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#ifndef BOOST_SERIALIZATION_SINGLETON_HPP
#define BOOST_SERIALIZATION_SINGLETON_HPP
/////////1/////////2///////// 3/////////4/////////5/////////6/////////7/////////8
// singleton.hpp
//
// Copyright David Abrahams 2006. Original version
//
// Copyright Robert Ramey 2007. Changes made to permit
// application throughout the serialization library.
//
// 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)
//
// The intention here is to define a template which will convert
// any class into a singleton with the following features:
//
// a) initialized before first use.
// b) thread-safe for const access to the class
// c) non-locking
//
// In order to do this,
// a) Initialize dynamically when used.
// b) Require that all singletons be initialized before main
// is called or any entry point into the shared library is invoked.
// This guarentees no race condition for initialization.
// In debug mode, we assert that no non-const functions are called
// after main is invoked.
//
// MS compatible compilers support #pragma once
#if defined(_MSC_VER)
# pragma once
#endif
#include <boost/assert.hpp>
#include <boost/config.hpp>
#include <boost/noncopyable.hpp>
#include <boost/serialization/force_include.hpp>
#include <boost/archive/detail/auto_link_archive.hpp>
#include <boost/serialization/config.hpp>
#include <boost/archive/detail/abi_prefix.hpp> // must be the last header
#ifdef BOOST_MSVC
# pragma warning(push)
# pragma warning(disable : 4511 4512)
#endif
namespace boost {
namespace serialization {
//////////////////////////////////////////////////////////////////////
// Provides a dynamically-initialized (singleton) instance of T in a
// way that avoids LNK1179 on vc6. See http://tinyurl.com/ljdp8 or
// http://lists.boost.org/Archives/boost/2006/05/105286.php for
// details.
//
// singletons created by this code are guarenteed to be unique
// within the executable or shared library which creates them.
// This is sufficient and in fact ideal for the serialization library.
// The singleton is created when the module is loaded and destroyed
// when the module is unloaded.
// This base class has two functions.
// First it provides a module handle for each singleton indicating
// the executable or shared library in which it was created. This
// turns out to be necessary and sufficient to implement the tables
// used by serialization library.
// Second, it provides a mechanism to detect when a non-const function
// is called after initialization.
// make a singleton to lock/unlock all singletons for alteration.
// The intent is that all singletons created/used by this code
// are to be initialized before main is called. A test program
// can lock all the singletons when main is entereed. This any
// attempt to retieve a mutable instances while locked will
// generate a assertion if compiled for debug.
class BOOST_SYMBOL_VISIBLE singleton_module :
public boost::noncopyable
{
private:
BOOST_SERIALIZATION_DECL static bool & get_lock();
public:
static void lock(){
get_lock() = true;
}
static void unlock(){
get_lock() = false;
}
static bool is_locked(){
return get_lock();
}
};
#include <boost/archive/detail/abi_suffix.hpp> // pops abi_suffix.hpp pragmas
namespace detail {
template<class T>
class singleton_wrapper : public T
{
public:
static bool m_is_destroyed;
~singleton_wrapper(){
m_is_destroyed = true;
}
};
template<class T>
bool detail::singleton_wrapper< T >::m_is_destroyed = false;
} // detail
// note usage of BOOST_DLLEXPORT. These functions are in danger of
// being eliminated by the optimizer when building an application in
// release mode. Usage of the macro is meant to signal the compiler/linker
// to avoid dropping these functions which seem to be unreferenced.
// This usage is not related to autolinking.
template <class T>
class singleton : public singleton_module
{
private:
BOOST_DLLEXPORT static T & instance;
// include this to provoke instantiation at pre-execution time
static void use(T const *) {}
BOOST_DLLEXPORT static T & get_instance() {
static detail::singleton_wrapper< T > t;
// refer to instance, causing it to be instantiated (and
// initialized at startup on working compilers)
BOOST_ASSERT(! detail::singleton_wrapper< T >::m_is_destroyed);
use(& instance);
return static_cast<T &>(t);
}
public:
BOOST_DLLEXPORT static T & get_mutable_instance(){
BOOST_ASSERT(! is_locked());
return get_instance();
}
BOOST_DLLEXPORT static const T & get_const_instance(){
return get_instance();
}
BOOST_DLLEXPORT static bool is_destroyed(){
return detail::singleton_wrapper< T >::m_is_destroyed;
}
};
template<class T>
BOOST_DLLEXPORT T & singleton< T >::instance = singleton< T >::get_instance();
} // namespace serialization
} // namespace boost
#ifdef BOOST_MSVC
#pragma warning(pop)
#endif
#endif // BOOST_SERIALIZATION_SINGLETON_HPP
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