Imported existing code

libraries/include/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