/*
Copyright (c) Microsoft Corporation

All rights reserved.

Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except in 
compliance with the License.  You may obtain a copy of the License 
at http://www.apache.org/licenses/LICENSE-2.0   


THIS CODE IS PROVIDED *AS IS* BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, EITHER 
EXPRESS OR IMPLIED, INCLUDING WITHOUT LIMITATION ANY IMPLIED WARRANTIES OR CONDITIONS OF 
TITLE, FITNESS FOR A PARTICULAR PURPOSE, MERCHANTABLITY OR NON-INFRINGEMENT.  


See the Apache Version 2.0 License for specific language governing permissions and 
limitations under the License. 

*/

//+---------------------------------------------------------------------------
//
//  File:       auto_any.h
//
//  Contents:   automatic resource management, a-la std::auto_ptr
//
//  Classes:    auto_any<> and various typedefs
//
//  Functions:  get
//              reset
//              release
//              valid
//              address
//
//----------------------------------------------------------------------------

#ifndef AUTO_ANY
#define AUTO_ANY
#include <cassert>
#include "smart_any_fwd.h"

#pragma warning(push)

// 4284 warning for operator-> returning non-pointer;
//      compiler issues it even if -> is not used for the specific instance
#pragma warning(disable: 4284)

namespace detail
{
    // friend function definitions go in auto_any_helper
    template<typename T,class close_policy,class invalid_value,int unique>
    struct auto_any_helper;
}

// proxy reference for auto_any copying
template<typename T,class close_policy,class invalid_value,int unique>
struct auto_any_ref
{
    // construct from compatible auto_any
    auto_any_ref( auto_any<T,close_policy,invalid_value,unique> & that )
        : m_that( that )
    {
    }

    // reference to constructor argument
    auto_any<T,close_policy,invalid_value,unique> & m_that;

private:
    auto_any_ref * operator=( auto_any_ref const & );
};

// wrap a resource to enforce strict ownership and ensure proper cleanup
template<typename T,class close_policy,class invalid_value,int unique>
class auto_any
{
    typedef detail::safe_types<T,close_policy>  safe_types;

    // disallow comparison of auto_any's
    bool operator==( detail::safe_bool ) const;
    bool operator!=( detail::safe_bool ) const;

public:
    typedef typename detail::holder<T>::type    element_type;
    typedef close_policy                        close_policy_type;
    typedef typename safe_types::pointer_type   pointer_type;
    typedef typename safe_types::reference_type reference_type;

    // Fix-up the invalid_value type on older compilers
    typedef typename detail::fixup_invalid_value<invalid_value>::
        template rebind<T>::type invalid_value_type;

    friend struct detail::auto_any_helper<T,close_policy,invalid_value,unique>;

    // construct from object pointer
    explicit auto_any( T t = invalid_value_type() )
        : m_t( t )
    {
    }

    // construct by assuming pointer from right auto_any
    auto_any( auto_any<T,close_policy,invalid_value,unique> & right )
        : m_t( release( right ) )
    {
    }

    // construct by assuming pointer from right auto_any_ref
    auto_any( auto_any_ref<T,close_policy,invalid_value,unique> right )
        : m_t( release( right.m_that ) )
    {
    }

    // convert to compatible auto_any_ref
    operator auto_any_ref<T,close_policy,invalid_value,unique>()
    {
        return auto_any_ref<T,close_policy,invalid_value,unique>( *this );
    }

    // assign compatible right
    auto_any<T,close_policy,invalid_value,unique> & operator=(
        auto_any<T,close_policy,invalid_value,unique> & right )
    {
        reset( *this, release( right ) );
        return *this;
    }

    // assign compatible right.ref
    auto_any<T,close_policy,invalid_value,unique> & operator=(
        auto_any_ref<T,close_policy,invalid_value,unique> right )
    {
        reset( *this, release( right.m_that ) );
        return *this;
    }

    // destroy the object
    ~auto_any()
    {
        if( valid() )
        {
            close_policy::close( m_t );
        }
    }

    // return pointer to class object (assume pointer)
    pointer_type operator->() const
    {
        #ifdef SMART_ANY_PTS
        // You better not be applying operator-> to a handle!
        static detail::static_assert<!detail::is_handle<T>::value> const cannot_dereference_a_handle;
        #endif
        assert( valid() );
        return safe_types::to_pointer( m_t );
    }

    // for use when auto_any appears in a conditional
    operator detail::safe_bool() const
    {
        return valid() ? detail::safe_true : detail::safe_false;
    }

    // for use when auto_any appears in a conditional
    bool operator!() const
    {
        return ! valid();
    }

    #ifdef SMART_ANY_PTS
    // if this auto_any is managing an array, we can use operator[] to index it
    typename detail::deref<T>::type operator[]( int i ) const
    {
        static detail::static_assert<!detail::is_handle<T>::value> const cannot_dereference_a_handle;
        static detail::static_assert<!detail::is_delete<close_policy>::value> const accessed_like_an_array_but_not_deleted_like_an_array;
        assert( valid() );
        return m_t[ i ];
    }

    // unary operator* lets you write code like:
    // auto_any<foo*,close_delete> pfoo( new foo );
    // foo & f = *pfoo;
    reference_type operator*() const
    {
        static detail::static_assert<!detail::is_handle<T>::value> const cannot_dereference_a_handle;
        assert( valid() );
        return safe_types::to_reference( m_t );
    }
    #endif

private:

    bool valid() const
    {
        // see if the managed resource is in the invalid state.
        return m_t != static_cast<T>( invalid_value_type() );
    }

    // the wrapped object
    element_type m_t;
};

namespace detail
{
    // friend function definitions go in auto_any_helper
    template<typename T,class close_policy,class invalid_value,int unique>
    struct auto_any_helper
    {
        // return wrapped pointer
        static T get( auto_any<T,close_policy,invalid_value,unique> const & t )
        {
            return t.m_t;
        }

        // return wrapped pointer and give up ownership
        static T release( auto_any<T,close_policy,invalid_value,unique> & t )
        {
            // Fix-up the invalid_value type on older compilers
            typedef typename detail::fixup_invalid_value<invalid_value>::
                template rebind<T>::type invalid_value_type;

            T tmpT = t.m_t;
            t.m_t = static_cast<T>( invalid_value_type() );
            return tmpT;
        }

        // destroy designated object and store new pointer
        static void reset( auto_any<T,close_policy,invalid_value,unique> & t, T newT )
        {
            if( t.m_t != newT )
            {
                if( t.valid() )
                {
                    close_policy::close( t.m_t );
                }
                t.m_t = newT;
            }
        }

        typedef typename auto_any<T,close_policy,invalid_value,unique>::element_type element_type;

        // return the address of the wrapped pointer
        static element_type* address( auto_any<T,close_policy,invalid_value,unique> & t )
        {
            // check to make sure the wrapped object is in the invalid state
            assert( !t.valid() );
            return address_of( t.m_t );
        }
    };
}

// return wrapped resource
template<typename T,class close_policy,class invalid_value,int unique>
inline T get( auto_any<T,close_policy,invalid_value,unique> const & t )
{
    return detail::auto_any_helper<T,close_policy,invalid_value,unique>::get( t );
}

// return true if the auto_any contains a currently valid resource
template<typename T,class close_policy,class invalid_value,int unique>
inline bool valid( auto_any<T,close_policy,invalid_value,unique> const & t )
{
    return t;
}

// return wrapped resource and give up ownership
template<typename T,class close_policy,class invalid_value,int unique>
inline T release( auto_any<T,close_policy,invalid_value,unique> & t )
{
    return detail::auto_any_helper<T,close_policy,invalid_value,unique>::release( t );
}

// destroy designated object and store new resource
template<typename T,class close_policy,class invalid_value,int unique>
inline void reset( auto_any<T,close_policy,invalid_value,unique> & t )
{
    typedef typename detail::fixup_invalid_value<invalid_value>::
        template rebind<T>::type invalid_value_type;
    detail::auto_any_helper<T,close_policy,invalid_value,unique>::reset( t, invalid_value_type() );
}

// destroy designated object and store new resource
template<typename T,class close_policy,class invalid_value,int unique,typename U>
inline void reset( auto_any<T,close_policy,invalid_value,unique> & t, U newT )
{
    detail::auto_any_helper<T,close_policy,invalid_value,unique>::reset( t, newT );
}

// swap the contents of two shared_any objects
template<typename T,class close_policy,class invalid_value,int unique>
void swap( auto_any<T,close_policy,invalid_value,unique> & left,
           auto_any<T,close_policy,invalid_value,unique> & right )
{
    auto_any<T,close_policy,invalid_value,unique> tmp( left );
    left = right;
    right = tmp;
}

// return the address of the wrapped resource
// WARNING: this will assert if the value of the resource is
// anything other than invalid_value.
template<typename T,class close_policy,class invalid_value,int unique>
inline typename auto_any<T,close_policy,invalid_value,unique>::element_type*
    address( auto_any<T,close_policy,invalid_value,unique> & t )
{
    return detail::auto_any_helper<T,close_policy,invalid_value,unique>::address( t );
}

#pragma warning(pop)

#endif

// This causes the auto_* typedefs to be defined
DECLARE_SMART_ANY_TYPEDEFS(auto)

#if defined(_OBJBASE_H_) & !defined(AUTO_ANY_CO_INIT)
# define AUTO_ANY_CO_INIT
  typedef auto_any<HRESULT,close_co,co_not_init>                            auto_co_close;

  // Helper class for balancing calls to CoInitialize and CoUninitialize
  struct auto_co_init
  {
      explicit auto_co_init( DWORD dwCoInit = COINIT_APARTMENTTHREADED )
          : m_hr( smart_co_init_helper( dwCoInit ) )
      {
      }
      HRESULT hresult() const
      {
          return get(m_hr);
      }
      auto_co_close const m_hr;
  private:
      auto_co_init & operator=( auto_co_init const & );
  };
#endif