unique_ptr.hpp

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//////////////////////////////////////////////////////////////////////////////
// I, Howard Hinnant, hereby place this code in the public domain.
//////////////////////////////////////////////////////////////////////////////
//
// This file is the adaptation for Interprocess of
// Howard Hinnant's unique_ptr emulation code.
//
// (C) Copyright Ion Gaztanaga 2006. 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/interprocess for documentation.
//
//////////////////////////////////////////////////////////////////////////////

#ifndef BOOST_INTERPROCESS_UNIQUE_PTR_HPP_INCLUDED
#define BOOST_INTERPROCESS_UNIQUE_PTR_HPP_INCLUDED

#include <boost/interprocess/detail/config_begin.hpp>
#include <boost/interprocess/detail/workaround.hpp>
#include <boost/assert.hpp>
#include <boost/interprocess/detail/utilities.hpp>
#include <boost/interprocess/detail/pointer_type.hpp>
#include <boost/interprocess/detail/move.hpp>
#include <boost/compressed_pair.hpp>
#include <boost/static_assert.hpp>
#include <boost/interprocess/detail/mpl.hpp>
#include <boost/interprocess/detail/type_traits.hpp>
#include <boost/interprocess/smart_ptr/deleter.hpp>
#include <cstddef>

//!\file
//!Describes the smart pointer unique_ptr

namespace boost{
namespace interprocess{

/// @cond
template <class T, class D> class unique_ptr;

namespace detail {

template <class T> struct unique_ptr_error;

template <class T, class D>
struct unique_ptr_error<const unique_ptr<T, D> >
{
    typedef unique_ptr<T, D> type;
};

}  //namespace detail {
/// @endcond

//!Template unique_ptr stores a pointer to an object and deletes that object
//!using the associated deleter when it is itself destroyed (such as when
//!leaving block scope.
//!
//!The unique_ptr provides a semantics of strict ownership. A unique_ptr owns the
//!object it holds a pointer to.
//!
//!A unique_ptr is not CopyConstructible, nor CopyAssignable, however it is
//!MoveConstructible and Move-Assignable.
//!
//!The uses of unique_ptr include providing exception safety for dynamically
//!allocated memory, passing ownership of dynamically allocated memory to a
//!function, and returning dynamically allocated memory from a function
//!
//!A client-supplied template argument D must be a
//!function pointer or functor for which, given a value d of type D and a pointer
//!ptr to a type T*, the expression d(ptr) is
//!valid and has the effect of deallocating the pointer as appropriate for that
//!deleter. D may also be an lvalue-reference to a deleter.
//!
//!If the deleter D maintains state, it is intended that this state stay with
//!the associated pointer as ownership is transferred
//!from unique_ptr to unique_ptr. The deleter state need never be copied,
//!only moved or swapped as pointer ownership
//!is moved around. That is, the deleter need only be MoveConstructible,
//!MoveAssignable, and Swappable, and need not be CopyConstructible
//!(unless copied into the unique_ptr) nor CopyAssignable.
template <class T, class D>
class unique_ptr
{
   /// @cond
   struct nat {int for_bool_;};
   typedef typename detail::add_reference<D>::type deleter_reference;
   typedef typename detail::add_reference<const D>::type deleter_const_reference;
   /// @endcond

   public:
   typedef T element_type;
   typedef D deleter_type;
   typedef typename detail::pointer_type<T, D>::type pointer;

   //!Requires: D must be default constructible, and that construction must not
   //!throw an exception. D must not be a reference type.
   //!
   //!Effects: Constructs a unique_ptr which owns nothing.
   //!
   //!Postconditions: get() == 0. get_deleter() returns a reference to a
   //!default constructed deleter D.
   //!
   //!Throws: nothing.
   unique_ptr()
      :  ptr_(pointer(0))
   {}

   //!Requires: The expression D()(p) must be well formed. The default constructor
   //!of D must not throw an exception.
   //!
   //!D must not be a reference type.
   //!
   //!Effects: Constructs a unique_ptr which owns p.
   //!
   //!Postconditions: get() == p. get_deleter() returns a reference to a default constructed deleter D.
   //!
   //!Throws: nothing.
   explicit unique_ptr(pointer p)
      :  ptr_(p)
   {}

   //!Requires: The expression d(p) must be well formed.
   //!
   //!Postconditions: get() == p. get_deleter() returns a reference to the
   //!internally stored deleter. If D is a
   //!reference type then get_deleter() returns a reference to the lvalue d.
   //!
   //!Throws: nothing.
   unique_ptr(pointer p
             ,typename detail::if_<detail::is_reference<D>
                  ,D
                  ,typename detail::add_reference<const D>::type>::type d)
      : ptr_(p, d)
   {}

   //!Requires: If the deleter is not a reference type, construction of the
   //!deleter D from an lvalue D must not throw an exception.
   //!
   //!Effects: Constructs a unique_ptr which owns the pointer which u owns
   //!(if any). If the deleter is not a reference type, it is move constructed
   //!from u's deleter, otherwise the reference is copy constructed from u's deleter.
   //!
   //!After the construction, u no longer owns a pointer.
   //![ Note: The deleter constructor can be implemented with
   //!std::detail::forward_impl<D>. -end note ]
   //!
   //!Postconditions: get() == value u.get() had before the construction.
   //!get_deleter() returns a reference to the internally stored deleter which
   //!was constructed from u.get_deleter(). If D is a reference type then get_-
   //!deleter() and u.get_deleter() both reference the same lvalue deleter.
   //!
   //!Throws: nothing.
   #ifndef BOOST_INTERPROCESS_RVALUE_REFERENCE
   unique_ptr(detail::moved_object<unique_ptr> u)
      : ptr_(u.get().release(), detail::move_impl(u.get().get_deleter()))
   {}
   #else
   unique_ptr(unique_ptr &&u)
      : ptr_(u.release(), detail::forward_impl<D>(u.get_deleter()))
   {}
   #endif

   //!Requires: If D is not a reference type, construction of the deleter
   //!D from an rvalue of type E must be well formed
   //!and not throw an exception. If D is a reference type, then E must be
   //!the same type as D (diagnostic required). unique_ptr<U, E>::pointer
   //!must be implicitly convertible to pointer.
   //!
   //!Effects: Constructs a unique_ptr which owns the pointer which u owns
   //!(if any). If the deleter is not a reference
   //!type, it is move constructed from u's deleter, otherwise the reference
   //!is copy constructed from u's deleter.
   //!
   //!After the construction, u no longer owns a pointer.
   //!
   //!postconditions get() == value u.get() had before the construction,
   //!modulo any required offset adjustments
   //!resulting from the cast from U* to T*. get_deleter() returns a reference to the internally stored deleter which
   //!was constructed from u.get_deleter().
   //!
   //!Throws: nothing.
   #ifndef BOOST_INTERPROCESS_RVALUE_REFERENCE
   template <class U, class E>
   unique_ptr(detail::moved_object<unique_ptr<U, E> > u,
      typename detail::enable_if_c<
            detail::is_convertible<typename unique_ptr<U, E>::pointer, pointer>::value &&
            detail::is_convertible<E, D>::value &&
            (
               !detail::is_reference<D>::value ||
               detail::is_same<D, E>::value
            )
            ,
            nat
            >::type = nat())
      : ptr_(const_cast<unique_ptr<U,E>&>(u.get()).release(), detail::move_impl(u.get().get_deleter()))
   {}
   #else
   template <class U, class E>
   unique_ptr(unique_ptr<U, E> && u,
      typename detail::enable_if_c<
            detail::is_convertible<typename unique_ptr<U, E>::pointer, pointer>::value &&
            detail::is_convertible<E, D>::value &&
            (
               !detail::is_reference<D>::value ||
               detail::is_same<D, E>::value
            )
            ,
            nat
            >::type = nat())
      : ptr_(const_cast<unique_ptr<U,E>&>(u).release(), detail::forward_impl<D>(u.get_deleter()))
   {}
   #endif

   //!Effects: If get() == 0 there are no effects. Otherwise get_deleter()(get()).
   //!
   //!Throws: nothing.
   ~unique_ptr()
   {  reset(); }

   // assignment

   //!Requires: Assignment of the deleter D from an rvalue D must not throw an exception.
   //!
   //!Effects: reset(u.release()) followed by a move assignment from u's deleter to
   //!this deleter.
   //!
   //!Postconditions: This unique_ptr now owns the pointer which u owned, and u no
   //!longer owns it.
   //!
   //!Returns: *this.
   //!
   //!Throws: nothing.
   #ifndef BOOST_INTERPROCESS_RVALUE_REFERENCE
   unique_ptr& operator=(detail::moved_object<unique_ptr> u)
   {
      reset(u.get().release());
      ptr_.second() = detail::move_impl(u.get().get_deleter());
      return *this;
   }
   #else
   unique_ptr& operator=(unique_ptr && u)
   {
      reset(u.release());
      ptr_.second() = detail::move_impl(u.get_deleter());
      return *this;
   }
   #endif

   //!Requires: Assignment of the deleter D from an rvalue D must not
   //!throw an exception. U* must be implicitly convertible to T*.
   //!
   //!Effects: reset(u.release()) followed by a move assignment from
   //!u's deleter to this deleter. If either D or E is
   //!a reference type, then the referenced lvalue deleter participates
   //!in the move assignment.
   //!
   //!Postconditions: This unique_ptr now owns the pointer which u owned,
   //!and u no longer owns it.
   //!
   //!Returns: *this.
   //!
   //!Throws: nothing.
   template <class U, class E>
   #ifndef BOOST_INTERPROCESS_RVALUE_REFERENCE
   unique_ptr& operator=(detail::moved_object<unique_ptr<U, E> > mu)
   {
      reset(mu.get().release());
      ptr_.second() = detail::move_impl(mu.get().get_deleter());
      return *this;
   }
   #else
   unique_ptr& operator=(unique_ptr<U, E> && u)
   {
      reset(u.release());
      ptr_.second() = detail::move_impl(u.get_deleter());
      return *this;
   }
   #endif

   //!Assigns from the literal 0 or NULL.
   //!
   //!Effects: reset().
   //!
   //!Postcondition: get() == 0
   //!
   //!Returns: *this.
   //!
   //!Throws: nothing.
   unique_ptr& operator=(int nat::*)
   {
      reset();
      return *this;
   }

   //!Requires: get() != 0.
   //!Returns: *get().
   //!Throws: nothing.
   typename detail::add_reference<T>::type operator*()  const
   {  return *ptr_.first();   }

   //!Requires: get() != 0.
   //!Returns: get().
   //!Throws: nothing.
   pointer operator->() const
   {  return ptr_.first(); }

   //!Returns: The stored pointer.
   //!Throws: nothing.
   pointer get()        const
   {  return ptr_.first(); }