1 | // |
2 | // detail/consuming_buffers.hpp |
3 | // ~~~~~~~~~~~~~~~~~~~~~~~~~~~~ |
4 | // |
5 | // Copyright (c) 2003-2015 Christopher M. Kohlhoff (chris at kohlhoff dot com) |
6 | // |
7 | // Distributed under the Boost Software License, Version 1.0. (See accompanying |
8 | // file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt) |
9 | // |
10 | |
11 | #ifndef BOOST_ASIO_DETAIL_CONSUMING_BUFFERS_HPP |
12 | #define BOOST_ASIO_DETAIL_CONSUMING_BUFFERS_HPP |
13 | |
14 | #if defined(_MSC_VER) && (_MSC_VER >= 1200) |
15 | # pragma once |
16 | #endif // defined(_MSC_VER) && (_MSC_VER >= 1200) |
17 | |
18 | #include <boost/asio/detail/config.hpp> |
19 | #include <cstddef> |
20 | #include <iterator> |
21 | #include <boost/asio/buffer.hpp> |
22 | #include <boost/asio/detail/limits.hpp> |
23 | |
24 | #include <boost/asio/detail/push_options.hpp> |
25 | |
26 | namespace boost { |
27 | namespace asio { |
28 | namespace detail { |
29 | |
30 | // A proxy iterator for a sub-range in a list of buffers. |
31 | template <typename Buffer, typename Buffer_Iterator> |
32 | class consuming_buffers_iterator |
33 | { |
34 | public: |
35 | /// The type used for the distance between two iterators. |
36 | typedef std::ptrdiff_t difference_type; |
37 | |
38 | /// The type of the value pointed to by the iterator. |
39 | typedef Buffer value_type; |
40 | |
41 | /// The type of the result of applying operator->() to the iterator. |
42 | typedef const Buffer* pointer; |
43 | |
44 | /// The type of the result of applying operator*() to the iterator. |
45 | typedef const Buffer& reference; |
46 | |
47 | /// The iterator category. |
48 | typedef std::forward_iterator_tag iterator_category; |
49 | |
50 | // Default constructor creates an end iterator. |
51 | consuming_buffers_iterator() |
52 | : at_end_(true) |
53 | { |
54 | } |
55 | |
56 | // Construct with a buffer for the first entry and an iterator |
57 | // range for the remaining entries. |
58 | consuming_buffers_iterator(bool at_end, const Buffer& first, |
59 | Buffer_Iterator begin_remainder, Buffer_Iterator end_remainder, |
60 | std::size_t max_size) |
61 | : at_end_(max_size > 0 ? at_end : true), |
62 | first_(buffer(first, max_size)), |
63 | begin_remainder_(begin_remainder), |
64 | end_remainder_(end_remainder), |
65 | offset_(0), |
66 | max_size_(max_size) |
67 | { |
68 | } |
69 | |
70 | // Dereference an iterator. |
71 | const Buffer& operator*() const |
72 | { |
73 | return dereference(); |
74 | } |
75 | |
76 | // Dereference an iterator. |
77 | const Buffer* operator->() const |
78 | { |
79 | return &dereference(); |
80 | } |
81 | |
82 | // Increment operator (prefix). |
83 | consuming_buffers_iterator& operator++() |
84 | { |
85 | increment(); |
86 | return *this; |
87 | } |
88 | |
89 | // Increment operator (postfix). |
90 | consuming_buffers_iterator operator++(int) |
91 | { |
92 | consuming_buffers_iterator tmp(*this); |
93 | ++*this; |
94 | return tmp; |
95 | } |
96 | |
97 | // Test two iterators for equality. |
98 | friend bool operator==(const consuming_buffers_iterator& a, |
99 | const consuming_buffers_iterator& b) |
100 | { |
101 | return a.equal(b); |
102 | } |
103 | |
104 | // Test two iterators for inequality. |
105 | friend bool operator!=(const consuming_buffers_iterator& a, |
106 | const consuming_buffers_iterator& b) |
107 | { |
108 | return !a.equal(b); |
109 | } |
110 | |
111 | private: |
112 | void increment() |
113 | { |
114 | if (!at_end_) |
115 | { |
116 | if (begin_remainder_ == end_remainder_ |
117 | || offset_ + buffer_size(first_) >= max_size_) |
118 | { |
119 | at_end_ = true; |
120 | } |
121 | else |
122 | { |
123 | offset_ += buffer_size(first_); |
124 | first_ = buffer(*begin_remainder_++, max_size_ - offset_); |
125 | } |
126 | } |
127 | } |
128 | |
129 | bool equal(const consuming_buffers_iterator& other) const |
130 | { |
131 | if (at_end_ && other.at_end_) |
132 | return true; |
133 | return !at_end_ && !other.at_end_ |
134 | && buffer_cast<const void*>(first_) |
135 | == buffer_cast<const void*>(other.first_) |
136 | && buffer_size(first_) == buffer_size(other.first_) |
137 | && begin_remainder_ == other.begin_remainder_ |
138 | && end_remainder_ == other.end_remainder_; |
139 | } |
140 | |
141 | const Buffer& dereference() const |
142 | { |
143 | return first_; |
144 | } |
145 | |
146 | bool at_end_; |
147 | Buffer first_; |
148 | Buffer_Iterator begin_remainder_; |
149 | Buffer_Iterator end_remainder_; |
150 | std::size_t offset_; |
151 | std::size_t max_size_; |
152 | }; |
153 | |
154 | // A proxy for a sub-range in a list of buffers. |
155 | template <typename Buffer, typename Buffers> |
156 | class consuming_buffers |
157 | { |
158 | public: |
159 | // The type for each element in the list of buffers. |
160 | typedef Buffer value_type; |
161 | |
162 | // A forward-only iterator type that may be used to read elements. |
163 | typedef consuming_buffers_iterator<Buffer, typename Buffers::const_iterator> |
164 | const_iterator; |
165 | |
166 | // Construct to represent the entire list of buffers. |
167 | consuming_buffers(const Buffers& buffers) |
168 | : buffers_(buffers), |
169 | at_end_(buffers_.begin() == buffers_.end()), |
170 | begin_remainder_(buffers_.begin()), |
171 | max_size_((std::numeric_limits<std::size_t>::max)()) |
172 | { |
173 | if (!at_end_) |
174 | { |
175 | first_ = *buffers_.begin(); |
176 | ++begin_remainder_; |
177 | } |
178 | } |
179 | |
180 | // Copy constructor. |
181 | consuming_buffers(const consuming_buffers& other) |
182 | : buffers_(other.buffers_), |
183 | at_end_(other.at_end_), |
184 | first_(other.first_), |
185 | begin_remainder_(buffers_.begin()), |
186 | max_size_(other.max_size_) |
187 | { |
188 | typename Buffers::const_iterator first = other.buffers_.begin(); |
189 | typename Buffers::const_iterator second = other.begin_remainder_; |
190 | std::advance(begin_remainder_, std::distance(first, second)); |
191 | } |
192 | |
193 | // Assignment operator. |
194 | consuming_buffers& operator=(const consuming_buffers& other) |
195 | { |
196 | buffers_ = other.buffers_; |
197 | at_end_ = other.at_end_; |
198 | first_ = other.first_; |
199 | begin_remainder_ = buffers_.begin(); |
200 | typename Buffers::const_iterator first = other.buffers_.begin(); |
201 | typename Buffers::const_iterator second = other.begin_remainder_; |
202 | std::advance(begin_remainder_, std::distance(first, second)); |
203 | max_size_ = other.max_size_; |
204 | return *this; |
205 | } |
206 | |
207 | // Get a forward-only iterator to the first element. |
208 | const_iterator begin() const |
209 | { |
210 | return const_iterator(at_end_, first_, |
211 | begin_remainder_, buffers_.end(), max_size_); |
212 | } |
213 | |
214 | // Get a forward-only iterator for one past the last element. |
215 | const_iterator end() const |
216 | { |
217 | return const_iterator(); |
218 | } |
219 | |
220 | // Set the maximum size for a single transfer. |
221 | void prepare(std::size_t max_size) |
222 | { |
223 | max_size_ = max_size; |
224 | } |
225 | |
226 | // Consume the specified number of bytes from the buffers. |
227 | void consume(std::size_t size) |
228 | { |
229 | // Remove buffers from the start until the specified size is reached. |
230 | while (size > 0 && !at_end_) |
231 | { |
232 | if (buffer_size(first_) <= size) |
233 | { |
234 | size -= buffer_size(first_); |
235 | if (begin_remainder_ == buffers_.end()) |
236 | at_end_ = true; |
237 | else |
238 | first_ = *begin_remainder_++; |
239 | } |
240 | else |
241 | { |
242 | first_ = first_ + size; |
243 | size = 0; |
244 | } |
245 | } |
246 | |
247 | // Remove any more empty buffers at the start. |
248 | while (!at_end_ && buffer_size(first_) == 0) |
249 | { |
250 | if (begin_remainder_ == buffers_.end()) |
251 | at_end_ = true; |
252 | else |
253 | first_ = *begin_remainder_++; |
254 | } |
255 | } |
256 | |
257 | private: |
258 | Buffers buffers_; |
259 | bool at_end_; |
260 | Buffer first_; |
261 | typename Buffers::const_iterator begin_remainder_; |
262 | std::size_t max_size_; |
263 | }; |
264 | |
265 | // Specialisation for null_buffers to ensure that the null_buffers type is |
266 | // always passed through to the underlying read or write operation. |
267 | template <typename Buffer> |
268 | class consuming_buffers<Buffer, boost::asio::null_buffers> |
269 | : public boost::asio::null_buffers |
270 | { |
271 | public: |
272 | consuming_buffers(const boost::asio::null_buffers&) |
273 | { |
274 | // No-op. |
275 | } |
276 | |
277 | void prepare(std::size_t) |
278 | { |
279 | // No-op. |
280 | } |
281 | |
282 | void consume(std::size_t) |
283 | { |
284 | // No-op. |
285 | } |
286 | }; |
287 | |
288 | } // namespace detail |
289 | } // namespace asio |
290 | } // namespace boost |
291 | |
292 | #include <boost/asio/detail/pop_options.hpp> |
293 | |
294 | #endif // BOOST_ASIO_DETAIL_CONSUMING_BUFFERS_HPP |
295 | |