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      1 // Copyright 2014 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 BASE_ANDROID_JNI_WEAK_REF_H_
      6 #define BASE_ANDROID_JNI_WEAK_REF_H_
      7 
      8 #include <jni.h>
      9 
     10 #include "base/android/scoped_java_ref.h"
     11 #include "base/base_export.h"
     12 
     13 // Manages WeakGlobalRef lifecycle.
     14 // This class is not thread-safe w.r.t. get() and reset(). Multiple threads may
     15 // safely use get() concurrently, but if the user calls reset() (or of course,
     16 // calls the destructor) they'll need to provide their own synchronization.
     17 class BASE_EXPORT JavaObjectWeakGlobalRef {
     18  public:
     19   JavaObjectWeakGlobalRef();
     20   JavaObjectWeakGlobalRef(const JavaObjectWeakGlobalRef& orig);
     21   JavaObjectWeakGlobalRef(JNIEnv* env, jobject obj);
     22   virtual ~JavaObjectWeakGlobalRef();
     23 
     24   void operator=(const JavaObjectWeakGlobalRef& rhs);
     25 
     26   base::android::ScopedJavaLocalRef<jobject> get(JNIEnv* env) const;
     27 
     28   bool is_empty() const { return obj_ == NULL; }
     29 
     30   void reset();
     31 
     32  private:
     33   void Assign(const JavaObjectWeakGlobalRef& rhs);
     34 
     35   jweak obj_;
     36 };
     37 
     38 // Get the real object stored in the weak reference returned as a
     39 // ScopedJavaLocalRef.
     40 BASE_EXPORT base::android::ScopedJavaLocalRef<jobject> GetRealObject(
     41     JNIEnv* env, jweak obj);
     42 
     43 #endif  // BASE_ANDROID_JNI_WEAK_REF_H_
     44