Add iterator for DocumentMarker::MarkerTypes

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

 /*
  * This file is part of the DOM implementation for WebCore.
  *
  * Copyright (C) 2006 Apple Computer, Inc.
  *
  * This library is free software; you can redistribute it and/or
  * modify it under the terms of the GNU Library General Public
  * License as published by the Free Software Foundation; either
  * version 2 of the License, or (at your option) any later version.
  *
@@ skipping 37 matching lines @@
     MarkerTypeIndexesCount
   };
 
   enum MarkerType {
     Spelling = 1 << SpellingMarkerIndex,
     Grammar = 1 << GrammarMarkerIndex,
     TextMatch = 1 << TextMatchMarkerIndex,
     Composition = 1 << CompositionMarkerIndex,
   };
 
+  class MarkerTypesIterator
+      : public std::iterator<std::forward_iterator_tag, MarkerType> {
+   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 !operator==(other);
+    }
+
+    MarkerTypesIterator& operator++() {
+      DCHECK(m_remainingTypes);
+      // Turn off least significant 1-bit (from Hacker's Delight 2-1)
+      // Example:
+      // 7: 7 & 6 = 6
+      // 6: 6 & 5 = 4
+      // 4: 4 & 3 = 0
+      m_remainingTypes &= (m_remainingTypes - 1);
+      return *this;
+    }
+
+    MarkerType operator*() const {
+      DCHECK(m_remainingTypes);
+      // Isolate least significant 1-bit (from Hacker's Delight 2-1)
+      // Example:
+      // 7: 7 & -7 = 1
+      // 6: 6 & -6 = 2
+      // 4: 4 & -4 = 4
+      return static_cast<MarkerType>(m_remainingTypes & -m_remainingTypes);

[rlanday, 2017/03/22 18:38:18]

xiaochengh, MSVC is throwing a compiler warning on this line:
warning C4146: unary minus operator applied to unsigned type, result still
unsigned

I think m_remainingTypes should be signed but you said to make it unsigned, can
I change it back?

+    }
+
+   private:
+    unsigned m_remainingTypes;
+  };
+
   class MarkerTypes {
    public:
     // The constructor is intentionally implicit to allow conversion from the
     // bit-wise sum of above types
     MarkerTypes(unsigned mask) : m_mask(mask) {}
 
     bool contains(MarkerType type) const { return m_mask & type; }
     bool intersects(const MarkerTypes& types) const {
       return (m_mask & types.m_mask);
     }
     bool operator==(const MarkerTypes& other) const {
       return m_mask == other.m_mask;
     }
 
     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;
   };
 
   class AllMarkers : public MarkerTypes {
    public:
     AllMarkers() : MarkerTypes(Spelling | Grammar | TextMatch | Composition) {}
   };
 
   class MisspellingMarkers : public MarkerTypes {
@@ skipping 69 matching lines @@
   virtual bool isDescription() const { return false; }
   virtual bool isTextMatch() const { return false; }
   virtual bool isComposition() const { return false; }
 
   DEFINE_INLINE_VIRTUAL_TRACE() {}
 };
 
 }  // namespace blink
 
 #endif  // DocumentMarker_h