Struct ResourceScope 

pub struct ResourceScope(/* private fields */);

A program tree’s slot for its host’s ResourceAccessor.

Cloning a scope yields another handle to the same slot, which is how every program and kernel of one tree shares it. An accessor is installed at most once per scope. A scope with none installed resolves a lookup through the parent it joined (Self::join), and answers None when it joined none, which is the norm for a program that runs without a host.

Implementations

impl ResourceScope

pub fn new() -> Self

A scope with no accessor installed, for a new program tree.

pub fn with_accessor(accessor: Arc<dyn ResourceAccessor>) -> Self

A scope with accessor already installed.

pub fn install( &self, accessor: Arc<dyn ResourceAccessor>, ) -> Result<(), Arc<dyn ResourceAccessor>>

Install accessor for every program and kernel of this tree. A scope has one accessor for its life: when one is already installed the call returns accessor back as the error and the installed one stays. An accessor installed here takes precedence over the parent the scope joined.

pub fn is_installed(&self) -> bool

Whether an accessor is installed on this scope itself. A scope that resolves through its parent reports false.

pub fn parent(&self) -> Option<&ResourceScope>

The parent this scope delegates to, when it joined one.

pub fn join(&self, parent: &ResourceScope) -> Result<(), ScopeJoinError>

Join this scope to parent, so that while no accessor is installed here, lookups resolve through parent. Binding a kernel under a parent kernel (crate::kernel::bind_under) joins the child program’s scope to the parent’s.

A scope joins at most one parent, the first it is joined to, and keeps it for its life. The join changes nothing when:

• this scope has an accessor installed, which it keeps;
• parent is this scope, or already resolves through it (this scope is parent’s ancestor), so joining would make a scope delegate to itself;
• this scope already joined a parent, parent or another. The first join wins: a node holds its program’s one scope, so a program whose kernels are bound under two trees resolves through the first. A host that binds one program under trees with different accessors installs one on the program itself.

Otherwise this scope joins parent. The one error is a join that raced others into a cycle (ScopeJoinError::Cycle).

pub fn lookup(&self, key: &str) -> Option<Arc<dyn Any + Send + Sync>>

Look up an already-attached resource’s accessor payload by fingerprint key: through this scope’s accessor when one is installed, and otherwise through the parent it joined.

Returns None when no scope on the way has an accessor or when the accessor that answers holds no live entry under key. The lookup is synchronous and never blocks.

pub fn same_scope(&self, other: &ResourceScope) -> bool

Whether self and other are handles to one scope.

Trait Implementations

impl Clone for ResourceScope

fn clone(&self) -> Self

Returns a duplicate of the value.

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

Performs copy-assignment from source.

impl Debug for ResourceScope

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

Formats the value using the given formatter.

impl Default for ResourceScope

fn default() -> Self

Returns the “default value” for a type.