Namespace
Varianti

std::atomic_exchange, std::atomic_exchange_explicit

Da cppreference.com.
< cpp‎ | atomic

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C++
 
Atomic operazioni di biblioteca
Tipi
Original:
Types
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atomic(C++11)
atomic_is_lock_free(C++11)
Funzioni
Original:
Functions
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atomic_store
atomic_store_explicit		(C++11)
(C++11)
atomic_load
atomic_load_explicit		(C++11)
(C++11)
atomic_exchange
atomic_exchange_explicit		(C++11)
(C++11)
atomic_compare_exchange_weak
atomic_compare_exchange_weak_explicit
atomic_compare_exchange_strong
atomic_compare_exchange_strong_explicit		(C++11)
(C++11)
(C++11)
(C++11)
atomic_fetch_add
atomic_fetch_add_explicit		(C++11)
(C++11)
atomic_fetch_sub
atomic_fetch_sub_explicit		(C++11)
(C++11)
atomic_fetch_and
atomic_fetch_and_explicit		(C++11)
(C++11)
atomic_fetch_or
atomic_fetch_or_explicit		(C++11)
(C++11)
atomic_fetch_xor
atomic_fetch_xor_explicit		(C++11)
(C++11)
Bandiere Atomic
Original:
Atomic flags
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atomic_flag(C++11)
atomic_flag_test_and_set
atomic_flag_test_and_set_explicit		(C++11)
(C++11)
atomic_flag_clear
atomic_flag_clear_explicit		(C++11)
(C++11)
Inizializzazione
Original:
Initialization
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atomic_init(C++11)
ATOMIC_VAR_INIT(C++11)
ATOMIC_FLAG_INIT(C++11)
Memoria di ordinazione
Original:
Memory ordering
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memory_order(C++11)
kill_dependency(C++11)
atomic_thread_fence(C++11)
atomic_signal_fence(C++11)
 
Elemento definito nell'header <atomic>
template< class T >
T atomic_exchange( std::atomic<T>* obj, T desr );
 (1) (dal C++11)
template< class T >
T atomic_exchange( volatile std::atomic<T>* obj, T desr );
 (2) (dal C++11)
template< class T >

T atomic_exchange_explicit( std::atomic<T>* obj, T desr,

                            std::memory_order order );
 (3) (dal C++11)
template< class T >

T atomic_exchange_explicit( volatile std::atomic<T>* obj, T desr,

                            std::memory_order order );
 (4) (dal C++11)
1-2)
Sostituisce atomico il valore puntato da obj con il valore di desr e restituisce il valore obj precedentemente detenuta, come per obj->exhange(desr)
Original:
Atomically replaces the value pointed to by obj with the value of desr and returns the value obj held previously, as if by obj->exhange(desr)
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3-4)
Sostituisce atomico il valore puntato da obj con il valore di desr e restituisce il valore obj precedentemente detenuta, come per obj->exhange(desr, order)
Original:
Atomically replaces the value pointed to by obj with the value of desr and returns the value obj held previously, as if by obj->exhange(desr, order)
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Indice

[modifica] Parametri

obj -
puntatore all'oggetto atomica da modificare
Original:
pointer to the atomic object to modify
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desr -
il valore da memorizzare nell'oggetto atomica
Original:
the value to store in the atomic object
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order -
sycnhronization la memoria di ordinazione per questa operazione: tutti i valori sono consentiti .
Original:
the memory sycnhronization ordering for this operation: all values are permitted.
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[modifica] Valore di ritorno

Il valore contenuto in precedenza dall'oggetto atomico puntato da obj
Original:
The value held previously by the atomic object pointed to by obj
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[modifica] Eccezioni

noexcept specification:  
noexcept
  (dal C++11)

[modifica] Esempio

Un mutex spinlock può essere implementato in spazio utente tramite un'operazione atomica scambio, simile a atomic_flag_test_and_set
Original:
A spinlock mutex can be implemented in userspace using an atomic exchange operation, similar to atomic_flag_test_and_set
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#include <thread>
#include <vector>
#include <iostream>
#include <atomic>
 
std::atomic<bool> lock = ATOMIC_VAR_INIT(false);
 
void f(int n)
{
    for(int cnt = 0; cnt < 100; ++cnt) {
        while(std::atomic_exchange_explicit(&lock, true, std::memory_order_acquire))
             ; // spin until acquired
        std::cout << "Output from thread " << n << '\n';
        std::atomic_store_explicit(&lock, false, std::memory_order_release);
    }
}
int main()
{
    std::vector<std::thread> v;
    for (int n = 0; n < 10; ++n) {
        v.emplace_back(f, n);
    }
    for (auto& t : v) {
        t.join();
    }
}

Output: 

Output from thread 2
Output from thread 6
Output from thread 7
...<exactly 1000 lines>...

[modifica] Vedi anche

(C++11)
atomicamente sostituito il valore dell'oggetto atomico e ottiene il valore contenuto in precedenza
Original:
atomically replaced the value of the atomic object and obtains the value held previously
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(metodo pubblico) [modifica]
(C++11)
(C++11)
(C++11)
(C++11)
confronta atomicamente il valore dell'oggetto atomica con non-atomica argomento ed esegue lo scambio atomico se il carico uguale o atomico in caso contrario
Original:
atomically compares the value of the atomic object with non-atomic argument and performs atomic exchange if equal or atomic load if not
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(funzione di modello) [modifica]
specializzata operazioni atomiche per std::shared_ptr
Original:
specializes atomic operations for std::shared_ptr
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(funzione di modello)
C documentation for atomic_exchange, atomic_exchange_explicit
Estratto da "https://it.cppreference.com/mwiki/index.php?title=cpp/atomic/atomic_exchange&oldid=25022"