Added some comments and exceptions to handle errors

main.cpp

@@ -15,15 +15,13 @@ struct User {
 
 websockets::TestProtocol<User> default_protocol{
 	// connection established
-	[](User& user) -> int{
+	[](User& user){
 		user.index = uid++;
 		people_online[user.index] = "";
-		return 0;
 	},
 	// connection closed
-	[](User& user) -> int{
+	[](User& user){
 		people_online.erase(user.index);
-		return 0;
 	},
 	// write (will always come after receive)
 	[](User& user) -> std::string{
@@ -32,9 +30,8 @@ websockets::TestProtocol<User> default_protocol{
 		return string_to_send;
 	},
 	// receive
-	[](User& user, std::string in) -> int{
+	[](User& user, std::string in){
 		people_online[user.index] = in;
-		return 0;
 	}
 };
 

websockets.h

@@ -12,6 +12,23 @@
 #include <lib/libwebsockets.h>
 
 namespace websockets {
+	// Will be caught in the callback and program will continue to run (but connection will be closed)
+	struct runtime_error : public std::runtime_error {
+		int return_value;
+
+		runtime_error(const char * message, int return_value = -1)
+		: std::runtime_error(message)
+		, return_value(return_value)
+		{}
+	};
+
+	// Will never be caught (by us), and hence things will terminate
+	struct fatal_error : public std::runtime_error {
+		fatal_error(const char * message)
+		: std::runtime_error(message)
+		{}
+	};
+
 	struct Log {
 		Log(std::string const & name, int syslog_options, int debug_level){
 			setlogmask(LOG_UPTO (LOG_DEBUG));
@@ -37,6 +54,7 @@ namespace websockets {
 		}
 	};
 
+	// Basic wrapper for the context pointer
 	struct Context {
 		std::unique_ptr<libwebsocket_context, decltype(libwebsocket_context_destroy)*> context;
 
@@ -58,6 +76,7 @@ namespace websockets {
 		}
 	};
 
+	// Basic protocol to extend, already casts the void* to the actual type
 	template <typename T>
 	struct Protocol	{
 		typedef T user_type;
@@ -69,12 +88,16 @@ namespace websockets {
 		};
 	};
 
+	// 4-function Protocol, provide functions to handle establishment, closing, receiving and writing (follows receiving)
+	// To let the callback return something non-zero (in case of error), use websockets::runtime_error
 	template <typename T>
-	struct TestProtocol : public Protocol<T> {
-		std::function<int(T&)> establish_func;
-		std::function<int(T&)> close_func;
-		std::function<std::string(T&)> write_func;
-		std::function<int(T&, std::string)> receive_func;
+	struct TestProtocol {
+		typedef T user_type;
+
+		std::function<void(user_type&)> establish_func;
+		std::function<void(user_type&)> close_func;
+		std::function<std::string(user_type&)> write_func;
+		std::function<void(user_type&, std::string)> receive_func;
 
 		TestProtocol(decltype(establish_func) establish_func, decltype(close_func) close_func, decltype(write_func) write_func, decltype(receive_func) receive_func)
 		: establish_func(establish_func)
@@ -83,7 +106,9 @@ namespace websockets {
 		, receive_func(receive_func)
 		{}
 
-		virtual int call(libwebsocket_context& context, libwebsocket& wsi, libwebsocket_callback_reasons reason, T& user, void *in, size_t len){
+		int callback(libwebsocket_context* context, libwebsocket* wsi, libwebsocket_callback_reasons reason, void* user_ptr, void *in, size_t len){
+			user_type& user = *static_cast<user_type*>(user_ptr);
+			try{
 				switch (reason) {
 					case LWS_CALLBACK_ESTABLISHED:
 						establish_func(user);
@@ -96,28 +121,28 @@ namespace websockets {
 						// we need the extra bytes padding on both sides :(
 						unsigned char * buf = new unsigned char [LWS_SEND_BUFFER_PRE_PADDING + string_to_send.size() + LWS_SEND_BUFFER_POST_PADDING];
 						memcpy(&buf[LWS_SEND_BUFFER_PRE_PADDING], string_to_send.c_str(), string_to_send.size());
-					int n = libwebsocket_write(&wsi, &buf[LWS_SEND_BUFFER_PRE_PADDING], string_to_send.size(), LWS_WRITE_TEXT);
-					if (n < 0) {
-						lwsl_err("ERROR %d writing to socket, hanging up\n", n);
-						return 1;
-					}
-					if (n < string_to_send.size()) {
-						lwsl_err("Partial write\n");
-						return -1;
-					}
+						int n = libwebsocket_write(wsi, &buf[LWS_SEND_BUFFER_PRE_PADDING], string_to_send.size(), LWS_WRITE_TEXT);
+						if (n < 0) throw runtime_error("Could not write", 1);
+						if (n < string_to_send.size()) throw runtime_error("Partial write", -1);
 						break;
 					}
 					case LWS_CALLBACK_RECEIVE:
 						receive_func(user, std::string((char*)in, len));
-					libwebsocket_callback_on_writable(&context, &wsi);
+						libwebsocket_callback_on_writable(context, wsi);
 						break;
 					default:
 						break;
 				}
+			} catch(runtime_error& e){
+				lwsl_err("Exception thrown: %s", e.what());
+				return e.return_value;
+			}
 			return 0;
 		}
 	};
 
+
+// Some wrappers to easily create the list of protocols from structs of above kind.
 #define WSprotocol_callback(protocol)\
 [](libwebsocket_context *context, libwebsocket *wsi, libwebsocket_callback_reasons reason, void *user, void *in, size_t len)\
 {return protocol.callback(context, wsi, reason, user, in, len);}