1 2 /* 3 * Copyright 2010 Google Inc. 4 * 5 * Use of this source code is governed by a BSD-style license that can be 6 * found in the LICENSE file. 7 */ 8 9 10 #ifndef SkTRelay_DEFINED 11 #define SkTRelay_DEFINED 12 13 #include "SkRefCnt.h" 14 15 /** 16 * Similar to a weakptr in java, a Relay allows for a back-ptr to an 17 * object to be "safe", without using a hard reference-count. 18 * 19 * Typically, the target creates a Relay with a pointer to itself. Whenever it 20 * wants to have another object maintain a safe-ptr to it, it gives them a 21 * Relay, which they ref()/unref(). Through the Relay each external object can 22 * retrieve a pointer to the Target. However, when the Target goes away, it 23 * clears the Relay pointer to it (relay->set(NULL)) and then unref()s the 24 * Relay. The other objects still have a ref on the Relay, but now when they 25 * call get() the receive a NULL. 26 */ 27 template <template T> class SkTRelay : public SkRefCnt { 28 public: SkTRelay(T * ptr)29 SkTRelay(T* ptr) : fPtr(ptr) {} 30 31 // consumers call this get()32 T* get() const { return fPtr; } 33 34 // producer calls this set(T * ptr)35 void set(T* ptr) { fPtr = ptr; } 36 clear()37 void clear() { this->set(NULL); } 38 39 private: 40 T* fPtr; 41 }; 42 43 #endif 44