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// Copyright (c) 2016, 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 'package:async/async.dart';
import 'src/guarantee_channel.dart';
import 'src/close_guarantee_channel.dart';
import 'src/stream_channel_transformer.dart';
export 'src/delegating_stream_channel.dart';
export 'src/disconnector.dart';
export 'src/json_document_transformer.dart';
export 'src/multi_channel.dart';
export 'src/stream_channel_completer.dart';
export 'src/stream_channel_controller.dart';
export 'src/stream_channel_transformer.dart';
/// An abstract class representing a two-way communication channel.
/// Users should consider the [stream] emitting a "done" event to be the
/// canonical indicator that the channel has closed. If they wish to close the
/// channel, they should close the [sink]—canceling the stream subscription is
/// not sufficient. Protocol errors may be emitted through the stream or through
/// [sink].done, depending on their underlying cause. Note that the sink may
/// silently drop events if the channel closes before [sink].close is called.
/// Implementations are strongly encouraged to mix in or extend
/// [StreamChannelMixin] to get default implementations of the various instance
/// methods. Adding new methods to this interface will not be considered a
/// breaking change if implementations are also added to [StreamChannelMixin].
/// Implementations must provide the following guarantees:
/// * The stream is single-subscription, and must follow all the guarantees of
/// single-subscription streams.
/// * Closing the sink causes the stream to close before it emits any more
/// events.
/// * After the stream closes, the sink is automatically closed. If this
/// happens, sink methods should silently drop their arguments until
/// [sink].close is called.
/// * If the stream closes before it has a listener, the sink should silently
/// drop events if possible.
/// * Canceling the stream's subscription has no effect on the sink. The channel
/// must still be able to respond to the other endpoint closing the channel
/// even after the subscription has been canceled.
/// * The sink *either* forwards errors to the other endpoint *or* closes as
/// soon as an error is added and forwards that error to the [sink].done
/// future.
/// These guarantees allow users to interact uniformly with all implementations,
/// and ensure that either endpoint closing the stream produces consistent
/// behavior.
abstract class StreamChannel<T> {
/// The single-subscription stream that emits values from the other endpoint.
Stream<T> get stream;
/// The sink for sending values to the other endpoint.
StreamSink<T> get sink;
/// Creates a new [StreamChannel] that communicates over [stream] and [sink].
/// Note that this stream/sink pair must provide the guarantees listed in the
/// [StreamChannel] documentation. If they don't do so natively,
/// [StreamChannel.withGuarantees] should be used instead.
factory StreamChannel(Stream<T> stream, StreamSink<T> sink) =>
_StreamChannel<T>(stream, sink);
/// Creates a new [StreamChannel] that communicates over [stream] and [sink].
/// Unlike [new StreamChannel], this enforces the guarantees listed in the
/// [StreamChannel] documentation. This makes it somewhat less efficient than
/// just wrapping a stream and a sink directly, so [new StreamChannel] should
/// be used when the guarantees are provided natively.
/// If [allowSinkErrors] is `false`, errors are not allowed to be passed to
/// [sink]. If any are, the connection will close and the error will be
/// forwarded to [sink].done.
factory StreamChannel.withGuarantees(Stream<T> stream, StreamSink<T> sink,
{bool allowSinkErrors = true}) =>
GuaranteeChannel(stream, sink, allowSinkErrors: allowSinkErrors);
/// Creates a new [StreamChannel] that communicates over [stream] and [sink].
/// This specifically enforces the second guarantee: closing the sink causes
/// the stream to close before it emits any more events. This guarantee is
/// invalidated when an asynchronous gap is added between the original
/// stream's event dispatch and the returned stream's, for example by
/// transforming it with a [StreamTransformer]. This is a lighter-weight way
/// of preserving that guarantee in particular than
/// [StreamChannel.withGuarantees].
factory StreamChannel.withCloseGuarantee(
Stream<T> stream, StreamSink<T> sink) =>
CloseGuaranteeChannel(stream, sink);
/// Connects this to [other], so that any values emitted by either are sent
/// directly to the other.
void pipe(StreamChannel<T> other);
/// Transforms this using [transformer].
/// This is identical to calling `transformer.bind(channel)`.
StreamChannel<S> transform<S>(StreamChannelTransformer<S, T> transformer);
/// Transforms only the [stream] component of this using [transformer].
StreamChannel<T> transformStream(StreamTransformer<T, T> transformer);
/// Transforms only the [sink] component of this using [transformer].
StreamChannel<T> transformSink(StreamSinkTransformer<T, T> transformer);
/// Returns a copy of this with [stream] replaced by [change]'s return
/// value.
StreamChannel<T> changeStream(Stream<T> Function(Stream<T>) change);
/// Returns a copy of this with [sink] replaced by [change]'s return
/// value.
StreamChannel<T> changeSink(StreamSink<T> Function(StreamSink<T>) change);
/// Returns a copy of this with the generic type coerced to [S].
/// If any events emitted by [stream] aren't of type [S], they're converted
/// into [TypeError] events (`CastError` on some SDK versions). Similarly, if
/// any events are added to [sink] that aren't of type [S], a [TypeError] is
/// thrown.
StreamChannel<S> cast<S>();
/// An implementation of [StreamChannel] that simply takes a stream and a sink
/// as parameters.
/// This is distinct from [StreamChannel] so that it can use
/// [StreamChannelMixin].
class _StreamChannel<T> extends StreamChannelMixin<T> {
final Stream<T> stream;
final StreamSink<T> sink;
_StreamChannel(, this.sink);
/// A mixin that implements the instance methods of [StreamChannel] in terms of
/// [stream] and [sink].
abstract class StreamChannelMixin<T> implements StreamChannel<T> {
void pipe(StreamChannel<T> other) {
StreamChannel<S> transform<S>(StreamChannelTransformer<S, T> transformer) =>
StreamChannel<T> transformStream(StreamTransformer<T, T> transformer) =>
StreamChannel<T> transformSink(StreamSinkTransformer<T, T> transformer) =>
StreamChannel<T> changeStream(Stream<T> Function(Stream<T>) change) =>
StreamChannel.withCloseGuarantee(change(stream), sink);
StreamChannel<T> changeSink(StreamSink<T> Function(StreamSink<T>) change) =>
StreamChannel.withCloseGuarantee(stream, change(sink));
StreamChannel<S> cast<S>() => StreamChannel(
stream.cast(), StreamController(sync: true)<T>().pipe(sink));