异步加载图片源代码的疑问

[yxriyin]

cocos2d-x中源代码是
void TextureCache::loadImage()
{
AsyncStruct *asyncStruct = nullptr;

while (true)
{
    std::queue<AsyncStruct*> *pQueue = _asyncStructQueue;
    _asyncStructQueueMutex.lock();
    if (pQueue->empty())
    {
        _asyncStructQueueMutex.unlock();
        if (_needQuit) {
            break;
        }
        else {
            std::unique_lock<std::mutex> lk(_sleepMutex);
            _sleepCondition.wait(lk);
            continue;
        }
    }
    else
    {
        asyncStruct = pQueue->front();
        pQueue->pop();
        _asyncStructQueueMutex.unlock();
    }        

    Image *image = nullptr;
    bool generateImage = false;

    auto it = _textures.find(asyncStruct->filename);
    if( it == _textures.end() )
    {
       _imageInfoMutex.lock();
       ImageInfo *imageInfo;
       size_t pos = 0;
       size_t infoSize = _imageInfoQueue->size();
       for (; pos < infoSize; pos++)
       {
           imageInfo = (*_imageInfoQueue);
           if(imageInfo->asyncStruct->filename.compare(asyncStruct->filename))
               break;
       }
       _imageInfoMutex.unlock();
       if(infoSize == 0 || pos < infoSize)
           generateImage = true;
      //这一段语义有点奇怪，我的理解应该是如果从队列中找到和要加载的文件名一样，那么就不需要加载了，因为已经有了
     //但代码中compare如果发现不相等就直接break了，也就是说只有队列中没有一样的，那么就重新new一个image ,求解答
    }

    if (generateImage)
    {
        const std::string& filename = asyncStruct->filename;
        // generate image      
        image = new Image();
        if (image && !image->initWithImageFileThreadSafe(filename))
        {
            CC_SAFE_RELEASE(image);
            CCLOG("can not load %s", filename.c_str());
            continue;
        }
    }    

    // generate image info
    ImageInfo *imageInfo = new ImageInfo();
    imageInfo->asyncStruct = asyncStruct;
    imageInfo->image = image;

    // put the image info into the queue
    _imageInfoMutex.lock();
    _imageInfoQueue->push_back(imageInfo);
    _imageInfoMutex.unlock();
}

if(_asyncStructQueue != nullptr)
{
    delete _asyncStructQueue;
    _asyncStructQueue = nullptr;
    delete _imageInfoQueue;
    _imageInfoQueue = nullptr;
}

}