code: сделан индивидуальный вариант

main.cpp

@@ -36,7 +36,7 @@ write_data(void* items, size_t item_size, size_t item_count, void* ctx){
     size_t data_size = item_size * item_count;
     stringstream* buffer = reinterpret_cast<stringstream*>(ctx);
     buffer->write(reinterpret_cast<const char*>(items), data_size);
-    return data_size;
+    return 0;
 }
 
 Input
@@ -46,17 +46,21 @@ download(const string& address) {
     curl_global_init(CURL_GLOBAL_ALL);
     CURL *curl = curl_easy_init();
     if(curl) {
-        CURLcode res;
+        CURLcode res, res1;
         curl_easy_setopt(curl, CURLOPT_URL, address.c_str());
         curl_easy_setopt(curl, CURLOPT_WRITEFUNCTION, write_data);
         curl_easy_setopt(curl, CURLOPT_WRITEDATA, &buffer);
         res = curl_easy_perform(curl);
         curl_easy_cleanup(curl);
-        if (res != CURLE_OK) {
-            fprintf(stderr, "curl_easy_perform() failed: %s\n", curl_easy_strerror(res));
+        if (!res){
+            curl_off_t speed;
+            res1 = curl_easy_getinfo(curl, CURLINFO_SPEED_DOWNLOAD_T, &speed);
+            if(!res1){
+                cout << "Upload speed bytes/sec\n" << speed;
                 exit(1);
             }
         }
+    }
 
     return input_data(buffer, false);
 }