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Diffstat (limited to 'src/boost/libs/asio/example/cpp14/operations')
9 files changed, 1637 insertions, 0 deletions
diff --git a/src/boost/libs/asio/example/cpp14/operations/Jamfile.v2 b/src/boost/libs/asio/example/cpp14/operations/Jamfile.v2 new file mode 100644 index 000000000..a01b42a3a --- /dev/null +++ b/src/boost/libs/asio/example/cpp14/operations/Jamfile.v2 @@ -0,0 +1,39 @@ +# +# 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) +# + +lib socket ; # SOLARIS +lib nsl ; # SOLARIS +lib ws2_32 ; # NT +lib mswsock ; # NT +lib ipv6 ; # HPUX +lib network ; # HAIKU + +project + : requirements + <library>/boost/system//boost_system + <library>/boost/chrono//boost_chrono + <define>BOOST_ALL_NO_LIB=1 + <threading>multi + <target-os>solaris:<library>socket + <target-os>solaris:<library>nsl + <target-os>windows:<define>_WIN32_WINNT=0x0501 + <target-os>windows,<toolset>gcc:<library>ws2_32 + <target-os>windows,<toolset>gcc:<library>mswsock + <target-os>windows,<toolset>gcc-cygwin:<define>__USE_W32_SOCKETS + <target-os>hpux,<toolset>gcc:<define>_XOPEN_SOURCE_EXTENDED + <target-os>hpux:<library>ipv6 + <target-os>haiku:<library>network + ; + +exe composed_1 : composed_1.cpp ; +exe composed_2 : composed_2.cpp ; +exe composed_3 : composed_3.cpp ; +exe composed_4 : composed_4.cpp ; +exe composed_5 : composed_5.cpp ; +exe composed_6 : composed_6.cpp ; +exe composed_7 : composed_7.cpp ; +exe composed_8 : composed_8.cpp ; 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(); +} diff --git a/src/boost/libs/asio/example/cpp14/operations/composed_2.cpp b/src/boost/libs/asio/example/cpp14/operations/composed_2.cpp new file mode 100644 index 000000000..4c16776a5 --- /dev/null +++ b/src/boost/libs/asio/example/cpp14/operations/composed_2.cpp @@ -0,0 +1,131 @@ +// +// composed_2.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 next simplest example of a composed asynchronous operation involves +// repackaging multiple operations but choosing to invoke just one of them. All +// of these underlying operations have the same completion signature. The +// asynchronous operation requirements are met by delegating responsibility to +// the underlying operations. + +template <typename CompletionToken> +auto async_write_message(tcp::socket& socket, + const char* message, bool allow_partial_write, + 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 +{ + // As the return type of the initiating function is deduced solely from the + // CompletionToken and completion signature, we know that two different + // asynchronous operations having the same completion signature will produce + // the same return type, when passed the same CompletionToken. This allows us + // to trivially delegate to alternate implementations. + if (allow_partial_write) + { + // When delegating to an 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 socket.async_write_some( + boost::asio::buffer(message, std::strlen(message)), + std::forward<CompletionToken>(token)); + } + else + { + // As above, we must perfectly forward the completion token when calling + // the alternate underlying operation. + 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", false, + [](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", false, 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(); +} diff --git a/src/boost/libs/asio/example/cpp14/operations/composed_3.cpp b/src/boost/libs/asio/example/cpp14/operations/composed_3.cpp new file mode 100644 index 000000000..00ab11206 --- /dev/null +++ b/src/boost/libs/asio/example/cpp14/operations/composed_3.cpp @@ -0,0 +1,186 @@ +// +// composed_3.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/bind_executor.hpp> +#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 <functional> +#include <iostream> +#include <string> +#include <type_traits> +#include <utility> + +using boost::asio::ip::tcp; + +// NOTE: This example requires the new boost::asio::async_initiate function. For +// an example that works with the Networking TS style of completion tokens, +// please see an older version of asio. + +//------------------------------------------------------------------------------ + +// In this composed operation we repackage an existing operation, but with a +// different completion handler signature. 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 always void. + // In this example, when the completion token is boost::asio::yield_context + // (used for stackful coroutines) the return type would be also be void, as + // there is no non-error argument to the completion handler. When the + // completion token is boost::asio::use_future it would be std::future<void>. + // + // In C++14 we can omit the return type as it is automatically deduced from + // the return type of boost::asio::async_initiate. +{ + // In addition to determining the mechanism by which an asynchronous + // operation delivers its result, a completion token also determines the time + // when the operation commences. For example, when the completion token is a + // simple callback the operation commences before the initiating function + // returns. However, if the completion token's delivery mechanism uses a + // future, we might instead want to defer initiation of the operation until + // the returned future object is waited upon. + // + // To enable this, when implementing an asynchronous operation we must + // package the initiation step as a function object. The initiation function + // object's call operator is passed the concrete completion handler produced + // by the completion token. This completion handler matches the asynchronous + // operation's completion handler signature, which in this example is: + // + // void(boost::system::error_code error) + // + // The initiation function object also receives any additional arguments + // required to start the operation. (Note: We could have instead passed these + // arguments in the lambda capture set. However, we should prefer to + // propagate them as function call arguments as this allows the completion + // token to optimise how they are passed. For example, a lazy future which + // defers initiation would need to make a decay-copy of the arguments, but + // when using a simple callback the arguments can be trivially forwarded + // straight through.) + auto initiation = [](auto&& completion_handler, + tcp::socket& socket, const char* message) + { + // The async_write operation has a completion handler signature of: + // + // void(boost::system::error_code error, std::size n) + // + // This differs from our operation's signature in that it is also passed + // the number of bytes transferred as an argument of type std::size_t. We + // will adapt our completion handler to async_write's completion handler + // signature by using std::bind, which drops the additional argument. + // + // However, it is essential to the correctness of our composed operation + // that we preserve the executor of the user-supplied completion handler. + // The std::bind function will not do this for us, so we must do this by + // first obtaining the completion handler's associated executor (defaulting + // to the I/O executor - in this case the executor of the socket - if the + // completion handler does not have its own) ... + auto executor = boost::asio::get_associated_executor( + completion_handler, socket.get_executor()); + + // ... and then binding this executor to our adapted completion handler + // using the boost::asio::bind_executor function. + boost::asio::async_write(socket, + boost::asio::buffer(message, std::strlen(message)), + boost::asio::bind_executor(executor, + std::bind(std::forward<decltype(completion_handler)>( + completion_handler), std::placeholders::_1))); + }; + + // The boost::asio::async_initiate function takes: + // + // - our initiation function object, + // - the completion token, + // - the completion handler signature, and + // - any additional arguments we need to initiate the operation. + // + // It then asks the completion token to create a completion handler (i.e. a + // callback) with the specified signature, and invoke the initiation function + // object with this completion handler as well as the additional arguments. + // The return value of async_initiate is the result of our operation's + // initiating function. + // + // Note that we wrap non-const reference arguments in std::reference_wrapper + // to prevent incorrect decay-copies of these objects. + return boost::asio::async_initiate< + CompletionToken, void(boost::system::error_code)>( + initiation, token, std::ref(socket), message); +} + +//------------------------------------------------------------------------------ + +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) + { + if (!error) + { + std::cout << "Message sent\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<void> f = async_write_message( + socket, "Testing future\r\n", boost::asio::use_future); + + io_context.run(); + + // Get the result of the operation. + try + { + // Get the result of the operation. + f.get(); + std::cout << "Message sent\n"; + } + catch (const std::exception& e) + { + std::cout << "Error: " << e.what() << "\n"; + } +} + +//------------------------------------------------------------------------------ + +int main() +{ + test_callback(); + test_future(); +} diff --git a/src/boost/libs/asio/example/cpp14/operations/composed_4.cpp b/src/boost/libs/asio/example/cpp14/operations/composed_4.cpp new file mode 100644 index 000000000..65e0bf21b --- /dev/null +++ b/src/boost/libs/asio/example/cpp14/operations/composed_4.cpp @@ -0,0 +1,201 @@ +// +// composed_4.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/bind_executor.hpp> +#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 <functional> +#include <iostream> +#include <string> +#include <type_traits> +#include <utility> + +using boost::asio::ip::tcp; + +// NOTE: This example requires the new boost::asio::async_initiate function. For +// an example that works with the Networking TS style of completion tokens, +// please see an older version of asio. + +//------------------------------------------------------------------------------ + +// In this composed operation we repackage an existing operation, but with a +// different completion handler signature. We will also intercept an empty +// message as an invalid argument, and propagate the corresponding error to the +// user. 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 always void. + // In this example, when the completion token is boost::asio::yield_context + // (used for stackful coroutines) the return type would be also be void, as + // there is no non-error argument to the completion handler. When the + // completion token is boost::asio::use_future it would be std::future<void>. + // + // In C++14 we can omit the return type as it is automatically deduced from + // the return type of boost::asio::async_initiate. +{ + // In addition to determining the mechanism by which an asynchronous + // operation delivers its result, a completion token also determines the time + // when the operation commences. For example, when the completion token is a + // simple callback the operation commences before the initiating function + // returns. However, if the completion token's delivery mechanism uses a + // future, we might instead want to defer initiation of the operation until + // the returned future object is waited upon. + // + // To enable this, when implementing an asynchronous operation we must + // package the initiation step as a function object. The initiation function + // object's call operator is passed the concrete completion handler produced + // by the completion token. This completion handler matches the asynchronous + // operation's completion handler signature, which in this example is: + // + // void(boost::system::error_code error) + // + // The initiation function object also receives any additional arguments + // required to start the operation. (Note: We could have instead passed these + // arguments in the lambda capture set. However, we should prefer to + // propagate them as function call arguments as this allows the completion + // token to optimise how they are passed. For example, a lazy future which + // defers initiation would need to make a decay-copy of the arguments, but + // when using a simple callback the arguments can be trivially forwarded + // straight through.) + auto initiation = [](auto&& completion_handler, + tcp::socket& socket, const char* message) + { + // The post operation has a completion handler signature of: + // + // void() + // + // and the async_write operation has a completion handler signature of: + // + // void(boost::system::error_code error, std::size n) + // + // Both of these operations' completion handler signatures differ from our + // operation's completion handler signature. We will adapt our completion + // handler to these signatures by using std::bind, which drops the + // additional arguments. + // + // However, it is essential to the correctness of our composed operation + // that we preserve the executor of the user-supplied completion handler. + // The std::bind function will not do this for us, so we must do this by + // first obtaining the completion handler's associated executor (defaulting + // to the I/O executor - in this case the executor of the socket - if the + // completion handler does not have its own) ... + auto executor = boost::asio::get_associated_executor( + completion_handler, socket.get_executor()); + + // ... and then binding this executor to our adapted completion handler + // using the boost::asio::bind_executor function. + std::size_t length = std::strlen(message); + if (length == 0) + { + boost::asio::post( + boost::asio::bind_executor(executor, + std::bind(std::forward<decltype(completion_handler)>( + completion_handler), boost::asio::error::invalid_argument))); + } + else + { + boost::asio::async_write(socket, + boost::asio::buffer(message, length), + boost::asio::bind_executor(executor, + std::bind(std::forward<decltype(completion_handler)>( + completion_handler), std::placeholders::_1))); + } + }; + + // The boost::asio::async_initiate function takes: + // + // - our initiation function object, + // - the completion token, + // - the completion handler signature, and + // - any additional arguments we need to initiate the operation. + // + // It then asks the completion token to create a completion handler (i.e. a + // callback) with the specified signature, and invoke the initiation function + // object with this completion handler as well as the additional arguments. + // The return value of async_initiate is the result of our operation's + // initiating function. + // + // Note that we wrap non-const reference arguments in std::reference_wrapper + // to prevent incorrect decay-copies of these objects. + return boost::asio::async_initiate< + CompletionToken, void(boost::system::error_code)>( + initiation, token, std::ref(socket), message); +} + +//------------------------------------------------------------------------------ + +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, "", + [](const boost::system::error_code& error) + { + if (!error) + { + std::cout << "Message sent\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<void> f = async_write_message( + socket, "", boost::asio::use_future); + + io_context.run(); + + try + { + // Get the result of the operation. + f.get(); + std::cout << "Message sent\n"; + } + catch (const std::exception& e) + { + std::cout << "Exception: " << e.what() << "\n"; + } +} + +//------------------------------------------------------------------------------ + +int main() +{ + test_callback(); + test_future(); +} diff --git a/src/boost/libs/asio/example/cpp14/operations/composed_5.cpp b/src/boost/libs/asio/example/cpp14/operations/composed_5.cpp new file mode 100644 index 000000000..f7bcb169a --- /dev/null +++ b/src/boost/libs/asio/example/cpp14/operations/composed_5.cpp @@ -0,0 +1,238 @@ +// +// composed_5.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 <functional> +#include <iostream> +#include <memory> +#include <sstream> +#include <string> +#include <type_traits> +#include <utility> + +using boost::asio::ip::tcp; + +// NOTE: This example requires the new boost::asio::async_initiate function. For +// an example that works with the Networking TS style of completion tokens, +// please see an older version of asio. + +//------------------------------------------------------------------------------ + +// This composed operation automatically serialises a message, using its I/O +// streams insertion operator, before sending it on the socket. To do this, it +// must allocate a buffer for the encoded message and ensure this buffer's +// validity until the underlying async_write operation completes. + +template <typename T, typename CompletionToken> +auto async_write_message(tcp::socket& socket, + const T& 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 always void. + // In this example, when the completion token is boost::asio::yield_context + // (used for stackful coroutines) the return type would be also be void, as + // there is no non-error argument to the completion handler. When the + // completion token is boost::asio::use_future it would be std::future<void>. + // + // In C++14 we can omit the return type as it is automatically deduced from + // the return type of boost::asio::async_initiate. +{ + // In addition to determining the mechanism by which an asynchronous + // operation delivers its result, a completion token also determines the time + // when the operation commences. For example, when the completion token is a + // simple callback the operation commences before the initiating function + // returns. However, if the completion token's delivery mechanism uses a + // future, we might instead want to defer initiation of the operation until + // the returned future object is waited upon. + // + // To enable this, when implementing an asynchronous operation we must + // package the initiation step as a function object. The initiation function + // object's call operator is passed the concrete completion handler produced + // by the completion token. This completion handler matches the asynchronous + // operation's completion handler signature, which in this example is: + // + // void(boost::system::error_code error) + // + // The initiation function object also receives any additional arguments + // required to start the operation. (Note: We could have instead passed these + // arguments in the lambda capture set. However, we should prefer to + // propagate them as function call arguments as this allows the completion + // token to optimise how they are passed. For example, a lazy future which + // defers initiation would need to make a decay-copy of the arguments, but + // when using a simple callback the arguments can be trivially forwarded + // straight through.) + auto initiation = [](auto&& completion_handler, + tcp::socket& socket, std::unique_ptr<std::string> encoded_message) + { + // In this example, the composed operation's intermediate completion + // handler is implemented as a hand-crafted function object, rather than + // using a lambda or std::bind. + struct intermediate_completion_handler + { + // The intermediate completion handler holds a reference to the socket so + // that it can obtain the I/O executor (see get_executor below). + tcp::socket& socket_; + + // The allocated buffer for the encoded message. The std::unique_ptr + // smart pointer is move-only, and as a consequence our intermediate + // completion handler is also move-only. + std::unique_ptr<std::string> encoded_message_; + + // The user-supplied completion handler. + typename std::decay<decltype(completion_handler)>::type handler_; + + // The function call operator matches the completion signature of the + // async_write operation. + void operator()(const boost::system::error_code& error, std::size_t /*n*/) + { + // Deallocate the encoded message before calling the user-supplied + // completion handler. + encoded_message_.reset(); + + // Call the user-supplied handler with the result of the operation. + // The arguments must match the completion signature of our composed + // operation. + handler_(error); + } + + // It is essential to the correctness of our composed operation that we + // preserve the executor of the user-supplied completion handler. With a + // hand-crafted function object we can do this by defining a nested type + // executor_type and member function get_executor. These obtain the + // completion handler's associated executor, and default to the I/O + // executor - in this case the executor of the socket - if the completion + // handler does not have its own. + using executor_type = boost::asio::associated_executor_t< + typename std::decay<decltype(completion_handler)>::type, + tcp::socket::executor_type>; + + executor_type get_executor() const noexcept + { + return boost::asio::get_associated_executor( + handler_, socket_.get_executor()); + } + + // Although not necessary for correctness, we may also preserve the + // allocator of the user-supplied completion handler. This is achieved by + // defining a nested type allocator_type and member function + // get_allocator. These obtain the completion handler's associated + // allocator, and default to std::allocator<void> if the completion + // handler does not have its own. + using allocator_type = boost::asio::associated_allocator_t< + typename std::decay<decltype(completion_handler)>::type, + std::allocator<void>>; + + allocator_type get_allocator() const noexcept + { + return boost::asio::get_associated_allocator( + handler_, std::allocator<void>{}); + } + }; + + // Initiate the underlying async_write operation using our intermediate + // completion handler. + auto encoded_message_buffer = boost::asio::buffer(*encoded_message); + boost::asio::async_write(socket, encoded_message_buffer, + intermediate_completion_handler{socket, std::move(encoded_message), + std::forward<decltype(completion_handler)>(completion_handler)}); + }; + + // Encode the message and copy it into an allocated buffer. The buffer will + // be maintained for the lifetime of the asynchronous operation. + std::ostringstream os; + os << message; + std::unique_ptr<std::string> encoded_message(new std::string(os.str())); + + // The boost::asio::async_initiate function takes: + // + // - our initiation function object, + // - the completion token, + // - the completion handler signature, and + // - any additional arguments we need to initiate the operation. + // + // It then asks the completion token to create a completion handler (i.e. a + // callback) with the specified signature, and invoke the initiation function + // object with this completion handler as well as the additional arguments. + // The return value of async_initiate is the result of our operation's + // initiating function. + // + // Note that we wrap non-const reference arguments in std::reference_wrapper + // to prevent incorrect decay-copies of these objects. + return boost::asio::async_initiate< + CompletionToken, void(boost::system::error_code)>( + initiation, token, std::ref(socket), + std::move(encoded_message)); +} + +//------------------------------------------------------------------------------ + +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, 123456, + [](const boost::system::error_code& error) + { + if (!error) + { + std::cout << "Message sent\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<void> f = async_write_message( + socket, 654.321, boost::asio::use_future); + + io_context.run(); + + try + { + // Get the result of the operation. + f.get(); + std::cout << "Message sent\n"; + } + catch (const std::exception& e) + { + std::cout << "Exception: " << e.what() << "\n"; + } +} + +//------------------------------------------------------------------------------ + +int main() +{ + test_callback(); + test_future(); +} diff --git a/src/boost/libs/asio/example/cpp14/operations/composed_6.cpp b/src/boost/libs/asio/example/cpp14/operations/composed_6.cpp new file mode 100644 index 000000000..8b6d01190 --- /dev/null +++ b/src/boost/libs/asio/example/cpp14/operations/composed_6.cpp @@ -0,0 +1,298 @@ +// +// composed_6.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/executor_work_guard.hpp> +#include <boost/asio/io_context.hpp> +#include <boost/asio/ip/tcp.hpp> +#include <boost/asio/steady_timer.hpp> +#include <boost/asio/use_future.hpp> +#include <boost/asio/write.hpp> +#include <functional> +#include <iostream> +#include <memory> +#include <sstream> +#include <string> +#include <type_traits> +#include <utility> + +using boost::asio::ip::tcp; + +// NOTE: This example requires the new boost::asio::async_initiate function. For +// an example that works with the Networking TS style of completion tokens, +// please see an older version of asio. + +//------------------------------------------------------------------------------ + +// This composed operation shows composition of multiple underlying operations. +// It automatically serialises a message, using its I/O streams insertion +// operator, before sending it N times on the socket. To do this, it must +// allocate a buffer for the encoded message and ensure this buffer's validity +// until all underlying async_write operation complete. A one second delay is +// inserted prior to each write operation, using a steady_timer. + +template <typename T, typename CompletionToken> +auto async_write_messages(tcp::socket& socket, + const T& message, std::size_t repeat_count, + 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 always void. + // In this example, when the completion token is boost::asio::yield_context + // (used for stackful coroutines) the return type would be also be void, as + // there is no non-error argument to the completion handler. When the + // completion token is boost::asio::use_future it would be std::future<void>. + // + // In C++14 we can omit the return type as it is automatically deduced from + // the return type of boost::asio::async_initiate. +{ + // In addition to determining the mechanism by which an asynchronous + // operation delivers its result, a completion token also determines the time + // when the operation commences. For example, when the completion token is a + // simple callback the operation commences before the initiating function + // returns. However, if the completion token's delivery mechanism uses a + // future, we might instead want to defer initiation of the operation until + // the returned future object is waited upon. + // + // To enable this, when implementing an asynchronous operation we must + // package the initiation step as a function object. The initiation function + // object's call operator is passed the concrete completion handler produced + // by the completion token. This completion handler matches the asynchronous + // operation's completion handler signature, which in this example is: + // + // void(boost::system::error_code error) + // + // The initiation function object also receives any additional arguments + // required to start the operation. (Note: We could have instead passed these + // arguments in the lambda capture set. However, we should prefer to + // propagate them as function call arguments as this allows the completion + // token to optimise how they are passed. For example, a lazy future which + // defers initiation would need to make a decay-copy of the arguments, but + // when using a simple callback the arguments can be trivially forwarded + // straight through.) + auto initiation = [](auto&& completion_handler, tcp::socket& socket, + std::unique_ptr<std::string> encoded_message, std::size_t repeat_count, + std::unique_ptr<boost::asio::steady_timer> delay_timer) + { + // In this example, the composed operation's intermediate completion + // handler is implemented as a hand-crafted function object. + struct intermediate_completion_handler + { + // The intermediate completion handler holds a reference to the socket as + // it is used for multiple async_write operations, as well as for + // obtaining the I/O executor (see get_executor below). + tcp::socket& socket_; + + // The allocated buffer for the encoded message. The std::unique_ptr + // smart pointer is move-only, and as a consequence our intermediate + // completion handler is also move-only. + std::unique_ptr<std::string> encoded_message_; + + // The repeat count remaining. + std::size_t repeat_count_; + + // A steady timer used for introducing a delay. + std::unique_ptr<boost::asio::steady_timer> delay_timer_; + + // To manage the cycle between the multiple underlying asychronous + // operations, our intermediate completion handler is implemented as a + // state machine. + enum { starting, waiting, writing } state_; + + // As our composed operation performs multiple underlying I/O operations, + // we should maintain a work object against the I/O executor. This tells + // the I/O executor that there is still more work to come in the future. + boost::asio::executor_work_guard<tcp::socket::executor_type> io_work_; + + // The user-supplied completion handler, called once only on completion + // of the entire composed operation. + typename std::decay<decltype(completion_handler)>::type handler_; + + // By having a default value for the second argument, this function call + // operator matches the completion signature of both the async_write and + // steady_timer::async_wait operations. + void operator()(const boost::system::error_code& error, std::size_t = 0) + { + if (!error) + { + switch (state_) + { + case starting: + case writing: + if (repeat_count_ > 0) + { + --repeat_count_; + state_ = waiting; + delay_timer_->expires_after(std::chrono::seconds(1)); + delay_timer_->async_wait(std::move(*this)); + return; // Composed operation not yet complete. + } + break; // Composed operation complete, continue below. + case waiting: + state_ = writing; + boost::asio::async_write(socket_, + boost::asio::buffer(*encoded_message_), std::move(*this)); + return; // Composed operation not yet complete. + } + } + + // This point is reached only on completion of the entire composed + // operation. + + // We no longer have any future work coming for the I/O executor. + io_work_.reset(); + + // Deallocate the encoded message before calling the user-supplied + // completion handler. + encoded_message_.reset(); + + // Call the user-supplied handler with the result of the operation. + handler_(error); + } + + // It is essential to the correctness of our composed operation that we + // preserve the executor of the user-supplied completion handler. With a + // hand-crafted function object we can do this by defining a nested type + // executor_type and member function get_executor. These obtain the + // completion handler's associated executor, and default to the I/O + // executor - in this case the executor of the socket - if the completion + // handler does not have its own. + using executor_type = boost::asio::associated_executor_t< + typename std::decay<decltype(completion_handler)>::type, + tcp::socket::executor_type>; + + executor_type get_executor() const noexcept + { + return boost::asio::get_associated_executor( + handler_, socket_.get_executor()); + } + + // Although not necessary for correctness, we may also preserve the + // allocator of the user-supplied completion handler. This is achieved by + // defining a nested type allocator_type and member function + // get_allocator. These obtain the completion handler's associated + // allocator, and default to std::allocator<void> if the completion + // handler does not have its own. + using allocator_type = boost::asio::associated_allocator_t< + typename std::decay<decltype(completion_handler)>::type, + std::allocator<void>>; + + allocator_type get_allocator() const noexcept + { + return boost::asio::get_associated_allocator( + handler_, std::allocator<void>{}); + } + }; + + // Initiate the underlying async_write operation using our intermediate + // completion handler. + auto encoded_message_buffer = boost::asio::buffer(*encoded_message); + boost::asio::async_write(socket, encoded_message_buffer, + intermediate_completion_handler{ + socket, std::move(encoded_message), + repeat_count, std::move(delay_timer), + intermediate_completion_handler::starting, + boost::asio::make_work_guard(socket.get_executor()), + std::forward<decltype(completion_handler)>(completion_handler)}); + }; + + // Encode the message and copy it into an allocated buffer. The buffer will + // be maintained for the lifetime of the composed asynchronous operation. + std::ostringstream os; + os << message; + std::unique_ptr<std::string> encoded_message(new std::string(os.str())); + + // Create a steady_timer to be used for the delay between messages. + std::unique_ptr<boost::asio::steady_timer> delay_timer( + new boost::asio::steady_timer(socket.get_executor())); + + // The boost::asio::async_initiate function takes: + // + // - our initiation function object, + // - the completion token, + // - the completion handler signature, and + // - any additional arguments we need to initiate the operation. + // + // It then asks the completion token to create a completion handler (i.e. a + // callback) with the specified signature, and invoke the initiation function + // object with this completion handler as well as the additional arguments. + // The return value of async_initiate is the result of our operation's + // initiating function. + // + // Note that we wrap non-const reference arguments in std::reference_wrapper + // to prevent incorrect decay-copies of these objects. + return boost::asio::async_initiate< + CompletionToken, void(boost::system::error_code)>( + initiation, token, std::ref(socket), + std::move(encoded_message), repeat_count, + std::move(delay_timer)); +} + +//------------------------------------------------------------------------------ + +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_messages(socket, "Testing callback\r\n", 5, + [](const boost::system::error_code& error) + { + if (!error) + { + std::cout << "Messages sent\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<void> f = async_write_messages( + socket, "Testing future\r\n", 5, boost::asio::use_future); + + io_context.run(); + + try + { + // Get the result of the operation. + f.get(); + std::cout << "Messages sent\n"; + } + catch (const std::exception& e) + { + std::cout << "Error: " << e.what() << "\n"; + } +} + +//------------------------------------------------------------------------------ + +int main() +{ + test_callback(); + test_future(); +} diff --git a/src/boost/libs/asio/example/cpp14/operations/composed_7.cpp b/src/boost/libs/asio/example/cpp14/operations/composed_7.cpp new file mode 100644 index 000000000..352693085 --- /dev/null +++ b/src/boost/libs/asio/example/cpp14/operations/composed_7.cpp @@ -0,0 +1,219 @@ +// +// composed_7.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/compose.hpp> +#include <boost/asio/io_context.hpp> +#include <boost/asio/ip/tcp.hpp> +#include <boost/asio/steady_timer.hpp> +#include <boost/asio/use_future.hpp> +#include <boost/asio/write.hpp> +#include <functional> +#include <iostream> +#include <memory> +#include <sstream> +#include <string> +#include <type_traits> +#include <utility> + +using boost::asio::ip::tcp; + +// NOTE: This example requires the new boost::asio::async_compose function. For +// an example that works with the Networking TS style of completion tokens, +// please see an older version of asio. + +//------------------------------------------------------------------------------ + +// This composed operation shows composition of multiple underlying operations. +// It automatically serialises a message, using its I/O streams insertion +// operator, before sending it N times on the socket. To do this, it must +// allocate a buffer for the encoded message and ensure this buffer's validity +// until all underlying async_write operation complete. A one second delay is +// inserted prior to each write operation, using a steady_timer. + +template <typename T, typename CompletionToken> +auto async_write_messages(tcp::socket& socket, + const T& message, std::size_t repeat_count, + 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 always void. + // In this example, when the completion token is boost::asio::yield_context + // (used for stackful coroutines) the return type would be also be void, as + // there is no non-error argument to the completion handler. When the + // completion token is boost::asio::use_future it would be std::future<void>. + // + // In C++14 we can omit the return type as it is automatically deduced from + // the return type of boost::asio::async_initiate. +{ + // Encode the message and copy it into an allocated buffer. The buffer will + // be maintained for the lifetime of the composed asynchronous operation. + std::ostringstream os; + os << message; + std::unique_ptr<std::string> encoded_message(new std::string(os.str())); + + // Create a steady_timer to be used for the delay between messages. + std::unique_ptr<boost::asio::steady_timer> delay_timer( + new boost::asio::steady_timer(socket.get_executor())); + + // To manage the cycle between the multiple underlying asychronous + // operations, our implementation is a state machine. + enum { starting, waiting, writing }; + + // The boost::asio::async_compose function takes: + // + // - our asynchronous operation implementation, + // - the completion token, + // - the completion handler signature, and + // - any I/O objects (or executors) used by the operation + // + // It then wraps our implementation, which is implemented here as a state + // machine in a lambda, in an intermediate completion handler that meets the + // requirements of a conforming asynchronous operation. This includes + // tracking outstanding work against the I/O executors associated with the + // operation (in this example, this is the socket's executor). + // + // The first argument to our lambda is a reference to the enclosing + // intermediate completion handler. This intermediate completion handler is + // provided for us by the boost::asio::async_compose function, and takes care + // of all the details required to implement a conforming asynchronous + // operation. When calling an underlying asynchronous operation, we pass it + // this enclosing intermediate completion handler as the completion token. + // + // All arguments to our lambda after the first must be defaulted to allow the + // state machine to be started, as well as to allow the completion handler to + // match the completion signature of both the async_write and + // steady_timer::async_wait operations. + return boost::asio::async_compose< + CompletionToken, void(boost::system::error_code)>( + [ + // The implementation holds a reference to the socket as it is used for + // multiple async_write operations. + &socket, + + // The allocated buffer for the encoded message. The std::unique_ptr + // smart pointer is move-only, and as a consequence our lambda + // implementation is also move-only. + encoded_message = std::move(encoded_message), + + // The repeat count remaining. + repeat_count, + + // A steady timer used for introducing a delay. + delay_timer = std::move(delay_timer), + + // To manage the cycle between the multiple underlying asychronous + // operations, our implementation is a state machine. + state = starting + ] + ( + auto& self, + const boost::system::error_code& error = {}, + std::size_t = 0 + ) mutable + { + if (!error) + { + switch (state) + { + case starting: + case writing: + if (repeat_count > 0) + { + --repeat_count; + state = waiting; + delay_timer->expires_after(std::chrono::seconds(1)); + delay_timer->async_wait(std::move(self)); + return; // Composed operation not yet complete. + } + break; // Composed operation complete, continue below. + case waiting: + state = writing; + boost::asio::async_write(socket, + boost::asio::buffer(*encoded_message), std::move(self)); + return; // Composed operation not yet complete. + } + } + + // This point is reached only on completion of the entire composed + // operation. + + // Deallocate the encoded message and delay timer before calling the + // user-supplied completion handler. + encoded_message.reset(); + delay_timer.reset(); + + // Call the user-supplied handler with the result of the operation. + self.complete(error); + }, + token, socket); +} + +//------------------------------------------------------------------------------ + +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_messages(socket, "Testing callback\r\n", 5, + [](const boost::system::error_code& error) + { + if (!error) + { + std::cout << "Messages sent\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<void> f = async_write_messages( + socket, "Testing future\r\n", 5, boost::asio::use_future); + + io_context.run(); + + try + { + // Get the result of the operation. + f.get(); + std::cout << "Messages sent\n"; + } + catch (const std::exception& e) + { + std::cout << "Error: " << e.what() << "\n"; + } +} + +//------------------------------------------------------------------------------ + +int main() +{ + test_callback(); + test_future(); +} diff --git a/src/boost/libs/asio/example/cpp14/operations/composed_8.cpp b/src/boost/libs/asio/example/cpp14/operations/composed_8.cpp new file mode 100644 index 000000000..9fe948cd6 --- /dev/null +++ b/src/boost/libs/asio/example/cpp14/operations/composed_8.cpp @@ -0,0 +1,212 @@ +// +// composed_8.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/compose.hpp> +#include <boost/asio/coroutine.hpp> +#include <boost/asio/io_context.hpp> +#include <boost/asio/ip/tcp.hpp> +#include <boost/asio/steady_timer.hpp> +#include <boost/asio/use_future.hpp> +#include <boost/asio/write.hpp> +#include <functional> +#include <iostream> +#include <memory> +#include <sstream> +#include <string> +#include <type_traits> +#include <utility> + +using boost::asio::ip::tcp; + +// NOTE: This example requires the new boost::asio::async_compose function. For +// an example that works with the Networking TS style of completion tokens, +// please see an older version of asio. + +//------------------------------------------------------------------------------ + +// This composed operation shows composition of multiple underlying operations, +// using asio's stackless coroutines support to express the flow of control. It +// automatically serialises a message, using its I/O streams insertion +// operator, before sending it N times on the socket. To do this, it must +// allocate a buffer for the encoded message and ensure this buffer's validity +// until all underlying async_write operation complete. A one second delay is +// inserted prior to each write operation, using a steady_timer. + +#include <boost/asio/yield.hpp> + +template <typename T, typename CompletionToken> +auto async_write_messages(tcp::socket& socket, + const T& message, std::size_t repeat_count, + 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 always void. + // In this example, when the completion token is boost::asio::yield_context + // (used for stackful coroutines) the return type would be also be void, as + // there is no non-error argument to the completion handler. When the + // completion token is boost::asio::use_future it would be std::future<void>. + // + // In C++14 we can omit the return type as it is automatically deduced from + // the return type of boost::asio::async_initiate. +{ + // Encode the message and copy it into an allocated buffer. The buffer will + // be maintained for the lifetime of the composed asynchronous operation. + std::ostringstream os; + os << message; + std::unique_ptr<std::string> encoded_message(new std::string(os.str())); + + // Create a steady_timer to be used for the delay between messages. + std::unique_ptr<boost::asio::steady_timer> delay_timer( + new boost::asio::steady_timer(socket.get_executor())); + + // The boost::asio::async_compose function takes: + // + // - our asynchronous operation implementation, + // - the completion token, + // - the completion handler signature, and + // - any I/O objects (or executors) used by the operation + // + // It then wraps our implementation, which is implemented here as a stackless + // coroutine in a lambda, in an intermediate completion handler that meets the + // requirements of a conforming asynchronous operation. This includes + // tracking outstanding work against the I/O executors associated with the + // operation (in this example, this is the socket's executor). + // + // The first argument to our lambda is a reference to the enclosing + // intermediate completion handler. This intermediate completion handler is + // provided for us by the boost::asio::async_compose function, and takes care + // of all the details required to implement a conforming asynchronous + // operation. When calling an underlying asynchronous operation, we pass it + // this enclosing intermediate completion handler as the completion token. + // + // All arguments to our lambda after the first must be defaulted to allow the + // state machine to be started, as well as to allow the completion handler to + // match the completion signature of both the async_write and + // steady_timer::async_wait operations. + return boost::asio::async_compose< + CompletionToken, void(boost::system::error_code)>( + [ + // The implementation holds a reference to the socket as it is used for + // multiple async_write operations. + &socket, + + // The allocated buffer for the encoded message. The std::unique_ptr + // smart pointer is move-only, and as a consequence our lambda + // implementation is also move-only. + encoded_message = std::move(encoded_message), + + // The repeat count remaining. + repeat_count, + + // A steady timer used for introducing a delay. + delay_timer = std::move(delay_timer), + + // The coroutine state. + coro = boost::asio::coroutine() + ] + ( + auto& self, + const boost::system::error_code& error = {}, + std::size_t = 0 + ) mutable + { + reenter (coro) + { + while (repeat_count > 0) + { + --repeat_count; + + delay_timer->expires_after(std::chrono::seconds(1)); + yield delay_timer->async_wait(std::move(self)); + if (error) + break; + + yield boost::asio::async_write(socket, + boost::asio::buffer(*encoded_message), std::move(self)); + if (error) + break; + } + + // Deallocate the encoded message and delay timer before calling the + // user-supplied completion handler. + encoded_message.reset(); + delay_timer.reset(); + + // Call the user-supplied handler with the result of the operation. + self.complete(error); + } + }, + token, socket); +} + +#include <boost/asio/unyield.hpp> + +//------------------------------------------------------------------------------ + +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_messages(socket, "Testing callback\r\n", 5, + [](const boost::system::error_code& error) + { + if (!error) + { + std::cout << "Messages sent\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<void> f = async_write_messages( + socket, "Testing future\r\n", 5, boost::asio::use_future); + + io_context.run(); + + try + { + // Get the result of the operation. + f.get(); + std::cout << "Messages sent\n"; + } + catch (const std::exception& e) + { + std::cout << "Error: " << e.what() << "\n"; + } +} + +//------------------------------------------------------------------------------ + +int main() +{ + test_callback(); + test_future(); +} |