GettingStarted - taking care of connection_state when starting connections

include/signalrclient/web_exception.h

@@ -12,7 +12,7 @@ namespace signalr
     class web_exception : public std::runtime_error
     {
     public:
-        explicit web_exception(const utility::string_t &what) 
+        explicit web_exception(const utility::string_t &what)
             : runtime_error(utility::conversions::to_utf8string(what))
         {}
     };

src/signalrclient/connection_impl.cpp

@@ -2,7 +2,9 @@
 // Licensed under the Apache License, Version 2.0. See License.txt in the project root for license information.
 
 #include "stdafx.h"
+#include <cpprest\asyncrt_utils.h>
 #include "connection_impl.h"
+#include "request_sender.h"
 
 namespace signalr
 {
@@ -14,11 +16,31 @@ namespace signalr
 
     pplx::task<void> connection_impl::start()
     {
+        if (!change_state(connection_state::disconnected, connection_state::connecting))
+        {
+            throw std::runtime_error(utility::conversions::to_utf8string(
+                _XPLATSTR("cannot start a connection that is not in the disconnected state")));
+        }
+
         return pplx::task_from_result();
     }
 
     connection_state connection_impl::get_connection_state() const
     {
-        return m_connection_state;
+        return m_connection_state.load();
+    }
+
+    bool connection_impl::change_state(connection_state old_state, connection_state new_state)
+    {
+        connection_state expected_state{ old_state };
+
+        if (!m_connection_state.compare_exchange_strong(expected_state, new_state, std::memory_order_seq_cst))
+        {
+            // TODO: add logging
+            // TODO: invoke state_changed callback
+            return false;
+        }
+
+        return true;
     }
 }

src/signalrclient/connection_impl.h

@@ -3,6 +3,7 @@
 
 #pragma once
 
+#include <atomic>
 #include <cpprest\http_client.h>
 #include "signalrclient\web_request_factory.h"
 #include "signalrclient\transport_factory.h"
@@ -29,9 +30,11 @@ namespace signalr
     private:
         web::uri m_base_uri;
         utility::string_t m_querystring;
-        connection_state m_connection_state;
+        std::atomic<connection_state> m_connection_state;
 
         web_request_factory &m_web_request_factory;
         transport_factory& m_transport_factory;
+
+        bool change_state(connection_state old_state, connection_state new_state);
     };
 }

test/signalrclienttests/connection_impl_tests.cpp

@@ -13,7 +13,41 @@ TEST(connection_impl_connection_state, initial_connection_state_is_disconnected)
     web_request_factory request_factory;
     transport_factory transport_factory;
 
-    ASSERT_EQ(
-        connection_state::disconnected, 
-        connection_impl(_XPLATSTR("url"), _XPLATSTR(""), request_factory, transport_factory).get_connection_state());
+    connection_impl connection{ _XPLATSTR("url"), _XPLATSTR(""), request_factory, transport_factory };
+
+    ASSERT_EQ(connection_state::disconnected, connection.get_connection_state());
 }
+
+TEST(connection_impl_start, cannot_start_non_disconnected_exception)
+{
+    web_request_factory request_factory;
+    transport_factory transport_factory;
+
+    connection_impl connection{ _XPLATSTR("url"), _XPLATSTR(""), request_factory, transport_factory };
+
+    connection.start().wait();
+
+    try
+    {
+        connection.start().wait();
+        ASSERT_TRUE(false); // exception not thrown
+    }
+    catch (const std::runtime_error& e)
+    {
+        ASSERT_EQ(
+            _XPLATSTR("cannot start a connection that is not in the disconnected state"),
+            utility::conversions::print_string(e.what()));
+    }
+}
+
+TEST(connection_impl_start, connection_state_is_connecting_when_connection_is_being_started)
+{
+    web_request_factory request_factory;
+    transport_factory transport_factory;
+
+    connection_impl connection{ _XPLATSTR("url"), _XPLATSTR(""), request_factory, transport_factory };
+
+    connection.start().wait();
+    ASSERT_EQ(connection.get_connection_state(), connection_state::connecting);
+}
+

test/signalrclienttests/http_sender_tests.cpp

@@ -25,7 +25,7 @@ TEST(http_sender_get_response, exception_thrown_if_status_code_not_200)
     try
     {
         http_sender::get(request).get();
-        ASSERT_TRUE(false); // exception not thrown 
+        ASSERT_TRUE(false); // exception not thrown
     }
     catch (const web_exception &e)
     {