Boost C++ Libraries of the most highly regarded and expertly designed C++ library projects in the world. Herb Sutter and Andrei Alexandrescu, C++ Coding Standards


// Boost.Signals library

// Copyright Douglas Gregor 2001-2004. Use, modification and
// distribution is subject to the Boost Software License, Version
// 1.0. (See accompanying file LICENSE_1_0.txt or copy at

// For more information, see


#include <boost/signals/detail/signals_common.hpp>
#include <boost/smart_ptr.hpp>
#include <boost/operators.hpp>
#include <boost/any.hpp>
#include <list>
#include <cassert>
#include <utility>


namespace boost {
    class trackable;

    namespace detail {
      // Represents an object that has been bound as part of a slot, and how
      // to notify that object of a disconnect
      struct bound_object {
        void* obj;
        void* data;
        void (*disconnect)(void*, void*);

        bool operator==(const bound_object& other) const
          { return obj == other.obj && data ==; }
        bool operator<(const bound_object& other) const
          { return obj < other.obj; }

        // To support intel 80 compiler, 2004/03/18 (Mark Rodgers)
        bool operator!=(const bound_object& other) const
        { return !(*this==other); }
        bool operator>(const bound_object& other) const
        { return !(*this < other); }

      // Describes the connection between a signal and the objects that are
      // bound for a specific slot. Enables notification of the signal and the
      // slots when a disconnect is requested.
      struct basic_connection {
        void* signal;
        void* signal_data;
        void (*signal_disconnect)(void*, void*);

        std::list<bound_object> bound_objects;
    } // end namespace detail

    // The user may freely pass around the "connection" object and terminate
    // the connection at any time using disconnect().
    class BOOST_SIGNALS_DECL connection :
      private less_than_comparable1<connection>,
      private equality_comparable1<connection>
      connection() : con(), controlling_connection(false) {}
      connection(const connection&);

      // Disconnect the signal and slot, if they are connected
      void disconnect() const;

      // Returns true if the signal and slot are connected
      bool connected() const { return con.get() && con->signal_disconnect; }

      // Comparison of connections
      bool operator==(const connection& other) const;
      bool operator<(const connection& other) const;

      // Connection assignment
      connection& operator=(const connection& other) ;

      // Swap connections
      void swap(connection& other);

    public: // TBD: CHANGE THIS
      // Set whether this connection object is controlling or not
      void set_controlling(bool control = true) 
      { controlling_connection = control; }

      get_connection() const 
      { return con; }

      friend class detail::signal_base_impl;
      friend class detail::slot_base;
      friend class trackable;

      // Reset this connection to refer to a different actual connection
      void reset(BOOST_SIGNALS_NAMESPACE::detail::basic_connection*);

      // Add a bound object to this connection (not for users)
      void add_bound_object(const BOOST_SIGNALS_NAMESPACE::detail::bound_object& b);

      friend class BOOST_SIGNALS_NAMESPACE::detail::bound_objects_visitor;

      // Pointer to the actual contents of the connection
      shared_ptr<BOOST_SIGNALS_NAMESPACE::detail::basic_connection> con;

      // True if the destruction of this connection object should disconnect
      bool controlling_connection;

    // Similar to connection, but will disconnect the connection when it is
    // destroyed unless release() has been called.
    class BOOST_SIGNALS_DECL scoped_connection : public connection {
      scoped_connection() : connection(), released(false) {}
      scoped_connection(const connection&);
      scoped_connection(const scoped_connection&);

      connection release();

      inline void swap(scoped_connection&);

      scoped_connection& operator=(const connection&);
      scoped_connection& operator=(const scoped_connection&);

      bool released;

    namespace detail {
      struct connection_slot_pair {
        connection first;
        any second;

        connection_slot_pair() {}

        connection_slot_pair(const connection& c, const any& a)
          : first(c), second(a)

        // Dummys to allow explicit instantiation to work
        bool operator==(const connection_slot_pair&) const { return false; }
        bool operator<(const connection_slot_pair&) const { return false;}

      // Determines if the underlying connection is disconnected
      struct is_disconnected {
        typedef connection_slot_pair argument_type;
        typedef bool result_type;

        inline bool operator()(const argument_type& c) const
          return !c.first.connected();

      // Autodisconnects the bound object when it is destroyed unless the
      // release method is invoked.
      class auto_disconnect_bound_object {
        auto_disconnect_bound_object(const bound_object& b) :
          binding(b), auto_disconnect(true)

          if (auto_disconnect)

        void release() { auto_disconnect = false; }

        bound_object binding;
        bool auto_disconnect;
    } // end namespace detail
  } // end namespace BOOST_SIGNALS_NAMESPACE
} // end namespace boost