static size_t write_data(void *buffer, size_t size, size_t nmemb, void *userp);
static int progress_callback(void *clientp, double dltotal, double dlnow,
double ultotal, double ulnow);
static size_t write_data(void *buffer, size_t size, size_t nmemb, void *userp);
static int progress_callback(void *clientp, double dltotal, double dlnow,
double ultotal, double ulnow);