runtime/tools/heapsnapshot/lib/src/load.dart

// Copyright (c) 2022, 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.

import 'dart:async';
import 'dart:typed_data';

import 'package:vm_service/vm_service.dart';
import 'package:vm_service/vm_service_io.dart';

Future<List<ByteData>> loadFromUri(Uri uri) async {
  final Uri wsUri;
  if (uri.isScheme("ws")) {
    wsUri = uri;
  } else {
    if (uri.path.isEmpty || uri.path == "/") {
      uri = uri.replace(path: "/ws");
    } else if (uri.path.endsWith("/")) {
      uri = uri.replace(path: "${uri.path}ws");
    } else {
      uri = uri.replace(path: "${uri.path}/ws");
    }
    wsUri = uri.replace(scheme: 'ws');
  }
  final service = await vmServiceConnectUri(wsUri.toString());
  try {
    final r = await _getHeapsnapshot(service);
    return r;
  } finally {
    await service.dispose();
  }
}

Future<List<ByteData>> _getHeapsnapshot(VmService service) async {
  final vm = await service.getVM();
  final vmIsolates = vm.isolates!;
  if (vmIsolates.isEmpty) {
    throw 'Could not find first isolate (expected it to be running already)';
  }
  final isolateRef = vmIsolates.first;

  await service.streamListen(EventStreams.kHeapSnapshot);

  final chunks = <ByteData>[];
  final done = Completer();
  late StreamSubscription streamSubscription;
  streamSubscription = service.onHeapSnapshotEvent.listen((e) async {
    chunks.add(e.data!);
    if (e.last!) {
      await service.streamCancel(EventStreams.kHeapSnapshot);
      await streamSubscription.cancel();
      done.complete();
    }
  });

  await service.requestHeapSnapshot(isolateRef.id!);
  await done.future;

  return chunks;
}