135 lines
4.1 KiB
C++
135 lines
4.1 KiB
C++
/*
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* Copyright (C) 2006 The Android Open Source Project
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*
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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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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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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 SkRefCnt_DEFINED
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#define SkRefCnt_DEFINED
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#include "SkThread.h"
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/** \class SkRefCnt
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SkRefCnt is the base class for objects that may be shared by multiple
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objects. When a new owner wants a reference, it calls ref(). When an owner
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wants to release its reference, it calls unref(). When the shared object's
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reference count goes to zero as the result of an unref() call, its (virtual)
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destructor is called. It is an error for the destructor to be called
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explicitly (or via the object going out of scope on the stack or calling
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delete) if getRefCnt() > 1.
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*/
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class SkRefCnt : SkNoncopyable {
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public:
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/** Default construct, initializing the reference count to 1.
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*/
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SkRefCnt() : fRefCnt(1) {}
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/** Destruct, asserting that the reference count is 1.
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*/
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virtual ~SkRefCnt() { SkASSERT(fRefCnt == 1); }
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/** Return the reference count.
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*/
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int32_t getRefCnt() const { return fRefCnt; }
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/** Increment the reference count. Must be balanced by a call to unref().
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*/
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void ref() const {
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SkASSERT(fRefCnt > 0);
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sk_atomic_inc(&fRefCnt);
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}
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/** Decrement the reference count. If the reference count is 1 before the
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decrement, then call delete on the object. Note that if this is the
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case, then the object needs to have been allocated via new, and not on
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the stack.
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*/
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void unref() const {
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SkASSERT(fRefCnt > 0);
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if (sk_atomic_dec(&fRefCnt) == 1) {
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fRefCnt = 1; // so our destructor won't complain
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SkDELETE(this);
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}
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}
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/** Helper version of ref(), that first checks to see if this is not null.
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If this is null, then do nothing.
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*/
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void safeRef() const {
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if (this) {
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this->ref();
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}
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}
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/** Helper version of unref(), that first checks to see if this is not null.
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If this is null, then do nothing.
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*/
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void safeUnref() const {
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if (this) {
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this->unref();
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}
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}
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private:
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mutable int32_t fRefCnt;
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};
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/** \class SkAutoUnref
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SkAutoUnref is a stack-helper class that will automatically call unref() on
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the object it points to when the SkAutoUnref object goes out of scope.
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If obj is null, do nothing.
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*/
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class SkAutoUnref : SkNoncopyable {
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public:
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SkAutoUnref(SkRefCnt* obj) : fObj(obj) {}
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~SkAutoUnref();
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SkRefCnt* get() const { return fObj; }
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/** If the hosted object is null, do nothing and return false, else call
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ref() on it and return true
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*/
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bool ref();
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/** If the hosted object is null, do nothing and return false, else call
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unref() on it, set its reference to null, and return true
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*/
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bool unref();
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/** If the hosted object is null, do nothing and return NULL, else call
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unref() on it, set its reference to null, and return the object
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*/
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SkRefCnt* detach();
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private:
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SkRefCnt* fObj;
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};
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///////////////////////////////////////////////////////////////////////////////
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/** Helper macro to safely assign one SkRefCnt[TS]* to another, checking for
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null in on each side of the assignment, and ensuring that ref() is called
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before unref(), in case the two pointers point to the same object.
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*/
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#define SkRefCnt_SafeAssign(dst, src) \
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do { \
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if (src) src->ref(); \
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if (dst) dst->unref(); \
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dst = src; \
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} while (0)
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#endif
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