Namespace
Varianti

std::pointer_traits

Da cppreference.com.
< cpp‎ | memory

 
 
Utilità libreria
Tipo di supporto (basic types, RTTI, type traits)
Gestione della memoria dinamica
La gestione degli errori
Programma di utilità
Funzioni variadic
Data e ora
Funzione oggetti
initializer_list(C++11)
bitset
hash(C++11)
Gli operatori relazionali
Original:
Relational operators
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rel_ops::operator!=
rel_ops::operator>
rel_ops::operator<=
rel_ops::operator>=
Coppie e tuple
Original:
Pairs and tuples
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pair
tuple(C++11)
piecewise_construct_t(C++11)
piecewise_construct(C++11)
Swap, in avanti e spostare
Original:
Swap, forward and move
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swap
forward(C++11)
move(C++11)
move_if_noexcept(C++11)
declval(C++11)
 
Gestione della memoria dinamica
Basso livello di gestione della memoria
Allocatori
Original:
Allocators
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allocator
allocator_traits(C++11)
allocator_arg_t(C++11)
allocator_arg(C++11)
uses_allocator(C++11)
scoped_allocator_adaptor(C++11)
Non inizializzata stoccaggio
Original:
Uninitialized storage
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uninitialized_copy
uninitialized_copy_n(C++11)
uninitialized_fill
uninitialized_fill_n
raw_storage_iterator
get_temporary_buffer
return_temporary_buffer
Puntatori intelligenti
Original:
Smart pointers
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unique_ptr(C++11)
shared_ptr(C++11)
weak_ptr(C++11)
auto_ptr(deprecato)
owner_less(C++11)
enable_shared_from_this(C++11)
bad_weak_ptr(C++11)
default_delete(C++11)
Garbage collection supporto
Original:
Garbage collection support
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declare_reachable(C++11)
undeclare_reachable(C++11)
declare_no_pointers(C++11)
undeclare_no_pointers(C++11)
pointer_safety(C++11)
get_pointer_safety(C++11)
Varie
Original:
Miscellaneous
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pointer_traits(C++11)
addressof(C++11)
align(C++11)
C Library
Original:
C Library
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Defined in header <memory>
template< class Ptr > struct pointer_traits;
(1) (dal C++11)
template< class T > struct pointer_traits<T*>;
(2) (dal C++11)
Il modello di classe pointer_traits fornisce il modo standard per accedere alle proprietà di alcuni tipi di puntatore di tipo. Il std::allocator_traits modello standard si basa su pointer_traits per determinare le impostazioni predefinite per diversi typedef richiede da 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.
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1)
Il non specializzato pointer_traits dichiara i seguenti tipi:
Original:
The non-specialized pointer_traits declares the following types:
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Indice

[modifica] Membri tipi

Tipo
Original:
Type
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Definition
pointer Ptr
element_type
Ptr::element_type se presente. In caso contrario, se T Ptr è un Template<T, Args...> istanziazione di template
Original:
Ptr::element_type if present. Otherwise T if Ptr is a template instantiation Template<T, Args...>
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difference_type
Ptr::difference_type se presente, altrimenti std::ptrdiff_t
Original:
Ptr::difference_type if present, otherwise std::ptrdiff_t
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[modifica] Membri alias modelli

Template
Original:
Template
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Definition
template <class U> using rebind
Ptr::rebind<U> se esiste, altrimenti se Tempate<U, Args...> Ptr è un Template<T, Args...> istanziazione di template
Original:
Ptr::rebind<U> if exists, otherwise Tempate<U, Args...> if Ptr is a template instantiation Template<T, Args...>
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[modifica] Membri funzioni

[statico]
ottiene un puntatore dereferencable al suo argomento
Original:
obtains a dereferencable pointer to its argument
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(public static membro funzione)
2)
Una specializzazione è previsto per i tipi di puntatore, T*, che dichiara i seguenti tipi
Original:
A specialization is provided for pointer types, T*, which declares the following types
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[modifica] Membri tipi

Tipo
Original:
Type
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Definition
pointer T*
element_type T
difference_type std::ptrdiff_t

[modifica] Membri alias modelli

Template
Original:
Template
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Definition
template< class U > using rebind U*

[modifica] Membri funzioni

[statico]
ottiene un puntatore dereferencable al suo argomento}
Original:
obtains a dereferencable pointer to its argument}
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(public static membro funzione)

[modifica] Note

Le riassociare alias modello utente permette, dato un puntatore come tipo che punta a T, per ottenere lo stesso puntatore come tipo che punta a U. Per esempio,
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,
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std :: is_same <std :: pointer_traits <std :: shared_ptr <int>> :: Rebind <double>, std :: unique_ptr <double>> :: valore), "")
Original:
std::is_same<std::pointer_traits< std::shared_ptr<int>>::rebind<double>, std::unique_ptr<double> >::value), "")
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[modifica] Esempio

#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';
}

Output:

​0​

[modifica] Vedi anche

fornisce informazioni sui tipi di allocatore
Original:
provides information about allocator types
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(classe template) [edit]
(C++11)
ottiene l'indirizzo reale di un oggetto, anche se l'operatore &' è sovraccarico
Original:
obtains actual address of an object, even if the & operator is overloaded
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(funzione di modello) [edit]