Struct boa_engine::job::NativeJob
source · pub struct NativeJob { /* private fields */ }
Expand description
An ECMAScript Job closure.
The specification allows scheduling any NativeJob
closure by the host into the job queue.
However, host-defined jobs must abide to a set of requirements.
§Requirements
- At some future point in time, when there is no running execution context and the execution
context stack is empty, the implementation must:
- Perform any host-defined preparation steps.
- Invoke the Job Abstract Closure.
- Perform any host-defined cleanup steps, after which the execution context stack must be empty.
- Only one Job may be actively undergoing evaluation at any point in time.
- Once evaluation of a Job starts, it must run to completion before evaluation of any other Job starts.
- The Abstract Closure must return a normal completion, implementing its own handling of errors.
NativeJob
s API differs slightly on the last requirement, since it allows closures returning
JsResult
, but it’s okay because NativeJob
s are handled by the host anyways; a host could
pass a closure returning Err
and handle the error on JobQueue::run_jobs
, making the closure
effectively run as if it never returned Err
.
§Trace
?
NativeJob
doesn’t implement Trace
because it doesn’t need to; all jobs can only be run once
and putting a JobQueue
on a garbage collected object is not allowed.
On the other hand, it seems like this type breaks all the safety checks of the
NativeFunction
API, since you can capture any Trace
variable into the closure… but it
doesn’t!
The garbage collector doesn’t need to trace the captured variables because the closures
are always stored on the JobQueue
, which is always rooted, which means the captured variables
are also rooted, allowing us to capture any variable in the closure for free!
Implementations§
source§impl NativeJob
impl NativeJob
sourcepub fn with_realm<F>(f: F, realm: Realm, _context: &mut Context) -> Self
pub fn with_realm<F>(f: F, realm: Realm, _context: &mut Context) -> Self
Creates a new NativeJob
from a closure and an execution realm.
Trait Implementations§
Auto Trait Implementations§
impl !RefUnwindSafe for NativeJob
impl !Send for NativeJob
impl !Sync for NativeJob
impl Unpin for NativeJob
impl !UnwindSafe for NativeJob
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source§impl<T> BorrowMut<T> for Twhere
T: ?Sized,
impl<T> BorrowMut<T> for Twhere
T: ?Sized,
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T: ?Sized,
impl<T> Pipe for Twhere
T: ?Sized,
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R: 'a,
self
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