Use iterator, moveNext(), current.

sdk/lib/utf/utf_core.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.
 
 // TODO(jmesserly): would be nice to have this on String (dartbug.com/6501).
 /**
  * Provide a list of Unicode codepoints for a given string.
  */
 List<int> stringToCodepoints(String str) {
   // Note: str.charCodes gives us 16-bit code units on all Dart implementations.
@@ skipping 50 matching lines @@
 const int UNICODE_UTF16_OFFSET = 0x10000;
 const int UNICODE_UTF16_SURROGATE_UNIT_0_BASE = 0xd800;
 const int UNICODE_UTF16_SURROGATE_UNIT_1_BASE = 0xdc00;
 const int UNICODE_UTF16_HI_MASK = 0xffc00;
 const int UNICODE_UTF16_LO_MASK = 0x3ff;
 
 /**
  * Encode code points as UTF16 code units.
  */
 List<int> _codepointsToUtf16CodeUnits(
-    List<int> codepoints, [int offset = 0, int length,
-    int replacementCodepoint = UNICODE_REPLACEMENT_CHARACTER_CODEPOINT]) {
+    List<int> codepoints,
+    [int offset = 0,
+     int length,
+     int replacementCodepoint = UNICODE_REPLACEMENT_CHARACTER_CODEPOINT]) {
 
   _ListRange listRange = new _ListRange(codepoints, offset, length);
   int encodedLength = 0;
   for (int value in listRange) {
     if ((value >= 0 && value < UNICODE_UTF16_RESERVED_LO) ||
         (value > UNICODE_UTF16_RESERVED_HI && value <= UNICODE_PLANE_ONE_MAX)) {
       encodedLength++;
     } else if (value > UNICODE_PLANE_ONE_MAX &&
         value <= UNICODE_VALID_RANGE_MAX) {
       encodedLength += 2;
@@ skipping 24 matching lines @@
   return codeUnitsBuffer;
 }
 
 /**
  * Decodes the utf16 codeunits to codepoints.
  */
 List<int> _utf16CodeUnitsToCodepoints(
     List<int> utf16CodeUnits, [int offset = 0, int length,
     int replacementCodepoint = UNICODE_REPLACEMENT_CHARACTER_CODEPOINT]) {
   _ListRangeIterator source =
-      (new _ListRange(utf16CodeUnits, offset, length)).iterator();
+      (new _ListRange(utf16CodeUnits, offset, length)).iterator;
   Utf16CodeUnitDecoder decoder = new Utf16CodeUnitDecoder
       .fromListRangeIterator(source, replacementCodepoint);
   List<int> codepoints = new List<int>(source.remaining);
   int i = 0;
-  while (decoder.hasNext) {
-    codepoints[i++] = decoder.next();
+  while (decoder.moveNext()) {
+    codepoints[i++] = decoder.current;
   }
   if (i == codepoints.length) {
     return codepoints;
   } else {
     List<int> codepointTrunc = new List<int>(i);
     codepointTrunc.setRange(0, i, codepoints);
     return codepointTrunc;
   }
 }
 
 /**
  * An Iterator<int> of codepoints built on an Iterator of UTF-16 code units.
  * The parameters can override the default Unicode replacement character. Set
  * the replacementCharacter to null to throw an ArgumentError
  * rather than replace the bad value.
  */
 class Utf16CodeUnitDecoder implements Iterator<int> {
   final _ListRangeIterator utf16CodeUnitIterator;
   final int replacementCodepoint;
+  int _current = -1;
 
   Utf16CodeUnitDecoder(List<int> utf16CodeUnits, [int offset = 0, int length,
       int this.replacementCodepoint =
       UNICODE_REPLACEMENT_CHARACTER_CODEPOINT]) :
-      utf16CodeUnitIterator = (new _ListRange(utf16CodeUnits, offset, length))
-          .iterator();
+      utf16CodeUnitIterator =
+          (new _ListRange(utf16CodeUnits, offset, length)).iterator;
 
   Utf16CodeUnitDecoder.fromListRangeIterator(
       _ListRangeIterator this.utf16CodeUnitIterator,
       int this.replacementCodepoint);
 
-  Iterator<int> iterator() => this;
+  Iterator<int> get iterator => this;
 
-  bool get hasNext => utf16CodeUnitIterator.hasNext;
+  int get current {
+    if (_current == -1) {
+      // TODO(floitsch): bad error message.
+      throw new StateError("No more elements");
+    }
+    return _current;
+  }
 
-  int next() {
-    int value = utf16CodeUnitIterator.next();
+  bool moveNext() {
+    _current = -1;
+    if (!utf16CodeUnitIterator.moveNext()) return false;
+
+    int value = utf16CodeUnitIterator.current;
     if (value < 0) {
       if (replacementCodepoint != null) {
-        return replacementCodepoint;
+        _current = replacementCodepoint;
       } else {
         throw new ArgumentError(
             "Invalid UTF16 at ${utf16CodeUnitIterator.position}");
       }
     } else if (value < UNICODE_UTF16_RESERVED_LO ||
         (value > UNICODE_UTF16_RESERVED_HI && value <= UNICODE_PLANE_ONE_MAX)) {
       // transfer directly
-      return value;
+      _current = value;
     } else if (value < UNICODE_UTF16_SURROGATE_UNIT_1_BASE &&
-        utf16CodeUnitIterator.hasNext) {
+        utf16CodeUnitIterator.moveNext()) {
       // merge surrogate pair
-      int nextValue = utf16CodeUnitIterator.next();
+      int nextValue = utf16CodeUnitIterator.current;
       if (nextValue >= UNICODE_UTF16_SURROGATE_UNIT_1_BASE &&
           nextValue <= UNICODE_UTF16_RESERVED_HI) {
         value = (value - UNICODE_UTF16_SURROGATE_UNIT_0_BASE) << 10;
         value += UNICODE_UTF16_OFFSET +
             (nextValue - UNICODE_UTF16_SURROGATE_UNIT_1_BASE);
-        return value;
+        _current = value;
       } else {
         if (nextValue >= UNICODE_UTF16_SURROGATE_UNIT_0_BASE &&
            nextValue < UNICODE_UTF16_SURROGATE_UNIT_1_BASE) {
           utf16CodeUnitIterator.backup();
         }
         if (replacementCodepoint != null) {
-          return replacementCodepoint;
+          _current = replacementCodepoint;
         } else {
           throw new ArgumentError(
               "Invalid UTF16 at ${utf16CodeUnitIterator.position}");
         }
       }
     } else if (replacementCodepoint != null) {
-      return replacementCodepoint;
+      _current = replacementCodepoint;
     } else {
       throw new ArgumentError(
           "Invalid UTF16 at ${utf16CodeUnitIterator.position}");
     }
+    return true;
   }
 }
 
 /**
  * _ListRange in an internal type used to create a lightweight Interable on a
  * range within a source list. DO NOT MODIFY the underlying list while
  * iterating over it. The results of doing so are undefined.
  */
 class _ListRange extends Iterable {
   final List _source;
   final int _offset;
   final int _length;
 
   _ListRange(source, [offset = 0, length]) :
       this._source = source,
       this._offset = offset,
       this._length = (length == null ? source.length - offset : length) {
     if (_offset < 0 || _offset > _source.length) {
       throw new RangeError.value(_offset);
     }
     if (_length != null && (_length < 0)) {
       throw new RangeError.value(_length);
     }
     if (_length + _offset > _source.length) {
       throw new RangeError.value(_length + _offset);
     }
   }
 
-  _ListRangeIterator iterator() =>
+  _ListRangeIterator get iterator =>
       new _ListRangeIteratorImpl(_source, _offset, _offset + _length);
 
   int get length => _length;
 }
 
 /**
  * The _ListRangeIterator provides more capabilities than a standard iterator,
  * including the ability to get the current position, count remaining items,
  * and move forward/backward within the iterator.
  */
 abstract class _ListRangeIterator implements Iterator<int> {
-  bool hasNext;
-  int next();
+  bool moveNext();
+  int get current;
   int get position;
   void backup([by]);
   int get remaining;
   void skip([count]);
 }
 
 class _ListRangeIteratorImpl implements _ListRangeIterator {
   final List<int> _source;
   int _offset;
   final int _end;
 
-  _ListRangeIteratorImpl(this._source, this._offset, this._end);
+  _ListRangeIteratorImpl(this._source, int offset, this._end)
+      : _offset = offset - 1;
 
-  bool get hasNext => _offset < _end;
+  int get current => _source[_offset];
 
-  int next() => _source[_offset++];
+  bool moveNext() => ++_offset < _end;
 
   int get position => _offset;
 
   void backup([int by = 1]) {
     _offset -= by;
   }
 
-  int get remaining => _end - _offset;
+  int get remaining => _end - _offset - 1;
 
   void skip([int count = 1]) {
     _offset += count;
   }
 }