ptr_cast.hpp

新版本TR1的stl

/* /////////////////////////////////////////////////////////////////////////
 * File:        stlsoft/conversion/ptr_cast.hpp
 *
 * Purpose:     A cast that throws bad_cast for dynamic pointer casting, as well
 *              as references.
 *
 * Created:     28th December 2002
 * Updated:     12th March 2007
 *
 * Home:        http://stlsoft.org/
 *
 * Copyright (c) 2002-2007, 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.
 *
 * ////////////////////////////////////////////////////////////////////// */


/** \file stlsoft/conversion/ptr_cast.hpp
 *
 * \brief [C++ only] Definition of the stlsoft::ptr_cast cast class
 *   (\ref group__library__conversion "Conversion" Library).
 */

#ifndef STLSOFT_INCL_STLSOFT_CONVERSION_HPP_PTR_CAST
#define STLSOFT_INCL_STLSOFT_CONVERSION_HPP_PTR_CAST

#ifndef STLSOFT_DOCUMENTATION_SKIP_SECTION
# define STLSOFT_VER_STLSOFT_CONVERSION_HPP_PTR_CAST_MAJOR      4
# define STLSOFT_VER_STLSOFT_CONVERSION_HPP_PTR_CAST_MINOR      0
# define STLSOFT_VER_STLSOFT_CONVERSION_HPP_PTR_CAST_REVISION   7
# define STLSOFT_VER_STLSOFT_CONVERSION_HPP_PTR_CAST_EDIT       34
#endif /* !STLSOFT_DOCUMENTATION_SKIP_SECTION */

/* /////////////////////////////////////////////////////////////////////////
 * Compatibility
 */

/*
[Incompatibilies-start]
STLSOFT_COMPILER_IS_INTEL: _MSC_VER<1310
STLSOFT_COMPILER_IS_MSVC: _MSC_VER<1310
STLSOFT_COMPILER_IS_WATCOM:
[Incompatibilies-end]
 */

/* /////////////////////////////////////////////////////////////////////////
 * Includes
 */

#ifndef STLSOFT_INCL_STLSOFT_H_STLSOFT
# include <stlsoft/stlsoft.h>
#endif /* !STLSOFT_INCL_STLSOFT_H_STLSOFT */
#ifndef STLSOFT_INCL_STLSOFT_META_HPP_BASE_TYPE_TRAITS
# include <stlsoft/meta/base_type_traits.hpp>
#endif /* !STLSOFT_INCL_STLSOFT_META_HPP_BASE_TYPE_TRAITS */
#include <typeinfo>

/* /////////////////////////////////////////////////////////////////////////
 * Namespace
 */

#ifndef _STLSOFT_NO_NAMESPACE
namespace stlsoft
{
#endif /* _STLSOFT_NO_NAMESPACE */

/* /////////////////////////////////////////////////////////////////////////
 * Classes
 */

/** \brief A cast that throws bad_cast for pointer cast failures, as well as
 *   for reference casts.
 *
 * \ingroup group__library__conversion
 *
 * Assume the following class hierarchy, and variables:
\code
class Parent
{
public:
  virtual ~Parent();
};

class A
  : public Parent
{
public:
  ~A();
};

class B
  : public Parent
{
public:
  ~B();
};

. . .

A   a;
B   b;
\endcode
 *
 * The following code segments illustrate the similarities and differences
 * between dynamic_cast and ptr_cast:
 *
 * (i) dynamic cast of reference that succeeds
\code
A   &ra1 = dynamic_cast<A&>(a);
A   &ra2 = stlsoft::ptr_cast<A&>(a);

assert(&ra1 == &ra2);
\endcode
 *
 * (ii) dynamic cast of pointer that succeeds
\code
A   *pa = dynamic_cast<A*>(&a);

assert(NULL != pa);
assert(stlsoft::ptr_cast<A*>(&a) == pa);
\endcode
 *
 * (iii) dynamic cast of reference that fails
\code
bool bCastFailed1 = false;

try
{
  B &b1 = dynamic_cast<B&>(a);

  . . . // Will never get here
}
catch(std::bad_cast &)
{
  bCastFailed1 = true;
}
assert(bCastFailed1);

bool bCastFailed2 = false;

try
{
  B &rb = stlsoft::ptr_cast<B&>(a);

  . . . // Will never get here
}
catch(std::bad_cast &)
{
  bCastFailed2 = true;
}
assert(bCastFailed2);
\endcode
 *
 * (iv) dynamic cast of pointer that fails
\code
assert(NULL == dynamic_cast<B*>(&a));

bool bCastFailed = false;

try
{
  B &rb = stlsoft::ptr_cast<B&>(&a);

  . . . // Will never get here
}
catch(std::bad_cast &)
{
  bCastFailed = true;
}
assert(bCastFailed);
\endcode
 *
 * \note This is described in detail in chapter 19 of
 *  <a href = "http://www.imperfectcplusplus.com/">Imperfect C++</a>.
 */
template <ss_typename_param_k Target>
struct ptr_cast
{
public:
    /// The target type
    typedef Target                                                          target_type;
    /// The current instantiation of the type
    typedef ptr_cast<Target>                                                class_type;
    /// The target base type
    typedef ss_typename_type_k stlsoft::base_type_traits<Target>::cv_type   target_base_type;
    /// The reference type
    typedef target_base_type                                                &reference_type;
    /// The pointer type
    typedef target_base_type                                                *pointer_type;

private:
    typedef ss_typename_type_k stlsoft::base_type_traits<Target>::base_type target_base_type_;
    static target_base_type_* manage_const(target_base_type_* p)
    {
        return p;
    }
#if defined(STLSOFT_COMPILER_IS_BORLAND)
    static target_base_type_* manage_const(target_base_type_ const* p)
    {
        return const_cast<target_base_type_*>(p);
    }
#else /* ? compiler */
    static target_base_type_ const* manage_const(target_base_type_ const* p)
    {
        return p;
    }
#endif /* compiler */

public:
    /// Constructor used when casting a reference
    template <ss_typename_param_k Source>
    ptr_cast(Source &s)
        : m_p(manage_const(&dynamic_cast<Target>(s)))
    {
        // Nothing to do: dynamic_cast throws for reference types
    }

    /// Constructor used when casting a pointer
    template <ss_typename_param_k Source>
#if defined(STLSOFT_COMPILER_IS_BORLAND) || \
    defined(STLSOFT_COMPILER_IS_GCC) || \
    defined(STLSOFT_COMPILER_IS_MWERKS)
    ptr_cast(Source*& s)
#else /* ? compiler */
    ptr_cast(Source* s)
#endif /* compiler */
        : m_p(manage_const(dynamic_cast<Target>(s)))
    {
        if(NULL == m_p)
        {
            STLSOFT_THROW_X(stlsoft_ns_qual_std(bad_cast)());
        }
    }

#ifndef STLSOFT_DOCUMENTATION_SKIP_SECTION
    ptr_cast(pointer_type pt)
        : m_p(pt)
    {}
    ptr_cast(reference_type t)
        : m_p(&t)
    {}
#endif /* !STLSOFT_DOCUMENTATION_SKIP_SECTION */

public:
    /// Converts an instance of the cast class to a reference
    operator reference_type () const
    {
        return const_cast<reference_type>(*m_p);
    }
    /// Converts an instance of the cast class to a pointer
    operator pointer_type () const
    {
        return const_cast<pointer_type>(m_p);
    }

private:
    pointer_type  m_p;

// Not to be implemented
private:
    ptr_cast(class_type const&);
};

////////////////////////////////////////////////////////////////////////////
// Unit-testing

#ifdef STLSOFT_UNITTEST
# include "./unittest/ptr_cast_unittest_.h"
#endif /* STLSOFT_UNITTEST */

/* ////////////////////////////////////////////////////////////////////// */

#ifndef _STLSOFT_NO_NAMESPACE
} // namespace stlsoft
#endif /* _STLSOFT_NO_NAMESPACE */

/* ////////////////////////////////////////////////////////////////////// */

#endif /* !STLSOFT_INCL_STLSOFT_CONVERSION_HPP_PTR_CAST */

/* ////////////////////////////////////////////////////////////////////// */