std::owner_hash

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

This function object provides owner-based (as opposed to value-based) hashing of bothstd::weak_ptr andstd::shared_ptr.

[edit]Nested types

Nested type	Definition
`is_transparent`	unspecified

[edit]Member functions

operator()

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

std::owner_hash::operator()

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

Equivalent toreturn key.owner_hash();.

Parameters

key

shared-ownership pointer to be hashed

Return value

A hash value that is identical for anystd::shared_ptr orstd::weak_ptr object sharing the same ownership.

[edit]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 inunordered associative containers

[edit]See also

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