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