121 lines
2.8 KiB
C++
121 lines
2.8 KiB
C++
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// Copyright Daniel Wallin 2006. Use, modification and distribution is
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// subject to 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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// 2009.10.21 TDS remove depenency on boost::python::detail::referent_storage
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//
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#ifndef BOOST_PARAMETER_MAYBE_091021_HPP
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# define BOOST_PARAMETER_MAYBE_091021_HPP
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# include <boost/mpl/if.hpp>
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# include <boost/mpl/identity.hpp>
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# include <boost/type_traits/is_reference.hpp>
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# include <boost/type_traits/add_reference.hpp>
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# include <boost/optional.hpp>
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# include <boost/aligned_storage.hpp>
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# include <boost/type_traits/remove_cv.hpp>
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# include <boost/type_traits/add_const.hpp>
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# include <boost/parameter/aux_/is_maybe.hpp>
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namespace boost { namespace parameter { namespace aux {
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template <class T> struct referent_size;
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template <class T>
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struct referent_size<T&>
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{
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BOOST_STATIC_CONSTANT(std::size_t, value = sizeof(T));
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};
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// A metafunction returning a POD type which can store U, where T ==
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// U&. If T is not a reference type, returns a POD which can store T.
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template <class T>
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struct referent_storage
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{
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typedef typename boost::aligned_storage<
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referent_size<T>::value
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>::type type;
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};
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template <class T>
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struct maybe : maybe_base
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{
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typedef typename add_reference<
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# if BOOST_WORKAROUND(__BORLANDC__, BOOST_TESTED_AT(0x564))
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T const
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# else
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typename add_const<T>::type
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# endif
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>::type reference;
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typedef typename remove_cv<
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BOOST_DEDUCED_TYPENAME remove_reference<reference>::type
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>::type non_cv_value;
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explicit maybe(T value_)
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: value(value_)
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, constructed(false)
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{}
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maybe()
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: constructed(false)
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{}
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~maybe()
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{
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if (constructed)
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this->destroy();
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}
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reference construct(reference value_) const
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{
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return value_;
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}
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template <class U>
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reference construct2(U const& value_) const
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{
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new (m_storage.address()) non_cv_value(value_);
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constructed = true;
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return *(non_cv_value*)m_storage.address();
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}
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template <class U>
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reference construct(U const& value_) const
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{
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return this->construct2(value_);
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}
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void destroy()
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{
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((non_cv_value*)m_storage.address())->~non_cv_value();
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}
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typedef reference(maybe<T>::*safe_bool)() const;
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operator safe_bool() const
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{
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return value ? &maybe<T>::get : 0 ;
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}
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reference get() const
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{
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return value.get();
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}
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private:
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boost::optional<T> value;
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mutable bool constructed;
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mutable typename referent_storage<
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reference
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>::type m_storage;
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};
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}}} // namespace boost::parameter::aux
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#endif // BOOST_PARAMETER_MAYBE_060211_HPP
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