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/*
* Copyright Andrey Semashev 2007 - 2015.
* 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)
*/
/*!
* \file type_dispatcher.hpp
* \author Andrey Semashev
* \date 15.04.2007
*
* The header contains definition of generic type dispatcher interfaces.
*/
#ifndef BOOST_LOG_TYPE_DISPATCHER_HPP_INCLUDED_
#define BOOST_LOG_TYPE_DISPATCHER_HPP_INCLUDED_
#include <typeinfo>
#include <boost/static_assert.hpp>
#include <boost/log/detail/config.hpp>
#include <boost/log/detail/visible_type.hpp>
#include <boost/utility/explicit_operator_bool.hpp>
#include <boost/log/detail/header.hpp>
#ifdef BOOST_HAS_PRAGMA_ONCE
#pragma once
#endif
namespace boost {
BOOST_LOG_OPEN_NAMESPACE
/*!
* \brief A type dispatcher interface
*
* All type dispatchers support this interface. It is used to acquire the
* visitor interface for the requested type.
*/
class type_dispatcher
{
public:
#ifndef BOOST_LOG_DOXYGEN_PASS
//! The base class for type dispatcher callbacks
class callback_base
{
protected:
void* m_pVisitor;
void* m_pTrampoline;
public:
explicit callback_base(void* visitor = 0, void* tramp = 0) BOOST_NOEXCEPT :
m_pVisitor(visitor),
m_pTrampoline(tramp)
{
}
template< typename ValueT >
explicit callback_base(void* visitor, void (*tramp)(void*, ValueT const&)) BOOST_NOEXCEPT :
m_pVisitor(visitor)
{
typedef void (*trampoline_t)(void*, ValueT const&);
BOOST_STATIC_ASSERT_MSG(sizeof(trampoline_t) == sizeof(void*), "Boost.Log: Unsupported platform, the size of a function pointer differs from the size of a pointer");
union
{
void* as_pvoid;
trampoline_t as_trampoline;
}
caster;
caster.as_trampoline = tramp;
m_pTrampoline = caster.as_pvoid;
}
template< typename VisitorT, typename T >
static void trampoline(void* visitor, T const& value)
{
(*static_cast< VisitorT* >(visitor))(value);
}
};
//! An interface to the callback for the concrete type visitor
template< typename T >
class callback :
private callback_base
{
private:
//! Type of the trampoline method
typedef void (*trampoline_t)(void*, T const&);
public:
//! The type, which the visitor is able to consume
typedef T supported_type;
public:
callback() BOOST_NOEXCEPT : callback_base()
{
}
explicit callback(callback_base const& base) BOOST_NOEXCEPT : callback_base(base)
{
}
void operator() (T const& value) const
{
BOOST_STATIC_ASSERT_MSG(sizeof(trampoline_t) == sizeof(void*), "Boost.Log: Unsupported platform, the size of a function pointer differs from the size of a pointer");
union
{
void* as_pvoid;
trampoline_t as_trampoline;
}
caster;
caster.as_pvoid = this->m_pTrampoline;
(caster.as_trampoline)(this->m_pVisitor, value);
}
BOOST_EXPLICIT_OPERATOR_BOOL_NOEXCEPT()
bool operator! () const BOOST_NOEXCEPT { return (this->m_pVisitor == 0); }
};
#else // BOOST_LOG_DOXYGEN_PASS
/*!
* This interface is used by type dispatchers to consume the dispatched value.
*/
template< typename T >
class callback
{
public:
/*!
* The operator invokes the visitor-specific logic with the given value
*
* \param value The dispatched value
*/
void operator() (T const& value) const;
/*!
* The operator checks if the visitor is attached to a receiver
*/
BOOST_EXPLICIT_OPERATOR_BOOL_NOEXCEPT()
/*!
* The operator checks if the visitor is not attached to a receiver
*/
bool operator! () const BOOST_NOEXCEPT;
};
#endif // BOOST_LOG_DOXYGEN_PASS
protected:
//! Pointer to the callback acquisition method
typedef callback_base (*get_callback_impl_type)(type_dispatcher*, std::type_info const&);
private:
//! Pointer to the callback acquisition method
get_callback_impl_type m_get_callback_impl;
protected:
/*!
* Initializing constructor
*/
explicit type_dispatcher(get_callback_impl_type get_callback_impl) BOOST_NOEXCEPT : m_get_callback_impl(get_callback_impl)
{
}
// Destructor and copying can only be called from the derived classes
BOOST_DEFAULTED_FUNCTION(~type_dispatcher(), {})
BOOST_DEFAULTED_FUNCTION(type_dispatcher(type_dispatcher const& that), : m_get_callback_impl(that.m_get_callback_impl) {})
BOOST_DEFAULTED_FUNCTION(type_dispatcher& operator= (type_dispatcher const& that), { m_get_callback_impl = that.m_get_callback_impl; return *this; })
public:
/*!
* The method requests a callback for the value of type \c T
*
* \return The type-specific callback or an empty value, if the type is not supported
*/
template< typename T >
callback< T > get_callback()
{
return callback< T >((this->m_get_callback_impl)(this, typeid(boost::log::aux::visible_type< T >)));
}
};
BOOST_LOG_CLOSE_NAMESPACE // namespace log
} // namespace boost
#include <boost/log/detail/footer.hpp>
#endif // BOOST_LOG_TYPE_DISPATCHER_HPP_INCLUDED_
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