1// Copyright (c) 2001-2011 Hartmut Kaiser
2//
3// Distributed under the Boost Software License, Version 1.0. (See accompanying
4// file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
5
6#ifndef BOOST_SPIRIT_KARMA_DIRECTIVE_OMIT_HPP
7#define BOOST_SPIRIT_KARMA_DIRECTIVE_OMIT_HPP
8
9#if defined(_MSC_VER)
10#pragma once
11#endif
12
13#include <boost/spirit/home/karma/meta_compiler.hpp>
14#include <boost/spirit/home/karma/generator.hpp>
15#include <boost/spirit/home/karma/domain.hpp>
16#include <boost/spirit/home/support/unused.hpp>
17#include <boost/spirit/home/support/info.hpp>
18#include <boost/spirit/home/support/common_terminals.hpp>
19#include <boost/spirit/home/support/has_semantic_action.hpp>
20#include <boost/spirit/home/support/handles_container.hpp>
21#include <boost/spirit/home/karma/detail/attributes.hpp>
22#include <boost/spirit/home/karma/detail/output_iterator.hpp>
23
24namespace boost { namespace spirit
25{
26 ///////////////////////////////////////////////////////////////////////////
27 // Enablers
28 ///////////////////////////////////////////////////////////////////////////
29 template <>
30 struct use_directive<karma::domain, tag::omit> // enables omit
31 : mpl::true_ {};
32
33 template <>
34 struct use_directive<karma::domain, tag::skip> // enables skip
35 : mpl::true_ {};
36}}
37
38namespace boost { namespace spirit { namespace karma
39{
40#ifndef BOOST_SPIRIT_NO_PREDEFINED_TERMINALS
41 using spirit::omit;
42 using spirit::skip;
43#endif
44 using spirit::omit_type;
45 using spirit::skip_type;
46
47 ///////////////////////////////////////////////////////////////////////////
48 // omit_directive consumes the attribute of subject generator without
49 // generating anything
50 ///////////////////////////////////////////////////////////////////////////
51 template <typename Subject, bool Execute>
52 struct omit_directive : unary_generator<omit_directive<Subject, Execute> >
53 {
54 typedef Subject subject_type;
55
56 typedef mpl::int_<
57 generator_properties::disabling | subject_type::properties::value
58 > properties;
59
60 omit_directive(Subject const& subject)
61 : subject(subject) {}
62
63 template <typename Context, typename Iterator = unused_type>
64 struct attribute
65 : traits::attribute_of<subject_type, Context, Iterator>
66 {};
67
68 template <typename OutputIterator, typename Context, typename Delimiter
69 , typename Attribute>
70 bool generate(OutputIterator& sink, Context& ctx, Delimiter const& d
71 , Attribute const& attr) const
72 {
73 // We need to actually compile the output operation as we don't
74 // have any other means to verify, whether the passed attribute is
75 // compatible with the subject.
76
77#if defined(_MSC_VER) && _MSC_VER < 1900
78# pragma warning(push)
79# pragma warning(disable: 4127) // conditional expression is constant
80#endif
81 // omit[] will execute the code, while skip[] doesn't execute it
82 if (Execute) {
83#if defined(_MSC_VER) && _MSC_VER < 1900
84# pragma warning(pop)
85#endif
86 // wrap the given output iterator to avoid output
87 detail::disable_output<OutputIterator> disable(sink);
88 return subject.generate(sink, ctx, d, attr);
89 }
90 return true;
91 }
92
93 template <typename Context>
94 info what(Context& context) const
95 {
96 return info(Execute ? "omit" : "skip", subject.what(context));
97 }
98
99 Subject subject;
100 };
101
102 ///////////////////////////////////////////////////////////////////////////
103 // Generator generators: make_xxx function (objects)
104 ///////////////////////////////////////////////////////////////////////////
105 template <typename Subject, typename Modifiers>
106 struct make_directive<tag::omit, Subject, Modifiers>
107 {
108 typedef omit_directive<Subject, true> result_type;
109 result_type operator()(unused_type, Subject const& subject
110 , unused_type) const
111 {
112 return result_type(subject);
113 }
114 };
115
116 template <typename Subject, typename Modifiers>
117 struct make_directive<tag::skip, Subject, Modifiers>
118 {
119 typedef omit_directive<Subject, false> result_type;
120 result_type operator()(unused_type, Subject const& subject
121 , unused_type) const
122 {
123 return result_type(subject);
124 }
125 };
126}}}
127
128namespace boost { namespace spirit { namespace traits
129{
130 ///////////////////////////////////////////////////////////////////////////
131 template <typename Subject, bool Execute>
132 struct has_semantic_action<karma::omit_directive<Subject, Execute> >
133 : unary_has_semantic_action<Subject> {};
134
135 ///////////////////////////////////////////////////////////////////////////
136 template <typename Subject, bool Execute, typename Attribute
137 , typename Context, typename Iterator>
138 struct handles_container<karma::omit_directive<Subject, Execute>, Attribute
139 , Context, Iterator>
140 : unary_handles_container<Subject, Attribute, Context, Iterator> {};
141}}}
142
143#endif
144

source code of boost/libs/spirit/include/boost/spirit/home/karma/directive/omit.hpp