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publisher & receiver examples, better completion token examples

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Reviewers: iljazovic, ivica

Reviewed By: ivica

Subscribers: miljen

Differential Revision: https://repo.mireo.local/D26582
This commit is contained in:
Korina Šimičević
2023-11-17 10:11:00 +01:00
parent 376393fbfa
commit 73620e5653
12 changed files with 372 additions and 149 deletions
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example/cpp20_coroutines.cpp
+31 -50
View File
@@ -1,5 +1,3 @@
//[cpp20_coroutines_examples
#include <boost/asio/as_tuple.hpp>
#include <boost/asio/co_spawn.hpp>
#include <boost/asio/detached.hpp>
@@ -15,16 +13,8 @@ namespace asio = boost::asio;
using stream_type = asio::ip::tcp::socket;
using client_type = async_mqtt5::mqtt_client<stream_type>;
/**
* An example of a coroutine. It must have a return type of boost::asio::awaitable<T>.
* When an asynchronous function is called, the coroutine is suspended.
* After the asynchronous operation finishes, the coroutine resumes from the point it was suspended.
*
* In this example, each asynchronous function is invoked with ``__USE_AWAITABLE__`` completion token.
* When using this completion token, co_await will throw exceptions instead of returning an error code.
* If you do not wish to throw exceptions, refer to the following use_nothrow_awaitable and nothrow_coroutine() example.
*/
asio::awaitable<void> coroutine(client_type& client) {
//[publish_coro
// Publish an Application Message with QoS 0.
// The handler signature for this function is void (error_code).
// However, when using asio::use_awaitable as a completion token,
@@ -52,32 +42,29 @@ asio::awaitable<void> coroutine(client_type& client) {
async_mqtt5::retain_e::yes, async_mqtt5::publish_props {},
asio::use_awaitable
);
//]
auto sub_topic = async_mqtt5::subscribe_topic {
"test/mqtt-test", {
async_mqtt5::qos_e::exactly_once,
async_mqtt5::subscribe_options::no_local_e::no,
async_mqtt5::subscribe_options::retain_as_published_e::retain,
async_mqtt5::subscribe_options::retain_handling_e::send
}
};
//[subscribe_coro
// Subscribe to a single Topic.
// The handler signature for this function is void (error_code, std::vector<reason_code>, suback_props).
// With asio::use_awaitable as a completion token, the co_await
// will return std::vector<reason_code> and suback_props.
auto [sub_codes, sub_props] = co_await client.async_subscribe(
sub_topic, async_mqtt5::subscribe_props {}, asio::use_awaitable
{ "test/mqtt-test", { async_mqtt5::qos_e::exactly_once } },
async_mqtt5::subscribe_props {}, asio::use_awaitable
);
//]
//[receive_coro
// Receive an Application Message.
// The co_await call will return std::string (topic), std::string (payload) and publish_props.
// Note: the coroutine will be suspended until an Application Message is ready to be received
// or an error has occurred. In theory, the coroutine could be suspended indefinitely.
// Avoid calling this if you have not successfully subscribed to a Topic.
if (!sub_codes[0])
auto [topic, payload, publish_props] = co_await client.async_receive(asio::use_awaitable);
auto [topic, payload, publish_props] = co_await client.async_receive(asio::use_awaitable);
//]
//[unsubscribe_coro
// Unsubscribe from the Topic.
// The handler signature for this function is void (error_code, std::vector<reason_code>, unsuback_props).
// With asio::use_awaitable as a completion token, the co_await
@@ -86,7 +73,9 @@ asio::awaitable<void> coroutine(client_type& client) {
"test/mqtt-test", async_mqtt5::unsubscribe_props {},
asio::use_awaitable
);
//]
//[disconnect_coro
// Disconnect the Client.
// With asio::use_awaitable as a completion token and void (error_code) as the completion signature,
// the co_await has nothing to return.
@@ -95,23 +84,18 @@ asio::awaitable<void> coroutine(client_type& client) {
async_mqtt5::disconnect_props {},
asio::use_awaitable
);
//]
co_return;
}
/**
* A modified completion token. Using this completion token instead of ``__USE_AWAITABLE__``
* will prevent co_await from throwing exceptions. Instead, co_await will return the error code
* along with other values specified in the handler signature.
*/
//[no_throw_awaitable
constexpr auto use_nothrow_awaitable = asio::as_tuple(asio::use_awaitable);
//]
/**
* In this coroutine, each asynchronous function is called with use_nothrow_awaitable completion token.
* Each co_await will return an error_code, similar to the behavior of using callbacks
* (see ``__EXAMPLE_CALLBACK__``).
*/
asio::awaitable<void> nothrow_coroutine(client_type& client) {
//[publish_coro_nothrow
async_mqtt5::error_code ec;
async_mqtt5::reason_code rc;
@@ -134,39 +118,38 @@ asio::awaitable<void> nothrow_coroutine(client_type& client) {
async_mqtt5::retain_e::yes, async_mqtt5::publish_props {},
use_nothrow_awaitable
);
//]
auto sub_topic = async_mqtt5::subscribe_topic{
"test/mqtt-test", {
async_mqtt5::qos_e::exactly_once,
async_mqtt5::subscribe_options::no_local_e::no,
async_mqtt5::subscribe_options::retain_as_published_e::retain,
async_mqtt5::subscribe_options::retain_handling_e::send
}
};
//[subscribe_coro_nothrow
std::vector<async_mqtt5::reason_code> rcs;
async_mqtt5::suback_props suback_props;
std::tie(ec, rcs, suback_props) = co_await client.async_subscribe(
sub_topic, async_mqtt5::subscribe_props {}, use_nothrow_awaitable
{ "test/mqtt-test", { async_mqtt5::qos_e::exactly_once } },
async_mqtt5::subscribe_props {}, use_nothrow_awaitable
);
//]
if (!rcs[0]) {
std::string topic, payload;
async_mqtt5::publish_props publish_props;
std::tie(ec, topic, payload, publish_props) = co_await client.async_receive(use_nothrow_awaitable);
}
//[receive_coro_nothrow
std::string topic, payload;
async_mqtt5::publish_props publish_props;
std::tie(ec, topic, payload, publish_props) = co_await client.async_receive(use_nothrow_awaitable);
//]
//[unsubscribe_coro_nothrow
async_mqtt5::unsuback_props unsuback_props;
std::tie(ec, rcs, unsuback_props) = co_await client.async_unsubscribe(
std::vector<std::string>{ "test/mqtt-test" }, async_mqtt5::unsubscribe_props {},
use_nothrow_awaitable
);
//]
//[disconnect_coro_nothrow
std::tie(ec) = co_await client.async_disconnect(
async_mqtt5::disconnect_rc_e::disconnect_with_will_message,
async_mqtt5::disconnect_props {},
use_nothrow_awaitable
);
//]
co_return;
}
@@ -188,5 +171,3 @@ int main(int argc, char** argv) {
ioc.run();
}
//]