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std::pointer_traits

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Dynamische Speicherverwaltung
Low-Level-Speicherverwaltung
Zuweiser
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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)
Initialisierter Speicher
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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
Intelligente Zeiger
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Smart pointers
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unique_ptr(C++11)
shared_ptr(C++11)
weak_ptr(C++11)
auto_ptr(veraltet)
owner_less(C++11)
enable_shared_from_this(C++11)
bad_weak_ptr(C++11)
default_delete(C++11)
Garbage Collection Unterstützung
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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)
Verschiedenes
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Miscellaneous
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pointer_traits(C++11)
addressof(C++11)
align(C++11)
C-Bibliothek
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C Library
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Defined in header <memory>
template< class Ptr > struct pointer_traits;
(1) (seit C++11)
template< class T > struct pointer_traits<T*>;
(2) (seit C++11)
Die pointer_traits Klassen-Template bietet die standardisierte Möglichkeit, bestimmte Eigenschaften der Zeiger-ähnliche Typen zugreifen. Das Standard-Template std::allocator_traits setzt auf pointer_traits, um die Standardeinstellungen für verschiedene typedefs bestimmen erfordert von 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)
Die nicht-spezialisierten pointer_traits erklärt die folgenden Typen:
Original:
The non-specialized pointer_traits declares the following types:
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Inhaltsverzeichnis

[Bearbeiten] Mitglied Typen

Type
Original:
Type
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Definition
pointer Ptr
element_type
Ptr::element_type falls vorhanden. Ansonsten T wenn Ptr ist eine Vorlage Instanziierung Template<T, Args...>
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 falls vorhanden, sonst std::ptrdiff_t
Original:
Ptr::difference_type if present, otherwise std::ptrdiff_t
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[Bearbeiten] Mitglied alias Vorlagen

Template
Original:
Template
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Definition
template <class U> using rebind
Ptr::rebind<U> wenn vorhanden, sonst Tempate<U, Args...> wenn Ptr ist eine Vorlage Instanziierung Template<T, Args...>
Original:
Ptr::rebind<U> if exists, otherwise Tempate<U, Args...> if Ptr is a template instantiation Template<T, Args...>
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[Bearbeiten] Member-Funktionen

[statisch]
erhält eine dereferencable Zeiger auf sein Argument
Original:
obtains a dereferencable pointer to its argument
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(public static Elementfunktion)
2)
Eine Spezialisierung ist für Zeigertypen, T*, die die folgenden Arten bereitgestellt erklärt
Original:
A specialization is provided for pointer types, T*, which declares the following types
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[Bearbeiten] Mitglied Typen

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

[Bearbeiten] Mitglied alias Vorlagen

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

[Bearbeiten] Member-Funktionen

[statisch]
erhält eine dereferencable Zeiger auf das Argument}
Original:
obtains a dereferencable pointer to its argument}
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(public static Elementfunktion)

[Bearbeiten] Notes

Die rebind Elementtemplate Alias ​​ist es möglich, da ein Zeiger-ähnliche Aktivität, die auf T, um die gleiche wie Typ-Zeiger, der auf U. Beispielsweise erhalten
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>> :: value), "")
Original:
std::is_same<std::pointer_traits< std::shared_ptr<int>>::rebind<double>, std::unique_ptr<double> >::value), "")
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[Bearbeiten] Beispiel

#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​

[Bearbeiten] Siehe auch

liefert Informationen über allocator Typen
Original:
provides information about allocator types
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(Klassen-Template) [edit]
(C++11)
erhält tatsächlichen Adresse eines Objekts, selbst wenn der Bediener' & überlastet ist
Original:
obtains actual address of an object, even if the & operator is overloaded
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(Funktions-Template) [edit]