---

comstl_interface_cast.h

Go to the documentation of this file.

/* 
 * File:        comstl_interface_cast.h
 *
 * Purpose:     Safe interface casting functions.
 *
 * Created:
 * Updated:     11th September 2004
 *
 * Home:        http://stlsoft.org/
 *
 * Copyright (c) 2002-2004, Matthew Wilson and Synesis Software
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions are met:
 *
 * - Redistributions of source code must retain the above copyright notice, this
 *   list of conditions and the following disclaimer.
 * - 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.
 * - Neither the name(s) of Matthew Wilson and Synesis Software nor the names of
 *   any 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 OWNER 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 COMSTL_INCL_H_COMSTL_INTERFACE_CAST
#define COMSTL_INCL_H_COMSTL_INTERFACE_CAST

#ifndef __STLSOFT_DOCUMENTATION_SKIP_SECTION
# define COMSTL_VER_H_COMSTL_INTERFACE_CAST_MAJOR       2
# define COMSTL_VER_H_COMSTL_INTERFACE_CAST_MINOR       0
# define COMSTL_VER_H_COMSTL_INTERFACE_CAST_REVISION    1
# define COMSTL_VER_H_COMSTL_INTERFACE_CAST_EDIT        61
#endif /* !__STLSOFT_DOCUMENTATION_SKIP_SECTION */

/* 
 * Compatibility
 */

/*
[Incompatibilies-start]
__STLSOFT_COMPILER_IS_MSVC: _MSC_VER<1200
[Incompatibilies-end]
 */

/* 
 * Includes
 */

#ifndef COMSTL_INCL_H_COMSTL
# include "comstl.h"                    // Include the COMSTL root header
#endif /* !COMSTL_INCL_H_COMSTL */

#if defined(__STLSOFT_COMPILER_IS_MSVC) && \
    _MSC_VER < 1200
# error comstl_interface_cast.h is not compatible with Visual C++ 5.0 or earlier
#endif /* _MSC_VER < 1200 */

#ifndef COMSTL_INCL_H_COMSTL_REFCOUNT_FUNCTIONS
# include "comstl_refcount_functions.h" // safe_addref, safe_release
#endif /* !COMSTL_INCL_H_COMSTL_REFCOUNT_FUNCTIONS */
#ifndef COMSTL_INCL_H_COMSTL_INTERFACE_TRAITS
# include "comstl_interface_traits.h"   // Include IID_traits
#endif /* !COMSTL_INCL_H_COMSTL_INTERFACE_TRAITS */
#ifndef COMSTL_INCL_H_COMSTL_BAD_INTERFACE_CAST
# include "comstl_bad_interface_cast.h" // bad_interface_cast
#endif /* !COMSTL_INCL_H_COMSTL_BAD_INTERFACE_CAST */
#ifndef STLSOFT_INCL_H_STLSOFT_OPERATOR_BOOL
# include "stlsoft_operator_bool.h"     // operator_bool_generator
#endif /* !STLSOFT_INCL_H_STLSOFT_OPERATOR_BOOL */

/* 
 * Namespace
 *
 * The COMSTL components are contained within the comstl namespace. This is
 * actually an alias for stlsoft::comstl_project,
 *
 * The definition matrix is as follows:
 *
 * _STLSOFT_NO_NAMESPACE    _COMSTL_NO_NAMESPACE    comstl definition
 * ---------------------    --------------------    -----------------
 *  not defined              not defined             = stlsoft::comstl_project
 *  not defined              defined                 not defined
 *  defined                  not defined             comstl
 *  defined                  defined                 not defined
 *
 */

#ifndef _COMSTL_NO_NAMESPACE
# if defined(_STLSOFT_NO_NAMESPACE) || \
     defined(__STLSOFT_DOCUMENTATION_SKIP_SECTION)
/* There is no stlsoft namespace, so must define ::comstl */
namespace comstl
{
# else
/* Define stlsoft::comstl_project */

namespace stlsoft
{

namespace comstl_project
{

# endif /* _STLSOFT_NO_NAMESPACE */
#endif /* !_COMSTL_NO_NAMESPACE */

/* 


/* 
 * Functions
 */

// This helper converts from an interface pointer to itself.
//
// It explicitly takes and returns pointer so that it disambiguates from any
// overload that takes an interface wrapper instance by value/reference.
template <ss_typename_param_k I>
inline I *simple_interface_cast(I *pi)
{
    return pi;
}

/* 
 * Functionals
 */

struct ignore_interface_cast_exception
{
public:
    struct thrown_type
    {
    };

public:
    void operator ()(HRESULT hr, REFIID riid) comstl_throw_0()
    {
        STLSOFT_SUPPRESS_UNUSED(hr);
        STLSOFT_SUPPRESS_UNUSED(riid);

        // Do nothing
    }
};

struct throw_bad_interface_cast_exception
{
public:
    typedef bad_interface_cast  thrown_type;

public:
    void operator ()(HRESULT hr, REFIID riid) comstl_throw_1(bad_interface_cast)
    {
        throw bad_interface_cast(riid, hr);
    }
};

template <ss_typename_param_k I>
struct noaddref_release
{
public:
    void operator ()(I pi)
    {
        release(pi);
    }
};

template <ss_typename_param_k I>
struct addref_release
{
public:
    void operator ()(I pi)
    {
        STLSOFT_SUPPRESS_UNUSED(pi);
    }
};

/* 
 * Raw-pointer safety
 *
 * Alas this requires partial template specialisation, so is not available in
 * all environments.
 */

#ifdef __STLSOFT_CF_TEMPLATE_PARTIAL_SPECIALISATION_SUPPORT

template <ss_typename_param_k I>
struct interface_pointer_traits;

template <ss_typename_param_k I>
struct interface_pointer_traits<I*>
{
    typedef I   interface_type;
};

template <ss_typename_param_k I>
interface protect_refcount
    : public I
{
private:
    STDMETHOD_(ULONG, AddRef)()
    {
        I   *pi = static_cast<I*>(this);

        return pi->AddRef();
    }
    STDMETHOD_(ULONG, Release)()
    {
        I   *pi = static_cast<I*>(this);

        return pi->Release();
    }
};

#endif /* __STLSOFT_CF_TEMPLATE_PARTIAL_SPECIALISATION_SUPPORT */

/* 
 * Classes
 */

template<   ss_typename_param_k I
        ,   ss_typename_param_k R
        ,   ss_typename_param_k X
        >
class interface_cast_base
{
public:
    typedef I                                                               interface_pointer_type;
#ifdef __STLSOFT_CF_TEMPLATE_PARTIAL_SPECIALISATION_SUPPORT

    typedef ss_typename_type_k interface_pointer_traits<I>::interface_type  interface_type;
#endif /* __STLSOFT_CF_TEMPLATE_PARTIAL_SPECIALISATION_SUPPORT */

    typedef R                                                               release_type;
    typedef X                                                               exception_policy_type;
    typedef ss_typename_type_k exception_policy_type::thrown_type           thrown_type;
    typedef interface_cast_base<I, R, X>                                    class_type;

// Construction
protected:
#ifdef __STLSOFT_CF_MEMBER_TEMPLATE_CTOR_SUPPORT
    template <ss_typename_param_k J>
    ss_explicit_k interface_cast_base(J &j)
        : m_pi(do_cast(simple_interface_cast(j)))
    {}
#else
    ss_explicit_k interface_cast_base(LPUNKNOWN punk)
        : m_pi(do_cast(punk))
    {}
#endif /* __STLSOFT_CF_MEMBER_TEMPLATE_CTOR_SUPPORT */

    ss_explicit_k interface_cast_base(interface_pointer_type pi)
        : m_pi(pi)
    {
        addref(m_pi);
    }

protected:
    ~interface_cast_base() comstl_throw_0()
    {
        if(NULL != m_pi)
        {
            release_type()(m_pi);
        }
    }

// Implementation
protected:
    static interface_pointer_type do_cast(LPUNKNOWN punk) comstl_throw_1(thrown_type)
    {
        interface_pointer_type  pi;

        if(NULL == punk)
        {
            pi = NULL;
        }
        else
        {
            REFIID  iid =   IID_traits<interface_pointer_type>().iid();
            HRESULT hr  =   punk->QueryInterface(iid, reinterpret_cast<void**>(&pi));

            if(FAILED(hr))
            {
                exception_policy_type()(hr, iid);

                pi = NULL;
            }
        }

        return pi;
    }

    interface_pointer_type const &get_pointer_()
    {
        return m_pi;
    }

    interface_pointer_type get_pointer_() const
    {
        return m_pi;
    }

// Members
private:
    interface_pointer_type const    m_pi;

// Not to be implemented
public:
    interface_cast_base(class_type const &rhs);
    class_type const &operator =(class_type const &rhs);
};


template<   ss_typename_param_k I
        ,   ss_typename_param_k X = throw_bad_interface_cast_exception
        >
class interface_cast_noaddref
    : protected interface_cast_base<I, noaddref_release<I>, X>
{
private:
    typedef interface_cast_base<I, noaddref_release<I>, X>                  parent_class_type;
public:
    typedef interface_cast_noaddref<I, X>                                   class_type;
    typedef ss_typename_type_k parent_class_type::interface_pointer_type    interface_pointer_type;
#ifdef __STLSOFT_CF_TEMPLATE_PARTIAL_SPECIALISATION_SUPPORT

    typedef ss_typename_type_k parent_class_type::interface_type            interface_type;
    typedef protect_refcount<interface_type>                                *protected_interface_pointer_type;
#else
    typedef interface_pointer_type                                          protected_interface_pointer_type;
#endif // __STLSOFT_CF_TEMPLATE_PARTIAL_SPECIALISATION_SUPPORT

// Construction
public:
#ifdef __STLSOFT_CF_MEMBER_TEMPLATE_CTOR_SUPPORT
    template <ss_typename_param_k J>
    ss_explicit_k interface_cast_noaddref(J &j)
        : parent_class_type(j)
    {}
#else
    ss_explicit_k interface_cast_noaddref(LPUNKNOWN punk)
        : parent_class_type(punk)
    {}
#endif /* __STLSOFT_CF_MEMBER_TEMPLATE_CTOR_SUPPORT */

    ss_explicit_k interface_cast_noaddref(interface_pointer_type pi)
        : parent_class_type(pi)
    {}

#ifndef __STLSOFT_DOCUMENTATION_SKIP_SECTION
    ~interface_cast_noaddref() comstl_throw_0()
    {} // We need to provide this to persuade VC6 to call the parent class dtor
#endif /* !__STLSOFT_DOCUMENTATION_SKIP_SECTION */

// Accessors
public:
    protected_interface_pointer_type operator -> () const
    {
        comstl_message_assert("Attempting to dereference null pointer. Exception model should not be null", NULL != get_pointer_());

        return static_cast<protected_interface_pointer_type>(get_pointer_());
    }

// Not to be implemented
private:
    interface_cast_noaddref(class_type const &rhs);
    class_type const &operator =(class_type const &rhs);

    // These are defined to placate Borland C/C++
    void *operator new(cs_size_t /* si */) { return 0; }
    void operator delete(void * /* pv */) {}
};

template<   ss_typename_param_k I
        ,   ss_typename_param_k X = ignore_interface_cast_exception
        >
class interface_cast_addref
    : protected interface_cast_base<I, addref_release<I>, X>
{
private:
    typedef interface_cast_base<I, addref_release<I>, X>                    parent_class_type;
public:
    typedef interface_cast_addref<I, X>                                     class_type;
    typedef ss_typename_type_k parent_class_type::interface_pointer_type    interface_pointer_type;

// Construction
public:
#ifdef __STLSOFT_CF_MEMBER_TEMPLATE_CTOR_SUPPORT
    template <ss_typename_param_k J>
    ss_explicit_k interface_cast_addref(J j)
        : parent_class_type(j)
    {}
#else
    ss_explicit_k interface_cast_addref(LPUNKNOWN punk)
        : parent_class_type(punk)
    {}
#endif /* __STLSOFT_CF_MEMBER_TEMPLATE_CTOR_SUPPORT */

    ss_explicit_k interface_cast_addref(interface_pointer_type pi)
        : parent_class_type(pi)
    {}

// Accessors
public:
    operator interface_pointer_type ()
    {
        return get_pointer_();
    }

// Not to be implemented
private:
    interface_cast_addref(class_type const &rhs);
    class_type const &operator =(class_type const &rhs);

    // These are defined to placate Borland C/C++
    void *operator new(cs_size_t /* si */) { return 0; }
    void operator delete(void * /* pv */) {}
};


template<   ss_typename_param_k I
        >
class interface_cast_test
    : protected interface_cast_base<I, noaddref_release<I>, ignore_interface_cast_exception>
{
private:
    typedef interface_cast_base<I, noaddref_release<I>, ignore_interface_cast_exception>    parent_class_type;
public:
    typedef interface_cast_test<I>                                                          class_type;
    typedef ss_typename_type_k parent_class_type::interface_pointer_type                    interface_pointer_type;
#ifdef __STLSOFT_CF_TEMPLATE_PARTIAL_SPECIALISATION_SUPPORT

    typedef ss_typename_type_k parent_class_type::interface_type                            interface_type;
    typedef protect_refcount<interface_type>                                                *protected_interface_pointer_type;
#else
    typedef interface_pointer_type                                                          protected_interface_pointer_type;
#endif // __STLSOFT_CF_TEMPLATE_PARTIAL_SPECIALISATION_SUPPORT

// Construction
public:
#ifdef __STLSOFT_CF_MEMBER_TEMPLATE_CTOR_SUPPORT
    template <ss_typename_param_k J>
    ss_explicit_k interface_cast_test(J &j)
        : parent_class_type(j)
    {}
#else
    ss_explicit_k interface_cast_test(LPUNKNOWN punk)
        : parent_class_type(punk)
    {}
#endif /* __STLSOFT_CF_MEMBER_TEMPLATE_CTOR_SUPPORT */

    ss_explicit_k interface_cast_test(interface_pointer_type pi)
        : parent_class_type(pi)
    {}

#ifndef __STLSOFT_DOCUMENTATION_SKIP_SECTION
    ~interface_cast_test() comstl_throw_0()
    {} // We need to provide this to persuade VC6 to call the parent class dtor
#endif /* !__STLSOFT_DOCUMENTATION_SKIP_SECTION */

private:
    STLSOFT_DEFINE_OPERATOR_BOOL_TYPES_T(class_type, operator_bool_generator_type, operator_bool_type);
public:
    operator operator_bool_type() const
    {
        return operator_bool_generator_type::translate(NULL != get_pointer_());
    }
    cs_bool_t operator !() const
    {
        return NULL == get_pointer_();
    }

// Not to be implemented
private:
    interface_cast_test(class_type const &rhs);
    class_type const &operator =(class_type const &rhs);

    // These are defined to placate Borland C/C++
    void *operator new(cs_size_t /* si */) { return 0; }
    void operator delete(void * /* pv */) {}
};

/* 

#ifndef _COMSTL_NO_NAMESPACE
# if defined(_STLSOFT_NO_NAMESPACE) || \
     defined(__STLSOFT_DOCUMENTATION_SKIP_SECTION)
} // namespace comstl
# else
} // namespace comstl_project
# endif /* _STLSOFT_NO_NAMESPACE */
#endif /* !_COMSTL_NO_NAMESPACE */

/* 
 * Shims
 */

template<   ss_typename_param_k I
        ,   ss_typename_param_k X
        >
inline I get_ptr(comstl_ns_qual(interface_cast_noaddref)<I, X> &p)
{
    return p.operator -> ();
}

template<   ss_typename_param_k I
        ,   ss_typename_param_k X
        >
inline I const get_ptr(comstl_ns_qual(interface_cast_noaddref)<I, X> const &p)
{
    return p.operator -> ();
}

template<   ss_typename_param_k I
        ,   ss_typename_param_k X
        >
inline I get_ptr(comstl_ns_qual(interface_cast_addref)<I, X> &p)
{
    return p;
}

template<   ss_typename_param_k I
        ,   ss_typename_param_k X
        >
inline I const get_ptr(comstl_ns_qual(interface_cast_addref)<I, X> const &p)
{
    return p;
}

/* 


/* 

#if 0
template<   ss_typename_param_k I
        >
inline cs_bool_t has_interface()
#endif /* 0 */

#ifndef _COMSTL_NO_NAMESPACE
# if defined(_STLSOFT_NO_NAMESPACE) || \
     defined(__STLSOFT_DOCUMENTATION_SKIP_SECTION)
namespace comstl {
# else
namespace comstl_project {
# endif /* _STLSOFT_NO_NAMESPACE */
#endif /* !_COMSTL_NO_NAMESPACE */

// Unit-testing

#ifdef STLSOFT_UNITTEST

namespace unittest
{
    ss_bool_t test_comstl_interface_cast(unittest_reporter *r)
    {
        using stlsoft::unittest::unittest_initialiser;

        ss_bool_t               bSuccess    =   true;

        unittest_initialiser    init(r, "COMSTL", "interface_cast", __FILE__);

        LPSTREAM    pstm;
        HRESULT     hr  =   ::CreateStreamOnHGlobal(NULL, true, &pstm);

        if(SUCCEEDED(hr))
        {
            if(!interface_cast_test<LPSTREAM>(pstm))
            {
                r->report("interface_cast_test failed to detect same type ", __LINE__);
                bSuccess = false;
            }

            if(get_ptr(interface_cast_noaddref<LPSTREAM>(pstm)) != pstm)
            {
                r->report("interface_cast_noaddref did not cast to same type ", __LINE__);
                bSuccess = false;
            }

            try
            {
                if(get_ptr(interface_cast_noaddref<LPSTORAGE>(pstm)) != NULL)
                {
                    r->report("interface_cast_noaddref cast to wrong type ", __LINE__);
                    bSuccess = false;
                }
            }
            catch(bad_interface_cast &x)
            {
                STLSOFT_SUPPRESS_UNUSED(x);
            }

            LPSTREAM    pstm2   =   interface_cast_addref<LPSTREAM>(pstm);
            LPSTORAGE   pstg    =   interface_cast_addref<LPSTORAGE>(pstm);

            if(NULL == pstm2)
            {
                r->report("interface_cast_addref did not cast to same type ", __LINE__);
                bSuccess = false;
            }
            else
            {
                pstm2->Release();
            }

            if(NULL != pstg)
            {
                r->report("interface_cast_addref cast to wrong type ", __LINE__);
                bSuccess = false;
                pstg->Release();
            }

            pstm->Release();
        }

        return bSuccess;
    }

    unittest_registrar    unittest_comstl_interface_cast(test_comstl_interface_cast);

} // namespace unittest

#endif /* STLSOFT_UNITTEST */

/* 

#ifndef _COMSTL_NO_NAMESPACE
# if defined(_STLSOFT_NO_NAMESPACE) || \
     defined(__STLSOFT_DOCUMENTATION_SKIP_SECTION)
} // namespace comstl
# else
} // namespace comstl_project
} // namespace stlsoft
# endif /* _STLSOFT_NO_NAMESPACE */
#endif /* !_COMSTL_NO_NAMESPACE */

/* 

#endif /* !COMSTL_INCL_H_COMSTL_INTERFACE_CAST */

/* 

STLSoft Libraries documentation © Synesis Software Pty Ltd, 2001-2004