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[mqtt-client] mqtt_client with asio::use_future documented

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Summary: related to T12804

Reviewers: ivica

Reviewed By: ivica

Subscribers: miljen, iljazovic

Differential Revision: https://repo.mireo.local/D26370
This commit is contained in:
Korina Šimičević
2023-11-02 13:15:23 +01:00
parent e7227d70ec
commit ed0e838d87
5 changed files with 153 additions and 18 deletions
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example/cpp20_coroutines.cpp
+19 -17
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@@ -22,7 +22,7 @@ using client_type = async_mqtt5::mqtt_client<stream_type>;
*
* In this example, each asynchronous function is invoked with boost::asio::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 nothrow_awaitable and nothrow_coroutine() example.
* 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 an Application Message with QoS 0.
@@ -75,14 +75,15 @@ asio::awaitable<void> coroutine(client_type& client) {
// 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.
auto [topic, payload, publish_props] = co_await client.async_receive(asio::use_awaitable);
if (!sub_codes[0])
auto [topic, payload, publish_props] = co_await client.async_receive(asio::use_awaitable);
// 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
// will return std::vector<reason_code> and unsuback_props.
auto [unsub_codes, unsub_props] = co_await client.async_unsubscribe(
std::vector<std::string>{ "test/mqtt-test" }, async_mqtt5::unsubscribe_props {},
"test/mqtt-test", async_mqtt5::unsubscribe_props {},
asio::use_awaitable
);
@@ -103,13 +104,12 @@ asio::awaitable<void> coroutine(client_type& client) {
* will prevent co_await from throwing exceptions. Instead, co_await will return the error code
* along with other values specified in the handler signature.
*/
constexpr auto nothrow_awaitable = asio::as_tuple(asio::use_awaitable);
constexpr auto use_nothrow_awaitable = asio::as_tuple(asio::use_awaitable);
/**
* In this coroutine, each asynchronous function is called with nothrow_awaitable completion token.
* Unlike the asio::use_awaitable completion token, nothrow_awaitable does not throw an exception
* when an error has occurred. Instead, each co_await will return an error_code, similar to
* the behavior of using callbacks.
* 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) {
async_mqtt5::error_code ec;
@@ -118,21 +118,21 @@ asio::awaitable<void> nothrow_coroutine(client_type& client) {
std::tie(ec) = co_await client.async_publish<async_mqtt5::qos_e::at_most_once>(
"test/mqtt-test", "Hello world!",
async_mqtt5::retain_e::yes, async_mqtt5::publish_props {},
nothrow_awaitable
use_nothrow_awaitable
);
async_mqtt5::puback_props puback_props;
std::tie(ec, rc, puback_props) = co_await client.async_publish<async_mqtt5::qos_e::at_least_once>(
"test/mqtt-test", "Hello world!",
async_mqtt5::retain_e::yes, async_mqtt5::publish_props {},
nothrow_awaitable
use_nothrow_awaitable
);
async_mqtt5::pubcomp_props pubcomp_props;
std::tie(ec, rc, pubcomp_props) = co_await client.async_publish<async_mqtt5::qos_e::exactly_once>(
"test/mqtt-test", "Hello world!",
async_mqtt5::retain_e::yes, async_mqtt5::publish_props {},
nothrow_awaitable
use_nothrow_awaitable
);
auto sub_topic = async_mqtt5::subscribe_topic{
@@ -147,23 +147,25 @@ asio::awaitable<void> nothrow_coroutine(client_type& client) {
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 {}, nothrow_awaitable
sub_topic, async_mqtt5::subscribe_props {}, use_nothrow_awaitable
);
std::string topic, payload;
async_mqtt5::publish_props publish_props;
std::tie(ec, topic, payload, publish_props) = co_await client.async_receive(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);
}
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 {},
nothrow_awaitable
use_nothrow_awaitable
);
std::tie(ec) = co_await client.async_disconnect(
async_mqtt5::disconnect_rc_e::disconnect_with_will_message,
async_mqtt5::disconnect_props {},
nothrow_awaitable
use_nothrow_awaitable
);
co_return;