By default use current code page on Windows for decoding string

sdk/lib/io/string_stream.dart

 // Copyright (c) 2012, 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.
 
 // Interface for decoders decoding binary data into string data. The
 // decoder keeps track of line breaks during decoding.
 abstract class _StringDecoder {
   // Add more binary data to be decoded. The ownership of the buffer
   // is transfered to the decoder and the caller most not modify it any more.
   int write(List<int> buffer);
@@ skipping 26 matching lines @@
 
 
 class _StringDecoders {
   static _StringDecoder decoder(Encoding encoding) {
     if (encoding == Encoding.UTF_8) {
       return new _UTF8Decoder();
     } else if (encoding == Encoding.ISO_8859_1) {
       return new _Latin1Decoder();
     } else if (encoding == Encoding.ASCII) {
       return new _AsciiDecoder();
+    } else if (encoding == Encoding.SYSTEM) {
+      if (Platform.operatingSystem == 'windows') {
+        return new _WindowsCodePageDecoder();
+      }
+      return new _UTF8Decoder();
     } else {
       if (encoding is Encoding) {
         throw new StreamException("Unsupported encoding ${encoding.name}");
       } else {
         throw new StreamException("Unsupported encoding ${encoding}");
       }
     }
   }
 }
 
@@ skipping 186 matching lines @@
   bool _processNext() {
     while (_bufferList.length > 0) {
       int byte = _bufferList.next();
       addChar(byte);
     }
     return true;
   }
 }
 
 
+// Utility class for decoding Windows current code page data delivered
+// as a stream of bytes.
+class _WindowsCodePageDecoder extends _StringDecoderBase {
+  // Process the next chunk of data.
+  bool _processNext() {
+    List<int> bytes = _bufferList.readBytes(_bufferList.length);
+    for (var charCode in _decodeBytes(bytes).charCodes) {
+      addChar(charCode);
+    }
+    return true;
+  }
+
+  external static String _decodeBytes(List<int> bytes);
+}
+
+
 // Interface for encoders encoding string data into binary data.
 abstract class _StringEncoder {
   List<int> encodeString(String string);
 }
 
 
 // Utility class for encoding a string into UTF-8 byte stream.
 class _UTF8Encoder implements _StringEncoder {
   List<int> encodeString(String string) {
     int size = _encodingSize(string);
@@ skipping 43 matching lines @@
         throw new EncoderException(
             "No ASCII encoding for code point $charCode");
       }
       result[i] = charCode;
     }
     return result;
   }
 }
 
 
+// Utility class for encoding a string into a current windows
+// code page byte list.
+class _WindowsCodePageEncoder implements _StringEncoder {
+  List<int> encodeString(String string) {
+    return _encodeString(string);
+  }
+
+  external static List<int> _encodeString(String string);
+}
+
+
 class _StringEncoders {
   static _StringEncoder encoder(Encoding encoding) {
     if (encoding == Encoding.UTF_8) {
       return new _UTF8Encoder();
     } else if (encoding == Encoding.ISO_8859_1) {
       return new _Latin1Encoder();
     } else if (encoding == Encoding.ASCII) {
       return new _AsciiEncoder();
+    } else if (encoding == Encoding.SYSTEM) {
+      if (Platform.operatingSystem == 'windows') {
+        return new _WindowsCodePageEncoder();
+      }
+      return new _UTF8Encoder();
     } else {
       throw new StreamException("Unsupported encoding ${encoding.name}");
     }
   }
 }
 
 
 class EncoderException implements Exception {
   const EncoderException([String this.message]);
   String toString() => "EncoderException: $message";
@@ skipping 174 matching lines @@
   bool _inputClosed = false;  // Is the underlying input stream closed?
   bool _closed = false;  // Is this stream closed.
   bool _eof = false;  // Has all data been read from the decoder?
   Timer _scheduledDataCallback;
   Timer _scheduledLineCallback;
   Timer _scheduledCloseCallback;
   Function _clientDataHandler;
   Function _clientLineHandler;
   Function _clientCloseHandler;
 }