Struct FetchStateMachine 

pub struct FetchStateMachine {
    state: FetchState,
}

Pure state machine for a MoQT fetch request. Transitions: Idle → Pending → Receiving → Done when the answer comes first, and Idle → Pending → Unanswered → Done when the response stream ends first.

Fields

state: FetchState

Implementations

impl FetchStateMachine

pub fn new() -> Self

Creates a new state machine in the FetchState::Idle state.

pub fn state(&self) -> FetchState

Returns the current state of the fetch request.

pub fn on_fetch_sent(&mut self) -> Result<(), FetchError>

Idle → Pending (FETCH sent).

pub fn on_fetch_ok(&mut self) -> Result<(), FetchError>

Pending → Receiving, Unanswered → Done (FETCH_OK received).

From Unanswered the objects have already been delivered, so the FETCH_OK describing them is the last thing the fetch was waiting for.

pub fn on_fetch_error(&mut self) -> Result<(), FetchError>

Pending | Unanswered → Done (FETCH_ERROR received).

pub fn on_fetch_cancel(&mut self) -> Result<(), FetchError>

Pending | Receiving | Unanswered → Done (FETCH_CANCEL sent).

pub fn on_stream_fin(&mut self) -> Result<(), FetchError>

Receiving → Done, Pending → Unanswered (stream FIN received).

A fetch that has already ended ignores the close of its response stream, whichever of QUIC’s two endings it is. Section 8.15: the publisher of a cancelled fetch “SHOULD close the unidirectional stream as soon as possible”, and the cancel is what ended the fetch, so that close arrives afterwards.

pub fn on_stream_reset(&mut self) -> Result<(), FetchError>

Receiving → Done, Pending → Unanswered (stream RESET received).

The same tolerance of a late close as FetchStateMachine::on_stream_fin, for the same reason.

impl FetchStateMachine

The same transitions, named for the end that serves the fetch.

A fetch this endpoint answers passes through the states in the same order as one it makes, with every message going the other way: the FETCH arrives instead of leaving, the answer leaves instead of arriving. Sharing the transitions and not the names is what lets a refusal say which event was refused, rather than naming the mirror image of it.

pub fn on_fetch_received(&mut self) -> Result<(), FetchError>

Idle -> Pending (FETCH received from the peer).

pub fn on_fetch_ok_sent(&mut self) -> Result<(), FetchError>

Pending -> Receiving, Unanswered -> Done (FETCH_OK sent).

The state is named for the requester’s view; for the end answering, the same node means the objects are being served rather than received. It is the same node in the graph, with the same edges, so it keeps its name.

pub fn on_fetch_error_sent(&mut self) -> Result<(), FetchError>

Pending | Unanswered -> Done (FETCH_ERROR sent).

pub fn on_fetch_cancel_received(&mut self) -> Result<(), FetchError>

Pending | Receiving | Unanswered -> Done (FETCH_CANCEL received).

pub fn on_stream_fin_sent(&mut self) -> Result<(), FetchError>

Receiving -> Done, Pending -> Unanswered (this endpoint finished the fetch data stream).

Trait Implementations

impl Default for FetchStateMachine

fn default() -> Self

Returns the “default value” for a type.