Use separate isolate for image loading. (#34188)

* Use separate isolate for image loading. Use TransferableTypedData to const-cost receive bytes from that isolate.

packages/flutter/lib/src/foundation/consolidate_response.dart

@@ -5,6 +5,7 @@
 import 'dart:async';
 import 'dart:convert';
 import 'dart:io';
+import 'dart:isolate';
 import 'dart:typed_data';
 
 /// Signature for getting notified when chunks of bytes are received while
@@ -22,11 +23,11 @@ import 'dart:typed_data';
 /// returned to the client and the total size of the response may not be known
 /// until the request has been fully processed).
 ///
-/// This is used in [consolidateHttpClientResponseBytes].
+/// This is used in [getHttpClientResponseBytes].
 typedef BytesReceivedCallback = void Function(int cumulative, int total);
 
 /// Efficiently converts the response body of an [HttpClientResponse] into a
-/// [Uint8List].
+/// [TransferableTypedData].
 ///
 /// The future returned will forward any error emitted by `response`.
 ///
@@ -43,13 +44,13 @@ typedef BytesReceivedCallback = void Function(int cumulative, int total);
 /// bytes from this method (assuming the response is sending compressed bytes),
 /// set both [HttpClient.autoUncompress] to false and the `autoUncompress`
 /// parameter to false.
-Future<Uint8List> consolidateHttpClientResponseBytes(
+Future<TransferableTypedData> getHttpClientResponseBytes(
   HttpClientResponse response, {
   bool autoUncompress = true,
   BytesReceivedCallback onBytesReceived,
 }) {
   assert(autoUncompress != null);
-  final Completer<Uint8List> completer = Completer<Uint8List>.sync();
+  final Completer<TransferableTypedData> completer = Completer<TransferableTypedData>.sync();
 
   final _OutputBuffer output = _OutputBuffer();
   ByteConversionSink sink = output;
@@ -89,41 +90,54 @@ Future<Uint8List> consolidateHttpClientResponseBytes(
     }
   }, onDone: () {
     sink.close();
-    completer.complete(output.bytes);
+    completer.complete(TransferableTypedData.fromList(output.chunks));
   }, onError: completer.completeError, cancelOnError: true);
 
   return completer.future;
 }
 
+/// Efficiently converts the response body of an [HttpClientResponse] into a
+/// [Uint8List].
+///
+/// (This method is deprecated - use [getHttpClientResponseBytes] instead.)
+///
+/// The future returned will forward any error emitted by `response`.
+///
+/// The `onBytesReceived` callback, if specified, will be invoked for every
+/// chunk of bytes that is received while consolidating the response bytes.
+/// If the callback throws an error, processing of the response will halt, and
+/// the returned future will complete with the error that was thrown by the
+/// callback. For more information on how to interpret the parameters to the
+/// callback, see the documentation on [BytesReceivedCallback].
+///
+/// If the `response` is gzipped and the `autoUncompress` parameter is true,
+/// this will automatically un-compress the bytes in the returned list if it
+/// hasn't already been done via [HttpClient.autoUncompress]. To get compressed
+/// bytes from this method (assuming the response is sending compressed bytes),
+/// set both [HttpClient.autoUncompress] to false and the `autoUncompress`
+/// parameter to false.
+@Deprecated('Use getHttpClientResponseBytes instead')
+Future<Uint8List> consolidateHttpClientResponseBytes(
+  HttpClientResponse response, {
+  bool autoUncompress = true,
+  BytesReceivedCallback onBytesReceived,
+}) async {
+  final TransferableTypedData bytes = await getHttpClientResponseBytes(
+    response,
+    autoUncompress: autoUncompress,
+    onBytesReceived: onBytesReceived,
+  );
+  return bytes.materialize().asUint8List();
+}
+
 class _OutputBuffer extends ByteConversionSinkBase {
-  List<List<int>> _chunks = <List<int>>[];
-  int _contentLength = 0;
-  Uint8List _bytes;
+  final List<Uint8List> chunks = <Uint8List>[];
 
   @override
   void add(List<int> chunk) {
-    assert(_bytes == null);
-    _chunks.add(chunk);
-    _contentLength += chunk.length;
+    chunks.add(chunk);
   }
 
   @override
-  void close() {
-    if (_bytes != null) {
-      // We've already been closed; this is a no-op
-      return;
-    }
-    _bytes = Uint8List(_contentLength);
-    int offset = 0;
-    for (List<int> chunk in _chunks) {
-      _bytes.setRange(offset, offset + chunk.length, chunk);
-      offset += chunk.length;
-    }
-    _chunks = null;
-  }
-
-  Uint8List get bytes {
-    assert(_bytes != null);
-    return _bytes;
-  }
+  void close() {}
 }

packages/flutter/lib/src/services/asset_bundle.dart

@@ -5,6 +5,7 @@
 import 'dart:async';
 import 'dart:convert';
 import 'dart:io';
+import 'dart:isolate';
 import 'dart:typed_data';
 
 import 'package:flutter/foundation.dart';
@@ -120,8 +121,8 @@ class NetworkAssetBundle extends AssetBundle {
         'Unable to load asset: $key\n'
         'HTTP status code: ${response.statusCode}'
       );
-    final Uint8List bytes = await consolidateHttpClientResponseBytes(response);
-    return bytes.buffer.asByteData();
+    final TransferableTypedData transferable = await getHttpClientResponseBytes(response);
+    return transferable.materialize().asByteData();
   }
 
   /// Retrieve a string from the asset bundle, parse it with the given function,

packages/flutter/test/foundation/consolidate_response_test.dart

@@ -6,6 +6,7 @@
 
 import 'dart:async';
 import 'dart:io';
+import 'dart:isolate';
 import 'dart:typed_data';
 
 import 'package:flutter/foundation.dart';
@@ -14,7 +15,7 @@ import 'package:mockito/mockito.dart';
 import '../flutter_test_alternative.dart';
 
 void main() {
-  group(consolidateHttpClientResponseBytes, () {
+  group(getHttpClientResponseBytes, () {
     final Uint8List chunkOne = Uint8List.fromList(<int>[0, 1, 2, 3, 4, 5]);
     final Uint8List chunkTwo = Uint8List.fromList(<int>[6, 7, 8, 9, 10]);
     MockHttpClientResponse response;
@@ -46,24 +47,24 @@ void main() {
     test('Converts an HttpClientResponse with contentLength to bytes', () async {
       when(response.contentLength)
           .thenReturn(chunkOne.length + chunkTwo.length);
-      final List<int> bytes =
-          await consolidateHttpClientResponseBytes(response);
+      final List<int> bytes = (await getHttpClientResponseBytes(response))
+          .materialize().asUint8List();
 
       expect(bytes, <int>[0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10]);
     });
 
     test('Converts a compressed HttpClientResponse with contentLength to bytes', () async {
       when(response.contentLength).thenReturn(chunkOne.length);
-      final List<int> bytes =
-          await consolidateHttpClientResponseBytes(response);
+      final List<int> bytes = (await getHttpClientResponseBytes(response))
+          .materialize().asUint8List();
 
       expect(bytes, <int>[0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10]);
     });
 
     test('Converts an HttpClientResponse without contentLength to bytes', () async {
       when(response.contentLength).thenReturn(-1);
-      final List<int> bytes =
-          await consolidateHttpClientResponseBytes(response);
+      final List<int> bytes = (await getHttpClientResponseBytes(response))
+          .materialize().asUint8List();
 
       expect(bytes, <int>[0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10]);
     });
@@ -72,7 +73,7 @@ void main() {
       final int syntheticTotal = (chunkOne.length + chunkTwo.length) * 2;
       when(response.contentLength).thenReturn(syntheticTotal);
       final List<int> records = <int>[];
-      await consolidateHttpClientResponseBytes(
+      await getHttpClientResponseBytes(
         response,
         onBytesReceived: (int cumulative, int total) {
           records.addAll(<int>[cumulative, total]);
@@ -110,13 +111,13 @@ void main() {
       });
       when(response.contentLength).thenReturn(-1);
 
-      expect(consolidateHttpClientResponseBytes(response),
+      expect(getHttpClientResponseBytes(response),
           throwsA(isInstanceOf<Exception>()));
     });
 
     test('Propagates error to Future return value if onBytesReceived throws', () async {
       when(response.contentLength).thenReturn(-1);
-      final Future<List<int>> result = consolidateHttpClientResponseBytes(
+      final Future<TransferableTypedData> result = getHttpClientResponseBytes(
         response,
         onBytesReceived: (int cumulative, int total) {
           throw 'misbehaving callback';
@@ -157,14 +158,14 @@ void main() {
       test('Uncompresses GZIP bytes if autoUncompress is true and response.compressionState is compressed', () async {
         when(response.compressionState).thenReturn(HttpClientResponseCompressionState.compressed);
         when(response.contentLength).thenReturn(gzipped.length);
-        final List<int> bytes = await consolidateHttpClientResponseBytes(response);
+        final List<int> bytes = (await getHttpClientResponseBytes(response)).materialize().asUint8List();
         expect(bytes, <int>[0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10]);
       });
 
       test('returns gzipped bytes if autoUncompress is false and response.compressionState is compressed', () async {
         when(response.compressionState).thenReturn(HttpClientResponseCompressionState.compressed);
         when(response.contentLength).thenReturn(gzipped.length);
-        final List<int> bytes = await consolidateHttpClientResponseBytes(response, autoUncompress: false);
+        final List<int> bytes = (await getHttpClientResponseBytes(response, autoUncompress: false)).materialize().asUint8List();
         expect(bytes, gzipped);
       });
 
@@ -172,7 +173,7 @@ void main() {
         when(response.compressionState).thenReturn(HttpClientResponseCompressionState.compressed);
         when(response.contentLength).thenReturn(gzipped.length);
         final List<int> records = <int>[];
-        await consolidateHttpClientResponseBytes(
+        await getHttpClientResponseBytes(
           response,
           onBytesReceived: (int cumulative, int total) {
             records.addAll(<int>[cumulative, total]);
@@ -192,7 +193,7 @@ void main() {
         when(response.compressionState).thenReturn(HttpClientResponseCompressionState.decompressed);
         when(response.contentLength).thenReturn(syntheticTotal);
         final List<int> records = <int>[];
-        await consolidateHttpClientResponseBytes(
+        await getHttpClientResponseBytes(
           response,
           onBytesReceived: (int cumulative, int total) {
             records.addAll(<int>[cumulative, total]);

packages/flutter/test/widgets/image_headers_test.dart

-// Copyright 2017 The Chromium Authors. 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:io';
-
-import 'package:flutter/widgets.dart';
-import 'package:flutter_test/flutter_test.dart';
-import 'package:mockito/mockito.dart';
-
-import '../painting/image_data.dart';
-
-void main() {
-  final MockHttpClient client = MockHttpClient();
-  final MockHttpClientRequest request = MockHttpClientRequest();
-  final MockHttpClientResponse response = MockHttpClientResponse();
-  final MockHttpHeaders headers = MockHttpHeaders();
-
-  testWidgets('Headers', (WidgetTester tester) async {
-    HttpOverrides.runZoned<Future<void>>(() async {
-      await tester.pumpWidget(Image.network(
-        'https://www.example.com/images/frame.png',
-        headers: const <String, String>{'flutter': 'flutter'},
-      ));
-
-      verify(headers.add('flutter', 'flutter')).called(1);
-
-    }, createHttpClient: (SecurityContext _) {
-      when(client.getUrl(any)).thenAnswer((_) => Future<HttpClientRequest>.value(request));
-      when(request.headers).thenReturn(headers);
-      when(request.close()).thenAnswer((_) => Future<HttpClientResponse>.value(response));
-      when(response.contentLength).thenReturn(kTransparentImage.length);
-      when(response.statusCode).thenReturn(HttpStatus.ok);
-      when(response.listen(any)).thenAnswer((Invocation invocation) {
-        final void Function(List<int>) onData = invocation.positionalArguments[0];
-        final void Function() onDone = invocation.namedArguments[#onDone];
-        final void Function(Object, [ StackTrace ]) onError = invocation.namedArguments[#onError];
-        final bool cancelOnError = invocation.namedArguments[#cancelOnError];
-        return Stream<List<int>>.fromIterable(<List<int>>[kTransparentImage]).listen(onData, onDone: onDone, onError: onError, cancelOnError: cancelOnError);
-      });
-      return client;
-    });
-  }, skip: isBrowser);
-}
-
-class MockHttpClient extends Mock implements HttpClient {}
-
-class MockHttpClientRequest extends Mock implements HttpClientRequest {}
-
-class MockHttpClientResponse extends Mock implements HttpClientResponse {}
-
-class MockHttpHeaders extends Mock implements HttpHeaders {}