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1acdd99f28
Summary: - refactor property encoding - change user property type to be std::pair<std::string, std::string> Reviewers: ivica Reviewed By: ivica Subscribers: korina Differential Revision: https://repo.mireo.local/D27867
58 lines
3.3 KiB
Plaintext
58 lines
3.3 KiB
Plaintext
[section:connect_props CONNECT properties]
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The last field in the Variable header of __CONNECT__ packet is a set of Properties.
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A set contains a Property Length followed by the Properties.
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A Property consists of an Identifier and a value.
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This section lists all possible __CONNECT__ Properties and describes their usage:
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[table:connect_props CONNECT properties
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[[Identifier] [Value type] [Description]]
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[[session_expiry_interval] [`uint32_t`] [Represents the Session Expiry Internal in seconds.]]
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[[receive_maximum] [`uint16_t`] [The maximum number of QoS 1 and QoS 2 publications that the Client is willing to process concurrently.]]
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[[maximum_packet_size] [`uint32_t`] [The maximum __PACKET_SIZE__ in bytes as defined by the specification that the Client is willing to process.]]
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[[topic_alias_maximum] [`uint16_t`] [The highest value that the Client will accept as a Topic Alias sent by the Server.]]
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[[request_response_information] [`uint8_t`] [The value of 0 signals that the Server MUST NOT return Response Information in __CONNACK__. If the value if 1, it MAY return it.]]
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[[request_problem_information] [`uint8_t`] [The value of 0 signals that the Server MAY return a Reason String or User Properties on a __CONNACK__ or __DISCONNECT__ packet,
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but MUST NOT send them on any packet other than __PUBLISH__, __CONNACK__, or __DISCONNECT__.
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If the value is 1, the Server MAY return a Reason String or User Properties where it is allowed.]]
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[[user_property] [`std::pair<std::string, std::string>`] [Name, value pair (__UTF8_STRING_PAIR__) defining User Property. There can be multiple pairs in one packet.
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The meaning of these properties is not defined by the specification.]]
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[[authentication_method] [`std::string`] [A UTF-8 Encoded String containing the name of the authentication method used for extended authentication.]]
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[[authentication_data] [`std::string`] [Binary Data containing authentication data. The contents of the data are defined by the authentication method.]]
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]
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[h4 Usage]
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After obtaining an instance of `async_mqtt5::connect_props`, 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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[note When accessing a property value, the subscript operator will 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 `std::vector<std::pair<std::string, std::string>>`.]
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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::connect_props props;
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props[async_mqtt5::prop::session_expiry_interval] = 1200;
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props[async_mqtt5::prop::receive_maximum] = uint16_t(100);
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props[async_mqtt5::prop::user_property].emplace_back("name", "value");
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The following example shows how to retrieve a Property value:
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[!c++]
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std::optional<std::string> auth_method = props[async_mqtt5::prop::authentication_method];
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if (auth_method.has_value())
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// authentication method property was previously set
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else
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// authentication method property was not set
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std::vector<std::pair<std::string, std::string>>& user_props = props[async_mqtt5::prop::user_property];
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if (!user_props.empty())
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// user property was previously set
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else
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// user property was not set
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[endsect]
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