third_party/WebKit/Source/bindings/core/v8/V8NodeFilterCondition.h

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#ifndef V8NodeFilterCondition_h
#define V8NodeFilterCondition_h

#include "bindings/core/v8/ScopedPersistent.h"
#include "core/dom/NodeFilterCondition.h"
#include "platform/heap/Handle.h"
#include "wtf/PassRefPtr.h"
#include <v8.h>

namespace blink {

class ExceptionState;
class Node;
class ScriptState;

// V8NodeFilterCondition maintains a Javascript implemented callback for
// filtering Node returned by NodeIterator/TreeWalker.
// A NodeFilterCondition is referenced by a NodeFilter, and A NodeFilter is
// referenced by a NodeIterator/TreeWalker. As V8NodeFilterCondition maintains
// a Javascript callback which may reference Document, we need to avoid circular
// reference spanning V8/Blink object space.
// To address this issue, V8NodeFilterCondition holds a weak reference to
// |m_filter|, the Javascript value, and the whole reference is exposed to V8 to
// let V8 GC handle collection of |m_filter|.
// (DOM)
// NodeIterator  ----RefPtr----> NodeFilter ----RefPtr----> NodeFilterCondition
//   |   ^                        |   ^                        |
//  weak |                       weak |                ScopedPersistent(weak)
//   | RefPtr                     | RefPtr                     |
//   v   |                        v   |                        v
// NodeIterator  --HiddenValue--> NodeFilter --HiddenValue--> JS Callback
// (V8)
class V8NodeFilterCondition final : public NodeFilterCondition {
 public:
  static V8NodeFilterCondition* create(v8::Local<v8::Value> filter,
                                       v8::Local<v8::Object> owner,
                                       ScriptState* scriptState) {
    return new V8NodeFilterCondition(filter, owner, scriptState);
  }

  ~V8NodeFilterCondition() override;

  unsigned acceptNode(Node*, ExceptionState&) const override;

 private:
  // As the value |filter| is maintained by V8GC, the |owner| which references
  // V8NodeFilterCondition, usually a wrapper of NodeFilter, is specified here
  // to hold a strong reference to |filter|.
  V8NodeFilterCondition(v8::Local<v8::Value> filter,
                        v8::Local<v8::Object> owner,
                        ScriptState*);

  RefPtr<ScriptState> m_scriptState;
  ScopedPersistent<v8::Value> m_filter;
};

}  // namespace blink

#endif  // V8NodeFilterCondition_h