Struct PacketWriter 

pub struct PacketWriter<B> {
    buf: B,
    max_packet_size: Option<NonZeroU32>,
}

A buffering, sans-io packet serializer.

Packets are encoded in place into a ByteBuffer with write; the accumulated bytes are then drained by an I/O driver with pending + consume. This is the outbound mirror of PacketReader: one reusable buffer holds many coalesced packets, so there is no per-packet allocation.

Pair it with ArrayBuffer on no_std targets or GrowBuffer when alloc is available.

Fields

buf: B

max_packet_size: Option<NonZeroU32>

Implementations

impl PacketWriter<GrowBuffer>

pub const fn new() -> Self

Available on crate feature alloc only.

Creates an empty heap-backed writer with no packet-size limit.

pub fn with_capacity(capacity: usize) -> Self

Available on crate feature alloc only.

Creates an empty heap-backed writer preallocating capacity bytes.

pub fn take(&mut self) -> Vec<u8>

Available on crate feature alloc only.

Takes all pending bytes as an owned Vec, leaving the writer empty.

Lets an I/O driver hand a batch of coalesced packets to a writer task by value without copying.

impl<B: ByteBuffer> PacketWriter<B>

pub const fn from_buffer(buf: B) -> Self

Creates a writer over the given byte storage with no packet-size limit.

pub const fn set_max_packet_size(&mut self, max: NonZeroU32)

Rejects any packet whose encoded size exceeds max bytes, before it is written into the buffer (§3.2.2.3.6).

pub fn write(&mut self, packet: &Packet<'_>) -> Result<(), WriteError>

Encodes packet, appending its bytes to the pending output.

Errors

• WriteError::TooLarge if the encoded packet exceeds the configured maximum packet size, or is too large to encode at all (its Remaining Length exceeds the VBI maximum); nothing is buffered.
• WriteError::BufferFull if a fixed-capacity buffer cannot fit it.
• WriteError::Encode if encoding fails (a bug; nothing is buffered).

pub(crate) fn write_with( &mut self, total_len: usize, encode: impl FnOnce(&mut Writer<'_>) -> Result<(), EncodeError>, ) -> Result<(), WriteError>

Encodes a packet produced incrementally by encode into the pending output; encode must write exactly total_len bytes. Building block for packets assembled from non-contiguous session storage (the SUBSCRIBE/UNSUBSCRIBE drain). Same size checks as write.

pub fn pending(&self) -> &[u8]

The encoded bytes waiting to be written to the transport.

pub fn is_empty(&self) -> bool

Returns true if no bytes are pending.

pub fn consume(&mut self, n: usize)

Marks the leading n pending bytes as written to the transport.

pub fn clear(&mut self)

Drops all pending bytes; call on connection loss before reusing.

Trait Implementations

impl Default for PacketWriter<GrowBuffer>

Available on crate feature alloc only.

fn default() -> Self

Returns the “default value” for a type.