JavaScriptCore-1218.34.tar.gz

[apple/javascriptcore.git] / heap / Weak.h

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#ifndef Weak_h
#define Weak_h

#include <wtf/Noncopyable.h>
#include <wtf/NullPtr.h>

namespace JSC {

template<typename T> class PassWeak;
class WeakImpl;
class WeakHandleOwner;

// This is a free function rather than a Weak<T> member function so we can put it in Weak.cpp.
JS_EXPORT_PRIVATE void weakClearSlowCase(WeakImpl*&);

template<typename T> class Weak {
    WTF_MAKE_NONCOPYABLE(Weak);
public:
    Weak()
        : m_impl(0)
    {
    }

    explicit Weak(std::nullptr_t)
        : m_impl(0)
    {
    }

    explicit Weak(T*, WeakHandleOwner* = 0, void* context = 0);

    enum HashTableDeletedValueTag { HashTableDeletedValue };
    bool isHashTableDeletedValue() const;
    Weak(HashTableDeletedValueTag);

    template<typename U> Weak(const PassWeak<U>&);

    ~Weak()
    {
        clear();
    }

    void swap(Weak&);
    Weak& operator=(const PassWeak<T>&);
    
    bool operator!() const;
    T* operator->() const;
    T& operator*() const;
    T* get() const;

    bool was(T*) const;

    // This conversion operator allows implicit conversion to bool but not to other integer types.
    typedef void* (Weak::*UnspecifiedBoolType);
    operator UnspecifiedBoolType*() const;

    PassWeak<T> release();
    void clear()
    {
        if (!m_impl)
            return;
        weakClearSlowCase(m_impl);
    }
    
private:
    static WeakImpl* hashTableDeletedValue();

    WeakImpl* m_impl;
};

} // namespace JSC

#endif // Weak_h