Steps towards making the convert library strong-mode compliant.

sdk/lib/convert/chunked_conversion.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;
 
 typedef void _ChunkedConversionCallback<T>(T accumulated);
 
 /**
+ * A converter that supports chunked conversions.
+ *
+ * In addition to immediate conversions from [S] to [T], a chunked converter
+ * also supports longer-running conversions from [S2] to [T2].
+ *
+ * Frequently, the source and target types are the same, but this is not a
+ * requirement. In particular, converters that work with lists in the
+ * immediate conversion, could flatten the type for the chunked conversion.
+ *
+ * For example, the [LineSplitter] class returns a `List<String>` for the
+ * immediate conversion, but returns individual `String`s in the chunked
+ * conversion.
+ */
+abstract class ChunkedConverter<S, T, S2, T2> extends Converter<S, T> {
+
+  const ChunkedConverter();
+
+  /**
+   * Starts a chunked conversion.
+   *
+   * The returned sink serves as input for the long-running conversion. The
+   * given [sink] serves as output.
+   */
+  ChunkedConversionSink<S2> startChunkedConversion(Sink<T2> sink) {
+    throw new UnsupportedError(
+        "This converter does not support chunked conversions: $this");
+  }
+
+  Stream<T2> bind(Stream<S2> stream) {
+    return new Stream<T2>.eventTransformed(
+        stream,
+        (EventSink<T2> sink) =>
+            new _ConverterStreamEventSink<S2, T2>(this, sink));
+  }
+
+  /**
+   * Fuses this instance with the given [other] converter.
+   *
+   * If [other] is a ChunkedConverter (with matching generic types), returns a
+   * [ChunkedConverter].
+   */
+  Converter<S, dynamic> fuse(Converter<T, dynamic> other) {
+    if (other is ChunkedConverter<T, dynamic, T2, dynamic>) {
+      return new _FusedChunkedConverter<S, T, dynamic, S2, T2, dynamic>(
+          this, other);
+    }
+    return super.fuse(other);
+  }
+}
+
+/**
  * A [ChunkedConversionSink] is used to transmit data more efficiently between
  * two converters during chunked conversions.
  *
  * The basic `ChunkedConversionSink` is just a [Sink], and converters should
  * work with a plain `Sink`, but may work more efficiently with certain
  * specialized types of `ChunkedConversionSink`.
  *
  * It is recommended that implementations of `ChunkedConversionSink` extends
  * this class, to inherit any further methods that may be added to the class.
  */
@@ skipping 28 matching lines @@
   final _ChunkedConversionCallback<List<T>> _callback;
   final List<T> _accumulated = <T>[];
 
   _SimpleCallbackSink(this._callback);
 
   void add(T chunk) { _accumulated.add(chunk); }
   void close() { _callback(_accumulated); }
 }
 
 /**
- * This class converts implements the logic for a chunked conversion as a
+ * This class implements the logic for a chunked conversion as a
  * stream transformer.
  *
  * It is used as strategy in the [EventTransformStream].
  *
  * It also implements the [ChunkedConversionSink] interface so that it
  * can be used as output sink in a chunked conversion.
  */
 class _ConverterStreamEventSink<S, T> implements EventSink<S> {
   /** The output sink for the converter. */
   final EventSink<T> _eventSink;
 
   /**
    * The input sink for new data. All data that is received with
    * [handleData] is added into this sink.
    */
-  ChunkedConversionSink _chunkedSink;
+  ChunkedConversionSink<S> _chunkedSink;
 
-  _ConverterStreamEventSink(Converter converter, EventSink<T> sink)
+  _ConverterStreamEventSink(
+      Converter/*=ChunkedConverter<dynamic, dynamic, S, T>*/ converter,
+      EventSink<T> sink)
       : this._eventSink = sink,
         _chunkedSink = converter.startChunkedConversion(sink);
 
   void add(S o) => _chunkedSink.add(o);
   void addError(Object error, [StackTrace stackTrace]) {
     _eventSink.addError(error, stackTrace);
   }
   void close() => _chunkedSink.close();
 }
+
+/**
+ * Fuses two chunked converters.
+ */
+class _FusedChunkedConverter<S, M, T, S2, M2, T2> extends
+    ChunkedConverter<S, T, S2, T2> {
+  final ChunkedConverter<S, M, S2, M2> _first;
+  final ChunkedConverter<M, T, M2, T2> _second;
+
+  _FusedChunkedConverter(this._first, this._second);
+
+  T convert(S input) => _second.convert(_first.convert(input));
+
+  ChunkedConversionSink<S2> startChunkedConversion(Sink<T2> sink) {
+    return _first.startChunkedConversion(_second.startChunkedConversion(sink));
+  }
+}