Provide a code point iterator to the String class to simplify iteration.

runtime/vm/object.h

 // 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.
 
 #ifndef VM_OBJECT_H_
 #define VM_OBJECT_H_
 
 #include "include/dart_api.h"
 #include "platform/assert.h"
 #include "platform/utils.h"
@@ skipping 3690 matching lines @@
 
   static const intptr_t kOneByteChar = 1;
   static const intptr_t kTwoByteChar = 2;
 
   // All strings share the same maximum element count to keep things
   // simple.  We choose a value that will prevent integer overflow for
   // 2 byte strings, since it is the worst case.
   static const intptr_t kSizeofRawString = sizeof(RawObject) + (2 * kWordSize);
   static const intptr_t kMaxElements = kSmiMax / kTwoByteChar;
 
+  class CodePointIterator : public ValueObject {
+   public:
+    explicit CodePointIterator(const String& str)
+        : str_(str),
+          index_(-1),
+          ch_(-1) {
+    }
+
+    int32_t Current() {
+      ASSERT(index_ >= 0);
+      ASSERT(index_ < str_.Length());
+      return ch_;
+    }
+
+    bool Next();
+
+   private:
+    const String& str_;
+    intptr_t index_;
+    int32_t ch_;
+    DISALLOW_IMPLICIT_CONSTRUCTORS(CodePointIterator);
+  };
+
   intptr_t Length() const { return Smi::Value(raw_ptr()->length_); }
   static intptr_t length_offset() { return OFFSET_OF(RawString, length_); }
 
   virtual intptr_t Hash() const;
   static intptr_t hash_offset() { return OFFSET_OF(RawString, hash_); }
   static intptr_t Hash(const String& str, intptr_t begin_index, intptr_t len);
   static intptr_t Hash(const uint8_t* characters, intptr_t len);
   static intptr_t Hash(const uint16_t* characters, intptr_t len);
   static intptr_t Hash(const uint32_t* characters, intptr_t len);
 
@@ skipping 2200 matching lines @@
     if (this->CharAt(i) != str.CharAt(begin_index + i)) {
       return false;
     }
   }
   return true;
 }
 
 }  // namespace dart
 
 #endif  // VM_OBJECT_H_