c++ Channel 的实现

#include 
#include 
#include 
#include 
#include 
#include 

using namespace std;

class Cv_Guard {
private:
    condition_variable &con;
public:
    explicit Cv_Guard(condition_variable &con) : con(con) {}

    ~Cv_Guard() {
        con.notify_one();
    }
};


template<typename T>
class Channel {
private:
    static constexpr int CHANNEL_SIZE_DEFAULT = 1;
    static constexpr int MICRO_SLEEP_TIME = 1;

    mutex m;
    condition_variable q_not_empty;
    queue<unique_ptr<T>> q;
    const int capacity;
    atomic_flag done;

    [[nodiscard]] int size() const {
        return q.size();
    }

public:
    [[nodiscard]] bool isDone() const {
        return done.test();
    }

    void close() {
        done.test_and_set();
    }

    explicit Channel(const int capacity = CHANNEL_SIZE_DEFAULT) : capacity(capacity) {
        assert(capacity > 0);
    }

    friend Channel &operator<<(Channel &ch, unique_ptr<T> data) {
        unique_lock<mutex> lock(ch.m);
        Cv_Guard cvg(ch.q_not_empty);
        while (!ch.isDone() && ch.size() >= ch.capacity) {
            lock.unlock();
            this_thread::sleep_for(chrono::microseconds(MICRO_SLEEP_TIME));
            lock.lock();
        }
        if (ch.isDone()) {
            return ch;
        }
        ch.q.push(move(data));
        return ch;
    }

    friend Channel &operator>>(Channel &ch, unique_ptr<T> &data) {
        unique_lock<mutex> lock(ch.m);
        ch.q_not_empty.wait(lock, [&ch] {
            return !(ch.q.empty() && !ch.isDone());
        });
        if (ch.isDone()) {
            return ch;
        }
        data = std::move(ch.q.front());
        ch.q.pop();
        return ch;
    }
};


void consumer(Channel<int>& chx) {
    unique_ptr<int> data;
    while (!chx.isDone()) {
        chx >> data;
        cout << *data << endl;
    }
}

void producer(Channel<int>& chx) {
    int i = 0;
    while (!chx.isDone()) {
        chx << make_unique<int>(i++);
    }
}

int main() {
    Channel<int> chx(100);
    thread consu(consumer, ref(chx));
    thread pro(producer, ref(chx));
    this_thread::sleep_for(chrono::seconds(1));
    chx.close();
    pro.join();
    consu.join();
}