...one of the most highly
regarded and expertly designed C++ library projects in the
world.
— Herb Sutter and Andrei
Alexandrescu, C++
Coding Standards
boost::interprocess::shared_ptr
// In header: <boost/interprocess/smart_ptr/shared_ptr.hpp> template<typename T, typename VoidAllocator, typename Deleter> class shared_ptr { public: // types typedef T element_type; typedef T value_type; typedef boost::container::allocator_traits< VoidAllocator >::pointer void_ptr; typedef boost::intrusive::pointer_traits< void_ptr >::template rebind_pointer< T >::type pointer; typedef unspecified reference; typedef unspecified const_reference; typedef boost::intrusive::pointer_traits< void_ptr >::template rebind_pointer< const Deleter >::type const_deleter_pointer; typedef boost::intrusive::pointer_traits< void_ptr >::template rebind_pointer< const VoidAllocator >::type const_allocator_pointer; // construct/copy/destruct shared_ptr(); explicit shared_ptr(const pointer &, const VoidAllocator & = VoidAllocator(), const Deleter & = Deleter()); shared_ptr(const shared_ptr &); shared_ptr(const shared_ptr &, const pointer &); template<typename Y> shared_ptr(shared_ptr< Y, VoidAllocator, Deleter > const &); template<typename Y> explicit shared_ptr(weak_ptr< Y, VoidAllocator, Deleter > const &); explicit shared_ptr(shared_ptr &&); template<typename Y> shared_ptr & operator=(shared_ptr< Y, VoidAllocator, Deleter > const &); shared_ptr & operator=(BOOST_COPY_ASSIGN_REF(shared_ptr)); shared_ptr & operator=(shared_ptr &&); // public member functions void reset(); template<typename Pointer> void reset(const Pointer &, const VoidAllocator & = VoidAllocator(), const Deleter & = Deleter()); template<typename Y> void reset(shared_ptr< Y, VoidAllocator, Deleter > const &, const pointer &); reference operator *() const; pointer operator->() const; pointer get() const; bool operator!() const; bool unique() const; long use_count() const; void swap(shared_ptr< T, VoidAllocator, Deleter > &); };
shared_ptr stores a pointer to a dynamically allocated object. The object pointed to is guaranteed to be deleted when the last shared_ptr pointing to it is destroyed or reset.
shared_ptr is parameterized on T (the type of the object pointed to), VoidAllocator (the void allocator to be used to allocate the auxiliary data) and Deleter (the deleter whose operator() will be used to delete the object.
The internal pointer will be of the same pointer type as typename VoidAllocator::pointer type (that is, if typename VoidAllocator::pointer is offset_ptr<void>, the internal pointer will be offset_ptr<T>).
Because the implementation uses reference counting, cycles of shared_ptr instances will not be reclaimed. For example, if main() holds a shared_ptr to A, which directly or indirectly holds a shared_ptr back to A, A's use count will be 2. Destruction of the original shared_ptr will leave A dangling with a use count of 1. Use weak_ptr to "break cycles."
shared_ptr
public
construct/copy/destructshared_ptr();
Constructs an empty shared_ptr
. Use_count() == 0 && get()== 0.
explicit shared_ptr(const pointer & p, const VoidAllocator & a = VoidAllocator(), const Deleter & d = Deleter());
Constructs a shared_ptr
that owns the pointer p. Auxiliary data will be allocated with a copy of a and the object will be deleted with a copy of d. Requirements: Deleter and A's copy constructor must not throw.
shared_ptr(const shared_ptr & r);
Copy constructs a shared_ptr
. If r is empty, constructs an empty shared_ptr
. Otherwise, constructs a shared_ptr
that shares ownership with r. Never throws.
shared_ptr(const shared_ptr & other, const pointer & p);
Constructs a shared_ptr
that shares ownership with other and stores p. Postconditions: get() == p && use_count() == r.use_count(). Throws: nothing.
template<typename Y> shared_ptr(shared_ptr< Y, VoidAllocator, Deleter > const & r);
If r is empty, constructs an empty shared_ptr
. Otherwise, constructs a shared_ptr
that shares ownership with r. Never throws.
template<typename Y> explicit shared_ptr(weak_ptr< Y, VoidAllocator, Deleter > const & r);
Constructs a shared_ptr
that shares ownership with r and stores a copy of the pointer stored in r.
explicit shared_ptr(shared_ptr && other);
Move-Constructs a shared_ptr
that takes ownership of other resource and other is put in default-constructed state. Throws: nothing.
template<typename Y> shared_ptr & operator=(shared_ptr< Y, VoidAllocator, Deleter > const & r);
Equivalent to shared_ptr(r).swap(*this). Never throws
shared_ptr & operator=(BOOST_COPY_ASSIGN_REF(shared_ptr) r);
Equivalent to shared_ptr(r).swap(*this). Never throws
shared_ptr & operator=(shared_ptr && other);
Move-assignment. Equivalent to shared_ptr(other).swap(*this). Never throws
shared_ptr
public member functionsvoid reset();
This is equivalent to: this_type().swap(*this);
template<typename Pointer> void reset(const Pointer & p, const VoidAllocator & a = VoidAllocator(), const Deleter & d = Deleter());
This is equivalent to: this_type(p, a, d).swap(*this);
template<typename Y> void reset(shared_ptr< Y, VoidAllocator, Deleter > const & r, const pointer & p);
reference operator *() const;
Returns a reference to the pointed type
pointer operator->() const;
Returns the pointer pointing to the owned object
pointer get() const;
Returns the pointer pointing to the owned object
bool operator!() const;
Not operator. Returns true if this->get() != 0, false otherwise
bool unique() const;
Returns use_count() == 1. unique() might be faster than use_count()
long use_count() const;
Returns the number of shared_ptr
objects, *this included, that share ownership with *this, or an unspecified nonnegative value when *this is empty. use_count() is not necessarily efficient. Use only for debugging and testing purposes, not for production code.
void swap(shared_ptr< T, VoidAllocator, Deleter > & other);
Exchanges the contents of the two smart pointers.