *
+ *  Use of this source code is governed by a BSD-style license
+ *  that can be found in the LICENSE file in the root of the source
+ *  tree. An additional intellectual property rights grant can be found
+ *  in the file PATENTS.  All contributing project authors may
+ *  be found in the AUTHORS file in the root of the source tree.
+ */
+
+#ifndef API_NOTIFIER_H_
+#define API_NOTIFIER_H_
+
+#include <list>
+
+#include "api/media_stream_interface.h"
+#include "api/sequence_checker.h"
+#include "rtc_base/checks.h"
+#include "rtc_base/system/no_unique_address.h"
+
+namespace webrtc {
+
+// Implements a template version of a notifier.
+// TODO(deadbeef): This is an implementation detail; move out of api/.
+template <class T>
+class Notifier : public T {
+ public:
+  Notifier() { sequence_checker_.Detach(); }
+
+  virtual void RegisterObserver(ObserverInterface* observer) {
+    RTC_DCHECK_RUN_ON(&sequence_checker_);
+    RTC_DCHECK(observer != nullptr);
+    observers_.push_back(observer);
+  }
+
+  virtual void UnregisterObserver(ObserverInterface* observer) {
+    RTC_DCHECK_RUN_ON(&sequence_checker_);
+    for (std::list<ObserverInterface*>::iterator it = observers_.begin();
+         it != observers_.end(); it++) {
+      if (*it == observer) {
+        observers_.erase(it);
+        break;
+      }
+    }
+  }
+
+  void FireOnChanged() {
+    RTC_DCHECK_RUN_ON(&sequence_checker_);
+    // Copy the list of observers to avoid a crash if the observer object
+    // unregisters as a result of the OnChanged() call. If the same list is used
+    // UnregisterObserver will affect the list make the iterator invalid.
+    std::list<ObserverInterface*> observers = observers_;
+    for (std::list<ObserverInterface*>::iterator it = observers.begin();
+         it != observers.end(); ++it) {
+      (*it)->OnChanged();
+    }
+  }
+
+ protected:
+  std::list<ObserverInterface*> observers_ RTC_GUARDED_BY(sequence_checker_);
+
+ private:
+  RTC_NO_UNIQUE_ADDRESS SequenceChecker sequence_checker_;
+};
+
+}  // namespace webrtc
+
+#endif  // API_NOTIFIER_H_