1//
2// detail/buffer_resize_guard.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_BUFFER_RESIZE_GUARD_HPP
12#define BOOST_ASIO_DETAIL_BUFFER_RESIZE_GUARD_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 <boost/asio/detail/limits.hpp>
20
21#include <boost/asio/detail/push_options.hpp>
22
23namespace boost {
24namespace asio {
25namespace detail {
26
27// Helper class to manage buffer resizing in an exception safe way.
28template <typename Buffer>
29class buffer_resize_guard
30{
31public:
32 // Constructor.
33 buffer_resize_guard(Buffer& buffer)
34 : buffer_(buffer),
35 old_size_(buffer.size())
36 {
37 }
38
39 // Destructor rolls back the buffer resize unless commit was called.
40 ~buffer_resize_guard()
41 {
42 if (old_size_ != (std::numeric_limits<size_t>::max)())
43 {
44 buffer_.resize(old_size_);
45 }
46 }
47
48 // Commit the resize transaction.
49 void commit()
50 {
51 old_size_ = (std::numeric_limits<size_t>::max)();
52 }
53
54private:
55 // The buffer being managed.
56 Buffer& buffer_;
57
58 // The size of the buffer at the time the guard was constructed.
59 size_t old_size_;
60};
61
62} // namespace detail
63} // namespace asio
64} // namespace boost
65
66#include <boost/asio/detail/pop_options.hpp>
67
68#endif // BOOST_ASIO_DETAIL_BUFFER_RESIZE_GUARD_HPP
69

source code of boost/boost/asio/detail/buffer_resize_guard.hpp