Introduction
Synopsis
Members
Free Functions
The intrusive_ptr class template stores a pointer to an object with an embedded reference count. Every new intrusive_ptr instance increments the reference count by using an unqualified call to the function intrusive_ptr_add_ref, passing the pointer as an argument. Similarly, when an intrusive_ptr is destroyed, it calls intrusive_ptr_release; this function is responsible for destroying the object when its reference count drops to zero. The user is expected to provide suitable definitions of these two functions. On compilers that support argument-dependent lookup, intrusive_ptr_add_ref and intrusive_ptr_release should be defined in the namespace that corresponds to their parameter; otherwise, the definitions need to go in namespace boost.
The class template is parameterized on T, the type of the object pointed to intrusive_ptr<T> can be implicitly converted to intrusive_ptr<U> whenever T* can be implicitly converted to U*.
The main reasons to use intrusive_ptr are:
Some existing frameworks or OSes provide objects with embedded reference counts;
The memory footprint of intrusive_ptr is the same as the corresponding raw pointer;
intrusive_ptr<T> can be constructed from an arbitrary raw pointer of type T *.
As a general rule, if it isn't obvious whether intrusive_ptr better fits the needs than shared_ptr, try a shared_ptr-based design first.
namespace boost {
template<class T> class intrusive_ptr {
public:
typedef T element_type;
intrusive_ptr(); // never throws
intrusive_ptr(T * p, bool add_ref = true);
intrusive_ptr(intrusive_ptr const & r);
template<class Y> intrusive_ptr(intrusive_ptr<Y> const & r);
~intrusive_ptr();
intrusive_ptr & operator=(intrusive_ptr const & r);
template<class Y> intrusive_ptr & operator=(intrusive_ptr<Y> const & r);
template<class Y> intrusive_ptr & operator=(T * r);
T & operator*() const; // never throws
T * operator->() const; // never throws
T * get() const; // never throws
operator unspecified-bool-type() const; // never throws
void swap(intrusive_ptr & b); // never throws
};
template<class T, class U>
bool operator==(intrusive_ptr<T> const & a, intrusive_ptr<U> const & b); // never throws
template<class T, class U>
bool operator!=(intrusive_ptr<T> const & a, intrusive_ptr<U> const & b); // never throws
template<class T>
bool operator==(intrusive_ptr<T> const & a, T * b); // never throws
template<class T>
bool operator!=(intrusive_ptr<T> const & a, T * b); // never throws
template<class T>
bool operator==(T * a, intrusive_ptr<T> const & b); // never throws
template<class T>
bool operator!=(T * a, intrusive_ptr<T> const & b); // never throws
template<class T, class U>
bool operator<(intrusive_ptr<T> const & a, intrusive_ptr<U> const & b); // never throws
template<class T> void swap(intrusive_ptr<T> & a, intrusive_ptr<T> & b); // never throws
template<class T> T * get_pointer(intrusive_ptr<T> const & p); // never throws
template<class T, class U>
intrusive_ptr<T> static_pointer_cast(intrusive_ptr<U> const & r); // never throws
template<class T, class U>
intrusive_ptr<T> const_pointer_cast(intrusive_ptr<U> const & r); // never throws
template<class T, class U>
intrusive_ptr<T> dynamic_pointer_cast(intrusive_ptr<U> const & r); // never throws
template<class E, class T, class Y>
std::basic_ostream<E, T> & operator<< (std::basic_ostream<E, T> & os, intrusive_ptr<Y> const & p);
}
typedef T element_type;
Provides the type of the template parameter T.
intrusive_ptr(); // never throws
Postconditions: get() == 0.
Throws: nothing
intrusive_ptr(T * p, bool add_ref = true);
Effects: if(p != 0 && add_ref) intrusive_ptr_add_ref(p);.
Postconditions: get() == p.
intrusive_ptr(intrusive_ptr const & r); template<class Y> intrusive_ptr(intrusive_ptr<Y> const & r);
Effects: if(r.get() != 0) intrusive_ptr_add_ref(r.get());
Postconditions: get() == r.get()
~intrusive_ptr();
Effects: if(get() != 0) intrusive_ptr_release(get());
intrusive_ptr & operator=(intrusive_ptr const & r); template<class Y> intrusive_ptr & operator=(intrusive_ptr<Y> const & r); intrusive_ptr & operator=(T * r);
Effects: Equivalent to intrusive_ptr(r).swap(*this).
Returns: *this
T & operator*() const; // never throws
Requirements: get() != 0
Returns: *get()
Throws: nothing
T * operator->() const; // never throws
Requirements: get() != 0
Returns: get()
Throws: nothing
T * get() const; // never throws
Returns: the stored pointer.
Throws: nothing
operator unspecified-bool-type () const; // never throws
Returns: an unspecified value that, when used in boolean contexts, is equivalent to get() != 0.
Throws: nothing.
Notes: This conversion operator allows intrusive_ptr objects to be used in boolean contexts, like if (p && p->valid()) {}. The actual target type is typically a pointer to a member function, avoiding many of the implicit conversion pitfalls.
void swap(intrusive_ptr & b); // never throws
Effects: Exchanges the contents of the two smart pointers.
Throws: nothing.
template<class T, class U> bool operator==(intrusive_ptr<T> const & a, intrusive_ptr<U> const & b); // never throws
Returns: a.get() == b.get()
Throws: nothing
template<class T, class U> bool operator!=(intrusive_ptr<T> const & a, intrusive_ptr<U> const & b); // never throws
Returns: a.get() != b.get()
Throws: nothing
template<class T, class U> bool operator==(intrusive_ptr<T> const & a, U * b); // never throws
Returns: a.get() == b
Throws: nothing
template<class T, class U> bool operator!=(intrusive_ptr<T> const & a, U * b); // never throws
Returns: a.get() != b
Throws: nothing
template<class T, class U> bool operator==(T * a, intrusive_ptr<U> const & b); // never throws
Returns: a == b.get()
Throws: nothing
template<class T, class U> bool operator!=(T * a, intrusive_ptr<U> const & b); // never throws
Returns: a != b.get()
Throws: nothing
template<class T, class U> bool operator<(intrusive_ptr<T> const & a, intrusive_ptr<U> const & b); // never throws
Returns: std::less<T *>()(a.get(), b.get())
Throws: nothing
Notes: Allows intrusive_ptr objects to be used as keys in associative containers.
template<class T> void swap(intrusive_ptr<T> & a, intrusive_ptr<T> & b); // never throws
Effects: Equivalent to a.swap(b)
Throws: nothing
Notes: Matches the interface of std::swap. Provided as an aid to generic programming.
template<class T> T * get_pointer(intrusive_ptr<T> const & p); // never throws
Returns: p.get()
Throws: nothing
Notes: Provided as an aid to generic programming. Used by mem_fn.
template<class T, class U> intrusive_ptr<T> static_pointer_cast(intrusive_ptr<U> const & r); // never throws
Returns: intrusive_ptr<T>(static_cast<T*>(r.get()))
Throws: nothing
template<class T, class U> intrusive_ptr<T> const_pointer_cast(intrusive_ptr<U> const & r); // never throws
Returns: intrusive_ptr<T>(const_cast<T*>(r.get()))
Throws: nothing
template<class T, class U> intrusive_ptr<T> dynamic_pointer_cast(intrusive_ptr<U> const & r);
Returns: intrusive_ptr<T>(dynamic_cast<T*>(r.get()))
Throws: nothing
template<class E, class T, class Y>
std::basic_ostream<E, T> & operator<< (std::basic_ostream<E, T> & os, intrusive_ptr<Y> const & p);
Effects: os << p.get();
Returns: os
| Copyright © 2003-2005 Peter Dimov. Distributed under the Boost Software License, Version 1.0. See accompanying file License.html or copy at http://www.boost.org/License.html. |
|