Add browser-compatible version.

lib/src/io.dart

-// Copyright (c) 2015, 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.
-
-// dart:io based strategy for loading resources.
-
-import "dart:async" show Future, Stream;
-import "dart:convert" show Encoding, LATIN1, UTF8;
-import "dart:io" show
-    File, HttpClient, HttpClientResponse, HttpClientRequest, HttpHeaders;
-import "dart:typed_data" show Uint8List;
-import "package:typed_data/typed_buffers.dart" show Uint8Buffer;
-
-/// Read the bytes of a URI as a stream of bytes.
-Stream<List<int>> readAsStream(Uri uri) async* {
-  if (uri.scheme == "file") {
-    yield* new File.fromUri(uri).openRead();
-    return;
-  }
-  if (uri.scheme == "http" || uri.scheme == "https") {
-    HttpClientResponse response = await _httpGet(uri);
-    yield* response;
-    return;
-  }
-  if (uri.scheme == "data") {
-    yield uri.data.contentAsBytes();
-    return;
-  }
-  throw new UnsupportedError("Unsupported scheme: $uri");
-}
-
-/// Read the bytes of a URI as a list of bytes.
-Future<List<int>> readAsBytes(Uri uri) async {
-  if (uri.scheme == "file") {
-    return new File.fromUri(uri).readAsBytes();
-  }
-  if (uri.scheme == "http" || uri.scheme == "https") {
-    HttpClientResponse response = await _httpGet(uri);
-    int length = response.contentLength;
-    if (length < 0) length = 0;
-    var buffer = new Uint8Buffer(length);
-    await for (var bytes in response) {
-      buffer.addAll(bytes);
-    }
-    return buffer.toList();
-  }
-  if (uri.scheme == "data") {
-    return uri.data.contentAsBytes();
-  }
-  throw new UnsupportedError("Unsupported scheme: $uri");
-}
-
-/// Read the bytes of a URI as a string.
-Future<String> readAsString(Uri uri, Encoding encoding) async {
-  if (uri.scheme == "file") {
-    if (encoding == null) encoding = UTF8;
-    return new File.fromUri(uri).readAsString(encoding: encoding);
-  }
-  if (uri.scheme == "http" || uri.scheme == "https") {
-    HttpClientRequest request = await new HttpClient().getUrl(uri);
-    // Prefer text/plain, text/* if possible, otherwise take whatever is there.
-    request.headers.set(HttpHeaders.ACCEPT, "text/plain, text/*, */*");
-    if (encoding != null) {
-      request.headers.set(HttpHeaders.ACCEPT_CHARSET, encoding.name);
-    }
-    HttpClientResponse response = await request.close();
-    encoding ??= Encoding.getByName(response.headers.contentType?.charset);
-    if (encoding == null || encoding == LATIN1) {
-      // Default to LATIN-1 if no encoding found.
-      // Special case LATIN-1 since it is common and doesn't need decoding.
-      int length = response.contentLength;
-      if (length < 0) length = 0;
-      var buffer = new Uint8Buffer(length);
-      await for (var bytes in response) {
-        buffer.addAll(bytes);
-      }
-      var byteList = new Uint8List.view(buffer.buffer, 0, buffer.length);
-      return new String.fromCharCodes(byteList);
-    }
-    return response.transform(encoding.decoder).join();
-  }
-  if (uri.scheme == "data") {
-    return uri.data.contentAsString(encoding: encoding);
-  }
-  throw new UnsupportedError("Unsupported scheme: $uri");
-}
-
-Future<HttpClientResponse> _httpGet(Uri uri) async {
-  HttpClientRequest request = await new HttpClient().getUrl(uri);
-    request.headers.set(HttpHeaders.ACCEPT, "application/octet-stream, */*");
-  return request.close();
-}