| /* |
| * Copyright 2012 Google Inc. |
| * |
| * Licensed under the Apache License, Version 2.0 (the "License"); |
| * you may not use this file except in compliance with the License. |
| * You may obtain a copy of the License at |
| * |
| * http://www.apache.org/licenses/LICENSE-2.0 |
| * |
| * Unless required by applicable law or agreed to in writing, software |
| * distributed under the License is distributed on an "AS IS" BASIS, |
| * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. |
| * See the License for the specific language governing permissions and |
| * limitations under the License. |
| */ |
| |
| // Author: jefftk@google.com (Jeff Kaufman) |
| |
| #ifndef PAGESPEED_KERNEL_BASE_MANUALLY_REF_COUNTED_H_ |
| #define PAGESPEED_KERNEL_BASE_MANUALLY_REF_COUNTED_H_ |
| |
| #include "base/logging.h" |
| #include "pagespeed/kernel/base/atomic_int32.h" |
| #include "pagespeed/kernel/base/basictypes.h" |
| |
| namespace net_instaweb { |
| |
| // Class that assists with manual reference counting. Other classes should |
| // inherit from this one, and users of those classes should call IncrementRefs |
| // when making copies and DecrementRefs when they finish with those copies. |
| class ManuallyRefCounted { |
| public: |
| ManuallyRefCounted() : n_active(1) {} |
| |
| // Call this when duplicating a pointer to subclass instances: |
| // Example* e = other->GetExample(); |
| // e->IncrementRefs(); |
| void IncrementRefs() { |
| n_active.NoBarrierIncrement(1); |
| } |
| |
| // Call this when finished with a pointer to a subclass instance: |
| // class ExampleHolder { |
| // Example* e; |
| // ~ExampleHolder() { |
| // if (e != NULL) { |
| // // If e is the last pointer to *e then *e will be deleted. |
| // e->DecrementRefs(); |
| // } |
| // } |
| // } |
| void DecrementRefs() { |
| int n_others_active = n_active.BarrierIncrement(-1); |
| if (n_others_active == 0) { |
| delete this; |
| } |
| } |
| |
| protected: |
| // The destructor isn't public because instances of ManuallyRefCounted |
| // subclasses should not be directly deleted. They should be released via |
| // DecrementRefs(). |
| virtual ~ManuallyRefCounted() { |
| DCHECK_EQ(0, n_active.value()); |
| } |
| |
| private: |
| AtomicInt32 n_active; |
| |
| DISALLOW_COPY_AND_ASSIGN(ManuallyRefCounted); |
| }; |
| |
| } // namespace net_instaweb |
| |
| #endif // PAGESPEED_KERNEL_BASE_MANUALLY_REF_COUNTED_H_ |
| |