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// Copyright (c) 2012, the Dart project authors. Please see the AUTHORS file
// for details. All rights reserved. Use of this source code is governed by a
// BSD-style license that can be found in the LICENSE file.
/// Concurrent programming using _isolates_:
/// independent workers that are similar to threads
/// but don't share memory,
/// communicating only via messages.
///
/// To use this library in your code:
/// ```dart
/// import 'dart:isolate';
/// ```
/// {@category VM}
library dart.isolate;
import "dart:async";
import "dart:_internal" show Since;
import "dart:typed_data" show ByteBuffer, TypedData, Uint8List;
part "capability.dart";
/// Thrown when an isolate cannot be created.
class IsolateSpawnException implements Exception {
/// Error message reported by the spawn operation.
final String message;
@pragma("vm:entry-point")
IsolateSpawnException(this.message);
String toString() => "IsolateSpawnException: $message";
}
/// An isolated Dart execution context.
///
/// All Dart code runs in an isolate, and code can access classes and values
/// only from the same isolate. Different isolates can communicate by sending
/// values through ports (see [ReceivePort], [SendPort]).
///
/// An `Isolate` object is a reference to an isolate, usually different from
/// the current isolate.
/// It represents, and can be used to control, the other isolate.
///
/// When spawning a new isolate, the spawning isolate receives an `Isolate`
/// object representing the new isolate when the spawn operation succeeds.
///
/// Isolates run code in its own event loop, and each event may run smaller tasks
/// in a nested microtask queue.
///
/// An `Isolate` object allows other isolates to control the event loop
/// of the isolate that it represents, and to inspect the isolate,
/// for example by pausing the isolate or by getting events when the isolate
/// has an uncaught error.
///
/// The [controlPort] identifies and gives access to controlling the isolate,
/// and the [pauseCapability] and [terminateCapability] guard access
/// to some control operations.
/// For example, calling [pause] on an `Isolate` object created without a
/// [pauseCapability], has no effect.
///
/// The `Isolate` object provided by a spawn operation will have the
/// control port and capabilities needed to control the isolate.
/// New isolate objects can be created without some of these capabilities
/// if necessary, using the [Isolate.Isolate] constructor.
///
/// An `Isolate` object cannot be sent over a `SendPort`, but the control port
/// and capabilities can be sent, and can be used to create a new functioning
/// `Isolate` object in the receiving port's isolate.
class Isolate {
/// Argument to `ping` and `kill`: Ask for immediate action.
static const int immediate = 0;
/// Argument to `ping` and `kill`: Ask for action before the next event.
static const int beforeNextEvent = 1;
/// Control port used to send control messages to the isolate.
///
/// The control port identifies the isolate.
///
/// An `Isolate` object allows sending control messages
/// through the control port.
///
/// Some control messages require a specific capability to be passed along
/// with the message (see [pauseCapability] and [terminateCapability]),
/// otherwise the message is ignored by the isolate.
final SendPort controlPort;
/// Capability granting the ability to pause the isolate.
///
/// This capability is required by [pause].
/// If the capability is `null`, or if it is not the correct pause capability
/// of the isolate identified by [controlPort],
/// then calls to [pause] will have no effect.
///
/// If the isolate is spawned in a paused state, use this capability as
/// argument to the [resume] method in order to resume the paused isolate.
final Capability? pauseCapability;
/// Capability granting the ability to terminate the isolate.
///
/// This capability is required by [kill] and [setErrorsFatal].
/// If the capability is `null`, or if it is not the correct termination
/// capability of the isolate identified by [controlPort],
/// then calls to those methods will have no effect.
final Capability? terminateCapability;
/// The name of the [Isolate] displayed for debug purposes.
///
/// This can be set using the `debugName` parameter in [spawn] and [spawnUri].
///
/// This name does not uniquely identify an isolate. Multiple isolates in the
/// same process may have the same `debugName`.
///
/// For a given isolate, this value will be the same as the values returned by
/// `Dart_DebugName` in the C embedding API and the `debugName` property in
/// [IsolateMirror].
@Since("2.3")
external String? get debugName;
/// Creates a new [Isolate] object with a restricted set of capabilities.
///
/// The port should be a control port for an isolate, as taken from
/// another `Isolate` object.
///
/// The capabilities should be the subset of the capabilities that are
/// available to the original isolate.
/// Capabilities of an isolate are locked to that isolate, and have no effect
/// anywhere else, so the capabilities should come from the same isolate as
/// the control port.
///
/// Can also be used to create an [Isolate] object from a control port, and
/// any available capabilities, that have been sent through a [SendPort].
///
/// Example:
/// ```dart
/// Isolate isolate = findSomeIsolate();
/// Isolate restrictedIsolate = Isolate(isolate.controlPort);
/// untrustedCode(restrictedIsolate);
/// ```
/// This example creates a new `Isolate` object that cannot be used to
/// pause or terminate the isolate. All the untrusted code can do is to
/// inspect the isolate and see uncaught errors or when it terminates.
Isolate(this.controlPort, {this.pauseCapability, this.terminateCapability});
/// An [Isolate] object representing the current isolate.
///
/// The current isolate for code using [current]
/// is the isolate running the code.
///
/// The isolate object provides the capabilities required to inspect,
/// pause or kill the isolate, and allows granting these capabilities
/// to others.
///
/// It is possible to pause the current isolate, but doing so *without*
/// first passing the ability to resume it again to another isolate,
/// is a sure way to hang your program.
external static Isolate get current;
/// The package root of the current isolate, if any.
///
/// This getter returns `null`, as the `packages/` directory is not supported
/// in Dart 2.
@Deprecated('packages/ directory resolution is not supported in Dart 2.')
external static Future<Uri?> get packageRoot;
/// The location of the package configuration of the current isolate, if any.
///
/// If the isolate has not been setup for package resolution,
/// this location is `null`,
/// otherwise it is a URI referencing the package config file.
external static Future<Uri?> get packageConfig;
/// Maps a `package:` URI to a non-package Uri.
///
/// If there is no valid mapping from the `package:` URI in the current
/// isolate, then this call returns `null`. Non-`package:` URIs are
/// returned unmodified.
external static Future<Uri?> resolvePackageUri(Uri packageUri);
/// Creates and spawns an isolate that shares the same code as the current
/// isolate.
///
/// The argument [entryPoint] specifies the initial function to call
/// in the spawned isolate.
/// The entry-point function is invoked in the new isolate with [message]
/// as the only argument.
///
/// The function must be a top-level function or a static method
/// that can be called with a single argument,
/// that is, a compile-time constant function value
/// which accepts at least one positional parameter
/// and has at most one required positional parameter.
/// The function may accept any number of optional parameters,
/// as long as it *can* be called with just a single argument.
/// The function must not be the value of a function expression
/// or an instance method tear-off.
///
/// Usually the initial [message] contains a [SendPort] so
/// that the spawner and spawnee can communicate with each other.
///
/// If the [paused] parameter is set to `true`,
/// the isolate will start up in a paused state,
/// just before calling the [entryPoint] function with the [message],
/// as if by an initial call of `isolate.pause(isolate.pauseCapability)`.
/// To resume the isolate, call `isolate.resume(isolate.pauseCapability)`.
///
/// If the [errorsAreFatal], [onExit] and/or [onError] parameters are provided,
/// the isolate will act as if, respectively, [setErrorsFatal],
/// [addOnExitListener] and [addErrorListener] were called with the
/// corresponding parameter and was processed before the isolate starts
/// running.
///
/// If [debugName] is provided, the spawned [Isolate] will be identifiable by
/// this name in debuggers and logging.
///
/// If [errorsAreFatal] is omitted, the platform may choose a default behavior
/// or inherit the current isolate's behavior.
///
/// You can also call the [setErrorsFatal], [addOnExitListener] and
/// [addErrorListener] methods on the returned isolate, but unless the
/// isolate was started as [paused], it may already have terminated
/// before those methods can complete.
///
/// Returns a future which will complete with an [Isolate] instance if the
/// spawning succeeded. It will complete with an error otherwise.
external static Future<Isolate> spawn<T>(
void entryPoint(T message), T message,
{bool paused = false,
bool errorsAreFatal = true,
SendPort? onExit,
SendPort? onError,
@Since("2.3") String? debugName});
/// Creates and spawns an isolate that runs the code from the library with
/// the specified URI.
///
/// The isolate starts executing the top-level `main` function of the library
/// with the given URI.
///
/// The target `main` must be callable with zero, one or two arguments.
/// Examples:
///
/// * `main()`
/// * `main(args)`
/// * `main(args, message)`
///
/// When present, the parameter `args` is set to the provided [args] list.
/// When present, the parameter `message` is set to the initial [message].
///
/// If the [paused] parameter is set to `true`,
/// the isolate will start up in a paused state,
/// as if by an initial call of `isolate.pause(isolate.pauseCapability)`.
/// To resume the isolate, call `isolate.resume(isolate.pauseCapability)`.
///
/// If the [errorsAreFatal], [onExit] and/or [onError] parameters are provided,
/// the isolate will act as if, respectively, [setErrorsFatal],
/// [addOnExitListener] and [addErrorListener] were called with the
/// corresponding parameter and was processed before the isolate starts
/// running.
///
/// You can also call the [setErrorsFatal], [addOnExitListener] and
/// [addErrorListener] methods on the returned isolate, but unless the
/// isolate was started as [paused], it may already have terminated
/// before those methods can complete.
///
/// If the [checked] parameter is set to `true` or `false`,
/// the new isolate will run code in checked mode (enabling asserts and type
/// checks), respectively in production mode (disabling asserts and type
/// checks), if possible. If the parameter is omitted, the new isolate will
/// inherit the value from the current isolate.
///
/// In Dart2 strong mode, the `checked` parameter only controls asserts, but
/// not type checks.
///
/// It may not always be possible to honor the `checked` parameter.
/// If the isolate code was pre-compiled, it may not be possible to change
/// the checked mode setting dynamically.
/// In that case, the `checked` parameter is ignored.
///
/// WARNING: The [checked] parameter is not implemented on all platforms yet.
///
/// If the [packageConfig] parameter is provided, then it is used to find the
/// location of a package resolution configuration file for the spawned
/// isolate.
///
/// If the [automaticPackageResolution] parameter is provided, then the
/// location of the package sources in the spawned isolate is automatically
/// determined.
///
/// The [environment] is a mapping from strings to strings which the
/// spawned isolate uses when looking up [String.fromEnvironment] values.
/// The system may add its own entries to environment as well.
/// If `environment` is omitted, the spawned isolate has the same environment
/// declarations as the spawning isolate.
///
/// WARNING: The [environment] parameter is not implemented on all
/// platforms yet.
///
/// If [debugName] is provided, the spawned [Isolate] will be identifiable by
/// this name in debuggers and logging.
///
/// Returns a future that will complete with an [Isolate] instance if the
/// spawning succeeded. It will complete with an error otherwise.
external static Future<Isolate> spawnUri(
Uri uri,
List<String> args,
var message,
{bool paused = false,
SendPort? onExit,
SendPort? onError,
bool errorsAreFatal = true,
bool? checked,
Map<String, String>? environment,
@Deprecated('The packages/ dir is not supported in Dart 2')
Uri? packageRoot,
Uri? packageConfig,
bool automaticPackageResolution = false,
@Since("2.3")
String? debugName});
/// Requests the isolate to pause.
///
/// When the isolate receives the pause command, it stops
/// processing events from the event loop queue.
/// It may still add new events to the queue in response to, e.g., timers
/// or receive-port messages. When the isolate is resumed,
/// it starts handling the already enqueued events.
///
/// The pause request is sent through the isolate's command port,
/// which bypasses the receiving isolate's event loop.
/// The pause takes effect when it is received, pausing the event loop
/// as it is at that time.
///
/// The [resumeCapability] is used to identity the pause,
/// and must be used again to end the pause using [resume].
/// If [resumeCapability] is omitted, a new capability object is created
/// and used instead.
///
/// If an isolate is paused more than once using the same capability,
/// only one resume with that capability is needed to end the pause.
///
/// If an isolate is paused using more than one capability,
/// each pause must be individually ended before the isolate resumes.
///
/// Returns the capability that must be used to end the pause.
/// This is either [resumeCapability], or a new capability when
/// [resumeCapability] is omitted.
///
/// If [pauseCapability] is `null`, or it's not the pause capability
/// of the isolate identified by [controlPort],
/// the pause request is ignored by the receiving isolate.
Capability pause([Capability? resumeCapability]) {
resumeCapability ??= new Capability();
_pause(resumeCapability);
return resumeCapability;
}
/// Internal implementation of [pause].
external void _pause(Capability resumeCapability);
/// Resumes a paused isolate.
///
/// Sends a message to an isolate requesting that it ends a pause
/// that was previously requested.
///
/// When all active pause requests have been cancelled, the isolate
/// will continue processing events and handling normal messages.
///
/// If the [resumeCapability] is not one that has previously been used
/// to pause the isolate, or it has already been used to resume from
/// that pause, the resume call has no effect.
external void resume(Capability resumeCapability);
/// Requests an exit message on [responsePort] when the isolate terminates.
///
/// The isolate will send [response] as a message on [responsePort] as the last
/// thing before it terminates. It will run no further code after the message
/// has been sent.
///
/// Adding the same port more than once will only cause it to receive one exit
/// message, using the last response value that was added,
/// and it only needs to be removed once using [removeOnExitListener].
///
/// If the isolate has terminated before it can receive this request,
/// no exit message will be sent.
///
/// The [response] object must follow the same restrictions as enforced by
/// [SendPort.send].
/// It is recommended to only use simple values that can be sent to all
/// isolates, like `null`, booleans, numbers or strings.
///
/// Since isolates run concurrently, it's possible for it to exit before the
/// exit listener is established, and in that case no response will be
/// sent on [responsePort].
/// To avoid this, either use the corresponding parameter to the spawn
/// function, or start the isolate paused, add the listener and
/// then resume the isolate.
/* TODO(lrn): Can we do better? Can the system recognize this message and
* send a reply if the receiving isolate is dead?
*/
external void addOnExitListener(SendPort responsePort, {Object? response});
/// Stops listening for exit messages from the isolate.
///
/// Requests for the isolate to not send exit messages on [responsePort].
/// If the isolate isn't expecting to send exit messages on [responsePort],
/// because the port hasn't been added using [addOnExitListener],
/// or because it has already been removed, the request is ignored.
///
/// If the same port has been passed via [addOnExitListener] more than once,
/// only one call to `removeOnExitListener` is needed to stop it from receiving
/// exit messages.
///
/// Closing the receive port that is associated with the [responsePort] does
/// not stop the isolate from sending uncaught errors, they are just going to
/// be lost.
///
/// An exit message may still be sent if the isolate terminates
/// before this request is received and processed.
external void removeOnExitListener(SendPort responsePort);
/// Sets whether uncaught errors will terminate the isolate.
///
/// If errors are fatal, any uncaught error will terminate the isolate
/// event loop and shut down the isolate.
///
/// This call requires the [terminateCapability] for the isolate.
/// If the capability is absent or incorrect, no change is made.
///
/// Since isolates run concurrently, it's possible for the receiving isolate
/// to exit due to an error, before a request, using this method, has been
/// received and processed.
/// To avoid this, either use the corresponding parameter to the spawn
/// function, or start the isolate paused, set errors non-fatal and
/// then resume the isolate.
external void setErrorsFatal(bool errorsAreFatal);
/// Requests the isolate to shut down.
///
/// The isolate is requested to terminate itself.
/// The [priority] argument specifies when this must happen.
///
/// The [priority], when provided, must be one of [immediate] or
/// [beforeNextEvent] (the default).
/// The shutdown is performed at different times depending on the priority:
///
/// * `immediate`: The isolate shuts down as soon as possible.
/// Control messages are handled in order, so all previously sent control
/// events from this isolate will all have been processed.
/// The shutdown should happen no later than if sent with
/// `beforeNextEvent`.
/// It may happen earlier if the system has a way to shut down cleanly
/// at an earlier time, even during the execution of another event.
/// * `beforeNextEvent`: The shutdown is scheduled for the next time
/// control returns to the event loop of the receiving isolate,
/// after the current event, and any already scheduled control events,
/// are completed.
///
/// If [terminateCapability] is `null`, or it's not the terminate capability
/// of the isolate identified by [controlPort],
/// the kill request is ignored by the receiving isolate.
external void kill({int priority = beforeNextEvent});
/// Requests that the isolate send [response] on the [responsePort].
///
/// The [response] object must follow the same restrictions as enforced by
/// [SendPort.send].
/// It is recommended to only use simple values that can be sent to all
/// isolates, like `null`, booleans, numbers or strings.
///
/// If the isolate is alive, it will eventually send `response`
/// (defaulting to `null`) on the response port.
///
/// The [priority] must be one of [immediate] or [beforeNextEvent].
/// The response is sent at different times depending on the ping type:
///
/// * `immediate`: The isolate responds as soon as it receives the
/// control message. This is after any previous control message
/// from the same isolate has been received and processed,
/// but may be during execution of another event.
/// * `beforeNextEvent`: The response is scheduled for the next time
/// control returns to the event loop of the receiving isolate,
/// after the current event, and any already scheduled control events,
/// are completed.
external void ping(SendPort responsePort,
{Object? response, int priority = immediate});
/// Requests that uncaught errors of the isolate are sent back to [port].
///
/// The errors are sent back as two-element lists.
/// The first element is a `String` representation of the error, usually
/// created by calling `toString` on the error.
/// The second element is a `String` representation of an accompanying
/// stack trace, or `null` if no stack trace was provided.
/// To convert this back to a [StackTrace] object, use [StackTrace.fromString].
///
/// Listening using the same port more than once does nothing.
/// A port will only receive each error once,
/// and will only need to be removed once using [removeErrorListener].
///
/// Closing the receive port that is associated with the port does not stop
/// the isolate from sending uncaught errors, they are just going to be lost.
/// Instead use [removeErrorListener] to stop receiving errors on [port].
///
/// Since isolates run concurrently, it's possible for it to exit before the
/// error listener is established. To avoid this, start the isolate paused,
/// add the listener and then resume the isolate.
external void addErrorListener(SendPort port);
/// Stops listening for uncaught errors from the isolate.
///
/// Requests for the isolate to not send uncaught errors on [port].
/// If the isolate isn't expecting to send uncaught errors on [port],
/// because the port hasn't been added using [addErrorListener],
/// or because it has already been removed, the request is ignored.
///
/// If the same port has been passed via [addErrorListener] more than once,
/// only one call to `removeErrorListener` is needed to stop it from receiving
/// uncaught errors.
///
/// Uncaught errors message may still be sent by the isolate
/// until this request is received and processed.
external void removeErrorListener(SendPort port);
/// Returns a broadcast stream of uncaught errors from the isolate.
///
/// Each error is provided as an error event on the stream.
///
/// The actual error object and stackTraces will not necessarily
/// be the same object types as in the actual isolate, but they will
/// always have the same [Object.toString] result.
///
/// This stream is based on [addErrorListener] and [removeErrorListener].
Stream get errors {
StreamController controller = StreamController.broadcast(sync: true);
RawReceivePort? port;
void handleError(Object? message) {
var listMessage = message as List<Object?>;
var errorDescription = listMessage[0] as String;
var stackDescription = listMessage[1] as String;
var error = new RemoteError(errorDescription, stackDescription);
controller.addError(error, error.stackTrace);
}
controller.onListen = () {
RawReceivePort receivePort = new RawReceivePort(handleError);
port = receivePort;
this.addErrorListener(receivePort.sendPort);
};
controller.onCancel = () {
var listenPort = port!;
port = null;
this.removeErrorListener(listenPort.sendPort);
listenPort.close();
};
return controller.stream;
}
}
/// Sends messages to its [ReceivePort]s.
///
/// [SendPort]s are created from [ReceivePort]s. Any message sent through
/// a [SendPort] is delivered to its corresponding [ReceivePort]. There might be
/// many [SendPort]s for the same [ReceivePort].
///
/// [SendPort]s can be transmitted to other isolates, and they preserve equality
/// when sent.
abstract class SendPort implements Capability {
/// Sends an asynchronous [message] through this send port, to its
/// corresponding `ReceivePort`.
///
/// The content of [message] can be: primitive values
/// (null, num, bool, double, String), instances of [SendPort],
/// and lists and maps whose elements are any of these.
/// List and maps are also allowed to contain cyclic references.
///
/// In the special circumstances when two isolates share the same code and are
/// running in the same process (e.g. isolates created via [Isolate.spawn]),
/// it is also possible to send object instances (which would be copied in the
/// process). This is currently only supported by the
/// [Dart Native](https://dart.dev/platforms#dart-native-vm-jit-and-aot)
/// platform.
///
/// The send happens immediately and doesn't block. The corresponding receive
/// port can receive the message as soon as its isolate's event loop is ready
/// to deliver it, independently of what the sending isolate is doing.
void send(Object? message);
/// Tests whether [other] is a [SendPort] pointing to the same
/// [ReceivePort] as this one.
bool operator ==(var other);
/// A hash code for this send port that is consistent with the == operator.
int get hashCode;
}
/// Together with [SendPort], the only means of communication between isolates.
///
/// [ReceivePort]s have a `sendPort` getter which returns a [SendPort].
/// Any message that is sent through this [SendPort]
/// is delivered to the [ReceivePort] it has been created from. There, the
/// message is dispatched to the `ReceivePort`'s listener.
///
/// A [ReceivePort] is a non-broadcast stream. This means that it buffers
/// incoming messages until a listener is registered. Only one listener can
/// receive messages. See [Stream.asBroadcastStream] for transforming the port
/// to a broadcast stream.
///
/// A [ReceivePort] may have many [SendPort]s.
abstract class ReceivePort implements Stream<dynamic> {
/// Opens a long-lived port for receiving messages.
///
/// A [ReceivePort] is a non-broadcast stream. This means that it buffers
/// incoming messages until a listener is registered. Only one listener can
/// receive messages. See [Stream.asBroadcastStream] for transforming the port
/// to a broadcast stream.
///
/// The optional `debugName` parameter can be set to associate a name with
/// this port that can be displayed in tooling.
///
/// A receive port is closed by canceling its subscription.
external factory ReceivePort([String debugName = '']);
/// Creates a [ReceivePort] from a [RawReceivePort].
///
/// The handler of the given [rawPort] is overwritten during the construction
/// of the result.
external factory ReceivePort.fromRawReceivePort(RawReceivePort rawPort);
/// Listen for events from [Stream].
///
/// See [Stream.listen].
///
/// Note that [onError] and [cancelOnError] are ignored since a [ReceivePort]
/// will never receive an error.
///
/// The [onDone] handler will be called when the stream closes.
/// The stream closes when [close] is called.
StreamSubscription<dynamic> listen(void onData(var message)?,
{Function? onError, void onDone()?, bool? cancelOnError});
/// Closes the receive port.
///
/// No further events will be received by the receive port,
/// or emitted as stream events.
///
/// If [listen] has been called and the [StreamSubscription] has not
/// been canceled yet, the subscription will be closed with a "done"
/// event.
///
/// If the stream has already been canceled this method has no effect.
void close();
/// A [SendPort] which sends messages to this receive port.
SendPort get sendPort;
}
/// A low-level asynchronous message receiver.
///
/// A [RawReceivePort] is low level feature, and is not [Zone] aware.
/// The [handler] will always be invoked in the [Zone.root] zone.
///
/// The port cannot be paused. The data-handler must be set before the first
/// message is received, otherwise the message is lost.
///
/// Messages can be sent to this port using [sendPort].
abstract class RawReceivePort {
/// Opens a long-lived port for receiving messages.
///
/// A [RawReceivePort] is low level and does not work with [Zone]s. It
/// cannot be paused. The data-handler must be set before the first
/// message is received, otherwise the message is lost.
///
/// If [handler] is provided, it's set as the [RawReceivePort.handler].
///
/// The optional `debugName` parameter can be set to associate a name with
/// this port that can be displayed in tooling.
external factory RawReceivePort([Function? handler, String debugName = '']);
/// Sets the handler that is invoked for every incoming message.
///
/// The handler is invoked in the [Zone.root] zone.
/// If the handler should be invoked in the current zone, do:
/// ```dart
/// rawPort.handler = Zone.current.bind(actualHandler);
/// ```
///
/// The handler must be a function which can accept one argument
/// of the type of the messages sent to this port.
/// This means that if it is known that messages will all be [String]s,
/// a handler of type `void Function(String)` can be used.
/// The function is invoked dynamically with the actual messages,
/// and if this invocation fails,
/// the error becomes a top-level uncaught error in the [Zone.root] zone.
// TODO(44659): Change parameter type to `void Function(Never)` to only
// accept functions which can be called with one argument.
void set handler(Function? newHandler);
/// Closes the port.
///
/// After a call to this method, any incoming message is silently dropped.
/// The [handler] will never be called again.
void close();
/// Returns a [SendPort] that sends messages to this raw receive port.
SendPort get sendPort;
}
/// Description of an error from another isolate.
///
/// This error has the same `toString()` and `stackTrace.toString()` behavior
/// as the original error, but has no other features of the original error.
class RemoteError implements Error {
final String _description;
final StackTrace stackTrace;
RemoteError(String description, String stackDescription)
: _description = description,
stackTrace = new StackTrace.fromString(stackDescription);
String toString() => _description;
}
/// An efficiently transferable sequence of byte values.
///
/// A [TransferableTypedData] is created from a number of bytes.
/// This will take time proportional to the number of bytes.
///
/// The [TransferableTypedData] can be moved between isolates, so
/// sending it through a send port will only take constant time.
///
/// When sent this way, the local transferable can no longer be materialized,
/// and the received object is now the only way to materialize the data.
@Since("2.3.2")
abstract class TransferableTypedData {
/// Creates a new [TransferableTypedData] containing the bytes of [list].
///
/// It must be possible to create a single [Uint8List] containing the
/// bytes, so if there are more bytes than what the platform allows in
/// a single [Uint8List], then creation fails.
external factory TransferableTypedData.fromList(List<TypedData> list);
/// Creates a new [ByteBuffer] containing the bytes stored in this [TransferableTypedData].
///
/// The [TransferableTypedData] is a cross-isolate single-use resource.
/// This method must not be called more than once on the same underlying
/// transferable bytes, even if the calls occur in different isolates.
ByteBuffer materialize();
}