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:
unique()38             unique() {}
unique(T &)39             explicit unique(T&) {}
40 
swap(unique &)41             void swap(unique&) {}
42 
43         public:
44             template <typename MultiPass>
destroy(MultiPass &)45             static void destroy(MultiPass&) {}
46 
47             template <typename MultiPass>
get_input(MultiPass & mp)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>
advance_input(MultiPass & mp)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>
input_at_eof(MultiPass const & mp)68             static bool input_at_eof(MultiPass const& mp)
69             {
70                 return mp.shared()->eof_reached_;
71             }
72 
73             template <typename MultiPass>
input_is_valid(MultiPass const & mp,value_type const &)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:
sharedboost::spirit::iterator_policies::istream::shared90             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 
read_oneboost::spirit::iterator_policies::istream::shared97             void read_one()
98             {
99                 if (!(input_ >> curtok_)) {
100                     initialized_ = false;
101                     eof_reached_ = true;
102                 }
103                 else {
104                     initialized_ = true;
105                 }
106             }
107 
peek_oneboost::spirit::iterator_policies::istream::shared108             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
125