I. Overview
Async can start a thread (not guaranteed) to process logic, async call regrets returning a future, through the future can be used to wait for processing to complete or view the processing progress.
Two, the code
#pragma once
#include <future>
#include <chrono>
using namespace std;
class AsyncTest
{
private:
int count = 0;
int maxLoop = 2000000000;
public:
int process()
{
count = 0;
for (int i = 0; i < maxLoop; i++)
{
count++;
}
return count;
}
void doTest()
{
std::future<int> f1 = std::async([this]() {
return this->process(); });
int count1 = f1.get();
printf("count1=%d\n", count1);
std::future<int> f2 = std::async([this]() {
return this->process(); });
std::chrono::milliseconds span(1000);
while (f2.wait_for(span) != std::future_status::ready)
{
printf("count2=%d\n", count);
}
printf("count2=%d\n", count);
std::future<int> f3 = std::async([this]() {
return this->process(); });
while (f3.wait_until(chrono::system_clock::now() + span) != std::future_status::ready)
{
printf("count3=%d\n", count);
}
printf("count3=%d\n", count);
std::future<int> f4 = std::async([this]() {
return this->process(); });
f4.wait();
int count = f4.get();
printf("count4=%d\n", count);
}
};
Three, output
count1=2000000000
count2=717548276
count2=1417833895
count2=2000000000
count3=656570861
count3=1306866886
count3=1964142483
count3=2000000000
count4=2000000000