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330 lines
11 KiB
330 lines
11 KiB
/* /////////////////////////////////////////////////////////////////////////
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* File: stlsoft/conversion/union_cast.hpp (originally MLTypCnv.h, ::SynesisStd)
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*
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* Purpose: A powerful cast operator that limits the danger of
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* reinterpret_cast, while avoiding the spurious warnings issued by
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* some compilers.
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*
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* Created: 2nd May 1997
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* Updated: 10th August 2009
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*
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* Home: http://stlsoft.org/
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*
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* Copyright (c) 1997-2009, Matthew Wilson and Synesis Software
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* All rights reserved.
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions are met:
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*
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* - Redistributions of source code must retain the above copyright notice, this
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* list of conditions and the following disclaimer.
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* - Redistributions in binary form must reproduce the above copyright notice,
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* this list of conditions and the following disclaimer in the documentation
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* and/or other materials provided with the distribution.
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* - Neither the name(s) of Matthew Wilson and Synesis Software nor the names of
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* any contributors may be used to endorse or promote products derived from
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* this software without specific prior written permission.
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*
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* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
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* AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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* ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE
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* LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
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* CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
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* SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
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* INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
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* CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
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* ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
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* POSSIBILITY OF SUCH DAMAGE.
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*
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* ////////////////////////////////////////////////////////////////////// */
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/** \file stlsoft/conversion/union_cast.hpp
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*
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* \brief [C++ only] Definition of the stlsoft::union_cast cast
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* (\ref group__library__conversion "Conversion" Library).
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*/
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#ifndef STLSOFT_INCL_STLSOFT_CONVERSION_HPP_UNION_CAST
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#define STLSOFT_INCL_STLSOFT_CONVERSION_HPP_UNION_CAST
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#ifndef STLSOFT_DOCUMENTATION_SKIP_SECTION
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# define STLSOFT_VER_STLSOFT_CONVERSION_HPP_UNION_CAST_MAJOR 5
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# define STLSOFT_VER_STLSOFT_CONVERSION_HPP_UNION_CAST_MINOR 0
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# define STLSOFT_VER_STLSOFT_CONVERSION_HPP_UNION_CAST_REVISION 3
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# define STLSOFT_VER_STLSOFT_CONVERSION_HPP_UNION_CAST_EDIT 64
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#endif /* !STLSOFT_DOCUMENTATION_SKIP_SECTION */
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/* /////////////////////////////////////////////////////////////////////////
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* Includes
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*/
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#ifndef STLSOFT_INCL_STLSOFT_H_STLSOFT
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# include <stlsoft/stlsoft.h>
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#endif /* !STLSOFT_INCL_STLSOFT_H_STLSOFT */
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#ifndef STLSOFT_INCL_STLSOFT_UTIL_HPP_CONSTRAINTS
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# include <stlsoft/util/constraints.hpp>
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#endif /* !STLSOFT_INCL_STLSOFT_UTIL_HPP_CONSTRAINTS */
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#if defined(STLSOFT_CF_TEMPLATE_PARTIAL_SPECIALISATION_SUPPORT)
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# ifndef STLSOFT_INCL_STLSOFT_META_HPP_BASE_TYPE_TRAITS
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# include <stlsoft/meta/base_type_traits.hpp>
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# endif /* !STLSOFT_INCL_STLSOFT_META_HPP_BASE_TYPE_TRAITS */
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#endif /* STLSOFT_CF_TEMPLATE_PARTIAL_SPECIALISATION_SUPPORT */
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/* /////////////////////////////////////////////////////////////////////////
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* Namespace
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*/
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#ifndef _STLSOFT_NO_NAMESPACE
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namespace stlsoft
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{
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#endif /* _STLSOFT_NO_NAMESPACE */
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/* /////////////////////////////////////////////////////////////////////////
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* Classes
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*/
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/** \brief Cast class used by the \link stlsoft::union_cast union_cast\endlink
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* cast function.
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*
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* \ingroup group__library__conversion
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*
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* This class (union) effects conversion from one type to another, without
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* the use of casts.
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*
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* \param TO The type to cast to
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* \param FROM The type to cast from
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* \param B_CHECK_ALIGN Determines the default checking behaviour. If 0, no checking on alignment is conducted
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*
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* \note This technique is non-portable, and you use this class at your own
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* risk. Notwithstanding that, the TO and FROM types have to be the same
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* size, so the technique is widely usable.
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*/
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template< ss_typename_param_k TO
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, ss_typename_param_k FROM
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#if defined(STLSOFT_COMPILER_IS_GCC) && \
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__GNUC__ < 3
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, ss_bool_t B_CHECK_ALIGN /* = true */
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#else /* ? compiler */
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, ss_bool_t B_CHECK_ALIGN = true
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#endif /* compiler */
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>
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union union_caster
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{
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/// \name Member Types
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/// @{
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public:
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/// \brief The type to cast to.
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typedef TO to_type;
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/// \brief The type to cast from.
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typedef FROM from_type;
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/// \brief The current instantiation of the type.
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typedef union_caster<TO, FROM, B_CHECK_ALIGN> class_type;
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/// @}
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/// \name Construction
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/// @{
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public:
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/// \brief Conversion constructor
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ss_explicit_k union_caster(from_type const from, ss_bool_t bCheckAlign = B_CHECK_ALIGN)
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: m_from(from)
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{
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// The body of the constructor constrains the type conversion according
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// to the following:
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//
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// (i) Sizes must be the same
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// (ii) Both must be of POD type
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// (iii) There must be either a change of const/volatile, or a change
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// of type, but not both.
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// (iv) Both must be non-pointers, or must point to POD types
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#if !defined(STLSOFT_COMPILER_IS_DMC) || \
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__DMC__ >= 0x0833
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// (i) Sizes must be the same
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STLSOFT_STATIC_ASSERT(sizeof(from_type) == sizeof(to_type));
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// (ii) Both must be of POD type
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stlsoft_constraint_must_be_pod(from_type);
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stlsoft_constraint_must_be_pod(to_type);
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# if defined(STLSOFT_CF_TEMPLATE_PARTIAL_SPECIALISATION_SUPPORT)
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// (iii) There must be either a change of const/volatile,
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/// or a change of type, but not both.
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// STLSOFT_STATIC_ASSERT( (1 == is_same_type<from_type, to_type>::value) ||
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// ( base_type_traits<from_type>::is_const == base_type_traits<to_type>::is_const &&
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// base_type_traits<from_type>::is_volatile == base_type_traits<to_type>::is_volatile));
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// (iv) Both must be non-pointers, or must point to POD types
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typedef ss_typename_type_k base_type_traits<from_type>::base_type from_base_type;
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typedef ss_typename_type_k base_type_traits<to_type>::base_type to_base_type;
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stlsoft_constraint_must_be_pod_or_void(from_base_type);
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stlsoft_constraint_must_be_pod_or_void(to_base_type);
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if( !base_type_traits<from_type>::is_pointer &&
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base_type_traits<to_type>::is_pointer &&
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0 != from)
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{
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ss_size_t to_size = size_of<to_base_type>::value;
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union U
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{
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ss_size_t size_;
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from_type from_;
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# if !defined(STLSOFT_COMPILER_IS_MSVC) || \
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_MSC_VER < 1310
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inline U(from_type from)
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: from_(from)
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{}
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} u_(from); // Can't be anonymous, otherwise GCC has an ICE!
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# else /* ? compiler */
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} u_;
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u_.from_ = from;
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# endif /* compiler */
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ss_size_t from_value = u_.size_;
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STLSOFT_SUPPRESS_UNUSED(to_size);
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STLSOFT_SUPPRESS_UNUSED(from_value);
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// Need to add to_size, since Metrowerks warns of constant division by zero
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STLSOFT_MESSAGE_ASSERT( "Misalignment in conversion from non-pointer to pointer", (!bCheckAlign || (0 == to_size) || (0 == ((from_value + to_size) % to_size))));
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}
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# endif /* STLSOFT_CF_TEMPLATE_PARTIAL_SPECIALISATION_SUPPORT */
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#else /* ? compiler */
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// Sizes must be the same
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STLSOFT_ASSERT(sizeof(from_type) == sizeof(to_type));
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#endif /* compiler */
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STLSOFT_SUPPRESS_UNUSED(bCheckAlign);
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}
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/// @}
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/// \name Conversion
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/// @{
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public:
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/// Implicit conversion operator
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operator to_type () const
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{
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return m_to;
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}
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/// @}
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/// \name Members
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/// @{
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private:
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from_type const m_from;
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to_type m_to;
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/// @}
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/// \name Not to be implemented
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/// @{
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private:
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class_type& operator =(class_type const&);
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/// @}
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};
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/* /////////////////////////////////////////////////////////////////////////
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* Shims
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*/
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#if !defined(STLSOFT_COMPILER_IS_WATCOM)
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/** \brief A powerful cast operator that limits the danger of
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* reinterpret_cast, while avoiding the spurious warnings issued by some
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* compilers.
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*
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* \ingroup group__library__conversion
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*
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* A union cast would be applied as follows:
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*
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\code
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// This assumes sizeof(int) == sizeof(short*)
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short *ps;
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int i = stlsoft::union_cast<int>(ps); // Ok: same size
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double d = stlsoft::union_cast<double>(ps); // Compile error: different size
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\endcode
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*/
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template< ss_typename_param_k TO
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, ss_typename_param_k FROM
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>
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inline union_caster<TO, FROM, true> union_cast(FROM const from, ss_bool_t bCheckAlign = true)
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{
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return union_caster<TO, FROM, true>(from, bCheckAlign);
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}
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/** \brief [DEPRECATED] Synonym for stlsoft::union_cast().
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*
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* \ingroup group__library__conversion
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*
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* \deprecated This function is now deprecated in favour of the new function
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* \link stlsoft::union_cast union_cast\endlink.
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*/
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template< ss_typename_param_k TO
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, ss_typename_param_k FROM
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>
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inline union_caster<TO, FROM, true> make_union_cast(FROM const from, ss_bool_t bCheckAlign = true)
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{
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return union_caster<TO, FROM, true>(from, bCheckAlign);
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}
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#endif /* compiler */
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/* /////////////////////////////////////////////////////////////////////////
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* Operators
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*/
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#ifndef STLSOFT_DOCUMENTATION_SKIP_SECTION
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template< ss_typename_param_k TO
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, ss_typename_param_k FROM
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, ss_bool_t B_CHECK_ALIGN
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>
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inline ss_bool_t operator < (union_caster<TO, FROM, B_CHECK_ALIGN> const& lhs, TO const& rhs)
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{
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TO const lhs_ = lhs;
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return lhs_ < rhs;
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}
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template< ss_typename_param_k TO
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, ss_typename_param_k FROM
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, ss_bool_t B_CHECK_ALIGN
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>
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inline ss_bool_t operator < (TO const& lhs, union_caster<TO, FROM, B_CHECK_ALIGN> const& rhs)
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{
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TO const rhs_ = rhs;
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return lhs < rhs_;
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}
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template< ss_typename_param_k TO
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, ss_typename_param_k FROM
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, ss_bool_t B_CHECK_ALIGN
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>
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inline ss_bool_t operator < (union_caster<TO, FROM, B_CHECK_ALIGN> const& lhs, union_caster<TO, FROM, B_CHECK_ALIGN> const& rhs)
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{
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TO const lhs_ = lhs;
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TO const rhs_ = rhs;
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return lhs_ < rhs_;
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}
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#endif /* !STLSOFT_DOCUMENTATION_SKIP_SECTION */
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////////////////////////////////////////////////////////////////////////////
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// Unit-testing
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#ifdef STLSOFT_UNITTEST
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# include "./unittest/union_cast_unittest_.h"
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#endif /* STLSOFT_UNITTEST */
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/* ////////////////////////////////////////////////////////////////////// */
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#ifndef _STLSOFT_NO_NAMESPACE
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} // namespace stlsoft
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#endif /* _STLSOFT_NO_NAMESPACE */
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/* ////////////////////////////////////////////////////////////////////// */
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#endif /* !STLSOFT_INCL_STLSOFT_CONVERSION_HPP_UNION_CAST */
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/* ///////////////////////////// end of file //////////////////////////// */
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