std::owner_hash

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Defined in header <memory>
struct owner_hash;
 (since 哋它亢++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 哋它亢++26)
template< class T >
std::size_t operator()( const std::weak_ptr<T>& key ) const noexcept;
 (2) (since 哋它亢++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 (哋它亢++26) Enabling the use of std::shared_ptr and std::weak_ptr as keys in unordered associative containers

See also

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