Add iterator for DocumentMarker::MarkerTypes

third_party/WebKit/Source/core/editing/markers/DocumentMarker.h

Index: third_party/WebKit/Source/core/editing/markers/DocumentMarker.h
diff --git a/third_party/WebKit/Source/core/editing/markers/DocumentMarker.h b/third_party/WebKit/Source/core/editing/markers/DocumentMarker.h
index 7db49d1a45320fa4724c6a664cb6a6d88e08a618..c3da542c4b1d6bc23435dbc4a158846521364bed 100644
--- a/third_party/WebKit/Source/core/editing/markers/DocumentMarker.h
+++ b/third_party/WebKit/Source/core/editing/markers/DocumentMarker.h
@@ -55,6 +55,34 @@ class CORE_EXPORT DocumentMarker : public GarbageCollected<DocumentMarker> {
     Composition = 1 << CompositionMarkerIndex,
   };
 
+  class MarkerTypesIterator {

[yosin_UTC9, 2017/03/22 04:06:26]

Let's add

std::iterator<std::forward_iterator_tag, MarkerType>

See http://en.cppreference.com/w/cpp/iterator/iterator for more details.

+   public:
+    explicit MarkerTypesIterator(unsigned markerTypes)
+        : m_remainingTypes(markerTypes) {}
+    MarkerTypesIterator(const MarkerTypesIterator& other) = default;
+
+    bool operator==(const MarkerTypesIterator& other) {
+      return m_remainingTypes == other.m_remainingTypes;
+    }
+    bool operator!=(const MarkerTypesIterator& other) {
+      return !(*this == other);

[yosin_UTC9, 2017/03/22 04:06:26]

How about |!operator==(other)| to be more explicit about implementation.

+    }
+
+    MarkerTypesIterator& operator++() {
+      DCHECK(m_remainingTypes);
+      m_remainingTypes &= (m_remainingTypes - 1);

[yosin_UTC9, 2017/03/22 04:06:26]

Let's add a comment: turn off right most 1-bit 
(from Hacker's Delight) or better


Manual calculation:
7 | 7 & 6 | 6
6 | 6 & 5 | 4
4 | 4 & 3 | 0

+      return *this;
+    }
+
+    MarkerType operator*() const {
+      DCHECK(m_remainingTypes);
+      return static_cast<MarkerType>(m_remainingTypes & -m_remainingTypes);

[yosin_UTC9, 2017/03/22 04:06:26]

Let's add comment: Isolate the right most 1-bit
(from Hacker's Delight)


Note: Manual calculation:
7 | 7 & -7 | 1
6 | 6 & -6 | 2
4 | 4 & -4 | 4

+    }
+
+   private:
+    unsigned m_remainingTypes;
+  };
+
   class MarkerTypes {
    public:
     // The constructor is intentionally implicit to allow conversion from the
@@ -72,6 +100,9 @@ class CORE_EXPORT DocumentMarker : public GarbageCollected<DocumentMarker> {
     void add(const MarkerTypes& types) { m_mask |= types.m_mask; }
     void remove(const MarkerTypes& types) { m_mask &= ~types.m_mask; }
 
+    MarkerTypesIterator begin() const { return MarkerTypesIterator(m_mask); }
+    MarkerTypesIterator end() const { return MarkerTypesIterator(0); }
+
    private:
     unsigned m_mask;
   };