ceph/src/boost/boost/spirit/home/qi/operator/optional.hpp

   1 /*=============================================================================
   2     Copyright (c) 2001-2011 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_OPTIONAL_MARCH_23_2007_1117PM)
   9 #define SPIRIT_OPTIONAL_MARCH_23_2007_1117PM
  10
  11 #if defined(_MSC_VER)
  12 #pragma once
  13 #endif
  14
  15 #include <boost/spirit/home/support/unused.hpp>
  16 #include <boost/spirit/home/qi/detail/attributes.hpp>
  17 #include <boost/spirit/home/support/has_semantic_action.hpp>
  18 #include <boost/spirit/home/support/handles_container.hpp>
  19 #include <boost/spirit/home/support/info.hpp>
  20 #include <boost/spirit/home/support/container.hpp>
  21 #include <boost/spirit/home/qi/parser.hpp>
  22 #include <boost/spirit/home/qi/meta_compiler.hpp>
  23 #include <boost/spirit/home/qi/detail/assign_to.hpp>
  24 #include <boost/optional.hpp>
  25 #include <vector>
  26
  27 namespace boost { namespace spirit
  28 {
  29     ///////////////////////////////////////////////////////////////////////////
  30     // Enablers
  31     ///////////////////////////////////////////////////////////////////////////
  32     template <>
  33     struct use_operator<qi::domain, proto::tag::negate> // enables -p
  34       : mpl::true_ {};
  35 }}
  36
  37 namespace boost { namespace spirit { namespace qi
  38 {
  39     template <typename Subject>
  40     struct optional : unary_parser<optional<Subject> >
  41     {
  42         typedef Subject subject_type;
  43
  44         template <typename Context, typename Iterator>
  45         struct attribute
  46         {
  47             // Build a boost::optional from the subject's attribute. Note
  48             // that boost::optional may return unused_type if the
  49             // subject's attribute is an unused_type.
  50             typedef typename
  51                 traits::build_optional<
  52                     typename traits::
  53                         attribute_of<Subject, Context, Iterator>::type
  54                 >::type
  55             type;
  56         };
  57
  58         optional(Subject const& subject_)
  59           : subject(subject_) {}
  60
  61         template <typename Iterator, typename Context
  62           , typename Skipper, typename Attribute>
  63         bool parse_impl(Iterator& first, Iterator const& last
  64           , Context& context, Skipper const& skipper
  65           , Attribute& attr_, mpl::false_) const
  66         {
  67             // create a local value if Attribute is not unused_type
  68             typename spirit::result_of::optional_value<Attribute>::type val =
  69                 typename spirit::result_of::optional_value<Attribute>::type();
  70
  71             if (subject.parse(first, last, context, skipper, val))
  72             {
  73                 // assign the parsed value into our attribute
  74                 spirit::traits::assign_to(val, attr_);
  75             }
  76             return true;
  77         }
  78
  79         template <typename Iterator, typename Context
  80           , typename Skipper, typename Attribute>
  81         bool parse_impl(Iterator& first, Iterator const& last
  82           , Context& context, Skipper const& skipper
  83           , Attribute& attr_, mpl::true_) const
  84         {
  85             subject.parse(first, last, context, skipper, attr_);
  86             return true;
  87         }
  88
  89         template <typename Iterator, typename Context
  90           , typename Skipper, typename Attribute>
  91         bool parse(Iterator& first, Iterator const& last
  92           , Context& context, Skipper const& skipper
  93           , Attribute& attr_) const
  94         {
  95             typedef typename spirit::result_of::optional_value<Attribute>::type
  96                 attribute_type;
  97
  98             return parse_impl(first, last, context, skipper, attr_
  99               , traits::is_container<attribute_type>());
 100         }
 101
 102         template <typename Context>
 103         info what(Context& context) const
 104         {
 105             return info("optional", subject.what(context));
 106         }
 107
 108         Subject subject;
 109     };
 110
 111     ///////////////////////////////////////////////////////////////////////////
 112     // Parser generators: make_xxx function (objects)
 113     ///////////////////////////////////////////////////////////////////////////
 114     template <typename Elements, typename Modifiers>
 115     struct make_composite<proto::tag::negate, Elements, Modifiers>
 116       : make_unary_composite<Elements, optional>
 117     {};
 118 }}}
 119
 120 namespace boost { namespace spirit { namespace traits
 121 {
 122     ///////////////////////////////////////////////////////////////////////////
 123     template <typename Subject>
 124     struct has_semantic_action<qi::optional<Subject> >
 125       : unary_has_semantic_action<Subject> {};
 126
 127     ///////////////////////////////////////////////////////////////////////////
 128     template <typename Subject, typename Attribute, typename Context
 129         , typename Iterator>
 130     struct handles_container<qi::optional<Subject>, Attribute
 131           , Context, Iterator>
 132       : mpl::true_ {};
 133 }}}
 134
 135 #endif