1 // Copyright (c) 2012 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 LIBRARIES_SDK_UTIL_REF_OBJECT 6 #define LIBRARIES_SDK_UTIL_REF_OBJECT 7 8 #include <stdlib.h> 9 #include "pthread.h" 10 11 #include "sdk_util/atomicops.h" 12 13 namespace sdk_util { 14 15 class ScopedRefBase; 16 17 /* 18 * RefObject 19 * 20 * A reference counted object. RefObjects should only be handled by ScopedRef 21 * objects. 22 * 23 * When the object is first created, it has a reference count of zero. It's 24 * first incremented when it gets assigned to a ScopedRef. When the last 25 * ScopedRef is reset or destroyed the object will get released. 26 */ 27 28 class RefObject { 29 public: RefObject()30 RefObject() { 31 ref_count_ = 0; 32 } 33 34 /* 35 * RefCount 36 * 37 * RefCount returns an instantaneous snapshot of the RefCount, which may 38 * change immediately after it is fetched. This is only stable when all 39 * pointers to the object are scoped pointers (ScopedRef), and the value 40 * is one implying the current thread is the only one, with visibility to 41 * the object. 42 */ RefCount()43 int RefCount() const { return ref_count_; } 44 45 protected: ~RefObject()46 virtual ~RefObject() {} 47 48 // Override to clean up object when last reference is released. Destroy()49 virtual void Destroy() {} 50 Acquire()51 void Acquire() { 52 AtomicAddFetch(&ref_count_, 1); 53 } 54 Release()55 bool Release() { 56 Atomic32 val = AtomicAddFetch(&ref_count_, -1); 57 if (val == 0) { 58 Destroy(); 59 delete this; 60 return false; 61 } 62 return true; 63 } 64 65 private: 66 Atomic32 ref_count_; 67 68 friend class ScopedRefBase; 69 }; 70 71 } // namespace sdk_util 72 73 #endif // LIBRARIES_SDK_UTIL_REF_OBJECT 74 75