#include <future>
#include <cassert>
typedef std::chrono::milliseconds ms;
void func1(std::promise<int> p)
{
std::this_thread::sleep_for(ms(500));
p.set_value(3);
}
int j = 0;
void func3(std::promise<int&> p)
{
std::this_thread::sleep_for(ms(500));
j = 5;
p.set_value(j);
}
void func5(std::promise<void> p)
{
std::this_thread::sleep_for(ms(500));
p.set_value();
}
int main()
{
typedef std::chrono::high_resolution_clock Clock;
{
typedef int T;
std::promise<T> p;
std::future<T> f = p.get_future();
std::thread(func1, std::move(p)).detach();
assert(f.valid());
assert(f.wait_for(ms(300)) == std::future_status::timeout);
assert(f.valid());
assert(f.wait_for(ms(300)) == std::future_status::ready);
assert(f.valid());
Clock::time_point t0 = Clock::now();
f.wait();
Clock::time_point t1 = Clock::now();
assert(f.valid());
assert(t1-t0 < ms(5));
}
{
typedef int& T;
std::promise<T> p;
std::future<T> f = p.get_future();
std::thread(func3, std::move(p)).detach();
assert(f.valid());
assert(f.wait_for(ms(300)) == std::future_status::timeout);
assert(f.valid());
assert(f.wait_for(ms(300)) == std::future_status::ready);
assert(f.valid());
Clock::time_point t0 = Clock::now();
f.wait();
Clock::time_point t1 = Clock::now();
assert(f.valid());
assert(t1-t0 < ms(5));
}
{
typedef void T;
std::promise<T> p;
std::future<T> f = p.get_future();
std::thread(func5, std::move(p)).detach();
assert(f.valid());
assert(f.wait_for(ms(300)) == std::future_status::timeout);
assert(f.valid());
assert(f.wait_for(ms(300)) == std::future_status::ready);
assert(f.valid());
Clock::time_point t0 = Clock::now();
f.wait();
Clock::time_point t1 = Clock::now();
assert(f.valid());
assert(t1-t0 < ms(5));
}
}