add original source

source/listing_3.12.cpp

@@ -0,0 +1,56 @@
+#include <mutex>
+
+struct connection_info
+{};
+
+struct data_packet
+{};
+
+struct connection_handle
+{
+    void send_data(data_packet const&)
+    {}
+    data_packet receive_data()
+    {
+        return data_packet();
+    }
+};
+
+struct remote_connection_manager
+{
+    connection_handle open(connection_info const&)
+    {
+        return connection_handle();
+    }
+} connection_manager;
+
+
+class X
+{
+private:
+    connection_info connection_details;
+    connection_handle connection;
+    std::once_flag connection_init_flag;
+
+    void open_connection()
+    {
+        connection=connection_manager.open(connection_details);
+    }
+public:
+    X(connection_info const& connection_details_):
+        connection_details(connection_details_)
+    {}
+    void send_data(data_packet const& data)
+    {
+        std::call_once(connection_init_flag,&X::open_connection,this);
+        connection.send_data(data);
+    }
+    data_packet receive_data()
+    {
+        std::call_once(connection_init_flag,&X::open_connection,this);
+        return connection.receive_data();
+    }
+};
+
+int main()
+{}