cocos2dx 3.x記憶體管理原始碼追蹤
cocos2dx的記憶體管理,我有空追蹤一下原始碼 理解一下。
我們都知道 cocos2dx是靠引用計數實現的,順便加入了物件池的管理。
涉及到一下幾個類,AutorealsePool,PoolManager,Ref,DisplayLinkDirector.
函式:
mainLoop,retain,release,autoRealse.
1.首先跳轉到Application::run()
,,,
int Application::run()
{
PVRFrameEnableControlWindow(false);
// Main message loop: LARGE_INTEGER nLast; LARGE_INTEGER nNow; QueryPerformanceCounter(&nLast); initGLContextAttrs(); // Initialize instance and cocos2d. if (!applicationDidFinishLaunching()) { return 0; } auto director = Director::getInstance(); auto glview = director->getOpenGLView(); // Retain glview to avoid glview being released in the while loop glview->retain(); //如果視窗未關閉 就是一個while死迴圈 while(!glview->windowShouldClose()) { QueryPerformanceCounter(&nNow); if (nNow.QuadPart - nLast.QuadPart > _animationInterval.QuadPart) { nLast.QuadPart = nNow.QuadPart - (nNow.QuadPart % _animationInterval.QuadPart); director->mainLoop(); glview->pollEvents(); } else { Sleep(1); } } // Director should still do a cleanup if the window was closed manually. if (glview->isOpenGLReady()) { director->end(); director->mainLoop(); director = nullptr; } glview->release(); return true;
}
,,,
2.跳轉到mainLoop函式中
void DisplayLinkDirector::mainLoop()
{
if (_purgeDirectorInNextLoop)
{
_purgeDirectorInNextLoop = false;
purgeDirector();
}
else if (_restartDirectorInNextLoop)
{
_restartDirectorInNextLoop = false;
restartDirector();
}
else if (! _invalid)
{
drawScene();
// release the objects
auto count = PoolManager::getInstance()->getPoolCount();//這個函式我自己加的,方便列印
CCLOG("$$$$$$$$$$=========== %d",count);
CCLOG("&&&&&&&&&&=========== %s",PoolManager::getInstance()->getCurrentPool()->getName()) ;//這個函式我自己加的,方便列印
auto pool = PoolManager::getInstance()->getCurrentPool();
CCLOG("前面pool count is %d",pool->getCount());
PoolManager::getInstance()->getCurrentPool()->clear();
CCLOG("後面pool count is %d",pool->getCount());
}
}
其他的先不管 ,就看PoolManager::getInstance()->getCurrentPool()->clear();這行程式碼。
PoolManager這個類,從字面上的意思它是個管理類,所以它被寫成單例模式。單例的程式碼:
PoolManager* PoolManager::getInstance()
{
if (s_singleInstance == nullptr)
{
s_singleInstance = new (std::nothrow) PoolManager();
// Add the first auto release pool
new AutoreleasePool("cocos2d autorelease pool");
}
return s_singleInstance;
}
以上程式碼是個典型的單例模式寫法,但是有行程式碼
new AutoreleasePool(“cocos2d autorelease pool”);我從沒看過生成一個物件 卻不用其他的引用或者指標指向它,寫的好奇怪。
3.檢視AutoreleasePool這個類
檢視他的建構函式:
AutoreleasePool::AutoreleasePool(const std::string &name)
: _name(name)
#if defined(COCOS2D_DEBUG) && (COCOS2D_DEBUG > 0)
, _isClearing(false)
#endif
{
_managedObjectArray.reserve(150);
PoolManager::getInstance()->push(this);
}
原來AutoreleasePool類生成物件的時候,在建構函式中呼叫
PoolManager::getInstance()->push(this)。
void PoolManager::push(AutoreleasePool *pool)
{
_releasePoolStack.push_back(pool);
}
看懂了吧,原來push函式原來在這裡呼叫了,但是這種寫法很奇怪,可能是我c++功力太淺了,要是我直接在單例getInstance函式中push了。
PoolManager類成員變數:
std::vector 《AutoreleasePool*》 _releasePoolStack
其實這個_releasePoolStack斷點的時候,只有在生成單例模式的push了一個AutoreleasePool物件,_releasePoolStack的size() = 1。
所以在mainLoop中:
auto count = PoolManager::getInstance()->getPoolCount();
CCLOG("$$$$$$$$$$=========== %d",count);
定義如下
int PoolManager::getPoolCount()
{
return _releasePoolStack.size();
}
列印始終都是size等於1
AutoreleasePool* PoolManager::getCurrentPool() const
{
return _releasePoolStack.back();
}
這個函式返回的是_releasePoolStack的末尾引用
而_releasePoolStack的資料size其實只有一條,既然是一條,那幹嘛用vector呢?這點沒弄明白 難道是因為喜歡用vector存貯資料?
接下來看AutoreleasePool::clear()函式
void AutoreleasePool::clear()
{
#if defined(COCOS2D_DEBUG) && (COCOS2D_DEBUG > 0)
_isClearing = true;
#endif
std::vector<Ref*> releasings;
releasings.swap(_managedObjectArray);
for (const auto &obj : releasings)
{
obj->release();
}
#if defined(COCOS2D_DEBUG) && (COCOS2D_DEBUG > 0)
_isClearing = false;
#endif
}
_managedObjectArray資料被清空,這個函式中有個重要的知識點 那就是vector的swap的用法,swap可以清空vector申請的記憶體,而clear卻不一定。詳情可參照:
追蹤release程式碼:
void Ref::release()
{
CCASSERT(_referenceCount > 0, "reference count should be greater than 0");
--_referenceCount;
if (_referenceCount == 0)
{
#if defined(COCOS2D_DEBUG) && (COCOS2D_DEBUG > 0)
auto poolManager = PoolManager::getInstance();
if (!poolManager->getCurrentPool()->isClearing() && poolManager->isObjectInPools(this))
{
CCASSERT(false, "The reference shouldn't be 0 because it is still in autorelease pool.");
}
#endif
#if CC_REF_LEAK_DETECTION
untrackRef(this);
#endif
delete this;
}
}
release函式 就是將計數自減一,將0的Ref析構掉。
每個集成了Ref的物件 都有屬性_referenceCount,那它在哪裡自增呢?
舉個例子,去看看Sprite的create函式
Sprite* Sprite::create(const std::string& filename)
{
Sprite *sprite = new (std::nothrow) Sprite();
if (sprite && sprite->initWithFile(filename))
{
sprite->autorelease();
return sprite;
}
CC_SAFE_DELETE(sprite);
return nullptr;
}
autorelease函式的定義
Ref* Ref::autorelease()
{
PoolManager::getInstance()->getCurrentPool()->addObject(this);
return this;
}
再追蹤addObject函式
void AutoreleasePool::addObject(Ref* object)
{
_managedObjectArray.push_back(object);
}
奇怪 不是說好 一個精靈建立的時候 引用計數就加1嗎?但是我們找了半天沒發現,原來是Ref構造的時候就預設設定成1了,如下程式碼:
Ref::Ref()
: _referenceCount(1) // when the Ref is created, the reference count of it is 1
{
#if CC_ENABLE_SCRIPT_BINDING
static unsigned int uObjectCount = 0;
_luaID = 0;
_ID = ++uObjectCount;
_scriptObject = nullptr;
#endif
#if CC_REF_LEAK_DETECTION
trackRef(this);
#endif
}
我們知道 cocos2dx 中node sprite都是繼承Ref,C++中物件生成的時候,先呼叫父類的建構函式 ,再呼叫自己的建構函式。
4.引用計數 自增和自減 在哪些地方出現?
- addChild()函式
Node下面好幾個addChild函式,都是函式過載,最終都用到這個函式:
addChildHelper()
void Node::addChildHelper(Node* child, int localZOrder, int tag, const std::string &name, bool setTag)
{
if (_children.empty())
{
this->childrenAlloc();
}
this->insertChild(child, localZOrder);
if (setTag)
child->setTag(tag);
else
child->setName(name);
child->setParent(this);
child->setOrderOfArrival(s_globalOrderOfArrival++);
#if CC_USE_PHYSICS
// Recursive add children with which have physics body.
auto scene = this->getScene();
if (scene && scene->getPhysicsWorld())
{
scene->addChildToPhysicsWorld(child);
}
#endif
if( _running )
{
child->onEnter();
// prevent onEnterTransitionDidFinish to be called twice when a node is added in onEnter
if (_isTransitionFinished)
{
child->onEnterTransitionDidFinish();
}
}
if (_cascadeColorEnabled)
{
updateCascadeColor();
}
if (_cascadeOpacityEnabled)
{
updateCascadeOpacity();
}
}
找到insertChild函式:
void Node::insertChild(Node* child, int z)
{
_transformUpdated = true;
_reorderChildDirty = true;
_children.pushBack(child);
child->_localZOrder = z;
}
接著找到pushBack函式,開始以為就是vector中的函式呢,其實不然:
void pushBack(T object)
{
CCASSERT(object != nullptr, "The object should not be nullptr");
_data.push_back( object );
object->retain();
}
終於找到retain函數了啊!
- setParent函式:
void Node::setParent(Node * parent)
{
_parent = parent;
_transformUpdated = _transformDirty = _inverseDirty = true;
}
發現這個函式根本沒有使引用計數增加,而我在專案中使用setParent的時候 根本一個節點沒有顯示出來,所以這個函式只是一個指向關係,並未將孩子真正加入到父節點中,所以我基本不使用它,我都是使用addChild函式。
所以當你生成一個Sprite並把它加入到layer之後,他的引用計數是2。
- removeFromParent函式:
void Node::removeFromParent()
{
this->removeFromParentAndCleanup(true);
}
void Node::removeFromParentAndCleanup(bool cleanup)
{
if (_parent != nullptr)
{
_parent->removeChild(this,cleanup);
}
}
我們可以看到這兩個函式幾乎等同,接著removeChild:
void Node::removeChild(Node* child, bool cleanup /* = true */)
{
// explicit nil handling
if (_children.empty())
{
return;
}
ssize_t index = _children.getIndex(child);
if( index != CC_INVALID_INDEX )
this->detachChild( child, index, cleanup );
}
接著detachChild:
void Node::detachChild(Node *child, ssize_t childIndex, bool doCleanup)
{
// IMPORTANT:
// -1st do onExit
// -2nd cleanup
if (_running)
{
child->onExitTransitionDidStart();
child->onExit();
}
#if CC_USE_PHYSICS
child->removeFromPhysicsWorld();
#endif
// If you don't do cleanup, the child's actions will not get removed and the
// its scheduledSelectors_ dict will not get released!
if (doCleanup)
{
child->cleanup();
}
// set parent nil at the end
child->setParent(nullptr);
_children.erase(childIndex);
}
接著cleanup函式:
void Node::cleanup()
{
// actions
this->stopAllActions();
this->unscheduleAllCallbacks();
#if CC_ENABLE_SCRIPT_BINDING
if ( _scriptType != kScriptTypeNone)
{
int action = kNodeOnCleanup;
BasicScriptData data(this,(void*)&action);
ScriptEvent scriptEvent(kNodeEvent,(void*)&data);
ScriptEngineManager::getInstance()->getScriptEngine()->sendEvent(&scriptEvent);
}
#endif // #if CC_ENABLE_SCRIPT_BINDING
// timers
for( const auto &child: _children)
child->cleanup();
}
可以看到 遞迴呼叫了cleanup函式 子節點都是處理一些事情,detachChild函式最後將子節點的父節點設定為空,最後看erase函式:
iterator erase(ssize_t index)
{
CCASSERT(!_data.empty() && index >=0 && index < size(), "Invalid index!");
auto it = std::next( begin(), index );
(*it)->release();
return _data.erase(it);
}
終於找到了release函數了。
有時候我容易將 std::vector和cocos2dx封裝的Vector搞混淆,真是眼睛不好啊!現在記憶體管理的基本思路搞清楚了。