Runtime C++ Download =link= May 2026
bool DownloadManager::downloadSync(const DownloadOptions& options, ProgressCallback progress) std::ios::binary; if (m_context->resume_mode) = std::ios::app; m_context->downloaded_bytes = existing_size; m_context->file.open(options.output_path, mode); if (!m_context->file.is_open()) m_lastError = "Cannot open output file: " + options.output_path; return false; // Setup CURL curl_easy_reset(m_curl); curl_easy_setopt(m_curl, CURLOPT_URL, options.url.c_str()); curl_easy_setopt(m_curl, CURLOPT_WRITEFUNCTION, writeCallback); curl_easy_setopt(m_curl, CURLOPT_WRITEDATA, m_context.get()); curl_easy_setopt(m_curl, CURLOPT_NOPROGRESS, 0L); curl_easy_setopt(m_curl, CURLOPT_XFERINFOFUNCTION, progressCallback); curl_easy_setopt(m_curl, CURLOPT_XFERINFODATA, m_context.get()); curl_easy_setopt(m_curl, CURLOPT_TIMEOUT, options.timeout_seconds); curl_easy_setopt(m_curl, CURLOPT_FOLLOWLOCATION, 1L); curl_easy_setopt(m_curl, CURLOPT_USERAGENT, options.user_agent.c_str()); // Resume download if needed if (m_context->resume_mode) curl_easy_setopt(m_curl, CURLOPT_RESUME_FROM_LARGE, existing_size); // Authentication if (!options.username.empty() && !options.password.empty()) std::string auth = options.username + ":" + options.password; curl_easy_setopt(m_curl, CURLOPT_USERPWD, auth.c_str()); // Perform download with retries CURLcode res; int retries = 0; bool success = false; while (retries <= options.max_retries && !m_cancel) res = curl_easy_perform(m_curl); if (res == CURLE_OK) success = true; break; if (res == CURLE_ABORTED_BY_CALLBACK && m_cancel) m_lastError = "Download cancelled"; break; retries++; if (retries <= options.max_retries) std::this_thread::sleep_for(std::chrono::seconds(2)); m_context->file.close(); if (!success && !m_cancel) m_lastError = curl_easy_strerror(res); return success && !m_cancel;
This is production-ready code that handles real-world download scenarios efficiently. runtime c++ download
find_package(CURL REQUIRED)
private: static size_t writeCallback(void* contents, size_t size, size_t nmemb, void* userp); static int progressCallback(void* userp, curl_off_t dltotal, curl_off_t dlnow, curl_off_t ultotal, curl_off_t ulnow); struct DownloadContext std::ofstream file; size_t downloaded_bytes = 0; size_t total_bytes = 0; ProgressCallback progress_cb; std::string output_path; bool resume_mode = false; ; std::unique_ptr<DownloadContext> m_context; std::thread m_downloadThread; std::atomic<bool> m_activefalse; std::atomic<bool> m_cancelfalse; std::string m_lastError; CURL* m_curl; ; ProgressCallback progress) std::ios::binary
DownloadManager::~DownloadManager() cancel(); if (m_downloadThread.joinable()) m_downloadThread.join(); if (m_curl) curl_easy_cleanup(m_curl); curl_global_cleanup(); resume_mode) = std::ios::app