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// 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
// http://www.boost.org/LICENSE_1_0.txt)
// For more information, see http://www.boost.org
#ifndef BOOST_SIGNALS_COMMON_HEADER
#define BOOST_SIGNALS_COMMON_HEADER
#ifndef BOOST_SIGNALS_NAMESPACE
# define BOOST_SIGNALS_NAMESPACE signals
#endif
#include <boost/type_traits/conversion_traits.hpp>
#include <boost/ref.hpp>
#include <boost/signals/detail/config.hpp>
#ifdef BOOST_HAS_ABI_HEADERS
# include BOOST_ABI_PREFIX
#endif
namespace boost {
namespace BOOST_SIGNALS_NAMESPACE {
namespace detail {
// The unusable class is a placeholder for unused function arguments
// It is also completely unusable except that it constructable from
// anything. This helps compilers without partial specialization
// handle slots returning void.
struct unusable {
unusable() {}
};
// Determine the result type of a slot call
template<typename R>
struct slot_result_type {
typedef R type;
};
template<>
struct slot_result_type<void> {
typedef unusable type;
};
// Determine if the given type T is a signal
class signal_base;
template<typename T>
struct is_signal {
BOOST_STATIC_CONSTANT(bool,
value = (is_convertible<T*, signal_base*>::value));
};
/*
* The IF implementation is temporary code. When a Boost metaprogramming
* library is introduced, Boost.Signals will use it instead.
*/
namespace intimate {
struct SelectThen
{
template<typename Then, typename Else>
struct Result
{
typedef Then type;
};
};
struct SelectElse
{
template<typename Then, typename Else>
struct Result
{
typedef Else type;
};
};
template<bool Condition>
struct Selector
{
typedef SelectThen type;
};
template<>
struct Selector<false>
{
typedef SelectElse type;
};
} // end namespace intimate
template<bool Condition, typename Then, typename Else>
struct IF
{
typedef typename intimate::Selector<Condition>::type select;
typedef typename select::template Result<Then,Else>::type type;
};
// Determine if the incoming argument is a reference_wrapper
template<typename T>
struct is_ref
{
BOOST_STATIC_CONSTANT(bool, value = false);
};
template<typename T>
struct is_ref<reference_wrapper<T> >
{
BOOST_STATIC_CONSTANT(bool, value = true);
};
// A slot can be a signal, a reference to a function object, or a
// function object.
struct signal_tag {};
struct reference_tag {};
struct value_tag {};
// Classify the given slot as a signal, a reference-to-slot, or a
// standard slot
template<typename S>
class get_slot_tag {
typedef typename IF<(is_signal<S>::value),
signal_tag,
value_tag>::type signal_or_value;
public:
typedef typename IF<(is_ref<S>::value),
reference_tag,
signal_or_value>::type type;
};
// Forward declaration needed in lots of places
class signal_base_impl;
class bound_objects_visitor;
class slot_base;
} // end namespace detail
} // end namespace BOOST_SIGNALS_NAMESPACE
} // end namespace boost
#ifdef BOOST_HAS_ABI_HEADERS
# include BOOST_ABI_SUFFIX
#endif
#endif // BOOST_SIGNALS_COMMON_HEADER
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