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 
23 namespace boost {
24 namespace asio {
25 namespace detail {
26 
27 // Helper class to manage buffer resizing in an exception safe way.
28 template <typename Buffer>
29 class buffer_resize_guard
30 {
31 public:
32   // Constructor.
buffer_resize_guard(Buffer & buffer)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.
~buffer_resize_guard()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.
commit()49   void commit()
50   {
51     old_size_ = (std::numeric_limits<size_t>::max)();
52   }
53 
54 private:
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