semaphore in c++

[Jessii]

Hi,

in der stl gibt es keine semaphore. braucht man sie nicht...
wie kann man sagen, das z.b. nur x writers gleichzeitig an einem problem arbeiten? kann ich mir dafuer eine semaphore bauen, thread pool, packaged tasks?

das beispiel hier ist nur ein test hier...

#include <iostream>
#include <vector>
#include <mutex>
#include <condition_variable>
#include <thread>
using namespace std;

class Semaphore {
public:
    int counter_;
    std::mutex m_;
    std::condition_variable cv_;

    Semaphore(int init): counter_(init) {}

    void aquire() {
        std::unique_lock<std::mutex> l(m_);

        // wait if counter_ == 0
        cv_.wait(l, [this]() { return counter_ != 0; });

        counter_--;
    }

    void release() {
        std::unique_lock<std::mutex> l(m_);

        counter_++;

        cv_.notify_one();
    }
};

class Writer {
public:
    Semaphore s;

    Writer(): s(2) {} // 2 writers at a time, not very usefule for std::cout ... but just to test...

    void write() {
        for (int i = 0; i < 100; i++) {
            s.aquire();

            cout << "hello world " << i << '\n';

            s.release();
        }
    }
};

int main() {
  // your code goes here

  Writer w;
  std::vector<std::thread> worker;

  for (int i = 0; i < 10; i++) {
    worker.push_back(std::thread(&Writer::write, &w));
  }

  for (auto &e: worker) {
    e.join(); 
  }

  return 0;
}