关于curl 断点续传的问题~

Cocos2d-x
#1 
    FILE *f;
    curl_off_t local_file_len = 0 ;
    long filesize =0 ;
    struct stat file_info;
    int use_resume = 0;
    if(stat(localpath, &file_info) == 0){
        local_file_len =  file_info.st_size;
        use_resume  = 1;
    }
    f = fopen(localpath, "ab+");
    if (f == NULL) {
        perror(NULL);
        return 0;
    }
    
    curl_easy_setopt(curlhandle, CURLOPT_URL, remotepath);
    curl_easy_setopt(curlhandle, CURLOPT_CONNECTTIMEOUT, timeout);
    curl_easy_setopt(curlhandle, CURLOPT_HEADERFUNCTION, getcontentlengthfunc);
    //将head写到返回体中
//    curl_easy_setopt(curlhandle, CURLOPT_HEADER, 1);
    curl_easy_setopt(curlhandle, CURLOPT_HEADERDATA, &filesize);
    curl_easy_setopt(curlhandle, CURLOPT_RESUME_FROM_LARGE, use_resume?local_file_len:0);
    curl_easy_setopt(curlhandle, CURLOPT_WRITEFUNCTION, wirtefunc);
    curl_easy_setopt(curlhandle, CURLOPT_WRITEDATA, f);
    
    curl_easy_setopt(curlhandle, CURLOPT_NOPROGRESS, 0L);
    curl_easy_setopt(curlhandle, CURLOPT_VERBOSE, 1L);

    CURLcode r = CURLE_GOT_NOTHING;
    r = curl_easy_perform(curlhandle);
    fclose(f);
    return r;

运行后返回错误码：56 求解答啊。困扰好久~~~