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1/*=============================================================================
2 Copyright (c) 2002-2003 Joel de Guzman
3 Copyright (c) 2002-2003 Martin Wille
4 http://spirit.sourceforge.net/
5
6 Distributed under the Boost Software License, Version 1.0. (See accompanying
7 file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
8=============================================================================*/
9#ifndef BOOST_SPIRIT_WHILE_HPP
10#define BOOST_SPIRIT_WHILE_HPP
11
12#include <boost/spirit/home/classic/namespace.hpp>
13#include <boost/spirit/home/classic/core/parser.hpp>
14#include <boost/spirit/home/classic/core/composite/composite.hpp>
15#include <boost/spirit/home/classic/dynamic/impl/conditions.ipp>
16
17////////////////////////////////////////////////////////////////////////////////
18namespace boost { namespace spirit {
19
20BOOST_SPIRIT_CLASSIC_NAMESPACE_BEGIN
21
22 namespace impl {
23
24 //////////////////////////////////
25 // while parser
26 // object are created by while_parser_gen and do_parser_gen
27 template <typename ParsableT, typename CondT, bool is_do_parser>
28 struct while_parser
29 : public condition_evaluator< typename as_parser<CondT>::type >
30 , public unary // the parent stores a copy of the body parser
31 <
32 typename as_parser<ParsableT>::type,
33 parser<while_parser<ParsableT, CondT, is_do_parser> >
34 >
35 {
36 typedef while_parser<ParsableT, CondT, is_do_parser> self_t;
37
38 typedef as_parser<ParsableT> as_parser_t;
39 typedef typename as_parser_t::type parser_t;
40 typedef as_parser<CondT> cond_as_parser_t;
41 typedef typename cond_as_parser_t::type condition_t;
42
43 typedef unary<parser_t, parser<self_t> > base_t;
44 typedef condition_evaluator<condition_t> eval_t;
45
46
47 //////////////////////////////
48 // constructor, saves condition and body parser
49 while_parser(ParsableT const &body, CondT const &cond)
50 : eval_t(cond_as_parser_t::convert(cond))
51 , base_t(as_parser_t::convert(body))
52 {}
53
54 //////////////////////////////
55 // result type computer.
56 template <typename ScannerT>
57 struct result
58 {
59 typedef typename match_result
60 <ScannerT, nil_t>::type type;
61 };
62
63 //////////////////////////////
64 // parse member function
65 template <typename ScannerT>
66 typename parser_result<self_t, ScannerT>::type
67 parse(ScannerT const& scan) const
68 {
69 typedef typename parser_result<parser_t, ScannerT>::type sresult_t;
70 typedef typename ScannerT::iterator_t iterator_t;
71
72 iterator_t save(scan.first);
73 std::size_t length = 0;
74 int eval_length = 0;
75
76 bool dont_check_condition = is_do_parser;
77
78 while (dont_check_condition || (eval_length=this->evaluate(scan))>=0)
79 {
80 dont_check_condition = false;
81 length += eval_length;
82 sresult_t tmp(this->subject().parse(scan));
83 if (tmp)
84 {
85 length+=tmp.length();
86 }
87 else
88 {
89 return scan.no_match();
90 }
91 }
92 return scan.create_match(length, nil_t(), save, scan.first);
93 }
94 };
95
96 //////////////////////////////////
97 // while-parser generator, takes the body-parser in brackets
98 // and returns the actual while-parser.
99 template <typename CondT>
100 struct while_parser_gen
101 {
102 //////////////////////////////
103 // constructor, saves the condition for use by operator[]
104 while_parser_gen(CondT const& cond_) : cond(cond_) {}
105
106 //////////////////////////////
107 // operator[] returns the actual while-parser object
108 template <typename ParsableT>
109 while_parser<ParsableT, CondT, false>
110 operator[](ParsableT const &subject) const
111 {
112 return while_parser<ParsableT, CondT, false>(subject, cond);
113 }
114 private:
115
116 //////////////////////////////
117 // the condition is stored by reference here.
118 // this should not cause any harm since object of type
119 // while_parser_gen<> are only used as temporaries
120 // the while-parser object constructed by the operator[]
121 // stores a copy of the condition.
122 CondT const &cond;
123 };
124
125 //////////////////////////////////
126 // do-while-parser generator, takes the condition as
127 // parameter to while_p member function and returns the
128 // actual do-while-parser.
129 template <typename ParsableT>
130 struct do_while_parser_gen
131 {
132 //////////////////////////////
133 // constructor. saves the body parser for use by while_p.
134 explicit do_while_parser_gen(ParsableT const &body_parser)
135 : body(body_parser)
136 {}
137
138 //////////////////////////////
139 // while_p returns the actual while-parser object
140 template <typename CondT>
141 while_parser<ParsableT, CondT, true>
142 while_p(CondT cond) const
143 {
144 return while_parser<ParsableT, CondT, true>(body, cond);
145 }
146 private:
147
148 //////////////////////////////
149 // the body is stored by reference here
150 // this should not cause any harm since object of type
151 // do_while_parser_gen<> are only used as temporaries
152 // the while-parser object constructed by the while_p
153 // member function stores a copy of the body parser.
154 ParsableT const &body;
155 };
156
157 struct do_parser_gen
158 {
159 inline do_parser_gen() {}
160
161 template <typename ParsableT>
162 impl::do_while_parser_gen<ParsableT>
163 operator[](ParsableT const& body) const
164 {
165 return impl::do_while_parser_gen<ParsableT>(body);
166 }
167 };
168} // namespace impl
169
170//////////////////////////////////
171// while_p function, while-parser generator
172// Usage: spirit::while_p(Condition)[Body]
173template <typename CondT>
174impl::while_parser_gen<CondT>
175while_p(CondT const& cond)
176{
177 return impl::while_parser_gen<CondT>(cond);
178}
179
180//////////////////////////////////
181// do_p functor, do-while-parser generator
182// Usage: spirit::do_p[Body].while_p(Condition)
183impl::do_parser_gen const do_p = impl::do_parser_gen();
184
185BOOST_SPIRIT_CLASSIC_NAMESPACE_END
186
187}} // namespace BOOST_SPIRIT_CLASSIC_NS
188
189#endif // BOOST_SPIRIT_WHILE_HPP