125 lines
3.4 KiB
Plaintext
125 lines
3.4 KiB
Plaintext
/*=============================================================================
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Copyright (c) 2006 Joao Abecasis
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http://spirit.sourceforge.net/
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Distributed under the Boost Software License, Version 1.0. (See accompanying
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file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
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=============================================================================*/
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#if !defined(BOOST_SPIRIT_STATIC_HPP)
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#define BOOST_SPIRIT_STATIC_HPP
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#include <boost/noncopyable.hpp>
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#include <boost/call_traits.hpp>
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#include <boost/aligned_storage.hpp>
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#include <boost/type_traits/add_pointer.hpp>
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#include <boost/type_traits/alignment_of.hpp>
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#include <boost/thread/once.hpp>
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#include <memory> // for placement new
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#include <boost/spirit/home/classic/namespace.hpp>
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namespace boost { namespace spirit {
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BOOST_SPIRIT_CLASSIC_NAMESPACE_BEGIN
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//
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// Provides thread-safe initialization of a single static instance of T.
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//
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// This instance is guaranteed to be constructed on static storage in a
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// thread-safe manner, on the first call to the constructor of static_.
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//
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// Requirements:
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// T is default constructible
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// (There's an alternate implementation that relaxes this
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// requirement -- Joao Abecasis)
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// T::T() MUST not throw!
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// this is a requirement of boost::call_once.
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//
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template <class T, class Tag>
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struct static_
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: boost::noncopyable
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{
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private:
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struct destructor
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{
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~destructor()
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{
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static_::get_address()->~value_type();
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}
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};
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struct default_ctor
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{
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static void construct()
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{
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::new (static_::get_address()) value_type();
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static destructor d;
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}
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};
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public:
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typedef T value_type;
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typedef typename boost::call_traits<T>::reference reference;
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typedef typename boost::call_traits<T>::const_reference const_reference;
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static_(Tag = Tag())
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{
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boost::call_once(&default_ctor::construct, constructed_);
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}
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operator reference()
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{
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return this->get();
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}
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operator const_reference() const
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{
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return this->get();
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}
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reference get()
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{
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return *this->get_address();
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}
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const_reference get() const
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{
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return *this->get_address();
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}
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private:
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typedef typename boost::add_pointer<value_type>::type pointer;
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static pointer get_address()
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{
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return static_cast<pointer>(data_.address());
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}
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typedef boost::aligned_storage<sizeof(value_type),
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boost::alignment_of<value_type>::value> storage_type;
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static storage_type data_;
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static once_flag constructed_;
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};
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template <class T, class Tag>
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typename static_<T, Tag>::storage_type static_<T, Tag>::data_;
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template <class T, class Tag>
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#ifndef BOOST_THREAD_PROVIDES_ONCE_CXX11
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once_flag static_<T, Tag>::constructed_ = BOOST_ONCE_INIT;
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#else
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once_flag static_<T, Tag>::constructed_;
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#endif
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BOOST_SPIRIT_CLASSIC_NAMESPACE_END
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}} // namespace BOOST_SPIRIT_CLASSIC_NS
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#endif // include guard
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