1 /* 2 Copyright 2010 Google Inc. 3 4 Licensed under the Apache License, Version 2.0 (the "License"); 5 you may not use this file except in compliance with the License. 6 You may obtain a copy of the License at 7 8 http://www.apache.org/licenses/LICENSE-2.0 9 10 Unless required by applicable law or agreed to in writing, software 11 distributed under the License is distributed on an "AS IS" BASIS, 12 WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 13 See the License for the specific language governing permissions and 14 limitations under the License. 15 */ 16 17 #ifndef SkTRelay_DEFINED 18 #define SkTRelay_DEFINED 19 20 #include "SkRefCnt.h" 21 22 /** 23 * Similar to a weakptr in java, a Relay allows for a back-ptr to an 24 * object to be "safe", without using a hard reference-count. 25 * 26 * Typically, the target creates a Relay with a pointer to itself. Whenever it 27 * wants to have another object maintain a safe-ptr to it, it gives them a 28 * Relay, which they ref()/unref(). Through the Relay each external object can 29 * retrieve a pointer to the Target. However, when the Target goes away, it 30 * clears the Relay pointer to it (relay->set(NULL)) and then unref()s the 31 * Relay. The other objects still have a ref on the Relay, but now when they 32 * call get() the receive a NULL. 33 */ 34 template <template T> class SkTRelay : public SkRefCnt { 35 public: 36 SkTRelay(T* ptr) : fPtr(ptr) {} 37 38 // consumers call this 39 T* get() const { return fPtr; } 40 41 // producer calls this 42 void set(T* ptr) { fPtr = ptr; } 43 44 void clear() { this->set(NULL); } 45 46 private: 47 T* fPtr; 48 }; 49 50 #endif 51
