51 lines
1.6 KiB
C
51 lines
1.6 KiB
C
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/*
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Copyright 2010 Google Inc.
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Licensed under the Apache License, Version 2.0 (the "License");
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you may not use this file except in compliance with the License.
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You may obtain a copy of the License at
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http://www.apache.org/licenses/LICENSE-2.0
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Unless required by applicable law or agreed to in writing, software
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distributed under the License is distributed on an "AS IS" BASIS,
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WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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See the License for the specific language governing permissions and
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limitations under the License.
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*/
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#ifndef SkTRelay_DEFINED
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#define SkTRelay_DEFINED
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#include "SkRefCnt.h"
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/**
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* Similar to a weakptr in java, a Relay allows for a back-ptr to an
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* object to be "safe", without using a hard reference-count.
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*
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* Typically, the target creates a Relay with a pointer to itself. Whenever it
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* wants to have another object maintain a safe-ptr to it, it gives them a
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* Relay, which they ref()/unref(). Through the Relay each external object can
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* retrieve a pointer to the Target. However, when the Target goes away, it
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* clears the Relay pointer to it (relay->set(NULL)) and then unref()s the
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* Relay. The other objects still have a ref on the Relay, but now when they
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* call get() the receive a NULL.
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*/
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template <template T> class SkTRelay : public SkRefCnt {
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public:
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SkTRelay(T* ptr) : fPtr(ptr) {}
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// consumers call this
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T* get() const { return fPtr; }
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// producer calls this
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void set(T* ptr) { fPtr = ptr; }
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void clear() { this->set(NULL); }
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private:
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T* fPtr;
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};
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#endif
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