Unify most of our utf8 implementations. This takes the implementation

frog/server/utf8.dart

-// Copyright (c) 2011, 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.
-
-
-// TODO(jmesserly): this should be in the corelib somewhere. They were taken
-// from samples/chat/http_impl.dart. There are actually various UTF8 decoders
-// in the codebase but this one has the API we need (StringStream not quite
-// flexible enough). I couldn't find another encoder.
-
-String decodeUtf8(List<int> bytes) {
-  var d = new UTF8Decoder();
-  d.writeList(bytes);
-  return d.toString();
-}
-
-List<int> encodeUtf8(String str) => UTF8Encoder.encodeString(str);
-
-// Utility class for decoding UTF-8 from data delivered as a stream of
-// bytes.
-class UTF8Decoder {
-  UTF8Decoder()
-      : _bufferList = new BufferList(),
-        _result = new StringBuffer();
-
-  // Add UTF-8 encoded data.
-  void writeList(List<int> buffer) {
-    _bufferList.add(buffer);
-    // Only process as much data as we know is safe.
-    while (_bufferList.length >= 4) {
-      _processNext();
-    }
-  }
-
-  // Return the decoded string.
-  String toString() {
-    // Process any leftover data.
-    while (_bufferList.length > 0) {
-      _processNext();
-    }
-    return _result.toString();
-  }
-
-  // Process the next UTF-8 encoded character.
-  void _processNext() {
-    int value = _bufferList.next() & 0xFF;
-    if ((value & 0x80) == 0x80) {
-      int additionalBytes;
-      if ((value & 0xe0) == 0xc0) {  // 110xxxxx
-        value = value & 0x1F;
-        additionalBytes = 1;
-      } else if ((value & 0xf0) == 0xe0) {  // 1110xxxx
-        value = value & 0x0F;
-        additionalBytes = 2;
-      } else {  // 11110xxx
-        value = value & 0x07;
-        additionalBytes = 3;
-      }
-      for (int i = 0; i < additionalBytes; i++) {
-        int byte = _bufferList.next();
-        value = value << 6 | (byte & 0x3F);
-      }
-    }
-    _result.addCharCode(value);
-  }
-
-  BufferList _bufferList;
-  StringBuffer _result;
-}
-
-// Utility class which can deliver bytes one by one from a number of
-// buffers added.
-class BufferList {
-  BufferList() : _index = 0, _length = 0, _buffers = new Queue<List<int>>();
-
-  void add(List<int> buffer) {
-    _buffers.addLast(buffer);
-    _length += buffer.length;
-  }
-
-  int next() {
-    int value = _buffers.first()[_index++];
-    _length--;
-    if (_index == _buffers.first().length) {
-      _buffers.removeFirst();
-      _index = 0;
-    }
-    return value;
-  }
-
-  int get length() => _length;
-
-  int _length;
-  Queue<List<int>> _buffers;
-  int _index;
-}
-
-
-// Utility class for encoding a string into UTF-8 byte stream.
-class UTF8Encoder {
-  static List<int> encodeString(String string) {
-    int size = _encodingSize(string);
-    List result = new List<int>(size);
-    _encodeString(string, result);
-    return result;
-  }
-
-  static int _encodingSize(String string) => _encodeString(string, null);
-
-  static int _encodeString(String string, List<int> buffer) {
-    int pos = 0;
-    int length = string.length;
-    for (int i = 0; i < length; i++) {
-      int additionalBytes;
-      int charCode = string.charCodeAt(i);
-      if (charCode <= 0x007F) {
-        additionalBytes = 0;
-        if (buffer != null) buffer[pos] = charCode;
-      } else if (charCode <= 0x07FF) {
-        // 110xxxxx (xxxxx is top 5 bits).
-        if (buffer != null) buffer[pos] = ((charCode >> 6) & 0x1F) | 0xC0;
-        additionalBytes = 1;
-      } else if (charCode <= 0xFFFF) {
-        // 1110xxxx (xxxx is top 4 bits)
-        if (buffer != null) buffer[pos] = ((charCode >> 12) & 0x0F)| 0xE0;
-        additionalBytes = 2;
-      } else {
-        // 11110xxx (xxx is top 3 bits)
-        if (buffer != null) buffer[pos] = ((charCode >> 18) & 0x07) | 0xF0;
-        additionalBytes = 3;
-      }
-      pos++;
-      if (buffer != null) {
-        for (int i = additionalBytes; i > 0; i--) {
-          // 10xxxxxx (xxxxxx is next 6 bits from the top).
-          buffer[pos++] = ((charCode >> (6 * (i - 1))) & 0x3F) | 0x80;
-        }
-      } else {
-        pos += additionalBytes;
-      }
-    }
-    return pos;
-  }
-}