Struct MessageBuilder 

pub struct MessageBuilder { /* private fields */ }

Submessage aggregator.

Initialized on open with a pre-allocated byte list starting at the RTPS header. Submessages are appended via try_add_submessage; when full the caller must finish() + open a new builder.

Implementations

impl MessageBuilder

pub fn open(header: RtpsHeader, targets: Rc<Vec<Locator>>, mtu: usize) -> Self

Opens a new builder with the given RTPS header, targets and MTU budget.

Panics: if mtu is smaller than the RTPS header (20 bytes).

pub fn submsg_count(&self) -> usize

Number of submessages inserted so far.

pub fn is_empty(&self) -> bool

True if the builder contains only the RTPS header.

pub fn len(&self) -> usize

Current total byte count (header + already appended submessages).

pub fn remaining(&self) -> usize

Remaining budget in bytes.

pub fn try_add_submessage( &mut self, id: SubmessageId, flags: u8, body: &[u8], ) -> Result<(), AddError>

Tries to append a submessage. Returns AddError::WouldExceedMtu if it no longer fits — then finish() + a new builder is due.

flags contains only the submessage-specific flags (F, L, Q, H, K, N etc.). The E bit (little-endian) is set by the builder itself, consistently for the whole datagram.

Errors

• AddError::WouldExceedMtu on size overflow.
• AddError::BodyTooLarge if body.len() > u16::MAX.

pub fn try_add_submessage_split( &mut self, id: SubmessageId, flags: u8, header_body: &[u8], payload_tail: &[u8], ) -> Result<(), AddError>

Like Self::try_add_submessage, but the body in two slices — avoids an intermediate Vec when the caller already has header_body and payload_tail separately. Exactly the hot- path case for the DATA submessage: 20-byte fixed header (the caller writes into a stack buffer) + N byte serializedData (borrowed from the cache Arc<[u8]>). Without this variant the caller needs Vec::with_capacity(20+N) + extend(header) + extend(payload) — a heap alloc + copy of N bytes, which is fully eliminated here. octets_to_next_header = header_body.len() + payload_tail.len().

Errors

Same as Self::try_add_submessage.

pub fn finish(self) -> Option<OutboundDatagram>

Converts into a finished OutboundDatagram.

Returns None for an empty builder (only the RTPS header without submessages) — this lets callers simply discard unused builders without having to check is_empty() first.

Trait Implementations

impl Debug for MessageBuilder

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

Formats the value using the given formatter.