#include <condition_variable>
#include <mutex>
#include <queue>
#include <thread>

bool
more_data_to_prepare()
{
  return false;
}

struct data_chunk {
};

data_chunk
prepare_data()
{
  return data_chunk();
}

void
process(data_chunk&)
{
}

bool
is_last_chunk(data_chunk&)
{
  return true;
}

std::mutex mut;
std::queue<data_chunk> data_queue;
std::condition_variable data_cond;

void
data_preparation_thread()
{
  while (more_data_to_prepare()) {
    data_chunk const data = prepare_data();
    std::lock_guard<std::mutex> lk(mut);
    data_queue.push(data);
    data_cond.notify_one();
  }
}

void
data_processing_thread()
{
  while (true) {
    std::unique_lock<std::mutex> lk(mut);
    data_cond.wait(lk, [] { return !data_queue.empty(); });
    data_chunk data = data_queue.front();
    data_queue.pop();
    lk.unlock();
    process(data);
    if (is_last_chunk(data))
      break;
  }
}

int
main()
{
  std::thread t1(data_preparation_thread);
  std::thread t2(data_processing_thread);

  t1.join();
  t2.join();
}