std::owner_hash

 

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Smart pointers unique_ptr (C++11) shared_ptr (C++11) weak_ptr (C++11) auto_ptr (until C++17*) owner_less (C++11) owner_less<void> (C++17) owner_hash (C++26) owner_equal (C++26) enable_shared_from_this (C++11) bad_weak_ptr (C++11) default_delete (C++11) out_ptr_t (C++23) inout_ptr_t (C++23) Low level memory management operator new operator new[] operator delete operator delete[] get_new_handler (C++11) set_new_handler launder (C++17) bad_alloc bad_array_new_length (C++11) nothrow_t align_val_t (C++17) destroying_delete_t (C++20) new_handler nothrow Miscellaneous pointer_traits (C++11) to_address (C++20) addressof (C++11) align (C++11) assume_aligned (C++20) C Library malloc calloc realloc    aligned_alloc (C++17) free

 

Defined in header <memory>
struct owner_hash;		(since C++26)

This function object provides owner-based (as opposed to value-based) hashing of both std::weak_ptr and std::shared_ptr.

Nested types

Nested type	Definition
is_transparent	unspecified

Member functions

operator()

calculates the hash of the shared-ownership pointer (function)

std::owner_hash::operator()

template< class T > std::size_t operator()( const std::shared_ptr<T>& key ) const noexcept;	(1)	(since C++26)
template< class T > std::size_t operator()( const std::weak_ptr<T>& key ) const noexcept;	(2)	(since C++26)

Equivalent to return key.owner_hash();.

Parameters

key

-

shared-ownership pointer to be hashed

Return value

A hash value that is identical for any std::shared_ptr or std::weak_ptr object sharing the same ownership.

Notes

Feature-test macro	Value	Std	Feature
__cpp_lib_smart_ptr_owner_equality	202306L	(C++26)	Enabling the use of std::shared_ptr and std::weak_ptr as keys in unordered associative containers

See also

owner_hash (C++26)	provides owner-based hashing of shared pointers (public member function of std::shared_ptr<T>)
owner_hash (C++26)	provides owner-based hashing of weak pointers (public member function of std::weak_ptr<T>)