move/detail/pointer_element.hpp

0001 //////////////////////////////////////////////////////////////////////////////
0002 //
0003 // (C) Copyright Ion Gaztanaga 2014-2017. Distributed under the Boost
0004 // Software License, Version 1.0. (See accompanying file
0005 // LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
0006 //
0007 // See http://www.boost.org/libs/move for documentation.
0008 //
0009 //////////////////////////////////////////////////////////////////////////////
0010
0011 #ifndef BOOST_MOVE_DETAIL_POINTER_ELEMENT_HPP
0012 #define BOOST_MOVE_DETAIL_POINTER_ELEMENT_HPP
0013
0014 #ifndef BOOST_CONFIG_HPP
0015 #  include <boost/config.hpp>
0016 #endif
0017
0018 #if defined(BOOST_HAS_PRAGMA_ONCE)
0019 #  pragma once
0020 #endif
0021
0022 #ifndef BOOST_MOVE_DETAIL_WORKAROUND_HPP
0023 #include <boost/move/detail/workaround.hpp>
0024 #endif   //BOOST_MOVE_DETAIL_WORKAROUND_HPP
0025
0026 namespace boost {
0027 namespace movelib {
0028 namespace detail{
0029
0030 //////////////////////
0031 //struct first_param
0032 //////////////////////
0033
0034 template <typename T> struct first_param
0035 {  typedef void type;   };
0036
0037 #if !defined(BOOST_NO_CXX11_VARIADIC_TEMPLATES)
0038
0039    template <template <typename, typename...> class TemplateClass, typename T, typename... Args>
0040    struct first_param< TemplateClass<T, Args...> >
0041    {
0042       typedef T type;
0043    };
0044
0045 #else //C++03 compilers
0046
0047    template < template  //0arg
0048                <class
0049                > class TemplateClass, class T
0050             >
0051    struct first_param
0052       < TemplateClass<T> >
0053    {  typedef T type;   };
0054
0055    template < template  //1arg
0056                <class,class
0057                > class TemplateClass, class T
0058             , class P0>
0059    struct first_param
0060       < TemplateClass<T, P0> >
0061    {  typedef T type;   };
0062
0063    template < template  //2arg
0064                <class,class,class
0065                > class TemplateClass, class T
0066             , class P0, class P1>
0067    struct first_param
0068       < TemplateClass<T, P0, P1> >
0069    {  typedef T type;   };
0070
0071    template < template  //3arg
0072                <class,class,class,class
0073                > class TemplateClass, class T
0074             , class P0, class P1, class P2>
0075    struct first_param
0076       < TemplateClass<T, P0, P1, P2> >
0077    {  typedef T type;   };
0078
0079    template < template  //4arg
0080                <class,class,class,class,class
0081                > class TemplateClass, class T
0082             , class P0, class P1, class P2, class P3>
0083    struct first_param
0084       < TemplateClass<T, P0, P1, P2, P3> >
0085    {  typedef T type;   };
0086
0087    template < template  //5arg
0088                <class,class,class,class,class,class
0089                > class TemplateClass, class T
0090             , class P0, class P1, class P2, class P3, class P4>
0091    struct first_param
0092       < TemplateClass<T, P0, P1, P2, P3, P4> >
0093    {  typedef T type;   };
0094
0095    template < template  //6arg
0096                <class,class,class,class,class,class,class
0097                > class TemplateClass, class T
0098             , class P0, class P1, class P2, class P3, class P4, class P5>
0099    struct first_param
0100       < TemplateClass<T, P0, P1, P2, P3, P4, P5> >
0101    {  typedef T type;   };
0102
0103    template < template  //7arg
0104                <class,class,class,class,class,class,class,class
0105                > class TemplateClass, class T
0106             , class P0, class P1, class P2, class P3, class P4, class P5, class P6>
0107    struct first_param
0108       < TemplateClass<T, P0, P1, P2, P3, P4, P5, P6> >
0109    {  typedef T type;   };
0110
0111    template < template  //8arg
0112                <class,class,class,class,class,class,class,class,class
0113                > class TemplateClass, class T
0114             , class P0, class P1, class P2, class P3, class P4, class P5, class P6, class P7>
0115    struct first_param
0116       < TemplateClass<T, P0, P1, P2, P3, P4, P5, P6, P7> >
0117    {  typedef T type;   };
0118
0119    template < template  //9arg
0120                <class,class,class,class,class,class,class,class,class,class
0121                > class TemplateClass, class T
0122             , class P0, class P1, class P2, class P3, class P4, class P5, class P6, class P7, class P8>
0123    struct first_param
0124       < TemplateClass<T, P0, P1, P2, P3, P4, P5, P6, P7, P8> >
0125    {  typedef T type;   };
0126
0127 #endif   //!defined(BOOST_NO_CXX11_VARIADIC_TEMPLATES)
0128
0129 template <typename T>
0130 struct has_internal_pointer_element
0131 {
0132    template <typename X>
0133    static char test(int, typename X::element_type*);
0134
0135    template <typename X>
0136    static int test(...);
0137
0138    static const bool value = (1 == sizeof(test<T>(0, 0)));
0139 };
0140
0141 template<class Ptr, bool = has_internal_pointer_element<Ptr>::value>
0142 struct pointer_element_impl
0143 {
0144    typedef typename Ptr::element_type type;
0145 };
0146
0147 template<class Ptr>
0148 struct pointer_element_impl<Ptr, false>
0149 {
0150    typedef typename boost::movelib::detail::first_param<Ptr>::type type;
0151 };
0152
0153 }  //namespace detail{
0154
0155 template <typename Ptr>
0156 struct pointer_element
0157 {
0158    typedef typename ::boost::movelib::detail::pointer_element_impl<Ptr>::type type;
0159 };
0160
0161 template <typename T>
0162 struct pointer_element<T*>
0163 {  typedef T type; };
0164
0165 }  //namespace movelib {
0166 }  //namespace boost {
0167
0168 #endif // defined(BOOST_MOVE_DETAIL_POINTER_ELEMENT_HPP)