Merge branch 'master' of https://github.com/ChristophAlbert/cpprestsdk into ws-race

Author: ras0219-msft

Release/src/websockets/client/ws_client_wspp.cpp

@@ -117,8 +117,7 @@ class wspp_callback_client : public websocket_client_callback_impl, public std::
 public:
     wspp_callback_client(websocket_client_config config) :
         websocket_client_callback_impl(std::move(config)),
-        m_state(CREATED),
-        m_num_sends(0)
+        m_state(CREATED)
 #if defined(__APPLE__) || (defined(ANDROID) || defined(__ANDROID__)) || defined(_WIN32)
         , m_openssl_failed(false)
 #endif
@@ -418,18 +417,22 @@ class wspp_callback_client : public websocket_client_callback_impl, public std::
             return pplx::task_from_exception<void>(websocket_exception("Message size too large. Ensure message length is less than UINT_MAX."));
         }
 
+        bool msg_pending = false;
         {
-            if (++m_num_sends == 1) // No sends in progress
-            {
-                // Start sending the message
-                send_msg(msg);
-            }
-            else
-            {
-                // Only actually have to take the lock if touching the queue.
-                std::lock_guard<std::mutex> lock(m_send_lock);
-                m_outgoing_msg_queue.push(msg);
-            }
+          std::lock_guard<std::mutex> lock(m_send_lock);
+          if (m_outgoing_msg_queue.size() > 0)
+          {
+            msg_pending = true;
+          }
+
+          m_outgoing_msg_queue.push(msg);
+        }
+
+        // No sends in progress
+        if (msg_pending == false)
+        {
+          // Start sending the message
+          send_msg(msg);
         }
 
         return pplx::create_task(msg.body_sent());
@@ -565,16 +568,25 @@ class wspp_callback_client : public websocket_client_callback_impl, public std::
                 msg.signal_body_sent();
             }
 
-            if (--this_client->m_num_sends > 0)
+            bool msg_pending = false;
+            websocket_outgoing_message next_msg;
             {
-                // Only hold the lock when actually touching the queue.
-                websocket_outgoing_message next_msg;
-                {
-                    std::lock_guard<std::mutex> lock(this_client->m_send_lock);
-                    next_msg = this_client->m_outgoing_msg_queue.front();
-                    this_client->m_outgoing_msg_queue.pop();
-                }
-                this_client->send_msg(next_msg);
+              // Only hold the lock when actually touching the queue.
+              std::lock_guard<std::mutex> lock(this_client->m_send_lock);
+
+              // First message in queue has been sent
+              this_client->m_outgoing_msg_queue.pop();
+
+              if (this_client->m_outgoing_msg_queue.size() > 0)
+              {
+                next_msg = this_client->m_outgoing_msg_queue.front();
+                msg_pending = true;
+              }
+            }
+
+            if (msg_pending)
+            {
+              this_client->send_msg(next_msg);
             }
         });
     }
@@ -766,12 +778,9 @@ class wspp_callback_client : public websocket_client_callback_impl, public std::
     // Guards access to m_outgoing_msg_queue
     std::mutex m_send_lock;
 
-    // Queue to order the sends
+    // Queue to track pending sends
     std::queue<websocket_outgoing_message> m_outgoing_msg_queue;
 
-    // Number of sends in progress and queued up.
-    std::atomic<int> m_num_sends;
-
     // External callback for handling received and close event
     std::function<void(websocket_incoming_message)> m_external_message_handler;
     std::function<void(websocket_close_status, const utility::string_t&, const std::error_code&)> m_external_close_handler;