Added FileDownloader utility based on libcurl to download files from URLs on native platforms

include/Helpers/FileDownloader.cpp

@@ -0,0 +1,135 @@
+#include "FileDownloader.hpp"
+#ifndef __EMSCRIPTEN__
+
+#include <curl/multi.h>
+#include <iostream>
+#include <curl/curl.h>
+
+std::mutex FileDownloader::newDownloadsMutex;
+std::vector<FileDownloader::DownloadHandler> FileDownloader::newDownloads;
+std::atomic<bool> FileDownloader::shutdownThread;
+FileDownloader::MultiHandle FileDownloader::mHandle;
+std::vector<FileDownloader::DownloadHandler> FileDownloader::currentDownloads;
+std::unique_ptr<std::thread> FileDownloader::downloadThread;
+
+void FileDownloader::init() {
+    curl_global_init(CURL_GLOBAL_DEFAULT);
+    shutdownThread = false;
+}
+
+std::shared_ptr<FileDownloader::DownloadData> FileDownloader::download_data_from_url(std::string_view url) {
+    DownloadHandler h;
+    auto downloadData = std::make_shared<DownloadData>();
+    h.data = downloadData;
+    h.data->status = DownloadData::Status::IN_PROGRESS;
+    h.eHandle = create_easy_handle();
+    curl_easy_setopt(h.eHandle.get(), CURLOPT_URL, url.data());
+    disable_ssl_verification(h.eHandle.get());
+    save_to_string(h.eHandle.get(), &h.data->str);
+
+    {
+        std::scoped_lock newDownloadsLock(newDownloadsMutex);
+        newDownloads.emplace_back(std::move(h));
+    }
+
+    if(!downloadThread)
+        downloadThread = std::make_unique<std::thread>(download_thread_update);
+
+    return downloadData;
+}
+
+void FileDownloader::add_new_handlers_to_multi() {
+    std::scoped_lock newDownloadsLock(newDownloadsMutex);
+    for(auto& handler : newDownloads) {
+        curl_multi_add_handle(mHandle.get(), handler.eHandle.get());
+        currentDownloads.emplace_back(std::move(handler));
+    }
+    newDownloads.clear();
+}
+
+void FileDownloader::download_thread_update() {
+    int stillRunning = 0;
+
+    mHandle = create_multi_handle();
+    add_new_handlers_to_multi();
+
+    do {
+        if(shutdownThread)
+            break;
+
+        CURLMcode mc;
+        int numfds;
+
+        mc = curl_multi_perform(mHandle.get(), &stillRunning);
+
+        for(;;) {
+            int msgCount;
+            CURLMsg* eHandleMsg = curl_multi_info_read(mHandle.get(), &msgCount);
+            if(!eHandleMsg)
+                break;
+            if(eHandleMsg->msg == CURLMSG_DONE) {
+                auto it = std::find_if(currentDownloads.begin(), currentDownloads.end(), [eHandleMsg](auto& d) {
+                    return eHandleMsg->easy_handle == d.eHandle.get();
+                });
+                if(it != currentDownloads.end()) {
+                    DownloadHandler& download = *it;
+                    download.data->status = eHandleMsg->data.result == CURLE_OK ? DownloadData::Status::SUCCESS : DownloadData::Status::FAILURE;
+                    currentDownloads.erase(it);
+                }
+            }
+        }
+
+        if(mc == CURLM_OK)
+            curl_multi_poll(mHandle.get(), nullptr, 0, 1000, &numfds);
+        else {
+            std::cout << "curl_multi failed" << std::endl;
+            break;
+        }
+    } while(stillRunning);
+
+    for(auto& download : currentDownloads)
+        download.data->status = DownloadData::Status::FAILURE;
+    currentDownloads.clear();
+}
+
+void FileDownloader::save_to_string(CURL* curl, std::string* str) {
+    curl_easy_setopt(curl, CURLOPT_WRITEFUNCTION, write_to_string);
+    curl_easy_setopt(curl, CURLOPT_WRITEDATA, reinterpret_cast<void*>(str));
+}
+
+void FileDownloader::disable_ssl_verification(CURL* curl) {
+    curl_easy_setopt(curl, CURLOPT_SSL_VERIFYHOST, 0);
+    curl_easy_setopt(curl, CURLOPT_SSL_VERIFYPEER, 0);
+}
+
+FileDownloader::EasyHandle FileDownloader::create_easy_handle() {
+    auto easyHandle = EasyHandle(curl_easy_init(), curl_easy_cleanup);
+    if(!easyHandle)
+        throw std::runtime_error("[FileDownloader::create_easy_handle] Failed to create CURL easy handle");
+    return easyHandle;
+}
+
+FileDownloader::MultiHandle FileDownloader::create_multi_handle() {
+    auto multiHandle = EasyHandle(curl_multi_init(), curl_multi_cleanup);
+    if(!multiHandle)
+        throw std::runtime_error("[FileDownloader::create_multi_handle] Failed to create CURL multi handle");
+    return multiHandle;
+}
+
+size_t FileDownloader::write_to_string(void* contents, size_t size, size_t nmemb, void* userp) {
+    size_t realsize = size * nmemb;
+    auto str = reinterpret_cast<std::string*>(userp);
+    str->append(reinterpret_cast<const char*>(contents), realsize);
+    return realsize;
+}
+
+void FileDownloader::cleanup() {
+    if(downloadThread && downloadThread->joinable()) {
+        shutdownThread = true;
+        downloadThread->join();
+    }
+
+    curl_global_cleanup();
+}
+
+#endif