218 lines
7.4 KiB
C++
218 lines
7.4 KiB
C++
//
|
|
// composed_8.cpp
|
|
// ~~~~~~~~~~~~~~
|
|
//
|
|
// Copyright (c) 2003-2019 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,
|
|
// 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>
|
|
|
|
// In this example, the composed operation's logic is implemented as a state
|
|
// machine within a hand-crafted function object.
|
|
struct async_write_messages_implementation
|
|
{
|
|
// The implementation holds a reference to the socket as it is used for
|
|
// multiple async_write operations.
|
|
tcp::socket& socket_;
|
|
|
|
// The allocated buffer for the encoded message. The std::unique_ptr smart
|
|
// pointer is move-only, and as a consequence our implementation 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_;
|
|
|
|
// The coroutine state.
|
|
boost::asio::coroutine coro_;
|
|
|
|
// The first argument to our function object's call operator 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 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.
|
|
template <typename Self>
|
|
void operator()(Self& self,
|
|
const boost::system::error_code& error = boost::system::error_code(),
|
|
std::size_t = 0)
|
|
{
|
|
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);
|
|
}
|
|
}
|
|
};
|
|
|
|
#include <boost/asio/unyield.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>.
|
|
-> typename boost::asio::async_result<
|
|
typename std::decay<CompletionToken>::type,
|
|
void(boost::system::error_code)>::return_type
|
|
{
|
|
// 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 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).
|
|
return boost::asio::async_compose<
|
|
CompletionToken, void(boost::system::error_code)>(
|
|
async_write_messages_implementation{socket,
|
|
std::move(encoded_message), repeat_count,
|
|
std::move(delay_timer), boost::asio::coroutine()},
|
|
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();
|
|
}
|