Struct WriteStamp 

pub struct WriteStamp {
    pub observed_at: Instant,
    pub source: ChangeSource,
}

When a value was observed, and by what.

The critical word is observed, not written. A fetch() reads the device at request time but only calls set_property when the SOAP response comes back, which can be hundreds of milliseconds later. If the stamp were taken at write time, a slow fetch() would always look newer than an event that arrived while it was in flight, and would overwrite a fresher value with a stale one — the speaker would visibly snap back to its old volume.

So the caller stamps the moment the observation was made (WriteStamp::observed_at) and the store rejects any write that is older than the one already recorded. Event and local-action writes have no such gap and use WriteStamp::now.

Fields

observed_at: Instant

When the underlying observation was made — not when it was written.

source: ChangeSource

What produced the observation.

Implementations

impl WriteStamp

pub fn now(source: ChangeSource) -> WriteStamp

Stamp an observation made right now.

Correct for ChangeSource::Event and ChangeSource::LocalAction, where observation and write happen in the same breath.

pub fn observed_at(source: ChangeSource, observed_at: Instant) -> WriteStamp

Stamp an observation made at a known earlier instant.

Use this for fetch(): pass the Instant captured before the SOAP request, so a response that lands after a newer event loses to it.

Trait Implementations

impl Clone for WriteStamp

fn clone(&self) -> WriteStamp

Returns a duplicate of the value.

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

Performs copy-assignment from source.

impl Copy for WriteStamp

impl Debug for WriteStamp

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

Formats the value using the given formatter.