Serialize barback assets more efficiently.

pkg/barback/lib/src/asset.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.
 
 library barback.asset;
 
 import 'dart:async';
-import 'dart:convert';
-import 'dart:io';
 
 import 'asset_id.dart';
-import 'file_pool.dart';
-import 'stream_replayer.dart';
-import 'utils.dart';
+import 'internal_asset.dart';
 
 /// A blob of content.
 ///
 /// Assets may come from the file system, or as the output of a [Transformer].
 /// They are identified by [AssetId].
+///
+/// Custom implementations of [Asset] are not currently supported.
 abstract class Asset {
   /// The ID for this asset.
   final AssetId id;
 
-  Asset(this.id);
-
   factory Asset.fromBytes(AssetId id, List<int> bytes) =>
-      new _BinaryAsset(id, bytes);
+      new BinaryAsset(id, bytes);
 
   factory Asset.fromFile(AssetId id, File file) =>
-      new _FileAsset(id, file);
+      new FileAsset(id, file.path);
 
   factory Asset.fromString(AssetId id, String content) =>
-      new _StringAsset(id, content);
+      new StringAsset(id, content);
 
   factory Asset.fromPath(AssetId id, String path) =>
-      new _FileAsset(id, new File(path));
+      new FileAsset(id, path);
 
-  /// Creates an asset from a stream.
-  ///
-  /// This immediately starts draining [stream].
   factory Asset.fromStream(AssetId id, Stream<List<int>> stream) =>
-      new _StreamAsset(id, stream);
+      new StreamAsset(id, stream);
 
   /// Returns the contents of the asset as a string.
   ///
   /// If the asset was created from a [String] the original string is always
   /// returned and [encoding] is ignored. Otherwise, the binary data of the
   /// asset is decoded using [encoding], which defaults to [UTF8].
   Future<String> readAsString({Encoding encoding});
 
   /// Streams the binary contents of the asset.
   ///
   /// If the asset was created from a [String], this returns its UTF-8 encoding.
   Stream<List<int>> read();
 }
-
-/// An asset whose data is stored in a list of bytes.
-class _BinaryAsset extends Asset {
-  final List<int> _contents;
-
-  _BinaryAsset(AssetId id, this._contents)
-      : super(id);
-
-  Future<String> readAsString({Encoding encoding}) {
-    if (encoding == null) encoding = UTF8;
-
-    return new Future.value(encoding.decode(_contents));
-  }
-
-  Stream<List<int>> read() => new Future<List<int>>.value(_contents).asStream();
-
-  String toString() {
-    var buffer = new StringBuffer();
-    buffer.write("Bytes [");
-
-    // Don't show the whole list if it's long.
-    if (_contents.length > 11) {
-      for (var i = 0; i < 5; i++) {
-        buffer.write(byteToHex(_contents[i]));
-        buffer.write(" ");
-      }
-
-      buffer.write("...");
-
-      for (var i = _contents.length - 5; i < _contents.length; i++) {
-        buffer.write(" ");
-        buffer.write(byteToHex(_contents[i]));
-      }
-    } else {
-      for (var i = 0; i < _contents.length; i++) {
-        if (i > 0) buffer.write(" ");
-        buffer.write(byteToHex(_contents[i]));
-      }
-    }
-
-    buffer.write("]");
-    return buffer.toString();
-  }
-}
-
-/// An asset backed by a file on the local file system.
-class _FileAsset extends Asset {
-  /// Use a [FilePool] to handle reads so we can try to cope with running out
-  /// of file descriptors more gracefully.
-  static final _pool = new FilePool();
-
-  final File _file;
-  _FileAsset(AssetId id, this._file)
-      : super(id);
-
-  Future<String> readAsString({Encoding encoding}) {
-    if (encoding == null) encoding = UTF8;
-    return _pool.readAsString(_file, encoding);
-  }
-
-  Stream<List<int>> read() => _pool.openRead(_file);
-
-  String toString() => 'File "${_file.path}"';
-}
-
-/// An asset whose data is stored in a string.
-class _StringAsset extends Asset {
-  final String _contents;
-
-  _StringAsset(AssetId id, this._contents)
-      : super(id);
-
-  Future<String> readAsString({Encoding encoding}) =>
-      new Future.value(_contents);
-
-  Stream<List<int>> read() =>
-      new Future<List<int>>.value(UTF8.encode(_contents)).asStream();
-
-  String toString() {
-    // Don't show the whole string if it's long.
-    var contents = _contents;
-    if (contents.length > 40) {
-      contents = contents.substring(0, 20) + " ... " +
-                 contents.substring(contents.length - 20);
-    }
-
-    contents = _escape(contents);
-    return 'String "$contents"';
-  }
-
-  String _escape(String string) {
-    return string
-        .replaceAll("\"", r'\"')
-        .replaceAll("\n", r"\n")
-        .replaceAll("\r", r"\r")
-        .replaceAll("\t", r"\t");
-  }
-}
-
-/// An asset whose data is available from a stream.
-class _StreamAsset extends Asset {
-  /// A stream replayer that records and replays the contents of the input
-  /// stream.
-  final StreamReplayer<List<int>> _replayer;
-
-  _StreamAsset(AssetId id, Stream<List<int>> stream)
-      : _replayer = new StreamReplayer(stream),
-        super(id);
-
-  Future<String> readAsString({Encoding encoding}) {
-    if (encoding == null) encoding = UTF8;
-    return _replayer.getReplay().toList()
-        .then((chunks) => encoding.decode(flatten(chunks)));
-  }
-
-  Stream<List<int>> read() => _replayer.getReplay();
-
-  String toString() => "Stream";
-}