Source/wtf/Ptr.h

/*
 * Copyright (C) 2014 Google Inc. All rights reserved.
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 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions are
 * met:
 *
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 * notice, this list of conditions and the following disclaimer.
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 * copyright notice, this list of conditions and the following disclaimer
 * in the documentation and/or other materials provided with the
 * distribution.
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 * contributors may be used to endorse or promote products derived from
 * this software without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
 * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
 * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
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 */

#ifndef WTF_Ptr_h
#define WTF_Ptr_h

// Ptr is a simple wrapper for a raw pointer that provides the
// interface (get, clear) of other pointer types such as RefPtr,
// Persistent and Member. This is used for the Blink garbage
// collection work in order to be able to write shared code that will
// use reference counting or garbage collection based on a
// compile-time flag.

namespace WTF {

template<typename T>
class Ptr {
public:
    Ptr(T* ptr) : m_ptr(ptr) { }
    Ptr(std::nullptr_t) : m_ptr(0) { }

    template<typename U>
    Ptr(const Ptr<U>& other)
        : m_ptr(other.get())
    {
    }

    T* get() const { return m_ptr; }
    void clear() { m_ptr = 0; }

    Ptr& operator=(T* ptr)
    {
        m_ptr = ptr;
        return *this;
    }

    Ptr& operator=(std::nullptr_t)
    {
        m_ptr = 0;
        return *this;
    }

    operator T*() const { return m_ptr; }
    T& operator*() const { return *m_ptr; }
    T* operator->() const { return m_ptr; }
    bool operator!() const { return !m_ptr; }

    // This conversion operator allows implicit conversion to bool but
    // not to other integer types.
    typedef T* Ptr::*UnspecifiedBoolType;
    operator UnspecifiedBoolType() const { return m_ptr ? &m_ptr : 0; }

private:
    T* m_ptr;
};

} // namespace WTF

using WTF::Ptr;

#endif