Add CppCon2018 chat server example and video

example/cppcon2018/shared_state.hpp

@@ -0,0 +1,45 @@
+//
+// Copyright (c) 2018 Vinnie Falco (vinnie dot falco at gmail dot com)
+//
+// Distributed under the Boost Software License, Version 1.0. (See accompanying
+// file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
+//
+// Official repository: https://github.com/vinniefalco/CppCon2018
+//
+
+#ifndef CPPCON2018_SHARED_STATE_HPP
+#define CPPCON2018_SHARED_STATE_HPP
+
+#include <memory>
+#include <string>
+#include <unordered_set>
+
+// Forward declaration
+class websocket_session;
+
+// Represents the shared server state
+class shared_state
+{
+    std::string doc_root_;
+
+    // This simple method of tracking
+    // sessions only works with an implicit
+    // strand (i.e. a single-threaded server)
+    std::unordered_set<websocket_session*> sessions_;
+
+public:
+    explicit
+    shared_state(std::string doc_root);
+
+    std::string const&
+    doc_root() const noexcept
+    {
+        return doc_root_;
+    }
+
+    void join  (websocket_session& session);
+    void leave (websocket_session& session);
+    void send  (std::string message);
+};
+
+#endif