ceph/src/boost/boost/range/detail/default_constructible_unary_fn.hpp

   1 // Boost.Range library
   2 //
   3 //  Copyright Neil Groves 2014. Use, modification and
   4 //  distribution is subject to the Boost Software License, Version
   5 //  1.0. (See accompanying file LICENSE_1_0.txt or copy at
   6 //  http://www.boost.org/LICENSE_1_0.txt)
   7 //
   8 // For more information, see http://www.boost.org/libs/range/
   9 //
  10 #ifndef BOOST_RANGE_DETAIL_DEFAULT_CONSTRUCTIBLE_UNARY_FN_HPP_INCLUDED
  11 #define BOOST_RANGE_DETAIL_DEFAULT_CONSTRUCTIBLE_UNARY_FN_HPP_INCLUDED
  12
  13 #include <boost/optional/optional.hpp>
  14 #include <boost/mpl/if.hpp>
  15 #include <boost/type_traits/has_trivial_constructor.hpp>
  16
  17 namespace boost
  18 {
  19     namespace range_detail
  20     {
  21
  22 template<typename F, typename R>
  23 class default_constructible_unary_fn_wrapper
  24 {
  25 public:
  26     typedef R result_type;
  27
  28     default_constructible_unary_fn_wrapper()
  29     {
  30     }
  31     default_constructible_unary_fn_wrapper(const F& source)
  32         : m_impl(source)
  33     {
  34     }
  35     default_constructible_unary_fn_wrapper(const default_constructible_unary_fn_wrapper& source)
  36         : m_impl(source.m_impl)
  37     {
  38     }
  39     default_constructible_unary_fn_wrapper& operator=(const default_constructible_unary_fn_wrapper& source)
  40     {
  41         if (source.m_impl)
  42         {
  43             // Lambda are not copy/move assignable.
  44             m_impl.emplace(*source.m_impl);
  45         }
  46         else
  47         {
  48             m_impl.reset();
  49         }
  50         return *this;
  51     }
  52     template<typename Arg>
  53     R operator()(const Arg& arg) const
  54     {
  55         BOOST_ASSERT(m_impl);
  56         return (*m_impl)(arg);
  57     }
  58     template<typename Arg>
  59     R operator()(Arg& arg) const
  60     {
  61         BOOST_ASSERT(m_impl);
  62         return (*m_impl)(arg);
  63     }
  64 private:
  65     boost::optional<F> m_impl;
  66 };
  67
  68 template<typename F, typename R>
  69 struct default_constructible_unary_fn_gen
  70 {
  71     typedef typename boost::mpl::if_<
  72         boost::has_trivial_default_constructor<F>,
  73         F,
  74         default_constructible_unary_fn_wrapper<F,R>
  75     >::type type;
  76 };
  77
  78     } // namespace range_detail
  79 } // namespace boost
  80
  81 #endif // include guard