1/*=============================================================================
2 Copyright (c) 2001-2014 Joel de Guzman
3
4 Distributed under the Boost Software License, Version 1.0. (See accompanying
5 file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
6=============================================================================*/
7#if !defined(BOOST_SPIRIT_X3_GUARD_FERBRUARY_02_2013_0649PM)
8#define BOOST_SPIRIT_X3_GUARD_FERBRUARY_02_2013_0649PM
9
10#include <boost/spirit/home/x3/support/context.hpp>
11#include <boost/spirit/home/x3/directive/expect.hpp>
12
13namespace boost { namespace spirit { namespace x3
14{
15 enum class error_handler_result
16 {
17 fail
18 , retry
19 , accept
20 , rethrow
21 };
22
23 template <typename Subject, typename Handler>
24 struct guard : unary_parser<Subject, guard<Subject, Handler>>
25 {
26 typedef unary_parser<Subject, guard<Subject, Handler>> base_type;
27 static bool const is_pass_through_unary = true;
28
29 constexpr guard(Subject const& subject, Handler handler)
30 : base_type(subject), handler(handler) {}
31
32 template <typename Iterator, typename Context
33 , typename RuleContext, typename Attribute>
34 bool parse(Iterator& first, Iterator const& last
35 , Context const& context, RuleContext& rcontext, Attribute& attr) const
36 {
37 for (;;)
38 {
39 try
40 {
41 Iterator i = first;
42 bool r = this->subject.parse(i, last, context, rcontext, attr);
43 if (r)
44 first = i;
45 return r;
46 }
47 catch (expectation_failure<Iterator> const& x)
48 {
49 switch (handler(first, last, x, context))
50 {
51 case error_handler_result::fail:
52 return false;
53 case error_handler_result::retry:
54 continue;
55 case error_handler_result::accept:
56 return true;
57 case error_handler_result::rethrow:
58 throw;
59 }
60 }
61 }
62 return false;
63 }
64
65 Handler handler;
66 };
67}}}
68
69#endif
70

source code of boost/libs/spirit/include/boost/spirit/home/x3/auxiliary/guard.hpp