Boost C++ Libraries

boost/shared_ptr.hpp

#ifndef BOOST_SHARED_PTR_HPP_INCLUDED
#define BOOST_SHARED_PTR_HPP_INCLUDED

//
//  shared_ptr.hpp
//
//  (C) Copyright Greg Colvin and Beman Dawes 1998, 1999.
//  Copyright (c) 2001-2006 Peter Dimov
//
//  Distributed under the Boost Software License, Version 1.0. (See
//  accompanying file LICENSE_1_0.txt or copy at
//  http://www.boost.org/LICENSE_1_0.txt)
//
//  See http://www.boost.org/libs/smart_ptr/shared_ptr.htm for documentation.
//

#include <boost/config.hpp>   // for broken compiler workarounds

#if defined(BOOST_NO_MEMBER_TEMPLATES) && !defined(BOOST_MSVC6_MEMBER_TEMPLATES)
#include <boost/detail/shared_ptr_nmt.hpp>
#else

#include <memory>               // for std::auto_ptr

#include <boost/assert.hpp>
#include <boost/checked_delete.hpp>
#include <boost/throw_exception.hpp>
#include <boost/detail/shared_count.hpp>
#include <boost/detail/workaround.hpp>

#include <algorithm>            // for std::swap
#include <functional>           // for std::less
#include <typeinfo>             // for std::bad_cast
#include <iosfwd>               // for std::basic_ostream

#ifdef BOOST_MSVC  // moved here to work around VC++ compiler crash
# pragma warning(push)
# pragma warning(disable:4284) // odd return type for operator->
#endif

namespace boost
{

template<class T> class weak_ptr;
template<class T> class enable_shared_from_this;

namespace detail
{

struct static_cast_tag {};
struct const_cast_tag {};
struct dynamic_cast_tag {};
struct polymorphic_cast_tag {};

template<class T> struct shared_ptr_traits
{
    typedef T & reference;
};

template<> struct shared_ptr_traits<void>
{
    typedef void reference;
};

#if !defined(BOOST_NO_CV_VOID_SPECIALIZATIONS)

template<> struct shared_ptr_traits<void const>
{
    typedef void reference;
};

template<> struct shared_ptr_traits<void volatile>
{
    typedef void reference;
};

template<> struct shared_ptr_traits<void const volatile>
{
    typedef void reference;
};

#endif

// enable_shared_from_this support

template<class T, class Y> void sp_enable_shared_from_this( shared_count const & pn, boost::enable_shared_from_this<T> const * pe, Y const * px )
{
    if(pe != 0) pe->_internal_weak_this._internal_assign(const_cast<Y*>(px), pn);
}

#ifdef sgi
// Turn off: the last argument of the varargs function "sp_enable_shared_from_this" is unnamed
# pragma set woff 3506
#endif

inline void sp_enable_shared_from_this( shared_count const & /*pn*/, ... )
{
}

#ifdef sgi
# pragma reset woff 3506
#endif

#if !defined( BOOST_NO_SFINAE ) && !defined( BOOST_NO_TEMPLATE_PARTIAL_SPECIALIZATION ) && !defined( BOOST_NO_AUTO_PTR )

// rvalue auto_ptr support based on a technique by Dave Abrahams

template< class T, class R > struct sp_enable_if_auto_ptr
{
};

template< class T, class R > struct sp_enable_if_auto_ptr< std::auto_ptr< T >, R >
{
    typedef R type;
}; 

#endif

} // namespace detail


//
//  shared_ptr
//
//  An enhanced relative of scoped_ptr with reference counted copy semantics.
//  The object pointed to is deleted when the last shared_ptr pointing to it
//  is destroyed or reset.
//

template<class T> class shared_ptr
{
private:

    // Borland 5.5.1 specific workaround
    typedef shared_ptr<T> this_type;

public:

    typedef T element_type;
    typedef T value_type;
    typedef T * pointer;
    typedef typename boost::detail::shared_ptr_traits<T>::reference reference;

    shared_ptr(): px(0), pn() // never throws in 1.30+
    {
    }

    template<class Y>
    explicit shared_ptr( Y * p ): px( p ), pn( p ) // Y must be complete
    {
        boost::detail::sp_enable_shared_from_this( pn, p, p );
    }

    //
    // Requirements: D's copy constructor must not throw
    //
    // shared_ptr will release p by calling d(p)
    //

    template<class Y, class D> shared_ptr(Y * p, D d): px(p), pn(p, d)
    {
        boost::detail::sp_enable_shared_from_this( pn, p, p );
    }

    // As above, but with allocator. A's copy constructor shall not throw.

    template<class Y, class D, class A> shared_ptr( Y * p, D d, A a ): px( p ), pn( p, d, a )
    {
        boost::detail::sp_enable_shared_from_this( pn, p, p );
    }

//  generated copy constructor, assignment, destructor are fine...

//  except that Borland C++ has a bug, and g++ with -Wsynth warns
#if defined(__BORLANDC__) || defined(__GNUC__)

    shared_ptr & operator=(shared_ptr const & r) // never throws
    {
        px = r.px;
        pn = r.pn; // shared_count::op= doesn't throw
        return *this;
    }

#endif

    template<class Y>
    explicit shared_ptr(weak_ptr<Y> const & r): pn(r.pn) // may throw
    {
        // it is now safe to copy r.px, as pn(r.pn) did not throw
        px = r.px;
    }

    template<class Y>
    shared_ptr(shared_ptr<Y> const & r): px(r.px), pn(r.pn) // never throws
    {
    }

    template<class Y>
    shared_ptr(shared_ptr<Y> const & r, boost::detail::static_cast_tag): px(static_cast<element_type *>(r.px)), pn(r.pn)
    {
    }

    template<class Y>
    shared_ptr(shared_ptr<Y> const & r, boost::detail::const_cast_tag): px(const_cast<element_type *>(r.px)), pn(r.pn)
    {
    }

    template<class Y>
    shared_ptr(shared_ptr<Y> const & r, boost::detail::dynamic_cast_tag): px(dynamic_cast<element_type *>(r.px)), pn(r.pn)
    {
        if(px == 0) // need to allocate new counter -- the cast failed
        {
            pn = boost::detail::shared_count();
        }
    }

    template<class Y>
    shared_ptr(shared_ptr<Y> const & r, boost::detail::polymorphic_cast_tag): px(dynamic_cast<element_type *>(r.px)), pn(r.pn)
    {
        if(px == 0)
        {
            boost::throw_exception(std::bad_cast());
        }
    }

#ifndef BOOST_NO_AUTO_PTR

    template<class Y>
    explicit shared_ptr(std::auto_ptr<Y> & r): px(r.get()), pn()
    {
        Y * tmp = r.get();
        pn = boost::detail::shared_count(r);
        boost::detail::sp_enable_shared_from_this( pn, tmp, tmp );
    }

#if !defined( BOOST_NO_SFINAE ) && !defined( BOOST_NO_TEMPLATE_PARTIAL_SPECIALIZATION )

    template<class Ap>
    explicit shared_ptr( Ap r, typename boost::detail::sp_enable_if_auto_ptr<Ap, int>::type = 0 ): px( r.get() ), pn()
    {
        typename Ap::element_type * tmp = r.get();
        pn = boost::detail::shared_count( r );
        boost::detail::sp_enable_shared_from_this( pn, tmp, tmp );
    }


#endif // BOOST_NO_SFINAE, BOOST_NO_TEMPLATE_PARTIAL_SPECIALIZATION

#endif // BOOST_NO_AUTO_PTR

#if !defined(BOOST_MSVC) || (BOOST_MSVC >= 1300)

    template<class Y>
    shared_ptr & operator=(shared_ptr<Y> const & r) // never throws
    {
        px = r.px;
        pn = r.pn; // shared_count::op= doesn't throw
        return *this;
    }

#endif

#ifndef BOOST_NO_AUTO_PTR

    template<class Y>
    shared_ptr & operator=( std::auto_ptr<Y> & r )
    {
        this_type(r).swap(*this);
        return *this;
    }

#if !defined( BOOST_NO_SFINAE ) && !defined( BOOST_NO_TEMPLATE_PARTIAL_SPECIALIZATION )

    template<class Ap>
    typename boost::detail::sp_enable_if_auto_ptr< Ap, shared_ptr & >::type operator=( Ap r )
    {
        this_type( r ).swap( *this );
        return *this;
    }


#endif // BOOST_NO_SFINAE, BOOST_NO_TEMPLATE_PARTIAL_SPECIALIZATION

#endif // BOOST_NO_AUTO_PTR

    void reset() // never throws in 1.30+
    {
        this_type().swap(*this);
    }

    template<class Y> void reset(Y * p) // Y must be complete
    {
        BOOST_ASSERT(p == 0 || p != px); // catch self-reset errors
        this_type(p).swap(*this);
    }

    template<class Y, class D> void reset( Y * p, D d )
    {
        this_type( p, d ).swap( *this );
    }

    template<class Y, class D, class A> void reset( Y * p, D d, A a )
    {
        this_type( p, d, a ).swap( *this );
    }

    reference operator* () const // never throws
    {
        BOOST_ASSERT(px != 0);
        return *px;
    }

    T * operator-> () const // never throws
    {
        BOOST_ASSERT(px != 0);
        return px;
    }
    
    T * get() const // never throws
    {
        return px;
    }

    // implicit conversion to "bool"

#if defined(__SUNPRO_CC) && BOOST_WORKAROUND(__SUNPRO_CC, <= 0x580)

    operator bool () const
    {
        return px != 0;
    }

#elif defined( _MANAGED )

    static void unspecified_bool( this_type*** )
    {
    }

    typedef void (*unspecified_bool_type)( this_type*** );

    operator unspecified_bool_type() const // never throws
    {
        return px == 0? 0: unspecified_bool;
    }

#elif \
    ( defined(__MWERKS__) && BOOST_WORKAROUND(__MWERKS__, < 0x3200) ) || \
    ( defined(__GNUC__) && (__GNUC__ * 100 + __GNUC_MINOR__ < 304) )

    typedef T * (this_type::*unspecified_bool_type)() const;
    
    operator unspecified_bool_type() const // never throws
    {
        return px == 0? 0: &this_type::get;
    }

#else 

    typedef T * this_type::*unspecified_bool_type;

    operator unspecified_bool_type() const // never throws
    {
        return px == 0? 0: &this_type::px;
    }

#endif

    // operator! is redundant, but some compilers need it

    bool operator! () const // never throws
    {
        return px == 0;
    }

    bool unique() const // never throws
    {
        return pn.unique();
    }

    long use_count() const // never throws
    {
        return pn.use_count();
    }

    void swap(shared_ptr<T> & other) // never throws
    {
        std::swap(px, other.px);
        pn.swap(other.pn);
    }

    template<class Y> bool _internal_less(shared_ptr<Y> const & rhs) const
    {
        return pn < rhs.pn;
    }

    void * _internal_get_deleter(std::type_info const & ti) const
    {
        return pn.get_deleter(ti);
    }

// Tasteless as this may seem, making all members public allows member templates
// to work in the absence of member template friends. (Matthew Langston)

#ifndef BOOST_NO_MEMBER_TEMPLATE_FRIENDS

private:

    template<class Y> friend class shared_ptr;
    template<class Y> friend class weak_ptr;


#endif

    T * px;                     // contained pointer
    boost::detail::shared_count pn;    // reference counter

};  // shared_ptr

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

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

#if __GNUC__ == 2 && __GNUC_MINOR__ <= 96

// Resolve the ambiguity between our op!= and the one in rel_ops

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

#endif

template<class T, class U> inline bool operator<(shared_ptr<T> const & a, shared_ptr<U> const & b)
{
    return a._internal_less(b);
}

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

template<class T, class U> shared_ptr<T> static_pointer_cast(shared_ptr<U> const & r)
{
    return shared_ptr<T>(r, boost::detail::static_cast_tag());
}

template<class T, class U> shared_ptr<T> const_pointer_cast(shared_ptr<U> const & r)
{
    return shared_ptr<T>(r, boost::detail::const_cast_tag());
}

template<class T, class U> shared_ptr<T> dynamic_pointer_cast(shared_ptr<U> const & r)
{
    return shared_ptr<T>(r, boost::detail::dynamic_cast_tag());
}

// shared_*_cast names are deprecated. Use *_pointer_cast instead.

template<class T, class U> shared_ptr<T> shared_static_cast(shared_ptr<U> const & r)
{
    return shared_ptr<T>(r, boost::detail::static_cast_tag());
}

template<class T, class U> shared_ptr<T> shared_dynamic_cast(shared_ptr<U> const & r)
{
    return shared_ptr<T>(r, boost::detail::dynamic_cast_tag());
}

template<class T, class U> shared_ptr<T> shared_polymorphic_cast(shared_ptr<U> const & r)
{
    return shared_ptr<T>(r, boost::detail::polymorphic_cast_tag());
}

template<class T, class U> shared_ptr<T> shared_polymorphic_downcast(shared_ptr<U> const & r)
{
    BOOST_ASSERT(dynamic_cast<T *>(r.get()) == r.get());
    return shared_static_cast<T>(r);
}

// get_pointer() enables boost::mem_fn to recognize shared_ptr

template<class T> inline T * get_pointer(shared_ptr<T> const & p)
{
    return p.get();
}

// operator<<

#if defined(__GNUC__) &&  (__GNUC__ < 3)

template<class Y> std::ostream & operator<< (std::ostream & os, shared_ptr<Y> const & p)
{
    os << p.get();
    return os;
}

#else

// in STLport's no-iostreams mode no iostream symbols can be used
#ifndef _STLP_NO_IOSTREAMS

# if defined(BOOST_MSVC) && BOOST_WORKAROUND(BOOST_MSVC, < 1300 && __SGI_STL_PORT)
// MSVC6 has problems finding std::basic_ostream through the using declaration in namespace _STL
using std::basic_ostream;
template<class E, class T, class Y> basic_ostream<E, T> & operator<< (basic_ostream<E, T> & os, shared_ptr<Y> const & p)
# else
template<class E, class T, class Y> std::basic_ostream<E, T> & operator<< (std::basic_ostream<E, T> & os, shared_ptr<Y> const & p)
# endif 
{
    os << p.get();
    return os;
}

#endif // _STLP_NO_IOSTREAMS

#endif // __GNUC__ < 3

// get_deleter (experimental)

#if ( defined(__GNUC__) && BOOST_WORKAROUND(__GNUC__, < 3) ) || \
    ( defined(__EDG_VERSION__) && BOOST_WORKAROUND(__EDG_VERSION__, <= 238) ) || \
    ( defined(__HP_aCC) && BOOST_WORKAROUND(__HP_aCC, <= 33500) )

// g++ 2.9x doesn't allow static_cast<X const *>(void *)
// apparently EDG 2.38 and HP aCC A.03.35 also don't accept it

template<class D, class T> D * get_deleter(shared_ptr<T> const & p)
{
    void const * q = p._internal_get_deleter(typeid(D));
    return const_cast<D *>(static_cast<D const *>(q));
}

#else

template<class D, class T> D * get_deleter(shared_ptr<T> const & p)
{
    return static_cast<D *>(p._internal_get_deleter(typeid(D)));
}

#endif

} // namespace boost

#ifdef BOOST_MSVC
# pragma warning(pop)
#endif    

#endif  // #if defined(BOOST_NO_MEMBER_TEMPLATES) && !defined(BOOST_MSVC6_MEMBER_TEMPLATES)

#endif  // #ifndef BOOST_SHARED_PTR_HPP_INCLUDED