Update PR

* Add libcurl check for websocket support

src/config.d

@@ -144,6 +144,10 @@ class ApplicationConfig {
 	bool fullScanTrueUpRequired = false;
 	bool suppressLoggingOutput = false;
 	
+	// WebSocket Operations
+	bool curlSupportsWebSockets = false;
+	bool websocketsSupportCheckDone = false;
+	
 	// Default number of concurrent threads when downloading and uploading data
 	ulong defaultConcurrentThreads = 8;
 	

src/curlEngine.d

@@ -13,6 +13,10 @@ import std.stdio;
 import std.range;
 import core.memory;
 import core.sys.posix.signal;
+// Required for WebSocket Support
+import core.stdc.stdlib : getenv;
+import core.stdc.string : strcmp;
+import core.sys.posix.dlfcn : dlopen, dlsym, dlclose, RTLD_NOW; // Posix elements
 
 // What other modules that we have created do we need to import?
 import log;
@@ -21,11 +25,83 @@ import util;
 // Shared pool of CurlEngine instances accessible across all threads
 __gshared CurlEngine[] curlEnginePool; // __gshared is used to declare a variable that is shared across all threads
 
+// WebSocket elements
+enum CURL_WS_MIN_NUM = 0x075600; // 7.86.0 (version which WebSocket support was added to cURL)
+// Flags (mirror curl/curl.h)
+enum CURLWS_TEXT   = 0x01u;
+enum CURLWS_BINARY = 0x02u;
+enum CURLWS_CONT   = 0x10u;
+enum CURLWS_CLOSE  = 0x20u;
+enum CURLWS_PING   = 0x40u;
+enum CURLWS_PONG   = 0x80u;
+
 extern (C) void sigpipeHandler(int signum) {
 	// Custom handler to ignore SIGPIPE signals
 	addLogEntry("ERROR: Handling a cURL SIGPIPE signal despite CURLOPT_NOSIGNAL being set (cURL Operational Bug) ...");
 }
 
+// Function pointer types matching libcurl WebSocket (WS) API
+extern(C) struct curl_ws_frame {
+	uint age;
+	uint flags;
+	size_t len;
+	size_t offset;
+	size_t bytesleft;
+}
+
+// WebSocket alias
+alias PFN_curl_ws_recv =
+	extern(C) CURLcode function(CURL*, void*, size_t, size_t*, const curl_ws_frame**);
+alias PFN_curl_ws_send =
+	extern(C) CURLcode function(CURL*, const void*, size_t, size_t*, long /*curl_off_t*/, uint);
+
+private __gshared {
+	void*                 _curlLib;
+	PFN_curl_ws_recv      p_curl_ws_recv;
+	PFN_curl_ws_send      p_curl_ws_send;
+	bool                  _wsSymbolsReady;
+	uint                  _wsProbeOnce; // 0=not run, 1=success, 2=fail
+}
+
+private void* loadCurlLib() {
+	// Respect LD_LIBRARY_PATH etc.
+	auto h = dlopen("libcurl.so.4", RTLD_NOW);
+	if (h is null) h = dlopen("libcurl.so", RTLD_NOW);
+	return h;
+}
+
+private void* findSymbol(const(char)* name) {
+	return dlsym(_curlLib, name);
+}
+
+private bool probeCurlWsSymbols() {
+	if (_wsProbeOnce == 1) return _wsSymbolsReady;
+	if (_wsProbeOnce == 2) return false;
+
+	// 1) libcurl version check
+	auto vi = curl_version_info(CURLVERSION_NOW);
+	if (vi is null || vi.version_num < CURL_WS_MIN_NUM) {
+		_wsProbeOnce = 2; _wsSymbolsReady = false; return false;
+	}
+
+	// 2) load libcurl and resolve symbols
+	_curlLib = loadCurlLib();
+	if (_curlLib is null) {
+		_wsProbeOnce = 2; _wsSymbolsReady = false; return false;
+	}
+
+	p_curl_ws_recv = cast(PFN_curl_ws_recv) findSymbol("curl_ws_recv");
+	p_curl_ws_send = cast(PFN_curl_ws_send) findSymbol("curl_ws_send");
+
+	_wsSymbolsReady = (p_curl_ws_recv !is null) && (p_curl_ws_send !is null);
+	_wsProbeOnce = _wsSymbolsReady ? 1 : 2;
+	return _wsSymbolsReady;
+}
+
+bool curlSupportsWebSockets() {
+	return probeCurlWsSymbols();
+}
+
 class CurlResponse {
 	HTTP.Method method;
 	const(char)[] url;

src/onedrive.d

@@ -144,6 +144,26 @@ class OneDriveApi {
 		if (curlEngine is null) {
 			curlEngine = getCurlInstance();
 			curlEngine.initialise(appConfig.getValueLong("dns_timeout"), appConfig.getValueLong("connect_timeout"), appConfig.getValueLong("data_timeout"), appConfig.getValueLong("operation_timeout"), appConfig.defaultMaxRedirects, appConfig.getValueBool("debug_https"), appConfig.getValueString("user_agent"), appConfig.getValueBool("force_http_11"), appConfig.getValueLong("rate_limit"), appConfig.getValueLong("ip_protocol_version"), appConfig.getValueLong("max_curl_idle"), keepAlive);
+		
+			// WebSocket capability available in OS cURL version
+			if (!appConfig.websocketsSupportCheckDone) {
+				// Check the underlying cURL capability to support websockets
+				if (debugLogging) {addLogEntry("Checking cURL Websocket support ...", ["debug"]);}
+				bool websocketSupport = curlSupportsWebSockets();
+				if (debugLogging) {addLogEntry("Checked cURL Websocket support = " ~ to!string(websocketSupport), ["debug"]);}
+				
+				// Update appConfig flags
+				appConfig.curlSupportsWebSockets = websocketSupport;
+				appConfig.websocketsSupportCheckDone = true;
+				
+				// Notify user if cURL vesion is too old to support websockets
+				if (!websocketSupport) {
+					addLogEntry();
+					addLogEntry("WARNING: Your libcurl is too old for WebSocket support. Please upgrade to libcurl 7.86.0 or newer.");
+					addLogEntry("         The near real-time processing of online changes cannot be enabled on your system.");
+					addLogEntry();
+				}
+			}
 		}
 
 		// Authorised value to return