断点下载 （记录上传、或下载的量

#pragma mark - test 断点下载 （记录上传、或下载的量）

- (void) test {

    NSURL *urlStr = [NSURL URLWithString:@"htt/"];

    NSMutableURLRequest *r = [[NSMutableURLRequest alloc]initWithURL:urlStr];

    // [r setValue:@"10M-50M" forHTTPHeaderField:@"Range"];

    //设置Http的请求头 

    [r setValue:@"50M-" forHTTPHeaderField:@"Range"];

    [r setValue:@"sinaiphoneFirfox/1.1" forHTTPHeaderField:@"User-Agent"];

    NSURLConnection *c = [[NSURLConnection alloc]initWithRequest:r delegate:self];

}