forked from boostorg/mqtt5
Korina Šimičević
5034734fc4
Summary: resolves T13155 Reviewers: ivica Reviewed By: ivica Subscribers: miljen, iljazovic Maniphest Tasks: T13155 Differential Revision: https://repo.mireo.local/D26681
55 lines
2.7 KiB
Plaintext
55 lines
2.7 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:will_props Will properties]
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The Will Properties consist of the properties that determine when to publish the [reflink2 will Will] Message
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and the Application Message properties to be sent with the [reflink2 will Will] Message.
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The Will Properties consists of a Property Length and the Properties.
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A Property consists of an Identifier and a value.
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This section lists all possible [reflink2 will Will] Properties and describes their usage:
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[table:will_props Will properties
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[[Identifier] [Value type] [Description]]
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[[will_delay_interval] [`int32_t`] [The delay in seconds that need to pass before Server publishes the Client's Will Message.]]
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[[payload_format_indicator] [`uint8_t`] [Value of 0 indicates that the Will Message is in unspecified bytes. Value of 1 indicates that the Will Message is UTF-8 Encoded Character Data.]]
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[[message_expiry_interval] [`int32_t`] [The lifetime of the Will Message in seconds. It is send as Publication Expiry Interval when it is published.]]
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[[content_type] [`std::string`] [A UTF-8 Encoded String describing the content of the Will Message.]]
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[[response_topic] [`std::string`] [A UTF-8 Encoded String which is used as the Topic Name for a response message.]]
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[[correlation_data] [`std::string`] [Binary Data used by the sender of the Request Message to identify which request the Response Message is for when it is received.]]
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[[user_property] [`std::vector<std::string>`] [A list of name, value pairs (__UTF8_STRING_PAIR__) defining User Properties.
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The meaning of these properties is not defined by the specification.]]
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]
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[h4 Usage]
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After creating an instance of [reflink2 will `async_mqtt5::will`], the subscript operator can be used to access a Property.
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The Identifiers listed in the table above are available within the `async_mqtt5::prop` namespace for Property access.
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[h4 Example]
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The following example shows how to set a Property value:
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[!c++]
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async_mqtt5::will will;
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will[async_mqtt5::prop::message_expiry_interval] = 90;
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will[async_mqtt5::prop::content_type] = "Notification";
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The following example shows how to retrieve a Property value:
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[note When retrieving a property value, the subscript operator will consistently return a `std::optional` of the value type for all properties,
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except for `async_mqtt5::prop::user_property`, where it will return an instance of its value type, `std::vector<std::string>`.]
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[!c++]
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std::optional<std::string> c_type = will[async_mqtt5::prop::content_type];
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if (c_type.has_value())
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// content type property was previously set
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else
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// content type property was not set
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[endsect]
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