cocos2d-x 2.2.3 CCTextureCache的addImage简单分析

CCTextureCache是用于缓存纹理的类，最常用的就是addImage了，下面简单分析下这部分的代码。

CCTexture2D * CCTextureCache::addImage(const char * path)
{
    CCAssert(path != NULL, "TextureCache: fileimage MUST not be NULL");

    CCTexture2D * texture = NULL;
    CCImage* pImage = NULL;
    // Split up directory and filename
    // MUTEX:
    // Needed since addImageAsync calls this method from a different thread
    
    //pthread_mutex_lock(m_pDictLock);
    // 使用文件完整路径作为tex的key，保证了key的唯一性，也可防止多次加载同一张图，但是少了点灵活性
    // 如果想使用自定义的key，可以自己搞个映射
    std::string pathKey = path;
    pathKey = CCFileUtils::sharedFileUtils()->fullPathForFilename(pathKey.c_str());
    if (pathKey.size() == 0)
    {
        return NULL;
    }
    texture = (CCTexture2D*)m_pTextures->objectForKey(pathKey.c_str());

    std::string fullpath = pathKey; // (CCFileUtils::sharedFileUtils()->fullPathFromRelativePath(path));
    if (! texture)	// 纹理没有加载过
    {
	// 转成小写 方便判断后缀，这个方法也可以在自己判断文件名后缀时借鉴
        std::string lowerCase(pathKey);
        for (unsigned int i = 0; i < lowerCase.length(); ++i)
        {
            lowerCase[i] = tolower(lowerCase[i]);
        }
        // all images are handled by UIImage except PVR extension that is handled by our own handler
        do 
        {
            if (std::string::npos != lowerCase.find(".pvr"))	// pvr pkm 有单独的处理
            {
                texture = this->addPVRImage(fullpath.c_str());
            }
            else if (std::string::npos != lowerCase.find(".pkm"))
            {
                // ETC1 file format, only supportted on Android
                texture = this->addETCImage(fullpath.c_str());
            }
            else
            {
                CCImage::EImageFormat eImageFormat = CCImage::kFmtUnKnown;
                if (std::string::npos != lowerCase.find(".png"))
                {
                    eImageFormat = CCImage::kFmtPng;
                }
                else if (std::string::npos != lowerCase.find(".jpg") || std::string::npos != lowerCase.find(".jpeg"))
                {
                    eImageFormat = CCImage::kFmtJpg;
                }
                else if (std::string::npos != lowerCase.find(".tif") || std::string::npos != lowerCase.find(".tiff"))
                {
                    eImageFormat = CCImage::kFmtTiff;
                }
                else if (std::string::npos != lowerCase.find(".webp"))
                {
                    eImageFormat = CCImage::kFmtWebp;
                }
                
                pImage = new CCImage();
                CC_BREAK_IF(NULL == pImage);

                bool bRet = pImage->initWithImageFile(fullpath.c_str(), eImageFormat);
                CC_BREAK_IF(!bRet);

                texture = new CCTexture2D();
                
                if( texture &&
                    texture->initWithImage(pImage) )
                {
#if CC_ENABLE_CACHE_TEXTURE_DATA
                    // 缓存tex以及文件名
                    VolatileTexture::addImageTexture(texture, fullpath.c_str(), eImageFormat);
#endif
                    m_pTextures->setObject(texture, pathKey.c_str());	// 使用完整路径名作为key
                    texture->release();
                }
                else
                {
                    CCLOG("cocos2d: Couldn't create texture for file:%s in CCTextureCache", path);
                }
            }
        } while (0);
    }

    CC_SAFE_RELEASE(pImage);

    //pthread_mutex_unlock(m_pDictLock);
    return texture;
}

这里使用了文件的完整路径名作为key。