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_ITERATOR_FIXED_SIZE_QUEUE_POLICY_MAR_16_2007_1134AM)
8#define BOOST_SPIRIT_ITERATOR_FIXED_SIZE_QUEUE_POLICY_MAR_16_2007_1134AM
9
10#include <boost/spirit/home/support/iterators/detail/multi_pass.hpp>
11#include <boost/spirit/home/support/iterators/detail/fixed_size_queue.hpp>
12#include <boost/core/invoke_swap.hpp>
13#include <boost/assert.hpp>
14#include <cstdlib>
15
16namespace boost { namespace spirit { namespace iterator_policies
17{
18 ///////////////////////////////////////////////////////////////////////////
19 // class fixed_size_queue
20 // Implementation of the StoragePolicy used by multi_pass
21 // fixed_size_queue keeps a circular buffer (implemented by
22 // boost::spirit::fixed_size_queue class) that is size N+1 and stores N
23 // elements.
24 //
25 // It is up to the user to ensure that there is enough look ahead for
26 // their grammar. Currently there is no way to tell if an iterator is
27 // pointing to forgotten data. The leading iterator will put an item in
28 // the queue and remove one when it is incremented. No dynamic allocation
29 // is done, except on creation of the queue (fixed_size_queue constructor).
30 ///////////////////////////////////////////////////////////////////////////
31 template <std::size_t N>
32 struct fixed_size_queue
33 {
34 ///////////////////////////////////////////////////////////////////////
35 template <typename Value>
36 class unique : public detail::default_storage_policy
37 {
38 private:
39 typedef detail::fixed_size_queue<Value, N> queue_type;
40
41 protected:
42 unique() {}
43
44 unique(unique const& x)
45 : queued_position(x.queued_position) {}
46
47 void swap(unique& x)
48 {
49 boost::core::invoke_swap(queued_position, x.queued_position);
50 }
51
52 // This is called when the iterator is dereferenced. It's a
53 // template method so we can recover the type of the multi_pass
54 // iterator and access the m_input data member.
55 template <typename MultiPass>
56 static typename MultiPass::reference
57 dereference(MultiPass const& mp)
58 {
59 if (!mp.queued_position.get_position().is_initialized())
60 mp.queued_position.get_position().set_queue(&mp.shared()->queued_elements);
61
62 if (mp.queued_position == mp.shared()->queued_elements.end())
63 return MultiPass::get_input(mp);
64
65 return *mp.queued_position;
66 }
67
68 // This is called when the iterator is incremented. It's a
69 // template method so we can recover the type of the multi_pass
70 // iterator and access the m_input data member.
71 template <typename MultiPass>
72 static void increment(MultiPass& mp)
73 {
74 if (!mp.queued_position.get_position().is_initialized())
75 mp.queued_position.get_position().set_queue(&mp.shared()->queued_elements);
76
77 if (mp.queued_position == mp.shared()->queued_elements.end())
78 {
79 // don't let the queue get larger than N
80 if (mp.shared()->queued_elements.size() >= N)
81 mp.shared()->queued_elements.pop_front();
82
83 mp.shared()->queued_elements.push_back(
84 MultiPass::get_input(mp));
85 MultiPass::advance_input(mp);
86 }
87 ++mp.queued_position;
88 }
89
90 // clear_queue is a no-op
91
92 // called to determine whether the iterator is an eof iterator
93 template <typename MultiPass>
94 static bool is_eof(MultiPass const& mp)
95 {
96 return mp.queued_position == mp.shared()->queued_elements.end() &&
97 MultiPass::input_at_eof(mp);
98 }
99
100 // called by operator==
101 template <typename MultiPass>
102 static bool equal_to(MultiPass const& mp, MultiPass const& x)
103 {
104 return mp.queued_position == x.queued_position;
105 }
106
107 // called by operator<
108 template <typename MultiPass>
109 static bool less_than(MultiPass const& mp, MultiPass const& x)
110 {
111 return mp.queued_position < x.queued_position;
112 }
113
114 protected:
115 mutable typename queue_type::iterator queued_position;
116 };
117
118 ///////////////////////////////////////////////////////////////////////
119 template <typename Value>
120 struct shared
121 {
122 typedef detail::fixed_size_queue<Value, N> queue_type;
123 queue_type queued_elements;
124 };
125 };
126
127}}}
128
129#endif
130

source code of boost/libs/spirit/include/boost/spirit/home/support/iterators/detail/fixed_size_queue_policy.hpp