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Diffstat (limited to 'src/boost/libs/asio/example/cpp14/operations/composed_1.cpp')
-rw-r--r-- | src/boost/libs/asio/example/cpp14/operations/composed_1.cpp | 113 |
1 files changed, 113 insertions, 0 deletions
diff --git a/src/boost/libs/asio/example/cpp14/operations/composed_1.cpp b/src/boost/libs/asio/example/cpp14/operations/composed_1.cpp new file mode 100644 index 000000000..4439fef6e --- /dev/null +++ b/src/boost/libs/asio/example/cpp14/operations/composed_1.cpp @@ -0,0 +1,113 @@ +// +// composed_1.cpp +// ~~~~~~~~~~~~~~ +// +// Copyright (c) 2003-2020 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) +// + +#include <boost/asio/io_context.hpp> +#include <boost/asio/ip/tcp.hpp> +#include <boost/asio/use_future.hpp> +#include <boost/asio/write.hpp> +#include <cstring> +#include <iostream> +#include <string> +#include <type_traits> +#include <utility> + +using boost::asio::ip::tcp; + +//------------------------------------------------------------------------------ + +// This is the simplest example of a composed asynchronous operation, where we +// simply repackage an existing operation. The asynchronous operation +// requirements are met by delegating responsibility to the underlying +// operation. + +template <typename CompletionToken> +auto async_write_message(tcp::socket& socket, + const char* message, CompletionToken&& token) + // The return type of the initiating function is deduced from the combination + // of CompletionToken type and the completion handler's signature. When the + // completion token is a simple callback, the return type is void. However, + // when the completion token is boost::asio::yield_context (used for stackful + // coroutines) the return type would be std::size_t, and when the completion + // token is boost::asio::use_future it would be std::future<std::size_t>. + // + // In C++14 we can omit the return type as it is automatically deduced from + // the return type of our underlying asynchronous operation +{ + // When delegating to the underlying operation we must take care to perfectly + // forward the completion token. This ensures that our operation works + // correctly with move-only function objects as callbacks, as well as other + // completion token types. + return boost::asio::async_write(socket, + boost::asio::buffer(message, std::strlen(message)), + std::forward<CompletionToken>(token)); +} + +//------------------------------------------------------------------------------ + +void test_callback() +{ + boost::asio::io_context io_context; + + tcp::acceptor acceptor(io_context, {tcp::v4(), 55555}); + tcp::socket socket = acceptor.accept(); + + // Test our asynchronous operation using a lambda as a callback. + async_write_message(socket, "Testing callback\r\n", + [](const boost::system::error_code& error, std::size_t n) + { + if (!error) + { + std::cout << n << " bytes transferred\n"; + } + else + { + std::cout << "Error: " << error.message() << "\n"; + } + }); + + io_context.run(); +} + +//------------------------------------------------------------------------------ + +void test_future() +{ + boost::asio::io_context io_context; + + tcp::acceptor acceptor(io_context, {tcp::v4(), 55555}); + tcp::socket socket = acceptor.accept(); + + // Test our asynchronous operation using the use_future completion token. + // This token causes the operation's initiating function to return a future, + // which may be used to synchronously wait for the result of the operation. + std::future<std::size_t> f = async_write_message( + socket, "Testing future\r\n", boost::asio::use_future); + + io_context.run(); + + try + { + // Get the result of the operation. + std::size_t n = f.get(); + std::cout << n << " bytes transferred\n"; + } + catch (const std::exception& e) + { + std::cout << "Error: " << e.what() << "\n"; + } +} + +//------------------------------------------------------------------------------ + +int main() +{ + test_callback(); + test_future(); +} |