Repo created

TMessagesProj/jni/voip/webrtc/base/scoped_observer.h

@@ -0,0 +1,87 @@
+// Copyright (c) 2012 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 BASE_SCOPED_OBSERVER_H_
+#define BASE_SCOPED_OBSERVER_H_
+
+#include <stddef.h>
+
+#include <algorithm>
+#include <vector>
+
+#include "base/logging.h"
+#include "base/macros.h"
+#include "base/stl_util.h"
+
+// ScopedObserver is used to keep track of the set of sources an object has
+// attached itself to as an observer. When ScopedObserver is destroyed it
+// removes the object as an observer from all sources it has been added to.
+// Basic example (as a member variable):
+//
+//   class MyFooObserver : public FooObserver {
+//     ...
+//    private:
+//     ScopedObserver<Foo, FooObserver> observed_foo_{this};
+//   };
+//
+// For cases with methods not named AddObserver/RemoveObserver:
+//
+//   class MyFooStateObserver : public FooStateObserver {
+//     ...
+//    private:
+//     ScopedObserver<Foo,
+//                    FooStateObserver,
+//                    &Foo::AddStateObserver,
+//                    &Foo::RemoveStateObserver>
+//       observed_foo_{this};
+//   };
+template <class Source,
+          class Observer,
+          void (Source::*AddObsFn)(Observer*) = &Source::AddObserver,
+          void (Source::*RemoveObsFn)(Observer*) = &Source::RemoveObserver>
+class ScopedObserver {
+ public:
+  explicit ScopedObserver(Observer* observer) : observer_(observer) {}
+
+  ~ScopedObserver() {
+    RemoveAll();
+  }
+
+  // Adds the object passed to the constructor as an observer on |source|.
+  void Add(Source* source) {
+    sources_.push_back(source);
+    (source->*AddObsFn)(observer_);
+  }
+
+  // Remove the object passed to the constructor as an observer from |source|.
+  void Remove(Source* source) {
+    auto it = std::find(sources_.begin(), sources_.end(), source);
+    DCHECK(it != sources_.end());
+    sources_.erase(it);
+    (source->*RemoveObsFn)(observer_);
+  }
+
+  void RemoveAll() {
+    for (size_t i = 0; i < sources_.size(); ++i)
+      (sources_[i]->*RemoveObsFn)(observer_);
+    sources_.clear();
+  }
+
+  bool IsObserving(Source* source) const {
+    return base::Contains(sources_, source);
+  }
+
+  bool IsObservingSources() const { return !sources_.empty(); }
+
+  size_t GetSourcesCount() const { return sources_.size(); }
+
+ private:
+  Observer* observer_;
+
+  std::vector<Source*> sources_;
+
+  DISALLOW_COPY_AND_ASSIGN(ScopedObserver);
+};
+
+#endif  // BASE_SCOPED_OBSERVER_H_