Struct Tcancel 

pub struct Tcancel {
    pub oldtag: u16,
    pub binding: u64,
}

r[impl jetstream.subscription.cancel] Cancellation bears a fresh tag and names its target in the payload, which is the shape 9P’s Tflush uses and the one this specification adopted after an earlier draft got the mechanics backwards. Sending it under the subscription’s own tag would put two calls under one correlation key while that tag is still in flight.

Fields

oldtag: u16

The tag of the subscription being cancelled.

binding: u64

r[impl jetstream.subscription.identity] Zero when the cancellation travels on the subscription’s own lane, where oldtag is unambiguous. Otherwise the binding identifier, because tags are allocated per lane and a concurrent subscription elsewhere on the session may hold the same number.

Zero is reserved and never a real binding, which is what makes the sentinel sound. Prefer Tcancel::on_lane and Tcancel::off_lane over writing this field: the specification used to recommend a counter starting at zero, so the first subscription of a session got a binding indistinguishable from “no binding” — and a receiver then resolved oldtag against the wrong lane.

Implementations

impl Tcancel

pub fn on_lane(oldtag: u16) -> Tcancel

Cancel a subscription on the lane this cancellation travels. oldtag is unambiguous there, so no binding is named.

pub fn off_lane(oldtag: u16, binding: u64) -> Tcancel

Cancel a subscription living on some other lane of the session, naming it by its binding identifier.

Panics

If binding is zero, which is reserved for the on-lane case. A caller reaching this has allocated bindings from a counter starting at zero — the allocation r[jetstream.subscription.identity] now forbids for exactly this reason.

pub fn target_binding(&self) -> Option<u64>

The binding this names, or None when it is on the subscription’s own lane.

Trait Implementations

impl Clone for Tcancel

fn clone(&self) -> Tcancel

Returns a duplicate of the value.

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

Performs copy-assignment from source.

impl Debug for Tcancel

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

Formats the value using the given formatter.

impl Eq for Tcancel

impl PartialEq for Tcancel

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

Equality operator ==.

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

Inequality operator !=.

impl StructuralPartialEq for Tcancel

impl WireFormat for Tcancel

fn byte_size(&self) -> u32

Returns the number of bytes necessary to fully encode self.

fn encode<W>(&self, _writer: &mut W) -> Result<(), Error>

where W: Write,

Encodes self into writer.

fn decode<R>(_reader: &mut R) -> Result<Tcancel, Error>

where R: Read,

Decodes Self from reader.