1 files changed, 78 insertions, 0 deletions
diff --git a/core/fxcrt/cfx_observable.h b/core/fxcrt/cfx_observable.h
new file mode 100644
index 0000000000..dc869b1766
--- /dev/null
+++ b/core/fxcrt/cfx_observable.h
@@ -0,0 +1,78 @@
+// Copyright 2016 PDFium 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 CORE_FXCRT_CFX_OBSERVABLE_H_
+#define CORE_FXCRT_CFX_OBSERVABLE_H_
+
+#include <set>
+
+#include "core/fxcrt/fx_system.h"
+#include "third_party/base/stl_util.h"
+
+template <class T>
+class CFX_Observable {
+ public:
+  class ObservedPtr {
+   public:
+    ObservedPtr() : m_pObservedPtr(nullptr) {}
+    explicit ObservedPtr(T* pObservedPtr) : m_pObservedPtr(pObservedPtr) {
+      if (m_pObservedPtr)
+        m_pObservedPtr->AddObservedPtr(this);
+    }
+    ObservedPtr(const ObservedPtr& that) = delete;
+    ~ObservedPtr() {
+      if (m_pObservedPtr)
+        m_pObservedPtr->RemoveObservedPtr(this);
+    }
+    void Reset(T* pObservedPtr = nullptr) {
+      if (m_pObservedPtr)
+        m_pObservedPtr->RemoveObservedPtr(this);
+      m_pObservedPtr = pObservedPtr;
+      if (m_pObservedPtr)
+        m_pObservedPtr->AddObservedPtr(this);
+    }
+    void OnDestroy() {
+      ASSERT(m_pObservedPtr);
+      m_pObservedPtr = nullptr;
+    }
+    ObservedPtr& operator=(const ObservedPtr& that) = delete;
+    bool operator==(const ObservedPtr& that) const {
+      return m_pObservedPtr == that.m_pObservedPtr;
+    }
+    bool operator!=(const ObservedPtr& that) const { return !(*this == that); }
+    explicit operator bool() const { return !!m_pObservedPtr; }
+    T* Get() const { return m_pObservedPtr; }
+    T& operator*() const { return *m_pObservedPtr; }
+    T* operator->() const { return m_pObservedPtr; }
+
+   private:
+    T* m_pObservedPtr;
+  };
+
+  CFX_Observable() {}
+  CFX_Observable(const CFX_Observable& that) = delete;
+  ~CFX_Observable() { NotifyObservedPtrs(); }
+  void AddObservedPtr(ObservedPtr* pObservedPtr) {
+    ASSERT(!pdfium::ContainsKey(m_ObservedPtrs, pObservedPtr));
+    m_ObservedPtrs.insert(pObservedPtr);
+  }
+  void RemoveObservedPtr(ObservedPtr* pObservedPtr) {
+    ASSERT(pdfium::ContainsKey(m_ObservedPtrs, pObservedPtr));
+    m_ObservedPtrs.erase(pObservedPtr);
+  }
+  void NotifyObservedPtrs() {
+    for (auto* pObservedPtr : m_ObservedPtrs)
+      pObservedPtr->OnDestroy();
+    m_ObservedPtrs.clear();
+  }
+  CFX_Observable& operator=(const CFX_Observable& that) = delete;
+
+ protected:
+  size_t ActiveObservedPtrsForTesting() const { return m_ObservedPtrs.size(); }
+
+ private:
+  std::set<ObservedPtr*> m_ObservedPtrs;
+};
+
+#endif  // CORE_FXCRT_CFX_OBSERVABLE_H_