Struct NestedReadonlySnapshot 

pub struct NestedReadonlySnapshot { /* private fields */ }

A nested read-only snapshot.

This is a read-only snapshot that has a parent snapshot. It inherits the parent’s invalid set and can be disposed independently.

Thread Safety

Contains Cell<T> and RefCell<T> which are not Send/Sync. This is safe because snapshots are stored in thread-local storage and never shared across threads. The Rc is used for cheap cloning within a single thread, not for cross-thread sharing.

Implementations

impl NestedReadonlySnapshot

pub fn new( id: SnapshotId, invalid: SnapshotIdSet, read_observer: Option<ReadObserver>, parent: Weak<NestedReadonlySnapshot>, ) -> Rc<Self>

Creates a nested read-only snapshot with the given id and invalid set. read_observer is called for reads inside it. parent is the snapshot it was taken from, if that snapshot is still alive.

pub fn snapshot_id(&self) -> SnapshotId

Returns the id of this snapshot. Ids grow with every snapshot taken.

pub fn invalid(&self) -> SnapshotIdSet

Returns the ids of snapshots whose writes this snapshot does not see.

pub fn read_only(&self) -> bool

Returns true: this snapshot rejects writes.

pub fn root_nested_readonly(&self) -> Rc<NestedReadonlySnapshot>

Returns the outermost parent that is still alive, or a copy of this snapshot when it has no live parent.

pub fn enter<T>(self: &Rc<Self>, f: impl FnOnce() -> T) -> T

Runs f with this snapshot as the current snapshot of the thread and returns its result. The previous current snapshot is restored when f returns.

pub fn take_nested_snapshot( &self, read_observer: Option<ReadObserver>, ) -> Rc<NestedReadonlySnapshot>

Takes another read-only snapshot with the same view of state. Reads inside the new snapshot call both read_observer and this snapshot’s own read observer.

pub fn has_pending_changes(&self) -> bool

Returns false: a read-only snapshot has no writes.

pub fn dispose(&self)

Releases the snapshot. Does nothing if it was already disposed.

pub fn record_read(&self, state: &dyn StateObject)

Calls the read observer, if any, with state.

pub fn record_write(&self, _state: Rc<dyn StateObject>)

Always panics: a read-only snapshot rejects writes.

pub fn is_disposed(&self) -> bool

Returns true once the snapshot was disposed.