Use iterator, moveNext(), current.

sdk/lib/utf/utf8.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.
 
 const int _UTF8_ONE_BYTE_MAX = 0x7f;
 const int _UTF8_TWO_BYTE_MAX = 0x7ff;
 const int _UTF8_THREE_BYTE_MAX = 0xffff;
 
 const int _UTF8_LO_SIX_BIT_MASK = 0x3f;
 
@@ skipping 118 matching lines @@
  */
 class IterableUtf8Decoder extends Iterable<int> {
   final List<int> bytes;
   final int offset;
   final int length;
   final int replacementCodepoint;
 
   IterableUtf8Decoder(this.bytes, [this.offset = 0, this.length = null,
       this.replacementCodepoint = UNICODE_REPLACEMENT_CHARACTER_CODEPOINT]);
 
-  Utf8Decoder iterator() => new Utf8Decoder(bytes, offset, length,
-          replacementCodepoint);
+  Utf8Decoder get iterator =>
+      new Utf8Decoder(bytes, offset, length, replacementCodepoint);
 }
 
 /**
  * Provides an iterator of Unicode codepoints from UTF-8 encoded bytes. The
  * parameters can set an offset into a list of bytes (as int), limit the length
  * of the values to be decoded, and override the default Unicode replacement
  * character. Set the replacementCharacter to null to throw an
  * ArgumentError rather than replace the bad value. The return value
  * from this method can be used as an Iterable (e.g. in a for-loop).
  */
 class Utf8Decoder implements Iterator<int> {
   final _ListRangeIterator utf8EncodedBytesIterator;
   final int replacementCodepoint;
+  int _current = -1;
 
   Utf8Decoder(List<int> utf8EncodedBytes, [int offset = 0, int length,
       this.replacementCodepoint =
       UNICODE_REPLACEMENT_CHARACTER_CODEPOINT]) :
-      utf8EncodedBytesIterator = (new _ListRange(utf8EncodedBytes, offset,
-          length)).iterator();
+      utf8EncodedBytesIterator =
+          (new _ListRange(utf8EncodedBytes, offset, length)).iterator;
 
 
   Utf8Decoder._fromListRangeIterator(_ListRange source, [
       this.replacementCodepoint =
       UNICODE_REPLACEMENT_CHARACTER_CODEPOINT]) :
-      utf8EncodedBytesIterator = source.iterator();
+      utf8EncodedBytesIterator = source.iterator;
 
   /** Decode the remaininder of the characters in this decoder
     * into a [List<int>].
     */
   List<int> decodeRest() {
     List<int> codepoints = new List<int>(utf8EncodedBytesIterator.remaining);
     int i = 0;
-    while (hasNext) {
-      codepoints[i++] = next();
+    while (moveNext()) {
+      codepoints[i++] = current;
     }
     if (i == codepoints.length) {
       return codepoints;
     } else {
       List<int> truncCodepoints = new List<int>(i);
       truncCodepoints.setRange(0, i, codepoints);
       return truncCodepoints;
     }
   }
 
-  bool get hasNext => utf8EncodedBytesIterator.hasNext;
+  int get current {
+    if (_current == -1) {
+      // TODO(floitsch): bad error message.
+      throw new StateError("No more elements");
+    }
+    return _current;
+  }
 
-  int next() {
-    int value = utf8EncodedBytesIterator.next();
+  bool moveNext() {
+    _current = -1;
+
+    if (!utf8EncodedBytesIterator.moveNext()) return false;
+
+    int value = utf8EncodedBytesIterator.current;
     int additionalBytes = 0;
 
     if (value < 0) {
       if (replacementCodepoint != null) {
-        return replacementCodepoint;
+        _current = replacementCodepoint;
+        return true;
       } else {
         throw new ArgumentError(
             "Invalid UTF8 at ${utf8EncodedBytesIterator.position}");
       }
     } else if (value <= _UTF8_ONE_BYTE_MAX) {
-      return value;
+      _current = value;
+      return true;
     } else if (value < _UTF8_FIRST_BYTE_OF_TWO_BASE) {
       if (replacementCodepoint != null) {
-        return replacementCodepoint;
+        _current = replacementCodepoint;
+        return true;
       } else {
         throw new ArgumentError(
             "Invalid UTF8 at ${utf8EncodedBytesIterator.position}");
       }
     } else if (value < _UTF8_FIRST_BYTE_OF_THREE_BASE) {
       value -= _UTF8_FIRST_BYTE_OF_TWO_BASE;
       additionalBytes = 1;
     } else if (value < _UTF8_FIRST_BYTE_OF_FOUR_BASE) {
       value -= _UTF8_FIRST_BYTE_OF_THREE_BASE;
       additionalBytes = 2;
     } else if (value < _UTF8_FIRST_BYTE_OF_FIVE_BASE) {
       value -= _UTF8_FIRST_BYTE_OF_FOUR_BASE;
       additionalBytes = 3;
     } else if (value < _UTF8_FIRST_BYTE_OF_SIX_BASE) {
       value -= _UTF8_FIRST_BYTE_OF_FIVE_BASE;
       additionalBytes = 4;
     } else if (value < _UTF8_FIRST_BYTE_BOUND_EXCL) {
       value -= _UTF8_FIRST_BYTE_OF_SIX_BASE;
       additionalBytes = 5;
     } else if (replacementCodepoint != null) {
-      return replacementCodepoint;
+      _current = replacementCodepoint;
+      return true;
     } else {
       throw new ArgumentError(
           "Invalid UTF8 at ${utf8EncodedBytesIterator.position}");
     }
     int j = 0;
-    while (j < additionalBytes && utf8EncodedBytesIterator.hasNext) {
-      int nextValue = utf8EncodedBytesIterator.next();
+    while (j < additionalBytes && utf8EncodedBytesIterator.moveNext()) {
+      int nextValue = utf8EncodedBytesIterator.current;
       if (nextValue > _UTF8_ONE_BYTE_MAX &&
           nextValue < _UTF8_FIRST_BYTE_OF_TWO_BASE) {
         value = ((value << 6) | (nextValue & _UTF8_LO_SIX_BIT_MASK));
       } else {
         // if sequence-starting code unit, reposition cursor to start here
         if (nextValue >= _UTF8_FIRST_BYTE_OF_TWO_BASE) {
           utf8EncodedBytesIterator.backup();
         }
         break;
       }
       j++;
     }
     bool validSequence = (j == additionalBytes && (
         value < UNICODE_UTF16_RESERVED_LO ||
         value > UNICODE_UTF16_RESERVED_HI));
     bool nonOverlong =
         (additionalBytes == 1 && value > _UTF8_ONE_BYTE_MAX) ||
         (additionalBytes == 2 && value > _UTF8_TWO_BYTE_MAX) ||
         (additionalBytes == 3 && value > _UTF8_THREE_BYTE_MAX);
     bool inRange = value <= UNICODE_VALID_RANGE_MAX;
     if (validSequence && nonOverlong && inRange) {
-      return value;
+      _current = value;
+      return true;
     } else if (replacementCodepoint != null) {
-      return replacementCodepoint;
+      _current = replacementCodepoint;
+      return true;
     } else {
       throw new ArgumentError(
           "Invalid UTF8 at ${utf8EncodedBytesIterator.position - j}");
     }
   }
 }