WebCore/platform/win/COMPtr.h

/*
 * Copyright (C) 2007 Apple Inc. All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 *
 * THIS SOFTWARE IS PROVIDED BY APPLE COMPUTER, INC. ``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 APPLE COMPUTER, INC. OR
 * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
 * EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
 * PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
 * PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY
 * OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
 * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. 
 */

#ifndef COMPtr_h
#define COMPtr_h

#define NOMINMAX

#include <guiddef.h>
#include <unknwn.h>
#include <WTF/Assertions.h>
#include <WTF/HashTraits.h>

typedef long HRESULT;

// FIXME: Should we put this into the WebCore namespace and use "using" on it
// as we do with things in WTF? 

enum AdoptCOMTag { AdoptCOM };
enum QueryTag { Query };
enum CreateTag { Create };

template <typename T> class COMPtr {
public:
    COMPtr() : m_ptr(0) { }
    COMPtr(T* ptr) : m_ptr(ptr) { if (m_ptr) m_ptr->AddRef(); }
    COMPtr(AdoptCOMTag, T* ptr) : m_ptr(ptr) { }
    COMPtr(const COMPtr& o) : m_ptr(o.m_ptr) { if (T* ptr = m_ptr) ptr->AddRef(); }

    inline COMPtr(QueryTag, IUnknown* ptr) : m_ptr(copyQueryInterfaceRef(ptr)) { }
    template <typename U> inline COMPtr(QueryTag, const COMPtr<U>& ptr) : m_ptr(copyQueryInterfaceRef(ptr.get())) { }

    inline COMPtr(CreateTag, const IID& clsid) : m_ptr(createInstance(clsid)) { }

    ~COMPtr() { if (m_ptr) m_ptr->Release(); }

    T* get() const { return m_ptr; }
    T* releaseRef() { T* tmp = m_ptr; m_ptr = 0; return tmp; }

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

    T** operator&() { ASSERT(!m_ptr); 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* (COMPtr::*UnspecifiedBoolType)() const;
    operator UnspecifiedBoolType() const { return m_ptr ? &COMPtr::get : 0; }

    COMPtr& operator=(const COMPtr&);
    COMPtr& operator=(T*);
    template <typename U> COMPtr& operator=(const COMPtr<U>&);

    void query(IUnknown* ptr) { adoptRef(copyQueryInterfaceRef(ptr)); }
    template <typename U> inline void query(const COMPtr<U>& ptr) { query(ptr.get()); }

    void create(const IID& clsid) { adoptRef(createInstance(clsid)); }

    template <typename U> HRESULT copyRefTo(U**);
    void adoptRef(T*);

private:
    static T* copyQueryInterfaceRef(IUnknown*);
    static T* createInstance(const IID& clsid);

    T* m_ptr;
};

template <typename T> inline T* COMPtr<T>::createInstance(const IID& clsid)
{
    T* result;
    if (FAILED(CoCreateInstance(clsid, 0, CLSCTX_ALL, __uuidof(result), reinterpret_cast<void**>(&result))))
        return 0;
    return result;
}

template <typename T> inline T* COMPtr<T>::copyQueryInterfaceRef(IUnknown* ptr)
{
    if (!ptr)
        return 0;
    T* result;
    if (FAILED(ptr->QueryInterface(&result)))
        return 0;
    return result;
}

template <typename T> template <typename U> inline HRESULT COMPtr<T>::copyRefTo(U** ptr)
{
    if (!ptr)
        return E_POINTER;
    *ptr = m_ptr;
    if (m_ptr)
        m_ptr->AddRef();
    return S_OK;
}

template <typename T> inline void COMPtr<T>::adoptRef(T *ptr)
{
    if (m_ptr)
        m_ptr->Release();
    m_ptr = ptr;
}

template <typename T> inline COMPtr<T>& COMPtr<T>::operator=(const COMPtr<T>& o)
{
    T* optr = o.get();
    if (optr)
        optr->AddRef();
    T* ptr = m_ptr;
    m_ptr = optr;
    if (ptr)
        ptr->Release();
    return *this;
}

template <typename T> template <typename U> inline COMPtr<T>& COMPtr<T>::operator=(const COMPtr<U>& o)
{
    T* optr = o.get();
    if (optr)
        optr->AddRef();
    T* ptr = m_ptr;
    m_ptr = optr;
    if (ptr)
        ptr->Release();
    return *this;
}

template <typename T> inline COMPtr<T>& COMPtr<T>::operator=(T* optr)
{
    if (optr)
        optr->AddRef();
    T* ptr = m_ptr;
    m_ptr = optr;
    if (ptr)
        ptr->Release();
    return *this;
}

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

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

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

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

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

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

namespace WTF {
    template<typename P> struct HashTraits<COMPtr<P> > : GenericHashTraits<COMPtr<P> > {
        typedef HashTraits<typename IntTypes<sizeof(P*)>::SignedType> StorageTraits;
        typedef typename StorageTraits::TraitType StorageType;
        static const bool emptyValueIsZero = true;
        static const bool needsRef = true;

        typedef union { 
            P* m_p; 
            StorageType m_s; 
        } UnionType;

        static void ref(const StorageType& s) 
        { 
            if (const P* p = reinterpret_cast<const UnionType*>(&s)->m_p) 
                const_cast<P*>(p)->AddRef(); 
        }
        static void deref(const StorageType& s) 
        { 
            if (const P* p = reinterpret_cast<const UnionType*>(&s)->m_p) 
                const_cast<P*>(p)->Release(); 
        }
    };

    template<typename P> struct HashKeyStorageTraits<PtrHash<COMPtr<P> >, HashTraits<COMPtr<P> > > {
        typedef typename IntTypes<sizeof(P*)>::SignedType IntType;
        typedef IntHash<IntType> Hash;
        typedef HashTraits<IntType> Traits;
    };

    template<typename P> struct DefaultHash<COMPtr<P> > { typedef PtrHash<COMPtr<P> > Hash; };

    template<typename P> struct PtrHash<COMPtr<P> > {
        static unsigned hash(const COMPtr<P>& key) { return PtrHash<P*>::hash(key.get()); }
        static bool equal(const COMPtr<P>& a, const COMPtr<P>& b) { return a == b; }
    };
}

#endif