Add keys(), values() and entries() methods on iterable<> interfaces

Source/core/dom/Iterable.h

Index: Source/core/dom/Iterable.h
diff --git a/Source/core/dom/Iterable.h b/Source/core/dom/Iterable.h
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+++ b/Source/core/dom/Iterable.h
@@ -0,0 +1,167 @@
+// Copyright 2015 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#ifndef Iterable_h
+#define Iterable_h
+
+#include "bindings/core/v8/V8IteratorResultValue.h"
+#include "core/dom/Iterator.h"
+
+namespace blink {
+
+// Typically, use one of ValueIterable<> and PairIterable<> (below) instead!
+template <typename KeyType, typename ValueType>
+class Iterable {
+public:
+    virtual ~Iterable() { }
+
+    Iterator* keys(ScriptState* scriptState, ExceptionState& exceptionState)
+    {
+        IterationSource* source = this->startIteration(scriptState, exceptionState);
+        if (!source)
+            return nullptr;
+        return new IterableIterator<KeySelector>(source);
+    }
+
+    Iterator* values(ScriptState* scriptState, ExceptionState& exceptionState)
+    {
+        IterationSource* source = this->startIteration(scriptState, exceptionState);
+        if (!source)
+            return nullptr;
+        return new IterableIterator<ValueSelector>(source);
+    }
+
+    Iterator* entries(ScriptState* scriptState, ExceptionState& exceptionState)
+    {
+        IterationSource* source = this->startIteration(scriptState, exceptionState);
+        if (!source)
+            return nullptr;
+        return new IterableIterator<EntrySelector>(source);
+    }
+
+    class IterationSource : public GarbageCollectedFinalized<IterationSource> {
+    public:
+        virtual ~IterationSource() { }
+
+        // If end of iteration has been reached or an exception thrown: return false.
+        // Otherwise: set |key| and |value| and return true.
+        virtual bool next(ScriptState*, KeyType&, ValueType&, ExceptionState&) = 0;
+
+        virtual void trace(Visitor*) { }
+    };
+
+private:
+    virtual IterationSource* startIteration(ScriptState*, ExceptionState&) = 0;
+
+    struct KeySelector {
+        static const KeyType& select(ScriptState*, const KeyType& key, const ValueType& value)
+        {
+            return key;
+        }
+    };
+    struct ValueSelector {
+        static const ValueType& select(ScriptState*, const KeyType& key, const ValueType& value)
+        {
+            return value;
+        }
+    };
+    struct EntrySelector {
+        static Vector<ScriptValue, 2> select(ScriptState* scriptState, const KeyType& key, const ValueType& value)
+        {
+            v8::Local<v8::Object> creationContext = scriptState->context()->Global();
+            v8::Isolate* isolate = scriptState->isolate();
+
+            Vector<ScriptValue, 2> entry;
+            entry.append(ScriptValue(scriptState, toV8(key, creationContext, isolate)));
+            entry.append(ScriptValue(scriptState, toV8(value, creationContext, isolate)));
+            return entry;
+        }
+    };
+
+    template <typename Selector>
+    class IterableIterator final : public Iterator {
+    public:
+        explicit IterableIterator(IterationSource* source)
+            : m_source(source)
+        {
+        }
+
+        ScriptValue next(ScriptState* scriptState, ExceptionState& exceptionState) override
+        {
+            KeyType key;
+            ValueType value;
+
+            if (!m_source->next(scriptState, key, value, exceptionState))
+                return v8IteratorResultDone(scriptState);
+
+            return v8IteratorResult(scriptState, Selector::select(scriptState, key, value));
+        }
+
+        ScriptValue next(ScriptState* scriptState, ScriptValue, ExceptionState& exceptionState) override
+        {
+            return next(scriptState, exceptionState);
+        }
+
+        void trace(Visitor* visitor) override
+        {
+            visitor->trace(m_source);
+            Iterator::trace(visitor);
+        }
+
+    private:
+        Member<IterationSource> m_source;
+    };
+};
+
+// Utiltity mixin base-class for classes implementing IDL interfaces with "iterable<T>".
+template <typename ValueType>
+class ValueIterable : public Iterable<unsigned, ValueType> {
+public:
+    Iterator* iterator(ScriptState* scriptState, ExceptionState& exceptionState)
+    {
+        return this->values(scriptState, exceptionState);
+    }
+
+    class IterationSource : public Iterable<unsigned, ValueType>::IterationSource {
+    public:
+        IterationSource()
+            : m_index(0)
+        {
+        }
+
+        ~IterationSource() override { }
+
+        // If end of iteration has been reached or an exception thrown: return false.
+        // Otherwise: set |value| and return true.
+        // Note: |this->m_index| is the index being accessed.
+        virtual bool next(ScriptState*, ValueType&, ExceptionState&) = 0;
+
+    protected:
+        unsigned m_index;
+
+    private:
+        bool next(ScriptState* scriptState, unsigned& key, ValueType& value, ExceptionState& exceptionState) final
+        {
+            if (!next(scriptState, value, exceptionState))
+                return false;
+            key = m_index;
+            ++m_index;
+            return true;
+        }
+    };
+};
+
+// Utiltity mixin base-class for classes implementing IDL interfaces with "iterable<T1, T2>".
+template <typename KeyType, typename ValueType>
+class PairIterable : public Iterable<KeyType, ValueType> {
+public:
+    Iterator* iterator(ScriptState* scriptState, ExceptionState& exceptionState)
+    {
+        return this->entries(scriptState, exceptionState);
+    }
+};
+
+} // namespace blink
+
+#endif // Iterable_h