std::pointer_traits
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<tbody> </tbody>| Definido no cabeçalho <memory>
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template< class Ptr > struct pointer_traits; |
(1) | (desde C++11) |
template< class T > struct pointer_traits<T*>; |
(2) | (desde C++11) |
O modelo de classe
pointer_traits fornece a maneira padronizada para acessar certas propriedades do ponteiro-como tipos. O std::allocator_traits modelo padrão depende pointer_traits para determinar os padrões para vários typedefs requer por Allocator.Original:
The
pointer_traits class template provides the standardized way to access certain properties of pointer-like types. The standard template std::allocator_traits relies on pointer_traits to determine the defaults for various typedefs requires by Allocator.The text has been machine-translated via Google Translate.
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1)
O
pointer_traits não especializado declara os seguintes tipos:Original:
The non-specialized
pointer_traits declares the following types:The text has been machine-translated via Google Translate.
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Tipos de membro
Tipo
Original: Type The text has been machine-translated via Google Translate. You can help to correct and verify the translation. Click here for instructions. |
Definition |
pointer
|
Ptr
|
element_type
|
Ptr::element_type se presente. Caso contrário T se Ptr é um Template<T, Args...> instanciação do modelo Original: Ptr::element_type if present. Otherwise T if Ptr is a template instantiation Template<T, Args...> The text has been machine-translated via Google Translate. You can help to correct and verify the translation. Click here for instructions. |
difference_type
|
Ptr::difference_type se presente, caso contrário std::ptrdiff_t Original: Ptr::difference_type if present, otherwise std::ptrdiff_t The text has been machine-translated via Google Translate. You can help to correct and verify the translation. Click here for instructions. |
Membros apelido modelos
Modelo
Original: Template The text has been machine-translated via Google Translate. You can help to correct and verify the translation. Click here for instructions. |
Definition |
| template <class U> using rebind | Ptr::rebind<U> se existir, caso contrário Tempate<U, Args...> se Ptr é um Template<T, Args...> instanciação do modelo Original: Ptr::rebind<U> if exists, otherwise Tempate<U, Args...> if Ptr is a template instantiation Template<T, Args...> The text has been machine-translated via Google Translate. You can help to correct and verify the translation. Click here for instructions. |
Funções de membro
[estática] |
obtém um ponteiro dereferencable a sua tese Original: obtains a dereferencable pointer to its argument The text has been machine-translated via Google Translate. You can help to correct and verify the translation. Click here for instructions. (função public static membro) |
2)
A especialização é fornecido para tipos de ponteiro,
T*, que declara os seguintes tiposOriginal:
A specialization is provided for pointer types,
T*, which declares the following typesThe text has been machine-translated via Google Translate.
You can help to correct and verify the translation. Click here for instructions.
You can help to correct and verify the translation. Click here for instructions.
Tipos de membro
Tipo
Original: Type The text has been machine-translated via Google Translate. You can help to correct and verify the translation. Click here for instructions. |
Definition |
pointer
|
T*
|
element_type
|
T
|
difference_type
|
std::ptrdiff_t |
Membros apelido modelos
Modelo
Original: Template The text has been machine-translated via Google Translate. You can help to correct and verify the translation. Click here for instructions. |
Definition |
| template< class U > using rebind | U*
|
Funções de membro
[estática] |
obtém um ponteiro dereferencable ao seu argumento} Original: obtains a dereferencable pointer to its argument} The text has been machine-translated via Google Translate. You can help to correct and verify the translation. Click here for instructions. (função public static membro) |
Notas
O alias modelo religar membros torna possível, dado um tipo de ponteiro-como que aponta para T, para obter o tipo de ponteiro-like mesmo que aponta para U. por exemplo,
Original:
The rebind member template alias makes it possible, given a pointer-like type that points to T, to obtain the same pointer-like type that points to U. For example,
The text has been machine-translated via Google Translate.
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std :: is_same <std :: pointer_traits <std :: shared_ptr <int>> :: reativação <double>, std :: unique_ptr <double>> :: value), "")
Original:
std::is_same<std::pointer_traits< std::shared_ptr<int>>::rebind<double>, std::unique_ptr<double> >::value), "")
The text has been machine-translated via Google Translate.
You can help to correct and verify the translation. Click here for instructions.
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Exemplo
#include <memory>
#include <iostream>
template <class Ptr>
struct BlockList
{
// Predefine a memory block
struct block;
// Define a pointer to a memory block from the kind of pointer Ptr s
// If Ptr is any kind of T*, block_ptr_t is block*
// If Ptr is smart_ptr<T>, block_ptr_t is smart_ptr<block>
typedef typename std::pointer_traits<Ptr>::template rebind<block> block_ptr_t;
struct block
{
std::size_t size;
block_ptr_t next_block;
};
block_ptr_t free_blocks;
};
int main()
{
BlockList<int*> bl1;
// The type of bl1.free_blocks is block*
BlockList<std::shared_ptr<char>> bl2;
// The type of bl2.free_blocks is std::shared_ptr<block>
std::cout << bl2.free_blocks.use_count() << '\n';
}
Saída:
0