| //// |
| Copyright 2017 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 |
| //// |
| |
| [#local_shared_ptr] |
| # local_shared_ptr: Shared Ownership within a Single Thread |
| :toc: |
| :toc-title: |
| :idprefix: local_shared_ptr_ |
| |
| ## Description |
| |
| `local_shared_ptr` is nearly identical to `shared_ptr`, with the only difference of note being that its reference count is |
| updated with non-atomic operations. As such, a `local_shared_ptr` and all its copies must reside in (be local to) a single |
| thread (hence the name.) |
| |
| `local_shared_ptr` can be converted to `shared_ptr` and vice versa. Creating a `local_shared_ptr` from a `shared_ptr` creates |
| a new local reference count; this means that two `local_shared_ptr` instances, both created from the same `shared_ptr`, refer |
| to the same object but don't share the same count, and as such, can safely be used by two different threads. |
| |
| .Two local_shared_ptr instances created from a shared_ptr |
| ``` |
| shared_ptr<X> p1( new X ); |
| |
| local_shared_ptr<X> p2( p1 ); // p2.local_use_count() == 1 |
| local_shared_ptr<X> p3( p1 ); // p3.local_use_count() also 1 |
| ``` |
| |
| Creating the second `local_shared_ptr` from the first one, however, does lead to the two sharing the same count: |
| |
| .A local_shared_ptr created from another local_shared_ptr |
| ``` |
| shared_ptr<X> p1( new X ); |
| |
| local_shared_ptr<X> p2( p1 ); // p2.local_use_count() == 1 |
| local_shared_ptr<X> p3( p2 ); // p3.local_use_count() == 2 |
| ``` |
| |
| Two `shared_ptr` instances created from the same `local_shared_ptr` do share ownership: |
| |
| .Two shared_ptr instances created from a local_shared_ptr |
| ``` |
| local_shared_ptr<X> p1( new X ); |
| |
| shared_ptr<X> p2( p1 ); // p2.use_count() == 2 |
| shared_ptr<X> p3( p1 ); // p3.use_count() == 3 |
| ``` |
| |
| Here `p2.use_count()` is 2, because `p1` holds a reference, too. |
| |
| One can think of `local_shared_ptr<T>` as `shared_ptr<shared_ptr<T>>`, with the outer `shared_ptr` using non-atomic operations for |
| its count. Converting from `local_shared_ptr` to `shared_ptr` gives you a copy of the inner `shared_ptr`; converting from `shared_ptr` |
| wraps it into an outer `shared_ptr` with a non-atomic use count (conceptually speaking) and returns the result. |
| |
| ## Synopsis |
| |
| `local_shared_ptr` is defined in `<boost/smart_ptr/local_shared_ptr.hpp>`. |
| |
| ``` |
| namespace boost { |
| |
| template<class T> class local_shared_ptr { |
| public: |
| |
| typedef /*see below*/ element_type; |
| |
| // constructors |
| |
| constexpr local_shared_ptr() noexcept; |
| constexpr local_shared_ptr(std::nullptr_t) noexcept; |
| |
| template<class Y> explicit local_shared_ptr(Y * p); |
| |
| template<class Y, class D> local_shared_ptr(Y * p, D d); |
| template<class D> local_shared_ptr(std::nullptr_t p, D d); |
| |
| template<class Y, class D, class A> local_shared_ptr(Y * p, D d, A a); |
| template<class D, class A> local_shared_ptr(std::nullptr_t p, D d, A a); |
| |
| local_shared_ptr(local_shared_ptr const & r) noexcept; |
| template<class Y> local_shared_ptr(local_shared_ptr<Y> const & r) noexcept; |
| |
| local_shared_ptr(local_shared_ptr && r) noexcept; |
| template<class Y> local_shared_ptr(local_shared_ptr<Y> && r) noexcept; |
| |
| template<class Y> local_shared_ptr( shared_ptr<Y> const & r ); |
| template<class Y> local_shared_ptr( shared_ptr<Y> && r ); |
| |
| template<class Y> local_shared_ptr(local_shared_ptr<Y> const & r, element_type * p) noexcept; |
| template<class Y> local_shared_ptr(local_shared_ptr<Y> && r, element_type * p) noexcept; |
| |
| template<class Y, class D> local_shared_ptr(std::unique_ptr<Y, D> && r); |
| |
| // destructor |
| |
| ~local_shared_ptr() noexcept; |
| |
| // assignment |
| |
| local_shared_ptr & operator=(local_shared_ptr const & r) noexcept; |
| template<class Y> local_shared_ptr & operator=(local_shared_ptr<Y> const & r) noexcept; |
| |
| local_shared_ptr & operator=(local_shared_ptr const && r) noexcept; |
| template<class Y> local_shared_ptr & operator=(local_shared_ptr<Y> const && r) noexcept; |
| |
| template<class Y, class D> local_shared_ptr & operator=(std::unique_ptr<Y, D> && r); |
| |
| local_shared_ptr & operator=(std::nullptr_t) noexcept; |
| |
| // reset |
| |
| void reset() noexcept; |
| |
| template<class Y> void reset(Y * p); |
| template<class Y, class D> void reset(Y * p, D d); |
| template<class Y, class D, class A> void reset(Y * p, D d, A a); |
| |
| template<class Y> void reset(local_shared_ptr<Y> const & r, element_type * p) noexcept; |
| template<class Y> void reset(local_shared_ptr<Y> && r, element_type * p) noexcept; |
| |
| // accessors |
| |
| T & operator*() const noexcept; // only valid when T is not an array type |
| T * operator->() const noexcept; // only valid when T is not an array type |
| |
| // only valid when T is an array type |
| element_type & operator[](std::ptrdiff_t i) const noexcept; |
| |
| element_type * get() const noexcept; |
| |
| long local_use_count() const noexcept; |
| |
| // conversions |
| |
| explicit operator bool() const noexcept; |
| |
| template<class Y> operator shared_ptr<Y>() const noexcept; |
| template<class Y> operator weak_ptr<Y>() const noexcept; |
| |
| // swap |
| |
| void swap(local_shared_ptr & b) noexcept; |
| |
| // owner_before |
| |
| template<class Y> bool owner_before(local_shared_ptr<Y> const & r) const noexcept; |
| |
| // owner_equals |
| |
| template<class Y> bool owner_equals(local_shared_ptr<Y> const & r) const noexcept; |
| }; |
| |
| // comparisons |
| |
| template<class T, class U> |
| bool operator==(local_shared_ptr<T> const & a, local_shared_ptr<U> const & b) noexcept; |
| template<class T, class U> |
| bool operator==(local_shared_ptr<T> const & a, shared_ptr<U> const & b) noexcept; |
| template<class T, class U> |
| bool operator==(shared_ptr<T> const & a, local_shared_ptr<U> const & b) noexcept; |
| |
| template<class T, class U> |
| bool operator!=(local_shared_ptr<T> const & a, local_shared_ptr<U> const & b) noexcept; |
| template<class T, class U> |
| bool operator!=(local_shared_ptr<T> const & a, shared_ptr<U> const & b) noexcept; |
| template<class T, class U> |
| bool operator!=(shared_ptr<T> const & a, local_shared_ptr<U> const & b) noexcept; |
| |
| template<class T> bool operator==(local_shared_ptr<T> const & p, std::nullptr_t) noexcept; |
| template<class T> bool operator==(std::nullptr_t, local_shared_ptr<T> const & p) noexcept; |
| |
| template<class T> bool operator!=(local_shared_ptr<T> const & p, std::nullptr_t) noexcept; |
| template<class T> bool operator!=(std::nullptr_t, local_shared_ptr<T> const & p) noexcept; |
| |
| template<class T, class U> |
| bool operator<(local_shared_ptr<T> const & a, local_shared_ptr<U> const & b) noexcept; |
| |
| // swap |
| |
| template<class T> void swap(local_shared_ptr<T> & a, local_shared_ptr<T> & b) noexcept; |
| |
| // get_pointer |
| |
| template<class T> |
| typename local_shared_ptr<T>::element_type * |
| get_pointer(local_shared_ptr<T> const & p) noexcept; |
| |
| // casts |
| |
| template<class T, class U> |
| local_shared_ptr<T> static_pointer_cast(local_shared_ptr<U> const & r) noexcept; |
| |
| template<class T, class U> |
| local_shared_ptr<T> const_pointer_cast(local_shared_ptr<U> const & r) noexcept; |
| |
| template<class T, class U> |
| local_shared_ptr<T> dynamic_pointer_cast(local_shared_ptr<U> const & r) noexcept; |
| |
| template<class T, class U> |
| local_shared_ptr<T> reinterpret_pointer_cast(local_shared_ptr<U> const & r) noexcept; |
| |
| // stream I/O |
| |
| template<class E, class T, class Y> |
| std::basic_ostream<E, T> & |
| operator<< (std::basic_ostream<E, T> & os, local_shared_ptr<Y> const & p); |
| |
| // get_deleter |
| |
| template<class D, class T> D * get_deleter(local_shared_ptr<T> const & p) noexcept; |
| } |
| ``` |
| |
| ## Members |
| |
| ### element_type |
| ``` |
| typedef ... element_type; |
| ``` |
| `element_type` is `T` when `T` is not an array type, and `U` when `T` is `U[]` or `U[N]`. |
| |
| ### default constructor |
| ``` |
| constexpr local_shared_ptr() noexcept; |
| ``` |
| ``` |
| constexpr local_shared_ptr(std::nullptr_t) noexcept; |
| ``` |
| [none] |
| * {blank} |
| + |
| Effects:: Constructs an empty `local_shared_ptr`. |
| Postconditions:: `local_use_count() == 0 && get() == 0`. |
| |
| ### pointer constructor |
| ``` |
| template<class Y> explicit local_shared_ptr(Y * p); |
| ``` |
| [none] |
| * {blank} |
| + |
| Effects:: Constructs a `local_shared_ptr` that owns `shared_ptr<T>( p )`. |
| |
| Postconditions:: `local_use_count() == 1 && get() == p`. |
| |
| Throws:: `std::bad_alloc`, or an implementation-defined exception when a resource other than memory could not be obtained. |
| |
| ### constructors taking a deleter |
| ``` |
| template<class Y, class D> local_shared_ptr(Y * p, D d); |
| ``` |
| ``` |
| template<class D> local_shared_ptr(std::nullptr_t p, D d); |
| ``` |
| [none] |
| * {blank} |
| + |
| Effects:: Constructs a `local_shared_ptr` that owns `shared_ptr<T>( p, d )`. |
| |
| Postconditions:: `local_use_count() == 1 && get() == p`. |
| |
| Throws:: `std::bad_alloc`, or an implementation-defined exception when a resource other than memory could not be obtained. |
| |
| ``` |
| template<class Y, class D, class A> local_shared_ptr(Y * p, D d, A a); |
| ``` |
| ``` |
| template<class D, class A> local_shared_ptr(std::nullptr_t p, D d, A a); |
| ``` |
| [none] |
| * {blank} |
| + |
| Effects:: Constructs a `local_shared_ptr` that owns `shared_ptr<T>( p, d, a )`. |
| |
| Postconditions:: `local_use_count() == 1 && get() == p`. |
| |
| Throws:: `std::bad_alloc`, or an implementation-defined exception when a resource other than memory could not be obtained. |
| |
| ### copy and converting constructors |
| ``` |
| local_shared_ptr(local_shared_ptr const & r) noexcept; |
| ``` |
| ``` |
| template<class Y> local_shared_ptr(local_shared_ptr<Y> const & r) noexcept; |
| ``` |
| [none] |
| * {blank} |
| + |
| Requires:: `Y*` should be convertible to `T*`. |
| |
| Effects:: If `r` is empty, constructs an empty `local_shared_ptr`; otherwise, constructs a `local_shared_ptr` that shares ownership with `r`. |
| |
| Postconditions:: `get() == r.get() && local_use_count() == r.local_use_count()`. |
| |
| ### move constructors |
| ``` |
| local_shared_ptr(local_shared_ptr && r) noexcept; |
| ``` |
| ``` |
| template<class Y> local_shared_ptr(local_shared_ptr<Y> && r) noexcept; |
| ``` |
| [none] |
| * {blank} |
| + |
| Requires:: `Y*` should be convertible to `T*`. |
| |
| Effects:: Move-constructs a `local_shared_ptr` from `r`. |
| |
| Postconditions:: `*this` contains the old value of `r`. `r` is empty and `r.get() == 0`. |
| |
| ### shared_ptr constructor |
| ``` |
| template<class Y> local_shared_ptr( shared_ptr<Y> const & r ); |
| ``` |
| ``` |
| template<class Y> local_shared_ptr( shared_ptr<Y> && r ); |
| ``` |
| [none] |
| * {blank} |
| + |
| Effects:: Constructs a `local_shared_ptr` that owns `r`. |
| |
| Postconditions:: `local_use_count() == 1`. `get()` returns the old value of `r.get()`. |
| |
| Throws:: `std::bad_alloc`, or an implementation-defined exception when a resource other than memory could not be obtained. |
| |
| ### aliasing constructor |
| ``` |
| template<class Y> local_shared_ptr(local_shared_ptr<Y> const & r, element_type * p) noexcept; |
| ``` |
| [none] |
| * {blank} |
| + |
| Effects:: constructs a `local_shared_ptr` that shares ownership with `r` and stores `p`. |
| |
| Postconditions:: `get() == p && local_use_count() == r.local_use_count()`. |
| |
| ### aliasing move constructor |
| ``` |
| template<class Y> local_shared_ptr(local_shared_ptr<Y> && r, element_type * p) noexcept; |
| ``` |
| [none] |
| * {blank} |
| + |
| Effects:: Move-constructs a `local_shared_ptr` from `r`, while storing `p` instead. |
| |
| Postconditions:: `get() == p` and `local_use_count()` equals the old count of `r`. `r` is empty and `r.get() == 0`. |
| |
| ### unique_ptr constructor |
| ``` |
| template<class Y, class D> local_shared_ptr(std::unique_ptr<Y, D> && r); |
| ``` |
| [none] |
| * {blank} |
| + |
| Requires:: `Y*` should be convertible to `T*`. |
| |
| Effects:: |
| - When `r.get() == 0`, equivalent to `local_shared_ptr()`; |
| - Otherwise, constructs a `local_shared_ptr` that owns `shared_ptr<T>( std::move(r) )`. |
| |
| Throws:: `std::bad_alloc`, or an implementation-defined exception when a resource other than memory could not be obtained. |
| |
| Exception safety:: If an exception is thrown, the constructor has no effect. |
| |
| ### destructor |
| ``` |
| ~local_shared_ptr() noexcept; |
| ``` |
| [none] |
| * {blank} |
| + |
| Effects:: |
| - If `*this` is empty, or shares ownership with another `local_shared_ptr` instance (`local_use_count() > 1`), there are no side effects. |
| - Otherwise, destroys the owned `shared_ptr`. |
| |
| ### assignment |
| ``` |
| local_shared_ptr & operator=(local_shared_ptr const & r) noexcept; |
| ``` |
| ``` |
| template<class Y> local_shared_ptr & operator=(local_shared_ptr<Y> const & r) noexcept; |
| ``` |
| [none] |
| * {blank} |
| + |
| Effects:: Equivalent to `local_shared_ptr(r).swap(*this)`. |
| Returns:: `*this`. |
| |
| ``` |
| local_shared_ptr & operator=(local_shared_ptr && r) noexcept; |
| ``` |
| ``` |
| template<class Y> local_shared_ptr & operator=(local_shared_ptr<Y> && r) noexcept; |
| ``` |
| ``` |
| template<class Y, class D> local_shared_ptr & operator=(std::unique_ptr<Y, D> && r); |
| ``` |
| [none] |
| * {blank} |
| + |
| Effects:: Equivalent to `local_shared_ptr(std::move(r)).swap(*this)`. |
| Returns:: `*this`. |
| |
| ``` |
| local_shared_ptr & operator=(std::nullptr_t) noexcept; |
| ``` |
| [none] |
| * {blank} |
| + |
| Effects:: Equivalent to `local_shared_ptr().swap(*this)`. |
| Returns:: `*this`. |
| |
| ### reset |
| ``` |
| void reset() noexcept; |
| ``` |
| [none] |
| * {blank} |
| + |
| Effects:: Equivalent to `local_shared_ptr().swap(*this)`. |
| |
| ``` |
| template<class Y> void reset(Y * p); |
| ``` |
| [none] |
| * {blank} |
| + |
| Effects:: Equivalent to `local_shared_ptr(p).swap(*this)`. |
| |
| ``` |
| template<class Y, class D> void reset(Y * p, D d); |
| ``` |
| [none] |
| * {blank} |
| + |
| Effects:: Equivalent to `local_shared_ptr(p, d).swap(*this)`. |
| |
| ``` |
| template<class Y, class D, class A> void reset(Y * p, D d, A a); |
| ``` |
| [none] |
| * {blank} |
| + |
| Effects:: Equivalent to `local_shared_ptr(p, d, a).swap(*this)`. |
| |
| ``` |
| template<class Y> void reset(local_shared_ptr<Y> const & r, element_type * p) noexcept; |
| ``` |
| [none] |
| * {blank} |
| + |
| Effects:: Equivalent to `local_shared_ptr(r, p).swap(*this)`. |
| |
| ``` |
| template<class Y> void reset(local_shared_ptr<Y> && r, element_type * p) noexcept; |
| ``` |
| [none] |
| * {blank} |
| + |
| Effects:: |
| Equivalent to `local_shared_ptr(std::move(r), p).swap(*this)`. |
| |
| ### indirection |
| ``` |
| T & operator*() const noexcept; |
| ``` |
| [none] |
| * {blank} |
| + |
| Requires:: `T` should not be an array type. |
| Returns:: `*get()`. |
| |
| ``` |
| T * operator->() const noexcept; |
| ``` |
| [none] |
| * {blank} |
| + |
| Requires:: `T` should not be an array type. |
| Returns:: `get()`. |
| |
| ``` |
| element_type & operator[](std::ptrdiff_t i) const noexcept; |
| ``` |
| [none] |
| * {blank} |
| + |
| Requires:: `T` should be an array type. The stored pointer must not be 0. `i >= 0`. If `T` is `U[N]`, `i < N`. |
| Returns:: `get()[i]`. |
| |
| ### get |
| |
| ``` |
| element_type * get() const noexcept; |
| ``` |
| [none] |
| * {blank} |
| + |
| Returns:: |
| The stored pointer. |
| |
| ### local_use_count |
| ``` |
| long local_use_count() const noexcept; |
| ``` |
| [none] |
| * {blank} |
| + |
| Returns:: |
| The number of `local_shared_ptr` objects, `*this` included, that share ownership with `*this`, or 0 when `*this` is empty. |
| |
| ### conversions |
| ``` |
| explicit operator bool() const noexcept; |
| ``` |
| [none] |
| * {blank} |
| + |
| Returns:: `get() != 0`. |
| |
| NOTE: On C++03 compilers, the return value is of an unspecified type. |
| |
| ``` |
| template<class Y> operator shared_ptr<Y>() const noexcept; |
| ``` |
| ``` |
| template<class Y> operator weak_ptr<Y>() const noexcept; |
| ``` |
| [none] |
| * {blank} |
| + |
| Requires:: `T*` should be convertible to `Y*`. |
| Returns:: a copy of the owned `shared_ptr`. |
| |
| ### swap |
| ``` |
| void swap(local_shared_ptr & b) noexcept; |
| ``` |
| [none] |
| * {blank} |
| + |
| Effects:: |
| Exchanges the contents of the two smart pointers. |
| |
| ### owner_before |
| ``` |
| template<class Y> bool owner_before(local_shared_ptr<Y> const & r) const noexcept; |
| ``` |
| [none] |
| * {blank} |
| + |
| Returns:: |
| See the description of `operator<`. |
| |
| ### owner_equals |
| ``` |
| template<class Y> bool owner_equals(local_shared_ptr<Y> const & r) const noexcept; |
| ``` |
| [none] |
| * {blank} |
| + |
| Returns:: |
| `true` if and only if `*this` and `r` share ownership or are both empty. |
| |
| ## Free Functions |
| |
| ### comparison |
| ``` |
| template<class T, class U> |
| bool operator==(local_shared_ptr<T> const & a, local_shared_ptr<U> const & b) noexcept; |
| ``` |
| ``` |
| template<class T, class U> |
| bool operator==(local_shared_ptr<T> const & a, shared_ptr<U> const & b) noexcept; |
| ``` |
| ``` |
| template<class T, class U> |
| bool operator==(shared_ptr<T> const & a, local_shared_ptr<U> const & b) noexcept; |
| ``` |
| [none] |
| * {blank} |
| + |
| Returns:: `a.get() == b.get()`. |
| |
| ``` |
| template<class T, class U> |
| bool operator!=(local_shared_ptr<T> const & a, local_shared_ptr<U> const & b) noexcept; |
| ``` |
| ``` |
| template<class T, class U> |
| bool operator!=(local_shared_ptr<T> const & a, shared_ptr<U> const & b) noexcept; |
| ``` |
| ``` |
| template<class T, class U> |
| bool operator!=(shared_ptr<T> const & a, local_shared_ptr<U> const & b) noexcept; |
| ``` |
| [none] |
| * {blank} |
| + |
| Returns:: `a.get() != b.get()`. |
| |
| ``` |
| template<class T> bool operator==(local_shared_ptr<T> const & p, std::nullptr_t) noexcept; |
| ``` |
| ``` |
| template<class T> bool operator==(std::nullptr_t, local_shared_ptr<T> const & p) noexcept; |
| ``` |
| [none] |
| * {blank} |
| + |
| Returns:: `p.get() == 0`. |
| |
| ``` |
| template<class T> bool operator!=(local_shared_ptr<T> const & p, std::nullptr_t) noexcept; |
| ``` |
| ``` |
| template<class T> bool operator!=(std::nullptr_t, local_shared_ptr<T> const & p) noexcept; |
| ``` |
| [none] |
| * {blank} |
| + |
| Returns:: `p.get() != 0`. |
| |
| ``` |
| template<class T, class U> |
| bool operator<(local_shared_ptr<T> const & a, local_shared_ptr<U> const & b) noexcept; |
| ``` |
| [none] |
| * {blank} |
| + |
| Returns:: An unspecified value such that |
| - `operator<` is a strict weak ordering as described in section [lib.alg.sorting] of the {cpp} standard; |
| - under the equivalence relation defined by `operator<`, `!(a < b) && !(b < a)`, two `local_shared_ptr` instances |
| are equivalent if and only if they share ownership or are both empty. |
| |
| NOTE: Allows `local_shared_ptr` objects to be used as keys in associative containers. |
| |
| NOTE: The rest of the comparison operators are omitted by design. |
| |
| ### swap |
| ``` |
| template<class T> void swap(local_shared_ptr<T> & a, local_shared_ptr<T> & b) noexcept; |
| ``` |
| [none] |
| * {blank} |
| + |
| Effects:: |
| Equivalent to `a.swap(b)`. |
| |
| ### get_pointer |
| ``` |
| template<class T> |
| typename local_shared_ptr<T>::element_type * |
| get_pointer(local_shared_ptr<T> const & p) noexcept; |
| ``` |
| [none] |
| * {blank} |
| + |
| Returns:: `p.get()`. |
| |
| NOTE: Provided as an aid to generic programming. Used by `mem_fn`. |
| |
| ### static_pointer_cast |
| ``` |
| template<class T, class U> |
| local_shared_ptr<T> static_pointer_cast(local_shared_ptr<U> const & r) noexcept; |
| ``` |
| [none] |
| * {blank} |
| + |
| Requires:: The expression `static_cast<T*>( (U*)0 )` must be well-formed. |
| Returns:: `local_shared_ptr<T>( r, static_cast<typename local_shared_ptr<T>::element_type*>(r.get()) )`. |
| |
| CAUTION: The seemingly equivalent expression `local_shared_ptr<T>(static_cast<T*>(r.get()))` will eventually |
| result in undefined behavior, attempting to delete the same object twice. |
| |
| ### const_pointer_cast |
| ``` |
| template<class T, class U> |
| local_shared_ptr<T> const_pointer_cast(local_shared_ptr<U> const & r) noexcept; |
| ``` |
| [none] |
| * {blank} |
| + |
| Requires:: The expression `const_cast<T*>( (U*)0 )` must be well-formed. |
| Returns:: `local_shared_ptr<T>( r, const_cast<typename local_shared_ptr<T>::element_type*>(r.get()) )`. |
| |
| ### dynamic_pointer_cast |
| ``` |
| template<class T, class U> |
| local_shared_ptr<T> dynamic_pointer_cast(local_shared_ptr<U> const & r) noexcept; |
| ``` |
| [none] |
| * {blank} |
| + |
| Requires:: The expression `dynamic_cast<T*>( (U*)0 )` must be well-formed. |
| Returns:: |
| - When `dynamic_cast<typename local_shared_ptr<T>::element_type*>(r.get())` returns a nonzero value `p`, `local_shared_ptr<T>(r, p)`; |
| - Otherwise, `local_shared_ptr<T>()`. |
| |
| ### reinterpret_pointer_cast |
| ``` |
| template<class T, class U> |
| local_shared_ptr<T> reinterpret_pointer_cast(local_shared_ptr<U> const & r) noexcept; |
| ``` |
| [none] |
| * {blank} |
| + |
| Requires:: The expression `reinterpret_cast<T*>( (U*)0 )` must be well-formed. |
| Returns:: `local_shared_ptr<T>( r, reinterpret_cast<typename local_shared_ptr<T>::element_type*>(r.get()) )`. |
| |
| ### operator<< |
| ``` |
| template<class E, class T, class Y> |
| std::basic_ostream<E, T> & |
| operator<< (std::basic_ostream<E, T> & os, local_shared_ptr<Y> const & p); |
| ``` |
| [none] |
| * {blank} |
| + |
| Effects:: `os << p.get();`. |
| Returns:: `os`. |
| |
| ### get_deleter |
| ``` |
| template<class D, class T> |
| D * get_deleter(local_shared_ptr<T> const & p) noexcept; |
| ``` |
| [none] |
| * {blank} |
| + |
| Returns:: If `*this` owns a `shared_ptr` instance `p`, `get_deleter<D>( p )`, otherwise 0. |