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// 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;
/// A [Converter] converts data from one representation into another.
/// It is recommended that implementations of `Converter` extend this class,
/// to inherit any further methods that may be added to the class.
abstract class Converter<S, T> extends StreamTransformerBase<S, T> {
const Converter();
/// Adapts [source] to be a `Converter<TS, TT>`.
/// This allows [source] to be used at the new type, but at run-time it
/// must satisfy the requirements of both the new type and its original type.
/// Conversion input must be both [SS] and [TS] and the output created by
/// [source] for those input must be both [ST] and [TT].
static Converter<TS, TT> castFrom<SS, ST, TS, TT>(Converter<SS, ST> source) =>
CastConverter<SS, ST, TS, TT>(source);
/// Converts [input] and returns the result of the conversion.
T convert(S input);
/// Fuses `this` with [other].
/// Encoding with the resulting converter is equivalent to converting with
/// `this` before converting with `other`.
Converter<S, TT> fuse<TT>(Converter<T, TT> other) {
return _FusedConverter<S, T, TT>(this, other);
/// Starts a chunked conversion.
/// The returned sink serves as input for the long-running conversion. The
/// given [sink] serves as output.
Sink<S> startChunkedConversion(Sink<T> sink) {
throw UnsupportedError(
"This converter does not support chunked conversions: $this");
Stream<T> bind(Stream<S> stream) {
return Stream<T>.eventTransformed(
stream, (EventSink sink) => _ConverterStreamEventSink(this, sink));
/// Provides a `Converter<RS, RT>` view of this stream transformer.
/// The resulting transformer will check at run-time that all conversion
/// inputs are actually instances of [S],
/// and it will check that all conversion output produced by this converter
/// are actually instances of [RT].
Converter<RS, RT> cast<RS, RT>() => Converter.castFrom<S, T, RS, RT>(this);
/// Fuses two converters.
/// For a non-chunked conversion converts the input in sequence.
class _FusedConverter<S, M, T> extends Converter<S, T> {
final Converter<S, M> _first;
final Converter<M, T> _second;
_FusedConverter(this._first, this._second);
T convert(S input) => _second.convert(_first.convert(input));
Sink<S> startChunkedConversion(Sink<T> sink) {
return _first.startChunkedConversion(_second.startChunkedConversion(sink));