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Diffstat (limited to 'ext/boost/utility/value_init.hpp')
-rw-r--r-- | ext/boost/utility/value_init.hpp | 143 |
1 files changed, 143 insertions, 0 deletions
diff --git a/ext/boost/utility/value_init.hpp b/ext/boost/utility/value_init.hpp new file mode 100644 index 0000000000..aa7ecb4ee8 --- /dev/null +++ b/ext/boost/utility/value_init.hpp @@ -0,0 +1,143 @@ +// (C) Copyright 2002-2008, Fernando Luis Cacciola Carballal. +// +// 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) +// +// 21 Ago 2002 (Created) Fernando Cacciola +// 24 Dec 2007 (Refactored and worked around various compiler bugs) Fernando Cacciola, Niels Dekker +// 23 May 2008 (Fixed operator= const issue, added initialized_value) Niels Dekker, Fernando Cacciola +// 21 Ago 2008 (Added swap) Niels Dekker, Fernando Cacciola +// +#ifndef BOOST_UTILITY_VALUE_INIT_21AGO2002_HPP +#define BOOST_UTILITY_VALUE_INIT_21AGO2002_HPP + +// Note: The implementation of boost::value_initialized had to deal with the +// fact that various compilers haven't fully implemented value-initialization. +// The constructor of boost::value_initialized<T> works around these compiler +// issues, by clearing the bytes of T, before constructing the T object it +// contains. More details on these issues are at libs/utility/value_init.htm + +#include <boost/aligned_storage.hpp> +#include <boost/detail/workaround.hpp> +#include <boost/static_assert.hpp> +#include <boost/type_traits/cv_traits.hpp> +#include <boost/type_traits/alignment_of.hpp> +#include <boost/swap.hpp> +#include <cstring> +#include <new> + +namespace boost { + +template<class T> +class value_initialized +{ + private : + struct wrapper + { +#if !BOOST_WORKAROUND(__BORLANDC__, BOOST_TESTED_AT(0x592)) + typename +#endif + remove_const<T>::type data; + }; + + mutable +#if !BOOST_WORKAROUND(__BORLANDC__, BOOST_TESTED_AT(0x592)) + typename +#endif + aligned_storage<sizeof(wrapper), alignment_of<wrapper>::value>::type x; + + wrapper * wrapper_address() const + { + return static_cast<wrapper *>( static_cast<void*>(&x)); + } + + public : + + value_initialized() + { + std::memset(&x, 0, sizeof(x)); +#ifdef BOOST_MSVC +#pragma warning(push) +#if _MSC_VER >= 1310 +// When using MSVC 7.1 or higher, the following placement new expression may trigger warning C4345: +// "behavior change: an object of POD type constructed with an initializer of the form () +// will be default-initialized". It is safe to ignore this warning when using value_initialized. +#pragma warning(disable: 4345) +#endif +#endif + new (wrapper_address()) wrapper(); +#ifdef BOOST_MSVC +#pragma warning(pop) +#endif + } + + value_initialized(value_initialized const & arg) + { + new (wrapper_address()) wrapper( static_cast<wrapper const &>(*(arg.wrapper_address()))); + } + + value_initialized & operator=(value_initialized const & arg) + { + // Assignment is only allowed when T is non-const. + BOOST_STATIC_ASSERT( ! is_const<T>::value ); + *wrapper_address() = static_cast<wrapper const &>(*(arg.wrapper_address())); + return *this; + } + + ~value_initialized() + { + wrapper_address()->wrapper::~wrapper(); + } + + T& data() const + { + return wrapper_address()->data; + } + + void swap(value_initialized & arg) + { + ::boost::swap( this->data(), arg.data() ); + } + + operator T&() const { return this->data(); } + +} ; + + + +template<class T> +T const& get ( value_initialized<T> const& x ) +{ + return x.data() ; +} +template<class T> +T& get ( value_initialized<T>& x ) +{ + return x.data() ; +} + +template<class T> +void swap ( value_initialized<T> & lhs, value_initialized<T> & rhs ) +{ + lhs.swap(rhs) ; +} + + +class initialized_value_t +{ + public : + + template <class T> operator T() const + { + return get( value_initialized<T>() ); + } +}; + +initialized_value_t const initialized_value = {} ; + + +} // namespace boost + + +#endif |