boost_shared_ptr.h

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// <tr1/boost_shared_ptr.h> -*- C++ -*-

// Copyright (C) 2005 Free Software Foundation, Inc.
//
// This file is part of the GNU ISO C++ Library.  This library is free
// software; you can redistribute it and/or modify it under the
// terms of the GNU General Public License as published by the
// Free Software Foundation; either version 2, or (at your option)
// any later version.

// This library is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
// GNU General Public License for more details.

// You should have received a copy of the GNU General Public License along
// with this library; see the file COPYING.  If not, write to the Free
// Software Foundation, 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301,
// USA.

// As a special exception, you may use this file as part of a free software
// library without restriction.  Specifically, if other files instantiate
// templates or use macros or inline functions from this file, or you compile
// this file and link it with other files to produce an executable, this
// file does not by itself cause the resulting executable to be covered by
// the GNU General Public License.  This exception does not however
// invalidate any other reasons why the executable file might be covered by
// the GNU General Public License.

//  shared_count.hpp
//  Copyright (c) 2001, 2002, 2003 Peter Dimov and Multi Media Ltd.

//  shared_ptr.hpp
//  Copyright (C) 1998, 1999 Greg Colvin and Beman Dawes.
//  Copyright (C) 2001, 2002, 2003 Peter Dimov

//  weak_ptr.hpp
//  Copyright (C) 2001, 2002, 2003 Peter Dimov

//  enable_shared_from_this.hpp
//  Copyright (C) 2002 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)

// GCC Note:  based on version 1.32.0 of the Boost library.

/** @file boost_memory.h
 *  This is an internal header file, included by other library headers.
 *  You should not attempt to use it directly.
 */

#ifndef _BOOST_SHARED_PTR_H
#define _BOOST_SHARED_PTR_H 1

// namespace std::tr1
namespace std
{
namespace tr1
{

class bad_weak_ptr : public std::exception
{
public:

  virtual char const*
  what() const throw()
  { return "tr1::bad_weak_ptr"; }
};

// Helper for exception objects in <tr1/memory>
// TODO this should be defined in a different file.
inline void
__throw_bad_weak_ptr()
{
#if __EXCEPTIONS
  throw bad_weak_ptr();
#else
  std::abort();
#endif
}


template<typename _Tp>
  struct _Sp_deleter
  {
    typedef void result_type;
    typedef _Tp* argument_type;

    void
    operator()(_Tp* p) const
    { delete p; }
  };


class _Sp_counted_base
{
public:

  _Sp_counted_base()
  : _M_use_count(1), _M_weak_count(1)
  {
    // For the case of __GTHREAD_MUTEX_INIT we haven't initialised
    // the mutex yet, so do it now.
#if defined(__GTHREADS) && defined(__GTHREAD_MUTEX_INIT)
    __gthread_mutex_t __tmp = __GTHREAD_MUTEX_INIT;
    _M_mutex = __tmp;
#endif
  }

  virtual
  ~_Sp_counted_base() // nothrow
  { }

  // dispose() is called when _M_use_count drops to zero, to release
  // the resources managed by *this.
  virtual void
  dispose() = 0; // nothrow

  // destroy() is called when _M_weak_count drops to zero.
  virtual void
  destroy() // nothrow
  {
    delete this;
  }

  virtual void*
  get_deleter(const std::type_info&) = 0;

  void
  add_ref_copy()
  {
    __gnu_cxx::__atomic_add(&_M_use_count, 1);
  }

  void
  add_ref_lock()
  {
    __gnu_cxx::lock lock(_M_mutex);
    if (__gnu_cxx::__exchange_and_add(&_M_use_count, 1) == 0)
      {
	_M_use_count = 0;
	__throw_bad_weak_ptr();
      }
  }

  void
  release() // nothrow
  {
    if (__gnu_cxx::__exchange_and_add(&_M_use_count, -1) == 1)
      {
	dispose();
#ifdef __GTHREADS	
	_GLIBCXX_READ_MEM_BARRIER;
	_GLIBCXX_WRITE_MEM_BARRIER;
#endif
	if (__gnu_cxx::__exchange_and_add(&_M_weak_count, -1) == 1)
	  destroy();
      }
  }

  void
  weak_add_ref() // nothrow
  {
    __gnu_cxx::__atomic_add(&_M_weak_count, 1);
  }

  void
  weak_release() // nothrow
  {
    if (__gnu_cxx::__exchange_and_add(&_M_weak_count, -1) == 1)
      {
#ifdef __GTHREADS
	_GLIBCXX_READ_MEM_BARRIER;
	_GLIBCXX_WRITE_MEM_BARRIER;
#endif
	destroy();
      }
  }

  long
  use_count() const // nothrow
  {
    return _M_use_count;  // XXX is this MT safe?
  }

private:

  _Sp_counted_base(_Sp_counted_base const&);
  _Sp_counted_base& operator=(_Sp_counted_base const&);

  _Atomic_word _M_use_count;        // #shared
  _Atomic_word _M_weak_count;       // #weak + (#shared != 0)
  __gnu_cxx::mutex_type _M_mutex;
};

template<typename _Ptr, typename _Deleter>
  class _Sp_counted_base_impl
  : public _Sp_counted_base
  {
  public:

    /**
     *  @brief   
     *  @pre     d(p) must not throw.
     */
    _Sp_counted_base_impl(_Ptr __p, _Deleter __d)
    : _M_ptr(__p), _M_del(__d)
    { }
    
    virtual void
    dispose() // nothrow
    {
      _M_del(_M_ptr);
    }
    
    virtual void*
    get_deleter(const std::type_info& __ti)
    {
      return __ti == typeid(_Deleter) ? &_M_del : 0;
    }
    
  private:
    _Sp_counted_base_impl(const _Sp_counted_base_impl&);
    _Sp_counted_base_impl& operator=(const _Sp_counted_base_impl&);
    
    _Ptr     _M_ptr; // copy constructor must not throw
    _Deleter _M_del; // copy constructor must not throw
  };

class weak_count;

class shared_count
{
private:

  _Sp_counted_base* _M_pi;

  friend class weak_count;

public:

  shared_count()
  : _M_pi(0) // nothrow
  { }

  template<typename _Ptr, typename _Deleter>
    shared_count(_Ptr __p, _Deleter __d)
    : _M_pi(0)
    {
      try
	{
	  _M_pi = new _Sp_counted_base_impl<_Ptr, _Deleter>(__p, __d);
	}
      catch(...)
	{
	  __d(__p); // delete __p
	  __throw_exception_again;
	}
    }

  // auto_ptr<_Tp> is special cased to provide the strong guarantee

  template<typename _Tp>
    explicit shared_count(std::auto_ptr<_Tp>& __r)
    : _M_pi(new _Sp_counted_base_impl<_Tp*,
	    _Sp_deleter<_Tp> >(__r.get(), _Sp_deleter<_Tp>()))
    { __r.release(); }

  // throws bad_weak_ptr when __r.use_count() == 0
  explicit shared_count(const weak_count& __r);

  ~shared_count() // nothrow
  {
    if (_M_pi != 0)
      _M_pi->release();
  }

  shared_count(const shared_count& __r)
  : _M_pi(__r._M_pi) // nothrow
  {
    if (_M_pi != 0)
      _M_pi->add_ref_copy();
  }

  shared_count&
  operator=(const shared_count& __r) // nothrow
  {
    _Sp_counted_base* __tmp = __r._M_pi;

    if(__tmp != _M_pi)
      {
	if(__tmp != 0)
	  __tmp->add_ref_copy();
	if(_M_pi != 0)
	  _M_pi->release();
	_M_pi = __tmp;
      }
    return *this;
  }

  void swap(shared_count& __r) // nothrow
  {
    _Sp_counted_base* __tmp = __r._M_pi;
    __r._M_pi = _M_pi;
    _M_pi = __tmp;
  }

  long
  use_count() const // nothrow
  { return _M_pi != 0 ? _M_pi->use_count() : 0; }

  bool
  unique() const // nothrow
  { return this->use_count() == 1; }

  friend inline bool
  operator==(const shared_count& __a, const shared_count& __b)
  { return __a._M_pi == __b._M_pi; }

  friend inline bool
  operator<(const shared_count& __a, const shared_count& __b)
  { return std::less<_Sp_counted_base*>()(__a._M_pi, __b._M_pi); }

  void*
  get_deleter(const std::type_info& __ti) const
  { return _M_pi ? _M_pi->get_deleter(__ti) : 0; }
};

class weak_count
{
private:

  _Sp_counted_base* _M_pi;

  friend class shared_count;

public:

  weak_count()
  : _M_pi(0) // nothrow
  { }

  weak_count(const shared_count& __r)
  : _M_pi(__r._M_pi) // nothrow
  {
    if (_M_pi != 0)
      _M_pi->weak_add_ref();
  }

  weak_count(const weak_count& __r)
  : _M_pi(__r._M_pi) // nothrow
  {
    if (_M_pi != 0)
      _M_pi->weak_add_ref();
  }

  ~weak_count() // nothrow
  {
    if (_M_pi != 0)
      _M_pi->weak_release();
  }

  weak_count&
  operator=(const shared_count& __r) // nothrow
  {
    _Sp_counted_base* __tmp = __r._M_pi;
    if (__tmp != 0)
      __tmp->weak_add_ref();
    if (_M_pi != 0)
      _M_pi->weak_release();
    _M_pi = __tmp;

    return *this;
  }

  weak_count&
  operator=(const weak_count& __r) // nothrow
  {
    _Sp_counted_base * __tmp = __r._M_pi;
    if (__tmp != 0)
      __tmp->weak_add_ref();
    if (_M_pi != 0)
      _M_pi->weak_release();
    _M_pi = __tmp;

    return *this;
  }

  void
  swap(weak_count& __r) // nothrow
  {
    _Sp_counted_base * __tmp = __r._M_pi;
    __r._M_pi = _M_pi;
    _M_pi = __tmp;
  }

  long
  use_count() const // nothrow
  { return _M_pi != 0 ? _M_pi->use_count() : 0; }

  friend inline bool
  operator==(const weak_count& __a, const weak_count& __b)
  { return __a._M_pi == __b._M_pi; }

  friend inline bool
  operator<(const weak_count& __a, const weak_count& __b)
  { return std::less<_Sp_counted_base*>()(__a._M_pi, __b._M_pi); }
};

inline
shared_count::shared_count(const weak_count& __r)
: _M_pi(__r._M_pi)
{
  if (_M_pi != 0)
    _M_pi->add_ref_lock();
  else
    __throw_bad_weak_ptr();
}


// fwd decls
template<typename _Tp>
  class shared_ptr;

template<typename _Tp>
  class weak_ptr;

template<typename _Tp>
  class enable_shared_from_this;

struct __static_cast_tag {};
struct __const_cast_tag {};
struct __dynamic_cast_tag {};
struct __polymorphic_cast_tag {};

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

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

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; };


// enable_shared_from_this support

// friend of enable_shared_from_this
template<typename _Tp1, typename _Tp2>
  void
  __enable_shared_from_this(const shared_count& __pn,
                            const enable_shared_from_this<_Tp1>* __pe,
                            const _Tp2* __px );

inline void
__enable_shared_from_this(const shared_count&, ...)
{ }


// get_deleter must be declared before friend declaration by shared_ptr.
template<typename _Del, typename _Tp>
  _Del* get_deleter(const shared_ptr<_Tp>&);

/**
 *  @class shared_ptr <tr1/memory>
 *
 *  A smart pointer with reference-counted copy semantics.
 *  The object pointed to is deleted when the last shared_ptr pointing to it
 *  is destroyed or reset.
 */
template<typename _Tp>
  class shared_ptr
  {
    typedef typename shared_ptr_traits<_Tp>::reference _Reference;

  public:

    typedef _Tp   element_type;