Add method to return the amount of queued outgoing data

include/amqpcpp/linux_tcp/tcpconnection.h

@@ -122,6 +122,12 @@ public:
      */
     int fileno() const;
 
+    /**
+     *  The number of outgoing bytes queued on this connection.
+     *  @return size_t
+     */
+    size_t bytesQueued() const;
+
     /**
      *  Process the TCP connection
      * 

src/linux_tcp/sslconnected.h

@@ -335,6 +335,12 @@ public:
      *  @return int
      */
     virtual int fileno() const override { return _socket; }
+
+    /**
+     *  The number of outgoing bytes queued on this connection.
+     *  @return size_t
+     */
+    virtual size_t bytesQueued() const { return _out.size(); }
      
     /**
      *  Process the filedescriptor in the object

src/linux_tcp/tcpconnected.h

@@ -157,7 +157,13 @@ public:
      *  @return int
      */
     virtual int fileno() const override { return _socket; }
-    
+
+    /**
+     *  The number of outgoing bytes queued on this connection.
+     *  @return size_t
+     */
+    virtual size_t bytesQueued() const { return _out.size(); }
+
     /**
      *  Process the filedescriptor in the object
      *  @param  monitor     Monitor to check if the object is still alive

src/linux_tcp/tcpconnection.cpp

@@ -43,6 +43,15 @@ int TcpConnection::fileno() const
     return _state->fileno();
 }
 
+/**
+ *  The number of outgoing bytes queued on this connection.
+ *  @return size_t
+ */
+size_t TcpConnection::bytesQueued() const
+{
+    return _state->bytesQueued();
+}
+
 /**
  *  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 int fileno() const { return -1; }
 
+    /**
+     *  The number of outgoing bytes queued on this connection.
+     *  @return size_t
+     */
+    virtual size_t bytesQueued() const { return 0; }
+
     /**
      *  Process the filedescriptor in the object
      *