exchange

描述 (Description)

它原子地替换原子对象的值并获得先前保存的值。

声明 (Declaration)

以下是std :: atomic :: exchange的声明。T exchange( T desired, std::memory_order order = std::memory_order_seq_cst );

C++11T exchange( T desired, std::memory_order order = std::memory_order_seq_cst ) volatile;

参数 (Parameters)desired - 用于分配值。

order - 用于强制执行内存顺序约束。

返回值 (Return Value)

它在调用之前返回原子变量的值。

异常 (Exceptions)

No-noexcept - 这个成员函数永远不会抛出异常。

例子 (Example)

在下面的示例中为std :: atomic :: exchange。#include

#include

#include

#include

std::atomic ready (false);

std::atomic winner (false);

void count1m (int id) {

while (!ready) {}

for (int i=0; i<1000000; ++i) {}

if (!winner.exchange(true)) { std::cout << "thread #" << id << " won!\n"; }

};

int main () {

std::vector<:thread> threads;

std::cout << "spawning 10 threads that count to 1 million...\n";

for (int i=1; i<=10; ++i) threads.push_back(std::thread(count1m,i));

ready = true;

for (auto& th : threads) th.join();

return 0;

}