std::hash<std::unique_ptr>

 

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智能指针 unique_ptr (C++11) shared_ptr (C++11) weak_ptr (C++11) auto_ptr (C++17 前*) 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) 低层内存管理 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 杂项 pointer_traits (C++11) to_address (C++20) addressof (C++11) align (C++11) assume_aligned (C++20) C 库 malloc calloc realloc    aligned_alloc (C++17) free

 

std::unique_ptr

成员函数

unique_ptr::unique_ptr

unique_ptr::~unique_ptr

unique_ptr::operator=

修改器

unique_ptr::release

unique_ptr::reset

unique_ptr::swap

观察器

unique_ptr::get

unique_ptr::get_deleter

unique_ptr::operator bool

unique_ptr::operator*unique_ptr::operator->

unique_ptr::operator[]

非成员函数

make_uniquemake_unique_for_overwrite (C++14)(C++20)

operator==operator!=operator<operator>operator<=operator>=operator<=> (C++20 前)(C++20)

operator<< (C++20)

swap(std::unique_ptr)

辅助类

hash<std::unique_ptr>

 

template< class T, class Deleter > struct hash<std::unique_ptr<T, Deleter>>;		(C++11 起)

std::hash 对 std::unique_ptr<T, Deleter> 的模板特化允许用户获得 std::unique_ptr<T, Deleter> 类型对象的散列值。

若启用 std::hash<typename std::unique_ptr<T,D>::pointer>，则启用特化 std::hash<std::unique_ptr<T,D>>（见 std::hash），否则禁用它。

启用时，对于给定的 std::unique_ptr<T, D> p，此特化确保 std::hash<std::unique_ptr<T, D>>()(p) == std::hash<typename std::unique_ptr<T, D>::pointer>()(p.get())。

此特化的成员函数不保证为 noexcept，因为指针可能是缀饰指针且其散列函数可能抛出异常。

示例

运行此代码

#include <functional>
#include <iostream>
#include <memory>
 
struct Foo
{
    Foo(int num) : nr(num) { std::cout << "Foo(" << nr << ")\n"; }
 
    ~Foo() { std::cout << "~Foo()\n"; }
 
    bool operator==(const Foo &other) const { return nr == other.nr; };
 
    int nr;
};
 
int main()
{
    std::cout << std::boolalpha << std::hex;
 
    Foo* foo = new Foo(5);
    std::unique_ptr<Foo> up(foo); 
    std::cout << "hash(up):    " << std::hash<std::unique_ptr<Foo>>()(up) << '\n'
              << "hash(foo):   " << std::hash<Foo*>()(foo) << '\n'
              << "*up==*foo:   " << (*up == *foo) << "\n\n";
 
    std::unique_ptr<Foo> other = std::make_unique<Foo>(5);
    std::cout << "hash(up):    " << std::hash<std::unique_ptr<Foo>>()(up) << '\n'
              << "hash(other): " << std::hash<std::unique_ptr<Foo>>()(other) << '\n'
              << "*up==*other: " <<(*up == *other) << "\n\n";
}

可能的输出：

Foo(5)
hash(up):    acac20
hash(foo):   acac20
*up==*foo:   true
 
Foo(5)
hash(up):    acac20
hash(other): acbc50
*up==*other: true
 
~Foo()
~Foo()

参阅

hash (C++11)

散列函数对象 (类模板)