Add UpgradeAsync example

Makefile

@@ -1,4 +1,4 @@
-EXAMPLE_FILES := HelloWorld EchoServer BroadcastingEchoServer UpgradeSync
+EXAMPLE_FILES := HelloWorld EchoServer BroadcastingEchoServer UpgradeSync UpgradeAsync
 THREADED_EXAMPLE_FILES := HelloWorldThreaded EchoServerThreaded
 override CXXFLAGS += -lpthread -Wconversion -std=c++17 -Isrc -IuSockets/src
 override LDFLAGS += uSockets/*.o -lz

examples/UpgradeAsync.cpp

@@ -0,0 +1,124 @@
+/* We simply call the root header file "App.h", giving you uWS::App and uWS::SSLApp */
+#include "App.h"
+
+/* This is a simple WebSocket "async" upgrade example.
+ * You may compile it with "WITH_OPENSSL=1 make" or with "make" */
+
+int main() {
+    /* ws->getUserData returns one of these */
+    struct PerSocketData {
+        /* Define your user data */
+        int something;
+    };
+
+    /* Keep in mind that uWS::SSLApp({options}) is the same as uWS::App() when compiled without SSL support.
+     * You may swap to using uWS:App() if you don't need SSL */
+    uWS::SSLApp({
+        /* There are example certificates in uWebSockets.js repo */
+	    .key_file_name = "../misc/key.pem",
+	    .cert_file_name = "../misc/cert.pem",
+	    .passphrase = "1234"
+	}).ws<PerSocketData>("/*", {
+        /* Settings */
+        .compression = uWS::SHARED_COMPRESSOR,
+        .maxPayloadLength = 16 * 1024,
+        .idleTimeout = 10,
+        .maxBackpressure = 1 * 1024 * 1024,
+        /* Handlers */
+        .upgrade = [](auto *res, auto *req, auto *context) {
+
+            /* HttpRequest (req) is only valid in this very callback, so we must COPY the headers
+             * we need later on while upgrading to WebSocket. You must not access req after first return.
+             * Here we create a heap allocated struct holding everything we will need later on. */
+
+            struct UpgradeData {
+                std::string secWebSocketKey;
+                std::string secWebSocketProtocol;
+                std::string secWebSocketExtensions;
+                struct us_socket_context_t *context;
+                decltype(res) httpRes;
+                bool aborted = false;
+            } *upgradeData = new UpgradeData {
+                std::string(req->getHeader("sec-websocket-key")),
+                std::string(req->getHeader("sec-websocket-protocol")),
+                std::string(req->getHeader("sec-websocket-extensions")),
+                context,
+                res
+            };
+
+            /* We have to attach an abort handler for us to be aware
+             * of disconnections while we perform async tasks */
+            res->onAborted([=]() {
+                /* We don't implement any kind of cancellation here,
+                 * so simply flag us as aborted */
+                upgradeData->aborted = true;
+                std::cout << "HTTP socket was closed before we upgraded it!" << std::endl;
+            });
+
+            /* Simulate checking auth for 5 seconds. This looks like crap, never write
+             * code that utilize us_timer_t like this; they are high-cost and should
+             * not be created and destroyed more than rarely!
+             *
+             * Also note that the code would be a lot simpler with capturing lambdas, maybe your
+             * database client has such a nice interface? Either way, here we go!*/
+            struct us_loop_t *loop = (struct us_loop_t *) uWS::Loop::get();
+            struct us_timer_t *delayTimer = us_create_timer(loop, 0, sizeof(UpgradeData *));
+            memcpy(us_timer_ext(delayTimer), &upgradeData, sizeof(UpgradeData *));
+            us_timer_set(delayTimer, [](struct us_timer_t *t) {
+                /* We wrote the upgradeData pointer to the timer's extension */
+                UpgradeData *upgradeData;
+                memcpy(&upgradeData, us_timer_ext(t), sizeof(UpgradeData *));
+
+                /* Were'nt we aborted before our async task finished? Okay, upgrade then! */
+                if (!upgradeData->aborted) {
+                    std::cout << "Async task done, upgrading to WebSocket now!" << std::endl;
+
+                    /* If you don't want to upgrade you can instead respond with custom HTTP here,
+                    * such as res->writeStatus(...)->writeHeader(...)->end(...); or similar.*/
+
+                    /* This call will immediately emit .open event */
+                    upgradeData->httpRes->template upgrade<PerSocketData>({
+                        /* We initialize PerSocketData struct here */
+                        .something = 13
+                    }, upgradeData->secWebSocketKey,
+                        upgradeData->secWebSocketProtocol,
+                        upgradeData->secWebSocketExtensions,
+                        upgradeData->context);
+                } else {
+                    std::cout << "Async task done, but the HTTP socket was closed. Skipping upgrade to WebSocket!" << std::endl;
+                }
+
+                delete upgradeData;
+
+                us_timer_close(t);
+            }, 5000, 0);
+
+        },
+        .open = [](auto *ws) {
+            /* Open event here, you may access ws->getUserData() which points to a PerSocketData struct.
+             * Here we simply validate that indeed, something == 13 as set in upgrade handler. */
+            std::cout << "Something is: " << static_cast<PerSocketData *>(ws->getUserData())->something << std::endl;
+        },
+        .message = [](auto *ws, std::string_view message, uWS::OpCode opCode) {
+            /* We simply echo whatever data we get */
+            ws->send(message, opCode);
+        },
+        .drain = [](auto *ws) {
+            /* Check ws->getBufferedAmount() here */
+        },
+        .ping = [](auto *ws) {
+            /* You don't need to handle this one, we automatically respond to pings as per standard */
+        },
+        .pong = [](auto *ws) {
+            /* You don't need to handle this one either */
+        },
+        .close = [](auto *ws, int code, std::string_view message) {
+            /* You may access ws->getUserData() here, but sending or
+             * doing any kind of I/O with the socket is not valid. */
+        }
+    }).listen(9001, [](auto *token) {
+        if (token) {
+            std::cout << "Listening on port " << 9001 << std::endl;
+        }
+    }).run();
+}