Use iterator, moveNext(), current.

sdk/lib/utf/utf32.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.
 
 /**
  * Decodes the UTF-32 bytes as an iterable. Thus, the consumer can only convert
  * as much of the input as needed. Determines the byte order from the BOM,
  * or uses big-endian as a default. This method always strips a leading BOM.
  * Set the replacementCharacter to null to throw an ArgumentError
  * rather than replace the bad value.
@@ skipping 167 matching lines @@
 /**
  * Return type of [decodeUtf32AsIterable] and variants. The Iterable type
  * provides an iterator on demand and the iterator will only translate bytes
  * as requested by the user of the iterator. (Note: results are not cached.)
  */
 class IterableUtf32Decoder extends Iterable<int> {
   final Utf32BytesDecoderProvider codeunitsProvider;
 
   IterableUtf32Decoder._(this.codeunitsProvider);
 
-  Utf32BytesDecoder iterator() => codeunitsProvider();
+  Utf32BytesDecoder get iterator => codeunitsProvider();
 }
 
 /**
  * Abstrace parent class converts encoded bytes to codepoints.
  */
 class Utf32BytesDecoder implements _ListRangeIterator {
   final _ListRangeIterator utf32EncodedBytesIterator;
   final int replacementCodepoint;
+  int _current = -1;
 
   Utf32BytesDecoder._fromListRangeIterator(
       this.utf32EncodedBytesIterator, this.replacementCodepoint);
 
   factory Utf32BytesDecoder(List<int> utf32EncodedBytes, [
       int offset = 0, int length,
       int replacementCodepoint = UNICODE_REPLACEMENT_CHARACTER_CODEPOINT]) {
     if (length == null) {
       length = utf32EncodedBytes.length - offset;
     }
     if (hasUtf32beBom(utf32EncodedBytes, offset, length)) {
       return new Utf32beBytesDecoder(utf32EncodedBytes, offset + 4, length - 4,
           false, replacementCodepoint);
     } else if (hasUtf32leBom(utf32EncodedBytes, offset, length)) {
       return new Utf32leBytesDecoder(utf32EncodedBytes, offset + 4, length - 4,
           false, replacementCodepoint);
     } else {
       return new Utf32beBytesDecoder(utf32EncodedBytes, offset, length, false,
           replacementCodepoint);
     }
   }
 
   List<int> decodeRest() {
     List<int> codeunits = new List<int>(remaining);
     int i = 0;
-    while (hasNext) {
-      codeunits[i++] = next();
+    while (moveNext()) {
+      codeunits[i++] = current;
     }
     return codeunits;
   }
 
-  bool get hasNext => utf32EncodedBytesIterator.hasNext;
+  int get current {
+    if (_current == -1) {
+      // TODO(floitsch): bad error message.
+      throw new StateError("No more elements");
+    }
+    return _current;
+  }
 
-  int next() {
+  bool moveNext() {
+    _current = -1;
     if (utf32EncodedBytesIterator.remaining < 4) {
       utf32EncodedBytesIterator.skip(utf32EncodedBytesIterator.remaining);
       if (replacementCodepoint != null) {
-          return replacementCodepoint;
+          _current = replacementCodepoint;
+          return true;
       } else {
         throw new ArgumentError(
             "Invalid UTF32 at ${utf32EncodedBytesIterator.position}");
       }
     } else {
       int codepoint = decode();
       if (_validCodepoint(codepoint)) {
-        return codepoint;
+        _current = codepoint;
+        return true;
       } else if (replacementCodepoint != null) {
-          return replacementCodepoint;
+        _current = replacementCodepoint;
+        return true;
       } else {
         throw new ArgumentError(
             "Invalid UTF32 at ${utf32EncodedBytesIterator.position}");
       }
     }
   }
 
   int get position => utf32EncodedBytesIterator.position ~/ 4;
 
   void backup([int by = 1]) {
@@ skipping 10 matching lines @@
 }
 
 /**
  * Convert UTF-32BE encoded bytes to codepoints by grouping 4 bytes
  * to produce the unicode codepoint.
  */
 class Utf32beBytesDecoder extends Utf32BytesDecoder {
   Utf32beBytesDecoder(List<int> utf32EncodedBytes, [int offset = 0,
       int length, bool stripBom = true,
       int replacementCodepoint = UNICODE_REPLACEMENT_CHARACTER_CODEPOINT]) :
-      super._fromListRangeIterator((new _ListRange(utf32EncodedBytes, offset,
-      length)).iterator(), replacementCodepoint) {
+      super._fromListRangeIterator(
+          (new _ListRange(utf32EncodedBytes, offset, length)).iterator,
+          replacementCodepoint) {
     if (stripBom && hasUtf32beBom(utf32EncodedBytes, offset, length)) {
       skip();
     }
   }
 
   int decode() {
-    int value = utf32EncodedBytesIterator.next();
-    value = (value << 8) + utf32EncodedBytesIterator.next();
-    value = (value << 8) + utf32EncodedBytesIterator.next();
-    value = (value << 8) + utf32EncodedBytesIterator.next();
+    utf32EncodedBytesIterator.moveNext();
+    int value = utf32EncodedBytesIterator.current;
+    utf32EncodedBytesIterator.moveNext();
+    value = (value << 8) + utf32EncodedBytesIterator.current;
+    utf32EncodedBytesIterator.moveNext();
+    value = (value << 8) + utf32EncodedBytesIterator.current;
+    utf32EncodedBytesIterator.moveNext();
+    value = (value << 8) + utf32EncodedBytesIterator.current;
     return value;
   }
 }
 
 /**
  * Convert UTF-32BE encoded bytes to codepoints by grouping 4 bytes
  * to produce the unicode codepoint.
  */
 class Utf32leBytesDecoder extends Utf32BytesDecoder {
   Utf32leBytesDecoder(List<int> utf32EncodedBytes, [int offset = 0,
       int length, bool stripBom = true,
       int replacementCodepoint = UNICODE_REPLACEMENT_CHARACTER_CODEPOINT]) :
-      super._fromListRangeIterator((new _ListRange(utf32EncodedBytes, offset,
-      length)).iterator(), replacementCodepoint) {
+      super._fromListRangeIterator(
+          (new _ListRange(utf32EncodedBytes, offset, length)).iterator,
+          replacementCodepoint) {
     if (stripBom && hasUtf32leBom(utf32EncodedBytes, offset, length)) {
       skip();
     }
   }
 
   int decode() {
-    int value = (utf32EncodedBytesIterator.next());
-    value += (utf32EncodedBytesIterator.next() << 8);
-    value += (utf32EncodedBytesIterator.next() << 16);
-    value += (utf32EncodedBytesIterator.next() << 24);
+    utf32EncodedBytesIterator.moveNext();
+    int value = utf32EncodedBytesIterator.current;
+    utf32EncodedBytesIterator.moveNext();
+    value += (utf32EncodedBytesIterator.current << 8);
+    utf32EncodedBytesIterator.moveNext();
+    value += (utf32EncodedBytesIterator.current << 16);
+    utf32EncodedBytesIterator.moveNext();
+    value += (utf32EncodedBytesIterator.current << 24);
     return value;
   }
 }
 
 bool _validCodepoint(int codepoint) {
   return (codepoint >= 0 && codepoint < UNICODE_UTF16_RESERVED_LO) ||
       (codepoint > UNICODE_UTF16_RESERVED_HI &&
       codepoint < UNICODE_VALID_RANGE_MAX);
 }