// 緩存主目錄
#define HSCachesDirectory [[NSSearchPathForDirectoriesInDomains(NSCachesDirectory, NSUserDomainMask, YES) lastObject] stringByAppendingPathComponent:@"HSCache"]
// 保存文件名
#define HSFileName(url) [[url componentsSeparatedByString:@"/"] lastObject]
// 文件的存放路徑（caches）
#define HSFileFullpath(url) [HSCachesDirectory stringByAppendingPathComponent:HSFileName(url)]
// 文件的已下載長度
#define HSDownloadLength(url) [[[NSFileManager defaultManager] attributesOfItemAtPath:HSFileFullpath(url) error:nil][NSFileSize] integerValue]
