ceph/src/boost/libs/spirit/include/boost/spirit/home/x3/nonterminal/detail/transform_attribute.hpp

   1 /*=============================================================================
   2     Copyright (c) 2001-2014 Joel de Guzman
   3     Copyright (c) 2001-2011 Hartmut Kaiser
   4
   5     Distributed under the Boost Software License, Version 1.0. (See accompanying
   6     file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
   7 =============================================================================*/
   8 #if !defined(SPIRIT_X3_DETAIL_ATTRIBUTES_APR_18_2010_0458PM)
   9 #define SPIRIT_X3_DETAIL_ATTRIBUTES_APR_18_2010_0458PM
  10
  11 #include <boost/spirit/home/x3/support/traits/transform_attribute.hpp>
  12 #include <boost/spirit/home/x3/support/traits/move_to.hpp>
  13 #include <utility>
  14
  15 ///////////////////////////////////////////////////////////////////////////////
  16 namespace boost { namespace spirit { namespace x3
  17 {
  18     struct parser_id;
  19
  20     template <typename Exposed, typename Transformed>
  21     struct default_transform_attribute
  22     {
  23         typedef Transformed type;
  24
  25         static Transformed pre(Exposed&) { return Transformed(); }
  26
  27         static void post(Exposed& val, Transformed&& attr)
  28         {
  29             traits::move_to(std::forward<Transformed>(attr), val);
  30         }
  31     };
  32
  33     // handle case where no transformation is required as the types are the same
  34     template <typename Attribute>
  35     struct default_transform_attribute<Attribute, Attribute>
  36     {
  37         typedef Attribute& type;
  38         static Attribute& pre(Attribute& val) { return val; }
  39         static void post(Attribute&, Attribute const&) {}
  40     };
  41
  42     // main specialization for x3
  43     template <typename Exposed, typename Transformed, typename Enable = void>
  44     struct transform_attribute
  45       : default_transform_attribute<Exposed, Transformed> {};
  46
  47     // reference types need special handling
  48     template <typename Attribute>
  49     struct transform_attribute<Attribute&, Attribute>
  50     {
  51         typedef Attribute& type;
  52         static Attribute& pre(Attribute& val) { return val; }
  53         static void post(Attribute&, Attribute const&) {}
  54     };
  55
  56     // unused_type needs some special handling as well
  57     template <>
  58     struct transform_attribute<unused_type, unused_type>
  59     {
  60         typedef unused_type type;
  61         static unused_type pre(unused_type) { return unused; }
  62         static void post(unused_type, unused_type) {}
  63     };
  64
  65     template <>
  66     struct transform_attribute<unused_type const, unused_type>
  67       : transform_attribute<unused_type, unused_type> {};
  68
  69     template <typename Attribute>
  70     struct transform_attribute<unused_type, Attribute>
  71       : transform_attribute<unused_type, unused_type> {};
  72
  73     template <typename Attribute>
  74     struct transform_attribute<unused_type const, Attribute>
  75       : transform_attribute<unused_type, unused_type> {};
  76
  77     template <typename Attribute>
  78     struct transform_attribute<Attribute, unused_type>
  79       : transform_attribute<unused_type, unused_type> {};
  80
  81     template <typename Attribute>
  82     struct transform_attribute<Attribute const, unused_type>
  83       : transform_attribute<unused_type, unused_type> {};
  84 }}}
  85
  86 ///////////////////////////////////////////////////////////////////////////////
  87 namespace boost { namespace spirit { namespace x3 { namespace traits
  88 {
  89     template <typename Exposed, typename Transformed>
  90     struct transform_attribute<Exposed, Transformed, x3::parser_id>
  91       : x3::transform_attribute<Exposed, Transformed> {};
  92
  93     template <typename Exposed, typename Transformed>
  94     struct transform_attribute<Exposed&, Transformed, x3::parser_id>
  95       : transform_attribute<Exposed, Transformed, x3::parser_id> {};
  96
  97     template <typename Attribute>
  98     struct transform_attribute<Attribute&, Attribute, x3::parser_id>
  99       : x3::transform_attribute<Attribute&, Attribute> {};
 100
 101     ///////////////////////////////////////////////////////////////////////////
 102     template <typename Exposed, typename Transformed>
 103     void post_transform(Exposed& dest, Transformed&& attr)
 104     {
 105         return transform_attribute<Exposed, Transformed, x3::parser_id>
 106             ::post(dest, std::forward<Transformed>(attr));
 107     }
 108 }}}}
 109
 110 #endif