Struct MessageInfo 

pub struct MessageInfo { /* private fields */ }

Metadata about a received message

Contains information about the source and timing of a message.

ADOPT-BOUNDED against rclrs’s MessageInfo, which exposes the whole rmw_message_info_t. This is a flat struct of what an embedded backend can fill: both timestamps, both sequence numbers and a 24-byte publisher gid. Whether a message carries it at all is a BACKEND property — zenoh fills it from the attachment, Cyclone from take_with_info, and a backend that reports no metadata hands the callback None rather than a zeroed value. How many gid bytes mean anything is backend-specific too: see publisher_gid.

Implementations

impl MessageInfo

pub const fn new() -> MessageInfo

Create a new MessageInfo with all fields set to defaults

pub const fn with_timestamps(source: Time, received: Time) -> MessageInfo

Create a MessageInfo with the given timestamps

pub const fn source_timestamp(&self) -> Time

Get the timestamp when the message was published

pub const fn received_timestamp(&self) -> Time

Get the timestamp when the message was received

pub const fn publication_sequence_number(&self) -> i64

Get the publication sequence number

pub const fn reception_sequence_number(&self) -> i64

Get the reception sequence number

pub const fn publisher_gid(&self) -> &[u8; 24]

Get the publisher’s Global Identifier (GID).

The array is 24 bytes. How many of them MEAN anything is a backend property.

The width is upstream’s (PUBLISHER_GID_SIZE), so this value and the rmw_gid_t the get_gid_for_publisher vtable slot fills are one type — and, since issue 1495, one VALUE on the backends that produce either:

• zenoh fills 16 and zero-pads 8. The 16 are XXH3-128 of the sending entity’s liveliness keyexpr — rmw_zenoh_cpp’s own derivation, so it is the gid the sender’s get_gid reports and the gid ros2 topic info --verbose prints for it, ours or a stock peer’s. RMW_ATTACHMENT_SIZE carries 16 because that is rmw_zenoh_cpp’s wire layout (its reader REJECTS any other length); the padding is written by pad_publisher_gid. Compare whole arrays anyway.
• Cyclone fills 16 and zero-pads 8: the sending WRITER’s GUID, which is what its get_gid reports and a DDS graph prints. A stock Humble rmw_cyclonedds_cpp subscriber reports something else here (the 8-byte publication handle), so do not compare this field against one read from such a peer.
• XRCE and uORB never fill it. A backend that reports no metadata leaves the message_info() callback a None, not a zeroed gid.

An all-zero gid therefore means “this backend did not say” (or, on Cyclone, that the writer unmatched before the take), never “the publisher’s id is zero”.

pub fn set_source_timestamp(&mut self, ts: Time)

Set the source timestamp

pub fn set_received_timestamp(&mut self, ts: Time)

Set the received timestamp

pub fn set_publication_sequence_number(&mut self, seq: i64)

Set the publication sequence number

pub fn set_reception_sequence_number(&mut self, seq: i64)

Set the reception sequence number

pub fn set_publisher_gid(&mut self, gid: [u8; 24])

Set the publisher GID.

Takes the full PUBLISHER_GID_SIZE width. A backend whose identity is narrower zero-extends it through pad_publisher_gid rather than building the array itself — see publisher_gid for what a reader may and may not conclude from the result.

Trait Implementations

impl Clone for MessageInfo

fn clone(&self) -> MessageInfo

Returns a duplicate of the value.

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

Performs copy-assignment from source.

impl Copy for MessageInfo

impl Debug for MessageInfo

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

Formats the value using the given formatter.

impl Default for MessageInfo

fn default() -> MessageInfo

Returns the “default value” for a type.

impl Eq for MessageInfo

impl PartialEq for MessageInfo

fn eq(&self, other: &MessageInfo) -> bool

Equality operator ==.

fn ne(&self, other: &Rhs) -> bool

Inequality operator !=.

impl StructuralPartialEq for MessageInfo