consuming_buffers.hpp 6.84 KB
Newer Older
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
//
// consuming_buffers.hpp
// ~~~~~~~~~~~~~~~~~~~~~
//
// Copyright (c) 2003-2010 Christopher M. Kohlhoff (chris at kohlhoff dot com)
//
// Distributed under the Boost Software License, Version 1.0. (See accompanying
// file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
//

#ifndef ASIO_DETAIL_CONSUMING_BUFFERS_HPP
#define ASIO_DETAIL_CONSUMING_BUFFERS_HPP

#if defined(_MSC_VER) && (_MSC_VER >= 1200)
# pragma once
#endif // defined(_MSC_VER) && (_MSC_VER >= 1200)

#include "asio/detail/push_options.hpp"

#include "asio/detail/push_options.hpp"
#include <algorithm>
#include <cstddef>
#include <boost/config.hpp>
#include <boost/iterator.hpp>
#include <boost/limits.hpp>
#include "asio/detail/pop_options.hpp"

#include "asio/buffer.hpp"

namespace asio {
namespace detail {

// A proxy iterator for a sub-range in a list of buffers.
template <typename Buffer, typename Buffer_Iterator>
class consuming_buffers_iterator
  : public boost::iterator<std::forward_iterator_tag, const Buffer>
{
public:
  // Default constructor creates an end iterator.
  consuming_buffers_iterator()
    : at_end_(true)
  {
  }

  // Construct with a buffer for the first entry and an iterator
  // range for the remaining entries.
  consuming_buffers_iterator(bool at_end, const Buffer& first,
      Buffer_Iterator begin_remainder, Buffer_Iterator end_remainder,
      std::size_t max_size)
    : at_end_(max_size > 0 ? at_end : true),
      first_(buffer(first, max_size)),
      begin_remainder_(begin_remainder),
      end_remainder_(end_remainder),
      offset_(0),
      max_size_(max_size)
  {
  }

  // Dereference an iterator.
  const Buffer& operator*() const
  {
    return dereference();
  }

  // Dereference an iterator.
  const Buffer* operator->() const
  {
    return &dereference();
  }

  // Increment operator (prefix).
  consuming_buffers_iterator& operator++()
  {
    increment();
    return *this;
  }

  // Increment operator (postfix).
  consuming_buffers_iterator operator++(int)
  {
    consuming_buffers_iterator tmp(*this);
    ++*this;
    return tmp;
  }

  // Test two iterators for equality.
  friend bool operator==(const consuming_buffers_iterator& a,
      const consuming_buffers_iterator& b)
  {
    return a.equal(b);
  }

  // Test two iterators for inequality.
  friend bool operator!=(const consuming_buffers_iterator& a,
      const consuming_buffers_iterator& b)
  {
    return !a.equal(b);
  }

private:
  void increment()
  {
    if (!at_end_)
    {
      if (begin_remainder_ == end_remainder_
          || offset_ + buffer_size(first_) >= max_size_)
      {
        at_end_ = true;
      }
      else
      {
        offset_ += buffer_size(first_);
        first_ = buffer(*begin_remainder_++, max_size_ - offset_);
      }
    }
  }

  bool equal(const consuming_buffers_iterator& other) const
  {
    if (at_end_ && other.at_end_)
      return true;
    return !at_end_ && !other.at_end_
      && buffer_cast<const void*>(first_)
        == buffer_cast<const void*>(other.first_)
      && buffer_size(first_) == buffer_size(other.first_)
      && begin_remainder_ == other.begin_remainder_
      && end_remainder_ == other.end_remainder_;
  }

  const Buffer& dereference() const
  {
    return first_;
  }

  bool at_end_;
  Buffer first_;
  Buffer_Iterator begin_remainder_;
  Buffer_Iterator end_remainder_;
  std::size_t offset_;
  std::size_t max_size_;
};

// A proxy for a sub-range in a list of buffers.
template <typename Buffer, typename Buffers>
class consuming_buffers
{
public:
  // The type for each element in the list of buffers.
  typedef Buffer value_type;

  // A forward-only iterator type that may be used to read elements.
  typedef consuming_buffers_iterator<Buffer, typename Buffers::const_iterator>
    const_iterator;

  // Construct to represent the entire list of buffers.
  consuming_buffers(const Buffers& buffers)
    : buffers_(buffers),
      at_end_(buffers_.begin() == buffers_.end()),
      first_(*buffers_.begin()),
      begin_remainder_(buffers_.begin()),
      max_size_((std::numeric_limits<std::size_t>::max)())
  {
    if (!at_end_)
      ++begin_remainder_;
  }

  // Copy constructor.
  consuming_buffers(const consuming_buffers& other)
    : buffers_(other.buffers_),
      at_end_(other.at_end_),
      first_(other.first_),
      begin_remainder_(buffers_.begin()),
      max_size_(other.max_size_)
  {
    typename Buffers::const_iterator first = other.buffers_.begin();
    typename Buffers::const_iterator second = other.begin_remainder_;
    std::advance(begin_remainder_, std::distance(first, second));
  }

  // Assignment operator.
  consuming_buffers& operator=(const consuming_buffers& other)
  {
    buffers_ = other.buffers_;
    at_end_ = other.at_end_;
    first_ = other.first_;
    begin_remainder_ = buffers_.begin();
    typename Buffers::const_iterator first = other.buffers_.begin();
    typename Buffers::const_iterator second = other.begin_remainder_;
    std::advance(begin_remainder_, std::distance(first, second));
    max_size_ = other.max_size_;
    return *this;
  }

  // Get a forward-only iterator to the first element.
  const_iterator begin() const
  {
    return const_iterator(at_end_, first_,
        begin_remainder_, buffers_.end(), max_size_);
  }

  // Get a forward-only iterator for one past the last element.
  const_iterator end() const
  {
    return const_iterator();
  }

  // Set the maximum size for a single transfer.
  void prepare(std::size_t max_size)
  {
    max_size_ = max_size;
  }

  // Consume the specified number of bytes from the buffers.
  void consume(std::size_t size)
  {
    // Remove buffers from the start until the specified size is reached.
    while (size > 0 && !at_end_)
    {
      if (buffer_size(first_) <= size)
      {
        size -= buffer_size(first_);
        if (begin_remainder_ == buffers_.end())
          at_end_ = true;
        else
          first_ = *begin_remainder_++;
      }
      else
      {
        first_ = first_ + size;
        size = 0;
      }
    }

    // Remove any more empty buffers at the start.
    while (!at_end_ && buffer_size(first_) == 0)
    {
      if (begin_remainder_ == buffers_.end())
        at_end_ = true;
      else
        first_ = *begin_remainder_++;
    }
  }

private:
  Buffers buffers_;
  bool at_end_;
  Buffer first_;
  typename Buffers::const_iterator begin_remainder_;
  std::size_t max_size_;
};

// Specialisation for null_buffers to ensure that the null_buffers type is
// always passed through to the underlying read or write operation.
template <typename Buffer>
class consuming_buffers<Buffer, asio::null_buffers>
  : public asio::null_buffers
{
public:
  consuming_buffers(const asio::null_buffers&)
  {
    // No-op.
  }

  void prepare(std::size_t)
  {
    // No-op.
  }

  void consume(std::size_t)
  {
    // No-op.
  }
};

} // namespace detail
} // namespace asio

#include "asio/detail/pop_options.hpp"

#endif // ASIO_DETAIL_CONSUMING_BUFFERS_HPP