Namespace
Varianti

std::atomic_flag

Da cppreference.com.
< cpp‎ | atomic

 
 
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)
 
std::atomic_flag
Membri funzioni
Original:
Member functions
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atomic_flag::atomic_flag
atomic_flag::operator=
atomic_flag::clear
atomic_flag::test_and_set
 
Defined in header <atomic>
class atomic_flag;
(dal C++11)
std::atomic_flag è un tipo atomico boolean. A differenza di tutte le specializzazioni di std::atomic, è garantita senza blocchi. A differenza di std::atomic<bool>, std::atomic_flag non fornisce le operazioni di carico o negozio.
Original:
std::atomic_flag is an atomic boolean type. Unlike all specializations of std::atomic, it is guaranteed to be lock-free. Unlike std::atomic<bool>, std::atomic_flag does not provide load or store operations.
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[modifica] Membri funzioni

costruisce un atomic_flag
Original:
constructs an atomic_flag
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(membro pubblico funzione)
l'operatore di assegnazione
Original:
the assignment operator
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(membro pubblico funzione)
imposta atomicamente bandiera false
Original:
atomically sets flag to false
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(membro pubblico funzione) [edit]
imposta atomicamente il flag su true e ottiene il suo valore precedente
Original:
atomically sets the flag to true and obtains its previous value
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(membro pubblico funzione) [edit]

[modifica] Esempio

Un mutex spinlock può essere implementato in spazio utente utilizzando un atomic_flag
Original:
A spinlock mutex can be implemented in userspace using an atomic_flag
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#include <thread>
#include <vector>
#include <iostream>
#include <atomic>
 
std::atomic_flag lock = ATOMIC_FLAG_INIT;
 
void f(int n)
{
    for(int cnt = 0; cnt < 100; ++cnt) {
        while(lock.test_and_set(std::memory_order_acquire))  // acquire lock
             ; // spin
        std::cout << "Output from thread " << n << '\n';
        lock.clear(std::memory_order_release);               // release lock
    }
}
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

imposta atomicamente il flag su true e restituisce il suo valore precedente
Original:
atomically sets the flag to true and returns its previous value
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(funzione) [edit]
imposta atomicamente il valore della bandiera false
Original:
atomically sets the value of the flag to false
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(funzione) [edit]
initializes an std::atomic_flag to false
(macro costante) [edit]
C documentation for atomic_flag