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

// Copyright (C) 2007, 2008, 2009, 2010, 2011, 2012

// 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 3, 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.

// Under Section 7 of GPL version 3, you are granted additional

// permissions described in the GCC Runtime Library Exception, version

// 3.1, as published by the Free Software Foundation.

// You should have received a copy of the GNU General Public License and

// a copy of the GCC Runtime Library Exception along with this program;

// see the files COPYING3 and COPYING.RUNTIME respectively.  If not, see

// <http://www.gnu.org/licenses/>.

//  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 tr1/shared_ptr.h

 *  This is an internal header file, included by other library headers.

 *  Do not attempt to use it directly. @headername{tr1/memory}

 */

#ifndef _TR1_SHARED_PTR_H

#define _TR1_SHARED_PTR_H 1

namespace std _GLIBCXX_VISIBILITY(default)

{

namespace tr1

{

_GLIBCXX_BEGIN_NAMESPACE_VERSION

 /**

   *  @brief  Exception possibly thrown by @c shared_ptr.

   *  @ingroup exceptions

   */

  class bad_weak_ptr : public std::exception

  {

  public:

    virtual char const*

    what() const throw()

    { return "tr1::bad_weak_ptr"; }

  };

  // Substitute for bad_weak_ptr object in the case of -fno-exceptions.

  inline void

  __throw_bad_weak_ptr()

  {

#if __EXCEPTIONS

    throw bad_weak_ptr();

#else

    __builtin_abort();

#endif

  }

  using __gnu_cxx::_Lock_policy;

  using __gnu_cxx::__default_lock_policy;

  using __gnu_cxx::_S_single;

  using __gnu_cxx::_S_mutex;

  using __gnu_cxx::_S_atomic;

  // Empty helper class except when the template argument is _S_mutex.

  template<_Lock_policy _Lp>

    class _Mutex_base

    {

    protected:

      // The atomic policy uses fully-fenced builtins, single doesn't care.

      enum { _S_need_barriers = 0 };

    };

  template<>

    class _Mutex_base<_S_mutex>

    : public __gnu_cxx::__mutex

    {

    protected:

      // This policy is used when atomic builtins are not available.

      // The replacement atomic operations might not have the necessary

      // memory barriers.

      enum { _S_need_barriers = 1 };

    };

  template<_Lock_policy _Lp = __default_lock_policy>

    class _Sp_counted_base

    : public _Mutex_base<_Lp>

    {

    public:

      _Sp_counted_base()

      : _M_use_count(1), _M_weak_count(1) { }

      virtual

      ~_Sp_counted_base() // nothrow 

      { }

      // Called when _M_use_count drops to zero, to release the resources

      // managed by *this.

      virtual void

      _M_dispose() = 0; // nothrow

      // Called when _M_weak_count drops to zero.

      virtual void

      _M_destroy() // nothrow

      { delete this; }

      virtual void*

      _M_get_deleter(const std::type_info&) = 0;

      void

      _M_add_ref_copy()

      { __gnu_cxx::__atomic_add_dispatch(&_M_use_count, 1); }

      void

      _M_add_ref_lock();

      void

      _M_release() // nothrow

      {

        // Be race-detector-friendly.  For more info see bits/c++config.

        _GLIBCXX_SYNCHRONIZATION_HAPPENS_BEFORE(&_M_use_count);

        if (__gnu_cxx::__exchange_and_add_dispatch(&_M_use_count, -1) == 1)

          {

            _GLIBCXX_SYNCHRONIZATION_HAPPENS_AFTER(&_M_use_count);

            _M_dispose();

            // There must be a memory barrier between dispose() and destroy()

            // to ensure that the effects of dispose() are observed in the

            // thread that runs destroy().

            // See http://gcc.gnu.org/ml/libstdc++/2005-11/msg00136.html

            if (_Mutex_base<_Lp>::_S_need_barriers)

              {

                _GLIBCXX_READ_MEM_BARRIER;

                _GLIBCXX_WRITE_MEM_BARRIER;

              }

            // Be race-detector-friendly.  For more info see bits/c++config.

            _GLIBCXX_SYNCHRONIZATION_HAPPENS_BEFORE(&_M_weak_count);

            if (__gnu_cxx::__exchange_and_add_dispatch(&_M_weak_count,

                                                       -1) == 1)

              {

                _GLIBCXX_SYNCHRONIZATION_HAPPENS_AFTER(&_M_weak_count);

                _M_destroy();

              }

          }

      }

      void

      _M_weak_add_ref() // nothrow

      { __gnu_cxx::__atomic_add_dispatch(&_M_weak_count, 1); }

      void

      _M_weak_release() // nothrow

      {

        // Be race-detector-friendly. For more info see bits/c++config.

        _GLIBCXX_SYNCHRONIZATION_HAPPENS_BEFORE(&_M_weak_count);

        if (__gnu_cxx::__exchange_and_add_dispatch(&_M_weak_count, -1) == 1)

          {

            _GLIBCXX_SYNCHRONIZATION_HAPPENS_AFTER(&_M_weak_count);

            if (_Mutex_base<_Lp>::_S_need_barriers)

              {

                // See _M_release(),

                // destroy() must observe results of dispose()

                _GLIBCXX_READ_MEM_BARRIER;

                _GLIBCXX_WRITE_MEM_BARRIER;

              }

            _M_destroy();

          }

      }

      long

      _M_get_use_count() const // nothrow

      {

        // No memory barrier is used here so there is no synchronization

        // with other threads.

        return const_cast<const volatile _Atomic_word&>(_M_use_count);

      }

    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)

    };

  template<>

    inline void

    _Sp_counted_base<_S_single>::

    _M_add_ref_lock()

    {

      if (__gnu_cxx::__exchange_and_add_dispatch(&_M_use_count, 1) == 0)

        {

          _M_use_count = 0;

          __throw_bad_weak_ptr();

        }

    }

  template<>

    inline void

    _Sp_counted_base<_S_mutex>::

    _M_add_ref_lock()

    {

      __gnu_cxx::__scoped_lock sentry(*this);

      if (__gnu_cxx::__exchange_and_add_dispatch(&_M_use_count, 1) == 0)

        {

          _M_use_count = 0;

          __throw_bad_weak_ptr();

        }

    }

  template<>

    inline void

    _Sp_counted_base<_S_atomic>::

    _M_add_ref_lock()

    {

      // Perform lock-free add-if-not-zero operation.

      _Atomic_word __count = _M_use_count;

      do

        {

          if (__count == 0)

            __throw_bad_weak_ptr();

          // Replace the current counter value with the old value + 1, as

          // long as it's not changed meanwhile. 

        }

      while (!__atomic_compare_exchange_n(&_M_use_count, &__count, __count + 1,

                                          true, __ATOMIC_ACQ_REL,

                                          __ATOMIC_RELAXED));

     }

  template<typename _Ptr, typename _Deleter, _Lock_policy _Lp>

    class _Sp_counted_base_impl

    : public _Sp_counted_base<_Lp>

    {

    public:

      // Precondition: __d(__p) must not throw.

      _Sp_counted_base_impl(_Ptr __p, _Deleter __d)

      : _M_ptr(__p), _M_del(__d) { }

      virtual void

      _M_dispose() // nothrow

      { _M_del(_M_ptr); }

      virtual void*

      _M_get_deleter(const std::type_info& __ti)

      {

#ifdef __GXX_RTTI

        return __ti == typeid(_Deleter) ? &_M_del : 0;

#else

        return 0;

#endif

      }

    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

    };

  template<_Lock_policy _Lp = __default_lock_policy>

    class __weak_count;

  template<typename _Tp>

    struct _Sp_deleter

    {

      typedef void result_type;

      typedef _Tp* argument_type;

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

    };

  template<_Lock_policy _Lp = __default_lock_policy>

    class __shared_count

    {

    public:

      __shared_count()

      : _M_pi(0) // nothrow

      { }

      template<typename _Ptr>

        __shared_count(_Ptr __p) : _M_pi(0)

        {

          __try

            {

              typedef typename std::tr1::remove_pointer<_Ptr>::type _Tp;

              _M_pi = new _Sp_counted_base_impl<_Ptr, _Sp_deleter<_Tp>, _Lp>(

                  __p, _Sp_deleter<_Tp>());

            }

          __catch(...)

            {

              delete __p;

              __throw_exception_again;

            }

        }

      template<typename _Ptr, typename _Deleter>

        __shared_count(_Ptr __p, _Deleter __d) : _M_pi(0)

        {

          __try

            {

              _M_pi = new _Sp_counted_base_impl<_Ptr, _Deleter, _Lp>(__p, __d);

            }

          __catch(...)

            {

              __d(__p); // Call _Deleter on __p.

              __throw_exception_again;

            }

        }

      // Special case for auto_ptr<_Tp> 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>, _Lp >(__r.get(), _Sp_deleter<_Tp>()))

        { __r.release(); }

      // Throw bad_weak_ptr when __r._M_get_use_count() == 0.

      explicit

      __shared_count(const __weak_count<_Lp>& __r);

      ~__shared_count() // nothrow

      {

        if (_M_pi != 0)

          _M_pi->_M_release();

      }

      __shared_count(const __shared_count& __r)

      : _M_pi(__r._M_pi) // nothrow

      {

        if (_M_pi != 0)

          _M_pi->_M_add_ref_copy();

      }

      __shared_count&

      operator=(const __shared_count& __r) // nothrow

      {

        _Sp_counted_base<_Lp>* __tmp = __r._M_pi;

        if (__tmp != _M_pi)

          {

            if (__tmp != 0)

              __tmp->_M_add_ref_copy();

            if (_M_pi != 0)

              _M_pi->_M_release();

            _M_pi = __tmp;

          }

        return *this;

      }

      void

      _M_swap(__shared_count& __r) // nothrow

      {

        _Sp_counted_base<_Lp>* __tmp = __r._M_pi;

        __r._M_pi = _M_pi;

        _M_pi = __tmp;

      }

      long

      _M_get_use_count() const // nothrow

      { return _M_pi != 0 ? _M_pi->_M_get_use_count() : 0; }

      bool

      _M_unique() const // nothrow

      { return this->_M_get_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<_Lp>*>()(__a._M_pi, __b._M_pi); }

      void*

      _M_get_deleter(const std::type_info& __ti) const

      { return _M_pi ? _M_pi->_M_get_deleter(__ti) : 0; }

    private:

      friend class __weak_count<_Lp>;

      _Sp_counted_base<_Lp>*  _M_pi;

    };

  template<_Lock_policy _Lp>

    class __weak_count

    {

    public:

      __weak_count()

      : _M_pi(0) // nothrow

      { }

      __weak_count(const __shared_count<_Lp>& __r)

      : _M_pi(__r._M_pi) // nothrow

      {

        if (_M_pi != 0)

          _M_pi->_M_weak_add_ref();

      }

      __weak_count(const __weak_count<_Lp>& __r)

      : _M_pi(__r._M_pi) // nothrow

      {

        if (_M_pi != 0)

          _M_pi->_M_weak_add_ref();

      }

      ~__weak_count() // nothrow

      {

        if (_M_pi != 0)

          _M_pi->_M_weak_release();

      }

      __weak_count<_Lp>&

      operator=(const __shared_count<_Lp>& __r) // nothrow

      {

        _Sp_counted_base<_Lp>* __tmp = __r._M_pi;

        if (__tmp != 0)

          __tmp->_M_weak_add_ref();

        if (_M_pi != 0)

          _M_pi->_M_weak_release();

        _M_pi = __tmp;

        return *this;

      }

      __weak_count<_Lp>&

      operator=(const __weak_count<_Lp>& __r) // nothrow

      {

        _Sp_counted_base<_Lp>* __tmp = __r._M_pi;

        if (__tmp != 0)

          __tmp->_M_weak_add_ref();

        if (_M_pi != 0)

          _M_pi->_M_weak_release();

        _M_pi = __tmp;

        return *this;

      }

      void

      _M_swap(__weak_count<_Lp>& __r) // nothrow

      {

        _Sp_counted_base<_Lp>* __tmp = __r._M_pi;

        __r._M_pi = _M_pi;

        _M_pi = __tmp;

      }

      long

      _M_get_use_count() const // nothrow

      { return _M_pi != 0 ? _M_pi->_M_get_use_count() : 0; }

      friend inline bool

      operator==(const __weak_count<_Lp>& __a, const __weak_count<_Lp>& __b)

      { return __a._M_pi == __b._M_pi; }

      friend inline bool

      operator<(const __weak_count<_Lp>& __a, const __weak_count<_Lp>& __b)

      { return std::less<_Sp_counted_base<_Lp>*>()(__a._M_pi, __b._M_pi); }

    private:

      friend class __shared_count<_Lp>;

      _Sp_counted_base<_Lp>*  _M_pi;

    };

  // now that __weak_count is defined we can define this constructor:

  template<_Lock_policy _Lp>

    inline

    __shared_count<_Lp>::

    __shared_count(const __weak_count<_Lp>& __r)

    : _M_pi(__r._M_pi)

    {

      if (_M_pi != 0)

        _M_pi->_M_add_ref_lock();

      else

        __throw_bad_weak_ptr();

    }

  // Forward declarations.

  template<typename _Tp, _Lock_policy _Lp = __default_lock_policy>

    class __shared_ptr;

  template<typename _Tp, _Lock_policy _Lp = __default_lock_policy>

    class __weak_ptr;

  template<typename _Tp, _Lock_policy _Lp = __default_lock_policy>

    class __enable_shared_from_this;

  template<typename _Tp>

    class shared_ptr;

  template<typename _Tp>

    class weak_ptr;

  template<typename _Tp>

    class enable_shared_from_this;

  // Support for enable_shared_from_this.

  // Friend of __enable_shared_from_this.

  template<_Lock_policy _Lp, typename _Tp1, typename _Tp2>

    void

    __enable_shared_from_this_helper(const __shared_count<_Lp>&,

                                     const __enable_shared_from_this<_Tp1,

                                     _Lp>*, const _Tp2*);

  // Friend of enable_shared_from_this.

  template<typename _Tp1, typename _Tp2>

    void

    __enable_shared_from_this_helper(const __shared_count<>&,

                                     const enable_shared_from_this<_Tp1>*,

                                     const _Tp2*);

  template<_Lock_policy _Lp>

    inline void

    __enable_shared_from_this_helper(const __shared_count<_Lp>&, ...)

    { }

  struct __static_cast_tag { };

  struct __const_cast_tag { };

  struct __dynamic_cast_tag { };

  // 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, _Lock_policy _Lp>

    class __shared_ptr

    {

    public:

      typedef _Tp   element_type;

      __shared_ptr()

      : _M_ptr(0), _M_refcount() // never throws

      { }

      template<typename _Tp1>

        explicit

        __shared_ptr(_Tp1* __p)

        : _M_ptr(__p), _M_refcount(__p)

        {

          __glibcxx_function_requires(_ConvertibleConcept<_Tp1*, _Tp*>)

          typedef int _IsComplete[sizeof(_Tp1)];

          __enable_shared_from_this_helper(_M_refcount, __p, __p);

        }

      template<typename _Tp1, typename _Deleter>

        __shared_ptr(_Tp1* __p, _Deleter __d)

        : _M_ptr(__p), _M_refcount(__p, __d)

        {

          __glibcxx_function_requires(_ConvertibleConcept<_Tp1*, _Tp*>)

          // TODO requires _Deleter CopyConstructible and __d(__p) well-formed

          __enable_shared_from_this_helper(_M_refcount, __p, __p);

        }

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

      template<typename _Tp1>

        __shared_ptr(const __shared_ptr<_Tp1, _Lp>& __r)

        : _M_ptr(__r._M_ptr), _M_refcount(__r._M_refcount) // never throws

        { __glibcxx_function_requires(_ConvertibleConcept<_Tp1*, _Tp*>) }

      template<typename _Tp1>

        explicit

        __shared_ptr(const __weak_ptr<_Tp1, _Lp>& __r)

        : _M_refcount(__r._M_refcount) // may throw

        {

          __glibcxx_function_requires(_ConvertibleConcept<_Tp1*, _Tp*>)

          // It is now safe to copy __r._M_ptr, as _M_refcount(__r._M_refcount)

          // did not throw.

          _M_ptr = __r._M_ptr;

        }

#if !defined(__GXX_EXPERIMENTAL_CXX0X__) || _GLIBCXX_USE_DEPRECATED

      // Postcondition: use_count() == 1 and __r.get() == 0

      template<typename _Tp1>

        explicit

        __shared_ptr(std::auto_ptr<_Tp1>& __r)

        : _M_ptr(__r.get()), _M_refcount()

        { // TODO requries delete __r.release() well-formed

          __glibcxx_function_requires(_ConvertibleConcept<_Tp1*, _Tp*>)

          typedef int _IsComplete[sizeof(_Tp1)];

          _Tp1* __tmp = __r.get();

          _M_refcount = __shared_count<_Lp>(__r);

          __enable_shared_from_this_helper(_M_refcount, __tmp, __tmp);

        }

#endif

      template<typename _Tp1>

        __shared_ptr(const __shared_ptr<_Tp1, _Lp>& __r, __static_cast_tag)

        : _M_ptr(static_cast<element_type*>(__r._M_ptr)),

          _M_refcount(__r._M_refcount)

        { }

      template<typename _Tp1>

        __shared_ptr(const __shared_ptr<_Tp1, _Lp>& __r, __const_cast_tag)

        : _M_ptr(const_cast<element_type*>(__r._M_ptr)),

          _M_refcount(__r._M_refcount)

        { }

      template<typename _Tp1>

        __shared_ptr(const __shared_ptr<_Tp1, _Lp>& __r, __dynamic_cast_tag)

        : _M_ptr(dynamic_cast<element_type*>(__r._M_ptr)),

          _M_refcount(__r._M_refcount)

        {

          if (_M_ptr == 0) // need to allocate new counter -- the cast failed

            _M_refcount = __shared_count<_Lp>();

        }

      template<typename _Tp1>

        __shared_ptr&

        operator=(const __shared_ptr<_Tp1, _Lp>& __r) // never throws

        {

          _M_ptr = __r._M_ptr;

          _M_refcount = __r._M_refcount; // __shared_count::op= doesn't throw

          return *this;

        }

#if !defined(__GXX_EXPERIMENTAL_CXX0X__) || _GLIBCXX_USE_DEPRECATED

      template<typename _Tp1>

        __shared_ptr&

        operator=(std::auto_ptr<_Tp1>& __r)

        {

          __shared_ptr(__r).swap(*this);

          return *this;

        }

#endif

      void

      reset() // never throws

      { __shared_ptr().swap(*this); }

      template<typename _Tp1>

        void

        reset(_Tp1* __p) // _Tp1 must be complete.

        {

          // Catch self-reset errors.

          _GLIBCXX_DEBUG_ASSERT(__p == 0 || __p != _M_ptr);

          __shared_ptr(__p).swap(*this);

        }

      template<typename _Tp1, typename _Deleter>

        void

        reset(_Tp1* __p, _Deleter __d)

        { __shared_ptr(__p, __d).swap(*this); }

      // Allow class instantiation when _Tp is [cv-qual] void.

      typename std::tr1::add_reference<_Tp>::type

      operator*() const // never throws

      {

        _GLIBCXX_DEBUG_ASSERT(_M_ptr != 0);

        return *_M_ptr;

      }

      _Tp*

      operator->() const // never throws

      {

        _GLIBCXX_DEBUG_ASSERT(_M_ptr != 0);

        return _M_ptr;

      }

      _Tp*

      get() const // never throws

      { return _M_ptr; }

      // Implicit conversion to "bool"

    private:

      typedef _Tp* __shared_ptr::*__unspecified_bool_type;

    public:

      operator __unspecified_bool_type() const // never throws

      { return _M_ptr == 0 ? 0 : &__shared_ptr::_M_ptr; }

      bool

      unique() const // never throws

      { return _M_refcount._M_unique(); }

      long

      use_count() const // never throws

      { return _M_refcount._M_get_use_count(); }

      void

      swap(__shared_ptr<_Tp, _Lp>& __other) // never throws