dart:convert library.

sdk/lib/convert/converter.dart

+// Copyright (c) 2013, 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.
+
+part of dart.convert;
+
+abstract class Converter<S, T> {
+  // Synchronous conversion.
+  T convert(S input) {
+    T result;
+    ChunkedConversionSink outSink =
+        new ChunkedConversionSink.withCallback((x) { result = x; });
+    startChunkedConversion(outSink).addNonChunked(input);
+    return result;
+  }
+
+
+  // Can be implemented as other.fuseInput(this).
+  // The receiver can try to recognize [other] and optimize for it. If it
+  // doesn't recognize [other] it should always invoke `other.fuseInput(this)`.
+  Converter<S, dynamic> fuse(Converter<T, dynamic> other) {
+    return other.fuseInput(this);
+  }
+  // Double-dispatch method for [fuse]. Allows the successor to optimize
+  // in case it recognizes the source.
+  Converter<dynamic, T> fuseInput(Converter<dynamic, S> other) {
+    return new FusedConverter(other, this);
+  }
+
+  ChunkedConversionSink startChunkedConversion(ChunkedConversionSink sink) {
+    return new _NonChunkedSink<S, T>(this, sink);
+  }
+
+  ChunkedConversionInterface get inputInterface =>
+      ChunkedConversionSink.INTERFACE;
+  ChunkedConversionInterface get outputInterface =>
+      ChunkedConversionSink.INTERFACE;
+}
+
+abstract class ChunkedConversionInterface {
+  const ChunkedConversionInterface();
+
+  ChunkedConversionSink adapt(ChunkedConversionSink sink);
+  ChunkedConversionSink adaptEventSink(EventSink sink);
+}
+
+/** A chunked producer needs an interface to feed *one* value in. */
+abstract class ChunkedConversionSink<S> {
+  static const ChunkedConversionInterface INTERFACE =
+      const _NonChunkedInterface();
+
+  ChunkedConversionSink();
+  factory ChunkedConversionSink.withCallback(void f(S input)) = _CallbackSink;
+  void addNonChunked(S input);
+
+  ChunkedConversionInterface get interface => INTERFACE;
+
+  // The type is dynamic on purpose since sinks can chose to have a different
+  // chunk-input then the non-chunked input.
+  void add(o) { throw new UnsupportedError("add"); }
+  void close() { throw new UnsupportedError("close"); }
+}
+
+class _CallbackSink<S> extends ChunkedConversionSink<S> {
+  final Function _callback;
+  _CallbackSink(this._callback);
+  void addNonChunked(S input) { _callback(input); }
+}
+
+class _NonChunkedInterface extends ChunkedConversionInterface {
+  const _NonChunkedInterface();
+
+  ChunkedConversionSink adapt(ChunkedConversionSink sink) {
+    // Every sink is suitable as a non-chunked sink.
+    return sink;
+  }
+
+  ChunkedConversionSink adaptEventSink(EventSink eventSink) {
+    throw new UnsupportedError("close");
+  }
+}
+
+class _NonChunkedSink<S, T> extends ChunkedConversionSink<S> {
+  final Converter<S, T> _converter;
+  final ChunkedConversionSink<T> _output;
+
+  _NonChunkedSink(this._converter, this._output);
+
+  void addNonChunked(S input) {
+    _output.addNonChunked(_converter.convert(input));
+  }
+}
+
+class FusedConverter<S, T> extends Converter<S, T> {
+  final Converter first;
+  final Converter second;
+  FusedConverter(this.first, this.second);
+
+  T convert(S input) => second.convert(first.convert(input));
+
+  fuse(Converter other) => other.fuseInput(this);
+  fuseInput(Converter other) => new FusedConverter(other, this);
+
+  ChunkedConversionSink startChunkedConversion(ChunkedConversionSink sink) {
+    return first.startChunkedConversion(second.startChunkedConversion(sink));
+  }
+
+  ChunkedConversionInterface get inputInterface => first.inputInterface;
+  ChunkedConversionInterface get outputInterface => second.outputInterface;
+}
+
+class ConverterTransformer<S, T> implements StreamTransformer<S, T> {
+  // We can't put in the generic type of the converter since the synchronous
+  // conversion type is not necessarily the same as the chunked/streamed one.
+  final Converter _converter;
+  ConverterTransformer(Converter converter) : this._converter = converter;
+
+  Stream<T> bind(Stream<S> source) {
+    return new _ConverterTransformStream<S, T>(source, _converter);
+  }
+}
+
+class _ConverterTransformStream<S, T> extends EventTransformStream<S, T> {
+  final _ConverterStreamEventTransformer<S, T> _eventTransformer;
+
+  _ConverterTransformStream(Stream<S> source, Converter converter)
+      : this._withEventTransformer(
+          source,
+          new _ConverterStreamEventTransformer<S, T>(converter));
+
+  _ConverterTransformStream._withEventTransformer(
+      Stream<S> source,
+      _ConverterStreamEventTransformer<S, T> eventTransformer)
+      : _eventTransformer = eventTransformer,
+        super(source, eventTransformer);
+
+  StreamSubscription<T> listen(void onData(T data),
+                               { void onError(error),
+                                 void onDone(),
+                                 bool cancelOnError }) {
+    _eventTransformer._start();
+    return super.listen(onData, onError: onError, onDone: onDone,
+                        cancelOnError: cancelOnError);
+  }
+}
+
+class _ConverterStreamEventTransformer<S, T>
+    implements EventSink<T>, StreamEventTransformer<S, T> {
+  final Converter _converter;
+  EventSink _eventSink;
+  ChunkedConversionSink _chunkedSink;
+
+  _ConverterStreamEventTransformer(this._converter);
+
+  void _start() {
+    ChunkedConversionInterface outputInterface = _converter.outputInterface;
+    ChunkedConversionSink chunkedOutputSink =
+        outputInterface.adaptEventSink(this);
+    _chunkedSink = _converter.startChunkedConversion(chunkedOutputSink);
+  }
+
+  Stream bind(Stream otherStream) {
+    throw new UnsupportedError("Converter streams must not call bind");
+  }
+  void add(T o) => _eventSink.add(o);
+  void close() => _eventSink.close();
+  void addError(var error) {
+    throw new UnsupportedError("converters should not use `addError`.");
+  }
+
+  void handleData(S event, EventSink<T> eventSink) {
+    _eventSink = eventSink;
+    try {
+      _chunkedSink.add(event);
+    } catch(e) {
+      eventSink.addError(e);
+    }
+    _eventSink = null;
+  }
+
+  void handleDone(EventSink<T> eventSink) {
+    _eventSink = eventSink;
+    try {
+      _chunkedSink.close();
+    } catch(e) {
+      eventSink.addError(e);
+    }
+    _eventSink = null;
+  }
+
+  void handleError(var errorEvent, EventSink<T> eventSink) {
+    eventSink.addError(errorEvent);
+  }
+}