std::atomic_exchange
STD：：原子[医]交换，STD：：原子[医]交换[医]显式
| Defined in header | | |
|---|---|---|
| | (1) | (since C++11) |
| template< class T > T atomic_exchange( std::atomic<T>* obj, T desr | | |
| template< class T > T atomic_exchange( volatile std::atomic<T>* obj, T desr | | |
| | (2) | (since C++11) |
| template< class T > T atomic_exchange_explicit( std::atomic<T>* obj, T desr, std::memory_order order | | |
| template< class T > T atomic_exchange_explicit( volatile std::atomic<T>* obj, T desr, std::memory_order order | |
1%29原子替换obj有价值的desr并返回值。obj以前持有的，好像是...obj->exchange(desr)
2%29原子替换obj有价值的desr并返回值。obj以前持有的，好像是...obj->exchange(desr, order)
参数
| obj | - | pointer to the atomic object to modify |
|---|---|---|
| desr | - | the value to store in the atomic object |
| order | - | the memory synchronization ordering for this operation: all values are permitted. |
返回值
所指向的原子对象先前持有的值。obj...
例外
noexcept规格：
noexcept
例
可以使用原子交换操作在用户空间中实现自旋锁互斥对象，类似于std::atomic_flag_test_and_set*
二次
#include <thread>
#include <vector>
#include <iostream>
#include <atomic>
std::atomic<bool> lock(false // holds true when locked
// holds false when unlocked
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(
}
}
二次
产出：
二次
Output from thread 2
Output from thread 6
Output from thread 7
...<exactly 1000 lines>...
二次
另见
| exchange | atomically replaces the value of the atomic object and obtains the value held previously (public member function of std::atomic) |
|---|---|
| atomic_compare_exchange_weakatomic_compare_exchange_weak_explicitatomic_compare_exchange_strongatomic_compare_exchange_strong_explicit (C++11)(C++11)(C++11)(C++11) | atomically compares the value of the atomic object with non-atomic argument and performs atomic exchange if equal or atomic load if not (function template) |
| std::atomic_exchange(std::shared_ptr) std::atomic_exchange_explicit(std::shared_ptr) | specializes atomic operations for std::shared_ptr (function template) |
C原子文档[医]交换，原子的[医]交换[医]显式
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