tree 131de3c19a5bdd62c3e3bc4bde15e18ccae3eac2
parent 527dffd21b6ddbf0bd6bc06469d318e4126da52b
author Alexander Aprelev <aam@google.com> 1559850547 +0000
committer commit-bot@chromium.org <commit-bot@chromium.org> 1559850547 +0000

[vm/isolate] Add TransferableTypedData class that allows low-cost passing of Uint8List between isolates.

TransferableTypedData instances are one-use kind of thing: once receiver materializes it, it can't be used
again, once sender sends it out to an isolate, sender can't send it to different isolate.

Example of use:

sender isolate:

```
Future<TransferableTypedData> consolidateHttpClientResponseBytes(HttpClientResponse response) {
  final completer = Completer<TransferableTypedData>();
  final chunks = <Uint8List>[];
  response.listen((List<int> chunk) {
    chunks.add(chunk);
  }, onDone: () {
    completer.complete(TransferableTypedData.fromList(chunks));
  });
  return completer.future;
}
...
sendPort.send(await consolidateHttpClientResponseBytes(response));
```

receiver isolate:
```
    RawReceivePort port = RawReceivePort((TransferableTypedData transferable) {
      Uint8List content = transferable.materialize().asUint8List();
      ...
    });
```

31959[tr] and 31960[tr] tests were inspired by dartbug.com/31959, dartbug.com/31960 that this CL attempts to address:
```
╰─➤  out/ReleaseX64/dart 31960.dart
sending...
163ms for round-trip
sending...
81ms for round-trip
sending...
20ms for round-trip
sending...
14ms for round-trip
sending...
20ms for round-trip
sending...
14ms for round-trip
```

(notice no "since last checking" pauses") vs

```
╰─➤  out/ReleaseX64/dart 31960.dart
sending...
154ms since last checkin
174ms for round-trip
sending...
68ms since last checkin
9ms since last checkin
171ms for round-trip
sending...
13ms since last checkin
108ms for round-trip
sending...
14ms since last checkin
108ms for round-trip
sending...
14ms since last checkin
107ms for round-trip
```

Change-Id: I0fcb5ce285394f498c3f1db4414204531f98199d
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/99623
Commit-Queue: Alexander Aprelev <aam@google.com>
Reviewed-by: Ryan Macnak <rmacnak@google.com>
Reviewed-by: Lasse R.H. Nielsen <lrn@google.com>
Reviewed-by: Martin Kustermann <kustermann@google.com>