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119 lines
2.8 KiB
Plaintext
119 lines
2.8 KiB
Plaintext
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Copyright (c) 2023 Mireo
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Distributed under the Boost Software License, Version 1.0. (See accompanying
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file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
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]
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[section:completion_tokens Completion tokens]
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The __Client__ is built upon __Asio__ and thus follows the same principles.
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This section illustrates the usage of __Client__ async
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functions with different __CompletionToken__.
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# [link async_mqtt5.examples.callbacks Async functions with callbacks]
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# [link async_mqtt5.examples.cpp20_coroutines Async functions with C++20 coroutines]
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# [link async_mqtt5.examples.futures Async functions with futures]
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[endsect]
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[section:callbacks Async functions with callbacks]
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The following list is a reference on how to use asynchrous functions in __Client__ with callbacks.
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[import ../../../example/callbacks.cpp]
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[h4 Publish]
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[publish_callback]
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[h4 Subscribe]
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[subscribe_callback]
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[h4 Receive]
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[receive_callback]
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[h4 Unsubscribe]
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[unsubscribe_callback]
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[h4 Disconnect]
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[disconnect_callback]
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[endsect]
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[section:cpp20_coroutines Async functions with C++20 coroutines]
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This example demonstrates how to use __Client__ asynchrous functions with C++20 coroutines
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using __USE_AWAITABLE__.
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[import ../../../example/cpp20_coroutines.cpp]
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[h2 use_awaitable]
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In this section, each asynchronous function is invoked with __USE_AWAITABLE__ completion token.
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When using this completion token, co_await will throw exceptions instead of returning an error code.
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If you do not wish to throw exceptions, refer to the following use_nothrow_awaitable section.
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[h4 Publish]
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[publish_coro]
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[h4 Subscribe]
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[subscribe_coro]
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[h4 Receive]
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[receive_coro]
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[h4 Unsubscribe]
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[unsubscribe_coro]
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[h4 Disconnect]
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[disconnect_coro]
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[h2 use_nothrow_awaitable]
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The following examples will use a modified completion token.
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Using this completion token instead of __USE_AWAITABLE__ will prevent co_await from throwing exceptions.
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Instead, co_await will return the error code along with other values specified in the handler signature.
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[no_throw_awaitable]
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[h4 Publish]
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[publish_coro_nothrow]
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[h4 Subscribe]
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[subscribe_coro_nothrow]
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[h4 Receive]
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[receive_coro_nothrow]
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[h4 Unsubscribe]
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[unsubscribe_coro_nothrow]
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[h4 Disconnect]
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[disconnect_coro_nothrow]
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[endsect]
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[section:futures Async functions with futures]
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The following list is a reference on how to use the mqtt_client with __USE_FUTURE__ as the completion token.
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Each get() call on std::future will block the current thread and wait until the future has a valid result.
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That is why it is essential to ensure that the execution context is running in more than one thread.
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[import ../../../example/futures.cpp]
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[h4 Publish]
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[publish_future]
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[h4 Subscribe]
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[subscribe_future]
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[h4 Receive]
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[receive_future]
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[h4 Unsubscribe]
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[unsubscribe_future]
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[h4 Disconnect]
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[disconnect_future]
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[endsect]
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