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1 | // Copyright (c) 2001 Daniel C. Nuffer |
2 | // Copyright (c) 2001-2011 Hartmut Kaiser | |
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_ISTREAM_POLICY_JAN_04_2010_0130PM) | |
8 | #define BOOST_SPIRIT_ISTREAM_POLICY_JAN_04_2010_0130PM | |
9 | ||
10 | #include <boost/spirit/home/support/iterators/multi_pass_fwd.hpp> | |
11 | #include <boost/spirit/home/support/iterators/detail/multi_pass.hpp> | |
12 | ||
13 | namespace boost { namespace spirit { namespace iterator_policies | |
14 | { | |
15 | /////////////////////////////////////////////////////////////////////////// | |
16 | // class istream | |
17 | // Implementation of the InputPolicy used by multi_pass | |
18 | // | |
19 | // The istream encapsulates an std::basic_istream | |
20 | /////////////////////////////////////////////////////////////////////////// | |
21 | struct istream | |
22 | { | |
23 | /////////////////////////////////////////////////////////////////////// | |
24 | template <typename T> | |
25 | class unique // : public detail::default_input_policy | |
26 | { | |
27 | private: | |
28 | typedef typename T::char_type result_type; | |
29 | ||
30 | public: | |
31 | typedef typename T::off_type difference_type; | |
32 | typedef typename T::off_type distance_type; | |
33 | typedef result_type const* pointer; | |
34 | typedef result_type const& reference; | |
35 | typedef result_type value_type; | |
36 | ||
37 | protected: | |
38 | unique() {} | |
39 | explicit unique(T&) {} | |
40 | ||
41 | void swap(unique&) {} | |
42 | ||
43 | public: | |
44 | template <typename MultiPass> | |
45 | static void destroy(MultiPass&) {} | |
46 | ||
47 | template <typename MultiPass> | |
48 | static typename MultiPass::reference get_input(MultiPass& mp) | |
49 | { | |
50 | if (!mp.shared()->initialized_) | |
51 | mp.shared()->read_one(); | |
52 | return mp.shared()->curtok_; | |
53 | } | |
54 | ||
55 | template <typename MultiPass> | |
56 | static void advance_input(MultiPass& mp) | |
57 | { | |
58 | // We invalidate the currently cached input character to avoid | |
59 | // reading more input from the underlying iterator than | |
60 | // required. Without this we would always read ahead one | |
61 | // character, even if this character never gets consumed by the | |
62 | // client. | |
63 | mp.shared()->peek_one(); | |
64 | } | |
65 | ||
66 | // test, whether we reached the end of the underlying stream | |
67 | template <typename MultiPass> | |
68 | static bool input_at_eof(MultiPass const& mp) | |
69 | { | |
70 | return mp.shared()->eof_reached_; | |
71 | } | |
72 | ||
73 | template <typename MultiPass> | |
74 | static bool input_is_valid(MultiPass const& mp, value_type const&) | |
75 | { | |
76 | return mp.shared()->initialized_; | |
77 | } | |
78 | ||
79 | // no unique data elements | |
80 | }; | |
81 | ||
82 | /////////////////////////////////////////////////////////////////////// | |
83 | template <typename T> | |
84 | struct shared | |
85 | { | |
86 | private: | |
87 | typedef typename T::char_type result_type; | |
88 | ||
89 | public: | |
90 | explicit shared(T& input) | |
91 | : input_(input), curtok_(-1) | |
92 | , initialized_(false), eof_reached_(false) | |
93 | { | |
94 | peek_one(); // istreams may be at eof right in the beginning | |
95 | } | |
96 | ||
97 | void read_one() | |
98 | { | |
99 | if (!(input_ >> curtok_)) { | |
100 | initialized_ = false; | |
101 | eof_reached_ = true; | |
102 | } | |
103 | else { | |
104 | initialized_ = true; | |
105 | } | |
106 | } | |
107 | ||
108 | void peek_one() | |
109 | { | |
110 | input_.peek(); // try for eof | |
111 | initialized_ = false; | |
112 | eof_reached_ = input_.eof(); | |
113 | } | |
114 | ||
115 | T& input_; | |
116 | result_type curtok_; | |
117 | bool initialized_; | |
118 | bool eof_reached_; | |
119 | }; | |
120 | }; | |
121 | ||
122 | }}} | |
123 | ||
124 | #endif |