先把上一篇忘记分析的autorelease说一下，在CCDirector.cpp的主循环有

void DisplayLinkDirector::mainLoop()
{
if (_purgeDirectorInNextLoop)
{
_purgeDirectorInNextLoop = false;
purgeDirector();
}
else if (! _invalid)
{
drawScene();

// release the objects
PoolManager::getInstance()->getCurrentPool()->clear();
}
}

显然表明了在每一帧结束的时候会进行PoolManager的一个清理工作，而通过CCRef.cpp可知道当进行autorelease的时候会把对象放入AutoreleasePool的verctor里面，所以调用了autorelease的对象会在一帧结束的时候调用了release的操作，即把引用计数减为0，然后会进行delete的操作，把对象给释放掉。

cocos是一个跨平台的游戏引擎，有必要分析一下cocos的启动流程，这里主要分析一下Win32的启动流程，其他平台的大同小异。

分析Win32的启动流程，首先要找到win32的应用入口，即通常说的main函数。

在新建的工程里面有一个main.cpp的文件，

int APIENTRY _tWinMain(HINSTANCE hInstance,
HINSTANCE hPrevInstance,
LPTSTR lpCmdLine,
int nCmdShow)
{
UNREFERENCED_PARAMETER(hPrevInstance);
UNREFERENCED_PARAMETER(lpCmdLine);


// create the application instance
AppDelegate app;
return Application::getInstance()->run();
}

显然这就是Win32的入口。显然接下来要分析一下Application的内容：

先浏览一下头文件的内容

//CCApplication.h

#ifndef __CC_APPLICATION_WIN32_H__
#define __CC_APPLICATION_WIN32_H__
#include "base/CCPlatformConfig.h"
#if CC_TARGET_PLATFORM == CC_PLATFORM_WIN32
#include "CCStdC.h"
#include "platform/CCCommon.h"
#include "platform/CCApplicationProtocol.h"
#include <string>
NS_CC_BEGIN
class Rect;
class CC_DLL Application : public ApplicationProtocol
{
public:
/**
* @js ctor
*/
Application();
/**
* @js NA
* @lua NA
*/
virtual ~Application();

/**
@brief Run the message loop.
*/
int run();

/**
@brief Get current applicaiton instance.
@return Current application instance pointer.
*/

//说明是采用单例模式实现的
static Application* getInstance();

/** @deprecated Use getInstance() instead */

//被废除的函数
CC_DEPRECATED_ATTRIBUTE static Application* sharedApplication();

/* override functions */
virtual void setAnimationInterval(double interval);
virtual LanguageType getCurrentLanguage();
virtual const char * getCurrentLanguageCode();
/**
@brief Get target platform
*/
virtual Platform getTargetPlatform();


/**
* Sets the Resource root path.
* @deprecated Please use FileUtils::getInstance()->setSearchPaths() instead.
*/
CC_DEPRECATED_ATTRIBUTE void setResourceRootPath(const std::string& rootResDir);


/**
* Gets the Resource root path.
* @deprecated Please use FileUtils::getInstance()->getSearchPaths() instead.
*/
CC_DEPRECATED_ATTRIBUTE const std::string& getResourceRootPath(void);


void setStartupScriptFilename(const std::string& startupScriptFile);


const std::string& getStartupScriptFilename(void)
{
return _startupScriptFilename;
}
protected:
HINSTANCE _instance;
HACCEL _accelTable;
LARGE_INTEGER _animationInterval;
std::string _resourceRootPath;
std::string _startupScriptFilename;

static Application * sm_pSharedApplication;
};
NS_CC_END
#endif // CC_TARGET_PLATFORM == CC_PLATFORM_WIN32
#endif // __CC_APPLICATION_WIN32_H__

在来看一下具体的实现：

\\CCApplication.cpp

#include "base/CCPlatformConfig.h"

//限定是Win32平台
#if CC_TARGET_PLATFORM == CC_PLATFORM_WIN32
#include "CCApplication.h"
#include "CCGLView.h"
#include "base/CCDirector.h"
#include <algorithm>
#include "platform/CCFileUtils.h"
/**
@brief This function change the PVRFrame show/hide setting in register.
@param bEnable If true show the PVRFrame window,otherwise hide.
*/
static void PVRFrameEnableControlWindow(bool bEnable);


NS_CC_BEGIN


// sharedApplication pointer
Application * Application::sm_pSharedApplication = 0;

//构造函数
Application::Application()
: _instance(nullptr)
,_accelTable(nullptr)
{
_instance = GetModuleHandle(nullptr);
_animationInterval.QuadPart = 0;
CC_ASSERT(! sm_pSharedApplication);
sm_pSharedApplication = this;
}

//析构函数，令sm_pSharedApplication的值为Null,猜测是为了防止野指针
Application::~Application()
{
CC_ASSERT(this == sm_pSharedApplication);
sm_pSharedApplication = NULL;
}

\\主要的内容,主要分析一下
int Application::run()
{

//这个函数是一些关于注册表的操作，大致的操作就是向注册表注册一些内容
PVRFrameEnableControlWindow(false);
// Main message loop:
LARGE_INTEGER nFreq;
LARGE_INTEGER nLast;
LARGE_INTEGER nNow;

//这两个也是Windows的接口函数，是精确到毫秒级的计时器函数
QueryPerformanceFrequency(&nFreq);
QueryPerformanceCounter(&nLast);

//这里回调用工程里面的Applidegrate.cpp的函数然后可以在里面进入游戏的场景
// Initialize instance and cocos2d.
if (!applicationDidFinishLaunching())
{
return 0;
}

auto director = Director::getInstance();
auto glview = director->getOpenGLView();
//对glview进行retain操作，防止被释放掉
// Retain glview to avoid glview being released in the while loop
glview->retain();
//判断窗口是否关掉
while(!glview->windowShouldClose())
{

//计时器判断两次执行的间隔是否大于设置的更新频率，如果大于进入游戏的主循环，如果小于则调用Sleep(0),查了相关的资料，知道如果当前的cpu有大于当前优先级的线程，则会调用优先级大的线程，否则继续当前线程的操作，所以如果两帧的间隔小于设置的函数，则会判断如果有大于当前线程的优先级的线程，则调用优先级大的函数，否则继续当前的线程
QueryPerformanceCounter(&nNow);
if (nNow.QuadPart - nLast.QuadPart > _animationInterval.QuadPart)
{
nLast.QuadPart = nNow.QuadPart;
//CCDirecotr的主循环，稍后分析
director->mainLoop();
glview->pollEvents();
}
else
{
Sleep(0);
}
}
//跳出循环后，判断当前的opengl是否准备好，进行清理的工作
// Director should still do a cleanup if the window was closed manually.
if (glview->isOpenGLReady())
{
director->end();
director->mainLoop();
director = nullptr;
}

//释放glview
glview->release();
return true;
}
//设置更新的间隔
void Application::setAnimationInterval(double interval)
{
LARGE_INTEGER nFreq;
QueryPerformanceFrequency(&nFreq);
_animationInterval.QuadPart = (LONGLONG)(interval * nFreq.QuadPart);
}

//////////////////////////////////////////////////////////////////////////
// static member function
//////////////////////////////////////////////////////////////////////////

//获得Application的实例，采用了单例模式
Application* Application::getInstance()
{
CC_ASSERT(sm_pSharedApplication);
return sm_pSharedApplication;
}
//废弃了的函数，此处不做分析了
// @deprecated Use getInstance() instead
Application* Application::sharedApplication()
{
return Application::getInstance();
}

//获得当前使用的语言
LanguageType Application::getCurrentLanguage()
{
LanguageType ret = LanguageType::ENGLISH;


LCID localeID = GetUserDefaultLCID();
unsigned short primaryLanguageID = localeID & 0xFF;

switch (primaryLanguageID)
{
case LANG_CHINESE:
ret = LanguageType::CHINESE;
break;
case LANG_ENGLISH:
ret = LanguageType::ENGLISH;
break;
case LANG_FRENCH:
ret = LanguageType::FRENCH;
break;
case LANG_ITALIAN:
ret = LanguageType::ITALIAN;
break;
case LANG_GERMAN:
ret = LanguageType::GERMAN;
break;
case LANG_SPANISH:
ret = LanguageType::SPANISH;
break;
case LANG_DUTCH:
ret = LanguageType::DUTCH;
break;
case LANG_RUSSIAN:
ret = LanguageType::RUSSIAN;
break;
case LANG_KOREAN:
ret = LanguageType::KOREAN;
break;
case LANG_JAPANESE:
ret = LanguageType::JAPANESE;
break;
case LANG_HUNGARIAN:
ret = LanguageType::HUNGARIAN;
break;
case LANG_PORTUGUESE:
ret = LanguageType::PORTUGUESE;
break;
case LANG_ARABIC:
ret = LanguageType::ARABIC;
break;
case LANG_NORWEGIAN:
ret = LanguageType::NORWEGIAN;
break;
case LANG_POLISH:
ret = LanguageType::POLISH;
break;
}
return ret;
}
//获得当前使用语言的代码
const char * Application::getCurrentLanguageCode()
{
LANGID lid = GetUserDefaultUILanguage();
const LCID locale_id = MAKELCID(lid,SORT_DEFAULT);
static char code[3] = { 0 };
GetLocaleInfoA(locale_id,LOCALE_SISO639LANGNAME,code,sizeof(code));
code[2] = '\0';
return code;
}
//返回平台
Application::Platform Application::getTargetPlatform()
{
return Platform::OS_WINDOWS;
}
//设置资源的路径，以后分析CCFileUtils的时候在分析
void Application::setResourceRootPath(const std::string& rootResDir)
{
_resourceRootPath = rootResDir;
std::replace(_resourceRootPath.begin(),_resourceRootPath.end(),'\\','/');
if (_resourceRootPath[_resourceRootPath.length() - 1] != '/')
{
_resourceRootPath += '/';
}
FileUtils* pFileUtils = FileUtils::getInstance();
std::vector<std::string> searchPaths = pFileUtils->getSearchPaths();
searchPaths.insert(searchPaths.begin(),_resourceRootPath);
pFileUtils->setSearchPaths(searchPaths);
}
//获得资源的根路径
const std::string& Application::getResourceRootPath(void)
{
return _resourceRootPath;
}
//设置脚本的启动名字，以后分析脚本的时候在分析
void Application::setStartupScriptFilename(const std::string& startupScriptFile)
{
_startupScriptFilename = startupScriptFile;
std::replace(_startupScriptFilename.begin(),_startupScriptFilename.end(),'/');
}
NS_CC_END
//////////////////////////////////////////////////////////////////////////
// Local function
//////////////////////////////////////////////////////////////////////////

//这个函数就是设置注册表的实现函数，暂时对注册表不太熟悉，不做具体分析，猜测就是对注册表做一些写入的操作
static void PVRFrameEnableControlWindow(bool bEnable)
{
HKEY hKey = 0;
// Open PVRFrame control key,if not exist create it.
if(ERROR_SUCCESS != RegCreateKeyExW(HKEY_CURRENT_USER,
L"Software\\Imagination Technologies\\PVRVFRame\\STARTUP\\",
0,
REG_OPTION_NON_VOLATILE,
KEY_ALL_ACCESS,
&hKey,
NULL))
{
return;
}
const WCHAR* wszValue = L"hide_gui";
const WCHAR* wszNewData = (bEnable) ? L"NO" : L"YES";
WCHAR wszOldData[256] = {0};
DWORD dwSize = sizeof(wszOldData);
LSTATUS status = RegQueryValueExW(hKey,wszValue,NULL,(LPBYTE)wszOldData,&dwSize);
if (ERROR_FILE_NOT_FOUND == status // the key not exist
|| (ERROR_SUCCESS == status // or the hide_gui value is exist
&& 0 != wcscmp(wszNewData,wszOldData))) // but new data and old data not equal
{
dwSize = sizeof(WCHAR) * (wcslen(wszNewData) + 1);
RegSetValueEx(hKey,REG_SZ,(const BYTE *)wszNewData,dwSize);
}
RegCloseKey(hKey);
}
#endif // CC_TARGET_PLATFORM == CC_PLATFORM_WIN32

applicationDidFinishLaunching这个函数是ApplicationProtocol的纯虚函数，然后Appdelegate继承Application并实现了这个函数，显然调用此函数时，进入了Appdelegate.cpp里面的applicationDidFinishLaunching的函数，这是面向对象的三大特性的多态的体现了。

从以上的分析可以知道，还有两个文件比较重要，一个是Appdelegate.cpp和CCDirector.cpp

分别贴出这两个文件

\\Appdelegate.h

#ifndef _APP_DELEGATE_H_
#define _APP_DELEGATE_H_


#include "cocos2d.h"


/**
@brief The cocos2d Application.


The reason for implement as private inheritance is to hide some interface call by Director.
*/
class AppDelegate : private cocos2d::Application
{
public:
AppDelegate();
virtual ~AppDelegate();
/**
@brief Implement Director and Scene init code here.
@return true Initialize success,app continue.
@return false Initialize Failed,app terminate.
*/
virtual bool applicationDidFinishLaunching();
/**
@brief The function be called when the application enter background
@param the pointer of the application
*/
virtual void applicationDidEnterBackground();
/**
@brief The function be called when the application enter foreground
@param the pointer of the application
*/
virtual void applicationWillEnterForeground();
};
#endif // _APP_DELEGATE_H_

\\标出红色的函数就是实现了虚函数，这就是抽象的体现了，跨平台抽象了接口，但是具体的实现就依据不同的平台不同的实现。我们在applicationDidFinishLaunching里面做的就是第一个场景的出现了，然后就进入了游戏，很简单，参考一下工程就明白了。接下来分析CCDirector.cpp文件，因为我们这里只用到了两个函数，我们在这里主要分析他们：end,mainLoop,

//实例化的时候返回了Director的子类，DisplayLinkDirector的实例，所以调用的是DisplayLinkDirector::mainLoop()

Director* Director::getInstance()
{
if (!s_SharedDirector)
{
s_SharedDirector = new DisplayLinkDirector();
s_SharedDirector->init();
}
return s_SharedDirector;
}

void DisplayLinkDirector::mainLoop()
{

//判断是否清除导演类，即游戏是否停止
if (_purgeDirectorInNextLoop)
{
_purgeDirectorInNextLoop = false;
purgeDirector();
}
else if (! _invalid)
{

//游戏的渲染，具体下次分析游戏的渲染的时候在分析
drawScene();
//这个就是本文首先提到的对于autorelease对象，会在此时进行清理的工作
// release the objects
PoolManager::getInstance()->getCurrentPool()->clear();
}
}

今天的分析暂时到这里，下一次打算分析一下cocos的渲染。本文纯属个人分析学习，如果有不当之处，请大神指教一下！