added TcpConnection::closed()

include/amqpcpp/linux_tcp/tcpconnection.h

@@ -238,6 +238,8 @@ public:
     
     /**
      *  Is the connection in a usable state / not yet closed or being closed
+     *  When a connection is usable, you can send further commands over it. When it is
+     *  unusable, it may still be connected and finished queued commands.
      *  @return bool
      */
     bool usable() const
@@ -245,6 +247,12 @@ public:
         return _connection.usable();
     }
     
+    /**
+     *  Is the connection closed and full dead? The entire TCP connection has been discarded.
+     *  @return bool
+     */
+    bool closed() const;
+    
     /**
      *  The max frame size. Useful if you set up a buffer to parse incoming data: it does not have to exceed this size.
      *  @return uint32_t

src/linux_tcp/tcpclosed.h

@@ -41,6 +41,12 @@ public:
      *  Destructor
      */
     virtual ~TcpClosed() noexcept = default;
+
+    /**
+     *  Is this a closed / dead state?
+     *  @return bool
+     */
+    virtual bool closed() const override { return true; }
 };
     
 /**

src/linux_tcp/tcpconnection.cpp

@@ -57,6 +57,15 @@ std::size_t TcpConnection::queued() const
     return _state->queued();
 }
 
+/**
+ *  Is the connection closed and full dead? The entire TCP connection has been discarded.
+ *  @return bool
+ */
+bool TcpConnection::closed() const
+{
+    return _state->closed();
+}
+
 /**
  *  Process the TCP connection
  *  This method should be called when the filedescriptor that is registered

src/linux_tcp/tcpstate.h

@@ -63,6 +63,12 @@ public:
      */
     virtual std::size_t queued() const { return 0; }
     
+    /**
+     *  Is this a closed / dead state?
+     *  @return bool
+     */
+    virtual bool closed() const { return false; }
+
     /**
      *  Process the filedescriptor in the object
      *