| // Copyright (c) 2017, 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 'cancelable_operation.dart'; |
| |
| /// Collects an asynchronous sequence of byte lists into a single list of bytes. |
| /// |
| /// If the [source] stream emits an error event, |
| /// the collection fails and the returned future completes with the same error. |
| /// |
| /// If any of the input data are not valid bytes, they will be truncated to |
| /// an eight-bit unsigned value in the resulting list. |
| Future<Uint8List> collectBytes(Stream<List<int>> source) { |
| return _collectBytes(source, (_, result) => result); |
| } |
| |
| /// Collects an asynchronous sequence of byte lists into a single list of bytes. |
| /// |
| /// Returns a [CancelableOperation] that provides the result future and a way |
| /// to cancel the collection early. |
| /// |
| /// If the [source] stream emits an error event, |
| /// the collection fails and the returned future completes with the same error. |
| /// |
| /// If any of the input data are not valid bytes, they will be truncated to |
| /// an eight-bit unsigned value in the resulting list. |
| CancelableOperation<Uint8List> collectBytesCancelable( |
| Stream<List<int>> source) { |
| return _collectBytes( |
| source, |
| (subscription, result) => CancelableOperation.fromFuture(result, |
| onCancel: subscription.cancel)); |
| } |
| |
| /// Generalization over [collectBytes] and [collectBytesCancelable]. |
| /// |
| /// Performs all the same operations, but the final result is created |
| /// by the [result] function, which has access to the stream subscription |
| /// so it can cancel the operation. |
| T _collectBytes<T>(Stream<List<int>> source, |
| T Function(StreamSubscription<List<int>>, Future<Uint8List>) result) { |
| var byteLists = <List<int>>[]; |
| var length = 0; |
| var completer = Completer<Uint8List>.sync(); |
| var subscription = source.listen( |
| (bytes) { |
| byteLists.add(bytes); |
| length += bytes.length; |
| }, |
| onError: completer.completeError, |
| onDone: () { |
| completer.complete(_collect(length, byteLists)); |
| }, |
| cancelOnError: true); |
| return result(subscription, completer.future); |
| } |
| |
| // Join a lists of bytes with a known total length into a single [Uint8List]. |
| Uint8List _collect(int length, List<List<int>> byteLists) { |
| var result = Uint8List(length); |
| var i = 0; |
| for (var byteList in byteLists) { |
| var end = i + byteList.length; |
| result.setRange(i, end, byteList); |
| i = end; |
| } |
| return result; |
| } |