Add chunked conversion to converters.

sdk/lib/convert/byte_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;
+
+/**
+ * The [ByteConversionSink] provides an interface for converters to
+ * efficiently transmit byte data.
+ *
+ * Instead of limiting the interface to one non-chunked list of bytes it
+ * accepts its input in chunks (themselves being lists of bytes).
+ */
+abstract class ByteConversionSink extends ChunkedConversionSink<List<int>> {
+  ByteConversionSink();
+  factory ByteConversionSink.withCallback(void callback(List<int> accumulated))
+      = _ByteCallbackSink;
+  factory ByteConversionSink.from(ChunkedConversionSink<List<int>> sink)
+      = _ByteAdapterSink;
+
+  /**
+   * Adds the next [chunk] to `this`.
+   *
+   * Adds the bytes defined by [start] and [end]-exclusive to `this`.
+   *
+   * If [isLast] is `true` closes `this`.
+   *
+   * The given [chunk] is not held onto. Once the method returns, it is safe to
+   * overwrite the data in it.
+   */
+  void addSlice(List<int> chunk, int start, int end, bool isLast);
+
+  // TODO(floitsch): add more methods:
+  // - iterateBytes.
+}
+
+/**
+ * This class provides a base-class for converters that need to accept byte
+ * inputs.
+ */
+abstract class ByteConversionSinkBase extends ByteConversionSink {
+
+  void add(List<int> chunk);
+  void close();
+
+  void addSlice(List<int> chunk, int start, int end, bool isLast) {
+    if (start != 0 || end != chunk.length) {
+      add(chunk.sublist(start, end));
+    } else {
+      add(chunk);
+    }
+    if (isLast) close();
+  }
+}
+
+/**
+ * This class adapts a simple [ChunkedConversionSink] to a [ByteConversionSink].
+ *
+ * All additional methods of the [ByteConversionSink] (compared to the
+ * ChunkedConversionSink) are redirected to the `add` method.
+ */
+class _ByteAdapterSink extends ByteConversionSinkBase {
+  final ChunkedConversionSink<List<int>> _sink;
+
+  _ByteAdapterSink(this._sink);
+
+  void add(List<int> chunk) => _sink.add(chunk);
+  void close() => _sink.close();
+}
+
+/**
+ * This class accumulates all chunks into one list of bytes
+ * and invokes a callback when the sink is closed.
+ *
+ * This class can be used to terminate a chunked conversion.
+ */
+class _ByteCallbackSink extends ByteConversionSinkBase {
+  static const _INITIAL_BUFFER_SIZE = 1024;
+
+  final _ChunkedConversionCallback<List<int>> _callback;
+  // TODO(11971, floitsch): use Uint8List instead of normal lists.
+  List<int> _buffer = new List<int>(_INITIAL_BUFFER_SIZE);
+  int _bufferIndex = 0;
+
+  _ByteCallbackSink(void callback(List<int> accumulated))
+      : this._callback = callback;
+
+  void add(Iterable<int> chunk) {
+    int freeCount = _buffer.length - _bufferIndex;
+    if (chunk.length > freeCount) {
+      // Grow the buffer.
+      int oldLength = _buffer.length;
+      int newLength = _roundToPowerOf2(chunk.length + oldLength) * 2;
+      // TODO(11971, floitsch): use Uint8List instead of normal lists.
+      List<int> grown = new List<int>(newLength);
+      grown.setRange(0, _buffer.length, _buffer);
+      _buffer = grown;
+    }
+    _buffer.setRange(_bufferIndex, _bufferIndex + chunk.length, chunk);
+    _bufferIndex += chunk.length;
+  }
+
+  static int _roundToPowerOf2(int v) {
+    assert(v > 0);
+    v--;
+    v |= v >> 1;
+    v |= v >> 2;
+    v |= v >> 4;
+    v |= v >> 8;
+    v |= v >> 16;
+    v++;
+    return v;
+  }
+
+  void close() {
+    _callback(_buffer.sublist(0, _bufferIndex));
+  }
+}