sl@0: // (C) Copyright Jonathan Turkanis 2005.
sl@0: // Distributed under the Boost Software License, Version 1.0. (See accompanying
sl@0: // file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt.)
sl@0: 
sl@0: // See http://www.boost.org/libs/iostreams for documentation.
sl@0: 
sl@0: // Recent changes to Boost.Optional involving assigment broke Boost.Iostreams,
sl@0: // in a way which could be remedied only by relying on the deprecated reset
sl@0: // functions; with VC6, even reset didn't work. Until this problem is 
sl@0: // understood, Iostreams will use a private version of optional with a smart 
sl@0: // pointer interface.
sl@0: 
sl@0: #ifndef BOOST_IOSTREAMS_DETAIL_OPTIONAL_HPP_INCLUDED
sl@0: #define BOOST_IOSTREAMS_DETAIL_OPTIONAL_HPP_INCLUDED
sl@0: 
sl@0: #if defined(_MSC_VER) && (_MSC_VER >= 1020)
sl@0: # pragma once
sl@0: #endif
sl@0: 
sl@0: #include <cassert>
sl@0: #include <boost/mpl/int.hpp>
sl@0: #include <boost/type_traits/aligned_storage.hpp>
sl@0: #include <boost/type_traits/alignment_of.hpp>
sl@0: 
sl@0: namespace boost { namespace iostreams { namespace detail {
sl@0: 
sl@0: // Taken from <boost/optional.hpp>.
sl@0: template<class T>
sl@0: class aligned_storage
sl@0: {
sl@0:     // Borland ICEs if unnamed unions are used for this!
sl@0:     union dummy_u
sl@0:     {
sl@0:         char data[ sizeof(T) ];
sl@0:         BOOST_DEDUCED_TYPENAME type_with_alignment<
sl@0:           ::boost::alignment_of<T>::value >::type aligner_;
sl@0:     } dummy_ ;
sl@0: 
sl@0:   public:
sl@0: 
sl@0:     void const* address() const { return &dummy_.data[0]; }
sl@0:     void      * address()       { return &dummy_.data[0]; }
sl@0: };
sl@0: 
sl@0: template<typename T>
sl@0: class optional {
sl@0: public:
sl@0:     typedef T element_type;
sl@0:     optional() : initialized_(false) { }
sl@0:     optional(const T& t) : initialized_(false) { reset(t); }
sl@0:     ~optional() { reset(); }
sl@0:     T& operator*() 
sl@0:     { 
sl@0:         assert(initialized_);
sl@0:         return *static_cast<T*>(address()); 
sl@0:     }
sl@0:     const T& operator*() const
sl@0:     { 
sl@0:         assert(initialized_);
sl@0:         return *static_cast<const T*>(address()); 
sl@0:     }
sl@0:     T* operator->() 
sl@0:     { 
sl@0:         assert(initialized_);
sl@0:         return static_cast<T*>(address()); 
sl@0:     }
sl@0:     const T* operator->() const
sl@0:     { 
sl@0:         assert(initialized_);
sl@0:         return static_cast<const T*>(address()); 
sl@0:     }
sl@0:     T* get() 
sl@0:     { 
sl@0:         assert(initialized_);
sl@0:         return static_cast<T*>(address()); 
sl@0:     }
sl@0:     const T* get() const
sl@0:     { 
sl@0:         assert(initialized_);
sl@0:         return static_cast<const T*>(address()); 
sl@0:     }
sl@0:     void reset() 
sl@0:     {
sl@0:         if (initialized_) { 
sl@0:         #if BOOST_WORKAROUND(__BORLANDC__, BOOST_TESTED_AT(0x564)) || \
sl@0:             BOOST_WORKAROUND(__IBMCPP__, BOOST_TESTED_AT(600)) \
sl@0:             /**/
sl@0:             T* t = static_cast<T*>(address());
sl@0:             t->~T();
sl@0:         #else
sl@0:             static_cast<T*>(address())->T::~T();
sl@0:         #endif
sl@0:             initialized_ = false;
sl@0:         }
sl@0:     }
sl@0:     void reset(const T& t) 
sl@0:     {
sl@0:         reset();
sl@0:         new (address()) T(t); 
sl@0:         initialized_ = true;
sl@0:     }
sl@0: private:
sl@0:     optional(const optional&);
sl@0:     optional& operator=(const optional&);
sl@0:     void* address() { return &storage_; }
sl@0:     const void* address() const { return &storage_; }
sl@0:     aligned_storage<T>  storage_;
sl@0:     bool                initialized_;
sl@0: };
sl@0: 
sl@0: } } } // End namespaces detail, iostreams, boost.
sl@0: 
sl@0: #endif // #ifndef BOOST_IOSTREAMS_DETAIL_OPTIONAL_HPP_INCLUDED