Source/wtf/RefPtr.h

/*
 *  Copyright (C) 2005, 2006, 2007, 2008, 2009, 2010, 2013 Apple Inc. All rights reserved.
 *
 *  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.
 *
 *  This library is distributed in the hope that it will be useful,
 *  but WITHOUT ANY WARRANTY; without even the implied warranty of
 *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 *  Library General Public License for more details.
 *
 *  You should have received a copy of the GNU Library General Public License
 *  along with this library; see the file COPYING.LIB.  If not, write to
 *  the Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor,
 *  Boston, MA 02110-1301, USA.
 *
 */

// RefPtr and PassRefPtr are documented at http://webkit.org/coding/RefPtr.html

#ifndef WTF_RefPtr_h
#define WTF_RefPtr_h

#include "wtf/HashTableDeletedValueType.h"
#include "wtf/PassRefPtr.h"
#include "wtf/RawPtr.h"
#include <algorithm>
#include <utility>

namespace WTF {

    template<typename T> class PassRefPtr;

    template<typename T> class RefPtr {
    public:
        ALWAYS_INLINE RefPtr() : m_ptr(0) { }
        ALWAYS_INLINE RefPtr(std::nullptr_t) : m_ptr(0) { }
        ALWAYS_INLINE RefPtr(T* ptr) : m_ptr(ptr) { refIfNotNull(ptr); }
        template<typename U> RefPtr(const RawPtr<U>& ptr, EnsurePtrConvertibleArgDecl(U, T)) : m_ptr(ptr.get()) { refIfNotNull(m_ptr); }
        ALWAYS_INLINE explicit RefPtr(T& ref) : m_ptr(&ref) { m_ptr->ref(); }
        ALWAYS_INLINE RefPtr(const RefPtr& o) : m_ptr(o.m_ptr) { refIfNotNull(m_ptr); }
        template<typename U> RefPtr(const RefPtr<U>& o, EnsurePtrConvertibleArgDecl(U, T)) : m_ptr(o.get()) { refIfNotNull(m_ptr); }

        RefPtr(RefPtr&& o) : m_ptr(o.m_ptr) { o.m_ptr = 0; }
        RefPtr& operator=(RefPtr&&);

        // See comments in PassRefPtr.h for an explanation of why this takes a const reference.
        template<typename U> RefPtr(const PassRefPtr<U>&, EnsurePtrConvertibleArgDecl(U, T));

        // Hash table deleted values, which are only constructed and never copied or destroyed.
        RefPtr(HashTableDeletedValueType) : m_ptr(hashTableDeletedValue()) { }
        bool isHashTableDeletedValue() const { return m_ptr == hashTableDeletedValue(); }

        ALWAYS_INLINE ~RefPtr() { derefIfNotNull(m_ptr); }

        ALWAYS_INLINE T* get() const { return m_ptr; }

        void clear();
        PassRefPtr<T> release() { PassRefPtr<T> tmp = adoptRef(m_ptr); m_ptr = 0; return tmp; }

        T& operator*() const { return *m_ptr; }
        ALWAYS_INLINE 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* (RefPtr::*UnspecifiedBoolType);
        operator UnspecifiedBoolType() const { return m_ptr ? &RefPtr::m_ptr : 0; }

        RefPtr& operator=(const RefPtr&);
        RefPtr& operator=(T*);
        RefPtr& operator=(const PassRefPtr<T>&);
        RefPtr& operator=(std::nullptr_t) { clear(); return *this; }

        template<typename U> RefPtr<T>& operator=(const RefPtr<U>&);
        template<typename U> RefPtr<T>& operator=(const PassRefPtr<U>&);
        template<typename U> RefPtr<T>& operator=(const RawPtr<U>&);

        void swap(RefPtr&);

        static T* hashTableDeletedValue() { return reinterpret_cast<T*>(-1); }

    private:
        T* m_ptr;
    };

    template<typename T> template<typename U> inline RefPtr<T>::RefPtr(const PassRefPtr<U>& o, EnsurePtrConvertibleArgDefn(U, T))
        : m_ptr(o.leakRef())
    {
    }

    template<typename T> inline void RefPtr<T>::clear()
    {
        T* ptr = m_ptr;
        m_ptr = 0;
        derefIfNotNull(ptr);
    }

    template<typename T> inline RefPtr<T>& RefPtr<T>::operator=(const RefPtr& o)
    {
        RefPtr ptr = o;
        swap(ptr);
        return *this;
    }

    template<typename T> inline RefPtr<T>& RefPtr<T>::operator=(RefPtr&& o)
    {
        // FIXME: Instead of explicitly casting to RefPtr&& here, we should use std::move, but that requires us to
        // have a standard library that supports move semantics.
        RefPtr ptr = static_cast<RefPtr&&>(o);
        swap(ptr);
        return *this;
    }

    template<typename T> template<typename U> inline RefPtr<T>& RefPtr<T>::operator=(const RefPtr<U>& o)
    {
        RefPtr ptr = o;
        swap(ptr);
        return *this;
    }

    template<typename T> inline RefPtr<T>& RefPtr<T>::operator=(T* optr)
    {
        RefPtr ptr = optr;
        swap(ptr);
        return *this;
    }

    template<typename T> inline RefPtr<T>& RefPtr<T>::operator=(const PassRefPtr<T>& o)
    {
        RefPtr ptr = o;
        swap(ptr);
        return *this;
    }

    template<typename T> template<typename U> inline RefPtr<T>& RefPtr<T>::operator=(const PassRefPtr<U>& o)
    {
        RefPtr ptr = o;
        swap(ptr);
        return *this;
    }

    template<typename T> template<typename U> inline RefPtr<T>& RefPtr<T>::operator=(const RawPtr<U>& o)
    {
        RefPtr ptr = o.get();
        swap(ptr);
        return *this;
    }

    template<class T> inline void RefPtr<T>::swap(RefPtr& o)
    {
        std::swap(m_ptr, o.m_ptr);
    }

    template<class T> inline void swap(RefPtr<T>& a, RefPtr<T>& b)
    {
        a.swap(b);
    }

    template<typename T, typename U> inline bool operator==(const RefPtr<T>& a, const RefPtr<U>& b)
    {
        return a.get() == b.get();
    }

    template<typename T, typename U> inline bool operator==(const RefPtr<T>& a, U* b)
    {
        return a.get() == b;
    }

    template<typename T, typename U> inline bool operator==(T* a, const RefPtr<U>& b)
    {
        return a == b.get();
    }

    template<typename T, typename U> inline bool operator!=(const RefPtr<T>& a, const RefPtr<U>& b)
    {
        return a.get() != b.get();
    }

    template<typename T, typename U> inline bool operator!=(const RefPtr<T>& a, U* b)
    {
        return a.get() != b;
    }

    template<typename T, typename U> inline bool operator!=(T* a, const RefPtr<U>& b)
    {
        return a != b.get();
    }

    template<typename T, typename U> inline RefPtr<T> static_pointer_cast(const RefPtr<U>& p)
    {
        return RefPtr<T>(static_cast<T*>(p.get()));
    }

    template<typename T> inline T* getPtr(const RefPtr<T>& p)
    {
        return p.get();
    }

    template<typename T> class RefPtrValuePeeker {
    public:
        ALWAYS_INLINE RefPtrValuePeeker(T* p): m_ptr(p) { }
        ALWAYS_INLINE RefPtrValuePeeker(std::nullptr_t): m_ptr(0) { }
        template<typename U> RefPtrValuePeeker(const RefPtr<U>& p): m_ptr(p.get()) { }
        template<typename U> RefPtrValuePeeker(const PassRefPtr<U>& p): m_ptr(p.get()) { }

        ALWAYS_INLINE operator T*() const { return m_ptr; }
    private:
        T* m_ptr;
    };

} // namespace WTF

using WTF::RefPtr;
using WTF::static_pointer_cast;

#endif // WTF_RefPtr_h