Move UTF-8 decoder to utils.

dart/frog/leg/scanner/byte_strings.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.
 
 /**
  * An abstract string representation.
  */
 class ByteString implements SourceString {
   final List<int> bytes;
   final int offset;
   final int length;
   int _hashCode;
 
   ByteString(List<int> this.bytes, int this.offset, int this.length);
 
   abstract String get charset();
 
-  String toString() {
-    var list;
-    try {
-      list = bytes.getRange(offset, length);
-    } catch (var ignored) {
-      // An exception may occur when running this on node. This is
-      // because [bytes] really is a buffer (or typed array).
-      list = new List<int>(length);
-      for (int i = 0; i < length; i++) {
-        list[i] = bytes[i + offset];
-      }
-    }
-    return new String.fromCharCodes(decodeUtf8(list));
-  }
-
-  static int decodeTrailing(int byte) {
-    if (byte < 0x80 || 0xBF < byte) {
-      throw new MalformedInputException('Cannot decode UTF-8 $byte');
-    } else {
-      return byte & 0x3F;
-    }
-  }
-
-  static List<int> decodeUtf8(List<int> bytes) {
-    List<int> result = new List<int>();
-    for (int i = 0; i < bytes.length; i++) {
-      if (bytes[i] < 0x80) {
-        result.add(bytes[i]);
-      } else if (bytes[i] < 0xC2) {
-        throw new MalformedInputException('Cannot decode UTF-8 @ $i');
-      } else if (bytes[i] < 0xE0) {
-        int char = (bytes[i++] & 0x1F) << 6;
-        char += decodeTrailing(bytes[i]);
-        if (char < 0x80) {
-          throw new MalformedInputException('Cannot decode UTF-8 @ ${i-1}');
-        } else {
-          result.add(char);
-        }
-      } else if (bytes[i] < 0xF0) {
-        int char = (bytes[i++] & 0x0F) << 6;
-        char += decodeTrailing(bytes[i++]);
-        char <<= 6;
-        char += decodeTrailing(bytes[i]);
-        if (char < 0x800 || (0xD800 <= char && char <= 0xDFFF)) {
-          throw new MalformedInputException('Cannot decode UTF-8 @ ${i-2}');
-        } else {
-          result.add(char);
-        }
-      } else if (bytes[i] < 0xF8) {
-        int char = (bytes[i++] & 0x07) << 6;
-        char += decodeTrailing(bytes[i++]);
-        char <<= 6;
-        char += decodeTrailing(bytes[i++]);
-        char <<= 6;
-        char += decodeTrailing(bytes[i]);
-        if (char < 0x10000) {
-          throw new MalformedInputException('Cannot decode UTF-8 @ ${i-3}');
-        } else {
-          result.add(char);
-        }
-      } else {
-        throw new MalformedInputException('Cannot decode UTF-8 @ $i');
-      }
-    }
-    return result;
-  }
+  String toString() => new Utf8Decoder(bytes, offset, length).toString();
 
   bool operator ==(other) {
     throw "should be overridden in subclass";
   }
 
   int hashCode() {
     if (_hashCode === null) {
       _hashCode = computeHashCode();
     }
     return _hashCode;
@@ skipping 55 matching lines @@
  * A ByteString-valued token.
  */
 class ByteStringToken extends Token {
   final ByteString value;
 
   ByteStringToken(PrecedenceInfo info, ByteString this.value, int charOffset)
     : super(info, charOffset);
 
   String toString() => value.toString();
 }