C++ sleep for undetermined amount of time - c++

Question

In my code I want my system to sleep, until a condition has been met. An after having searched i have found #include <unistd.h>, but to me it just looks like it sleeps until the time frame has been met. I was wondering if there was a easy way to make the program wait until the condition has been reached.
Here you have a sample of the code to clarify my point
bool check() {
while (condition) {
sleep.here();
} else {
run.the.rest();
}
}

Answer 1

Based on your incomplete pseudo-code and description, here is a class contidion_t, where you can set your condition via set_condition, and a thread blocking in loop will wake up, every time you set it.
#include <iostream>
#include <thread>
#include <mutex>
#include <condition_variable>
#include <atomic>
struct condition_t {
public:
template <typename T>
void loop(T the_rest) {
while(running) {
std::unique_lock<std::mutex> lock_guard(m);
cv.wait(lock_guard, [this] { return ready.load(); });
the_rest();
ready = false;
}
}
void set_condition(bool value) {
ready = value;
if (value) {
cv.notify_one();
}
}
void stop_running() {
running = false;
ready = true;
cv.notify_all();
}
~condition_t () {stop_running();}
private:
std::mutex m;
std::condition_variable cv;
std::atomic<bool> ready{false};
std::atomic<bool> running{true};
};
int main() {
condition_t condition;
std::thread thread(&condition_t::loop<void (void)>, &condition, [] () {
std::cout << "Doing the rest" << std::endl;
});
std::cout << "Thread created but waits\nInput something for continue:";
int something;
std::cin >> something;
std::cout << "Continueing\n";
condition.set_condition(true);
std::cout << "Input something to stop running:";
std::cin >> something;
condition.stop_running();
thread.join();
}