Struct MessageMeta 

#[non_exhaustive]
pub struct MessageMeta {
    pub qos: QoS,
    pub retain: bool,
    pub dup: bool,
    pub v5: Option<Mqtt5Meta>,
}

Protocol metadata attached to an incoming MQTT message.

Delivered alongside every message (as Arc<MessageMeta>, shared across all subscribers of one publish). Read its fields; you never construct it in the receive path — but MessageMeta::new is provided so you can build one in your own handler tests.

Fields (Non-exhaustive)

Non-exhaustive structs could have additional fields added in future. Therefore, non-exhaustive structs cannot be constructed in external crates using the traditional Struct { .. } syntax; cannot be matched against without a wildcard ..; and struct update syntax will not work.

qos: QoS

QoS of the delivered PUBLISH packet — NOT the subscription’s granted QoS. With overlapping filters on one client the broker sends a single packet at the highest matching granted QoS, so a QoS-0 subscriber can observe a higher value here.

retain: bool

The broker delivered this as a retained message.

dup: bool

The dup flag was set (a redelivery of a QoS > 0 packet).

v5: Option<Mqtt5Meta>

MQTT 5 properties. Always None on MQTT 3.1.1 (the only wire protocol in 0.3); reserved so v5 support lands additively.

Implementations

impl MessageMeta

pub fn new(qos: QoS, retain: bool, dup: bool) -> MessageMeta

Build metadata for an MQTT 3.1.1 message (v5 == None).

The library uses this on the receive path; it is public so downstream code can construct a MessageMeta in tests (the type is #[non_exhaustive], so a struct literal is not available off-crate).

pub fn with_v5( qos: QoS, retain: bool, dup: bool, v5: Option<Mqtt5Meta>, ) -> MessageMeta

Build metadata carrying optional MQTT 5 properties.

Additive companion to new (which is the v5 == None shorthand); used on the receive path when the packet carried v5 properties, and available to downstream tests.

Trait Implementations

impl Clone for MessageMeta

fn clone(&self) -> MessageMeta

Returns a duplicate of the value.

fn clone_from(&mut self, source: &Self)

Performs copy-assignment from source.

impl Debug for MessageMeta

fn fmt(&self, f: &mut Formatter<'_>) -> Result<(), Error>

Formats the value using the given formatter.