producer_and_consumer.cc

#include <cstdlib>
#include <unistd.h>
#include <iostream>
#include <mutex>
#include <thread>
#include <queue>
#include <condition_variable>

std::mutex m;
std::condition_variable cv1; //write
std::condition_variable cv2; //read
std::queue<int> q;
const size_t kMaxSize = 10;

void producer(int id) {
  while (1) {
    usleep(10 * 1000);
    std::unique_lock<std::mutex> lk(m);
    if (q.size() < kMaxSize) {
      int num= std::rand();
      q.push(num);
      printf("[producer:%d] (size:%d) num:%d\n", id, q.size(), num);
      cv2.notify_all();
    } else {
      cv2.notify_all();
      cv1.wait(lk, [] { return q.size() < kMaxSize; });
    }
  }
}

void consumer(int id) {
  while (1) {
    usleep(10 * 1000);
    std::unique_lock<std::mutex> lk(m);
    if (!q.empty()) {
      int num = q.front();
      q.pop();
      printf("[consumer:%d] (size:%d) num:%d\n", id, q.size(), num);
      cv1.notify_all();
    } else {
      cv1.notify_all();
      cv2.wait(lk, [] { return !q.empty(); });
    }
  }
}

int main(int argc, const char* argv[]) {
  std::srand(std::time(nullptr));
  for (int i = 0; i < kMaxSize; i += 2) {
    std::thread t1(producer, i);
    std::thread t2(consumer, i + 1);
    t1.detach();
    t2.detach();
  }

  while(1);
  return 0;
}