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Unified Diff: runtime/lib/async_patch.dart

Issue 1296973002: Revert "Don't zone-register async callbacks for every await call in the VM." (Closed) Base URL: git@github.com:dart-lang/sdk.git@master
Patch Set: Created 5 years, 4 months ago
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Index: runtime/lib/async_patch.dart
diff --git a/runtime/lib/async_patch.dart b/runtime/lib/async_patch.dart
index d78534719656c37ca06fc3cdc7354a930bbeadad..682ee8b10a4ec2d6b8496a5f06496f428819a00e 100644
--- a/runtime/lib/async_patch.dart
+++ b/runtime/lib/async_patch.dart
@@ -4,181 +4,3 @@
import "dart:_internal";
-// We need to pass the value as first argument and leave the second and third
-// arguments empty (used for error handling).
-// See vm/ast_transformer.cc for usage.
-Function _asyncThenWrapperHelper(continuation) {
- // Any function that is used as an asynchronous callback must be registered
- // in the current Zone. Normally, this is done by the future when a
- // callback is registered (for example with `.then` or `.catchError`). In our
- // case we want to reuse the same callback multiple times and therefore avoid
- // the multiple registrations. For our internal futures (`_Future`) we can
- // use the shortcut-version of `.then`, and skip the registration. However,
- // that means that the continuation must be registered by us.
- //
- // Furthermore, we know that the root-zone doesn't actually do anything and
- // we can therefore skip the registration call for it.
- //
- // Note, that the continuation accepts up to three arguments. If the current
- // zone is the root zone, we don't wrap the continuation, and a bad
- // `Future` implementation could potentially invoke the callback with the
- // wrong number of arguments.
- if (Zone.current == Zone.ROOT) return continuation;
- return Zone.current.registerUnaryCallback((x) => continuation(x, null, null));
-}
-
-// We need to pass the exception and stack trace objects as second and third
-// parameter to the continuation. See vm/ast_transformer.cc for usage.
-Function _asyncErrorWrapperHelper(continuation) {
- // See comments of `_asyncThenWrapperHelper`.
- var errorCallback = (e, s) => continuation(null, e, s);
- if (Zone.current == Zone.ROOT) return errorCallback;
- return Zone.current.registerBinaryCallback(errorCallback);
-}
-
-/// Registers the [thenCallback] and [errorCallback] on the given [object].
-///
-/// If [object] is not a future, then it is wrapped into one.
-///
-/// Returns the result of registering with `.then`.
-Future _awaitHelper(
- var object, Function thenCallback, Function errorCallback) {
- if (object is! Future) {
- object = new _Future().._setValue(object);
- } else if (object is! _Future) {
- return object.then(thenCallback, onError: errorCallback);
- }
- // `object` is a `_Future`.
- //
- // Since the callbacks have been registered in the current zone (see
- // [_asyncThenWrapperHelper] and [_asyncErrorWrapperHelper]), we can avoid
- // another registration and directly invoke the no-zone-registration `.then`.
- //
- // We can only do this for our internal futures (the default implementation of
- // all futures that are constructed by the `dart:async` library).
- return object._thenNoZoneRegistration(thenCallback, errorCallback);
-}
-
-// _AsyncStarStreamController is used by the compiler to implement
-// async* generator functions.
-class _AsyncStarStreamController {
- StreamController controller;
- Function asyncStarBody;
- bool isAdding = false;
- bool onListenReceived = false;
- bool isScheduled = false;
- bool isSuspendedAtYield = false;
- Completer cancellationCompleter = null;
-
- Stream get stream => controller.stream;
-
- void runBody() {
- isScheduled = false;
- isSuspendedAtYield = false;
- asyncStarBody();
- }
-
- void scheduleGenerator() {
- if (isScheduled || controller.isPaused || isAdding) {
- return;
- }
- isScheduled = true;
- scheduleMicrotask(runBody);
- }
-
- // Adds element to steam, returns true if the caller should terminate
- // execution of the generator.
- //
- // TODO(hausner): Per spec, the generator should be suspended before
- // exiting when the stream is closed. We could add a getter like this:
- // get isCancelled => controller.hasListener;
- // The generator would translate a 'yield e' statement to
- // controller.add(e);
- // suspend;
- // if (controller.isCancelled) return;
- bool add(event) {
- if (!onListenReceived) _fatal("yield before stream is listened to!");
- if (isSuspendedAtYield) _fatal("unexpected yield");
- // If stream is cancelled, tell caller to exit the async generator.
- if (!controller.hasListener) {
- return true;
- }
- controller.add(event);
- scheduleGenerator();
- isSuspendedAtYield = true;
- return false;
- }
-
- // Adds the elements of stream into this controller's stream.
- // The generator will be scheduled again when all of the
- // elements of the added stream have been consumed.
- // Returns true if the caller should terminate
- // execution of the generator.
- bool addStream(Stream stream) {
- if (!onListenReceived) _fatal("yield before stream is listened to!");
- // If stream is cancelled, tell caller to exit the async generator.
- if (!controller.hasListener) return true;
- isAdding = true;
- var whenDoneAdding =
- controller.addStream(stream as Stream, cancelOnError: false);
- whenDoneAdding.then((_) {
- isAdding = false;
- scheduleGenerator();
- });
- return false;
- }
-
- void addError(error, stackTrace) {
- if ((cancellationCompleter != null) && !cancellationCompleter.isCompleted) {
- // If the stream has been cancelled, complete the cancellation future
- // with the error.
- cancellationCompleter.completeError(error, stackTrace);
- return;
- }
- // If stream is cancelled, tell caller to exit the async generator.
- if (!controller.hasListener) return;
- controller.addError(error, stackTrace);
- // No need to schedule the generator body here. This code is only
- // called from the catch clause of the implicit try-catch-finally
- // around the generator body. That is, we are on the error path out
- // of the generator and do not need to run the generator again.
- }
-
- close() {
- if ((cancellationCompleter != null) && !cancellationCompleter.isCompleted) {
- // If the stream has been cancelled, complete the cancellation future
- // with the error.
- cancellationCompleter.complete();
- }
- controller.close();
- }
-
- _AsyncStarStreamController(this.asyncStarBody) {
- controller = new StreamController(onListen: this.onListen,
- onResume: this.onResume,
- onCancel: this.onCancel);
- }
-
- onListen() {
- assert(!onListenReceived);
- onListenReceived = true;
- scheduleGenerator();
- }
-
- onResume() {
- if (isSuspendedAtYield) {
- scheduleGenerator();
- }
- }
-
- onCancel() {
- if (controller.isClosed) {
- return null;
- }
- if (cancellationCompleter == null) {
- cancellationCompleter = new Completer();
- scheduleGenerator();
- }
- return cancellationCompleter.future;
- }
-}
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