#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <pthread.h>
#include <semaphore.h>

sem_t semProducer;
sem_t semCustomer;

typedef struct node  //节点结构
{
    int data;
    struct node* next;
} Node;

Node* g_head =  nullptr;  //永远指向链表头部的指针

void* funProducer(void* arg);  //生产者--添加一个头结点
void* funCustomer(void* arg);  //消费者--删除一个头结点

int main(int argc, char *argv[])
{
    pthread_t p1;
    pthread_t p2;

    sem_init(&semProducer, 0, 4);  //初始化生产者线程信号量， （赋予 4 个，对比下一行，让生产者先运行）
    sem_init(&semCustomer, 0, 0);  //初始化消费者线程信号量， (赋予 0 个， 一开始就让消费者处于阻塞状态)

    pthread_create(&p1, nullptr, funProducer, nullptr);  //创建生产者线程
    pthread_create(&p2, nullptr, funCustomer, nullptr);  //创建消费者线程

    pthread_join(p1, nullptr);  //阻塞回收子线程
    pthread_join(p2, nullptr);

    sem_destroy(&semProducer);  //销毁生产者信号量
    sem_destroy(&semCustomer);  //销毁消费者信号量

    return 0;
}

void* funProducer(void* arg)
{
    while (true) {
        sem_wait(&semProducer);  //semProducer--，  == 0， 则阻塞
        Node* pNew = new Node();
        pNew->data = rand() % 1000; 
        pNew->next = g_head;
        g_head = pNew;
        printf("-----funProducer(生产者): %lu, %d\n", pthread_self(), pNew->data);
        sem_post(&semCustomer); // semCustomer++

        sleep(rand() % 3);  //随机休息 0~2 s
    }
    
    return nullptr;
}

void* funCustomer(void* arg)
{
    while (true) {
        sem_wait(&semCustomer);  //semCustomer--，  == 0， 则阻塞
        Node* pDel = g_head;
        g_head = g_head->next;
        printf("-----funCustomer(消费者): %lu, %d\n", pthread_self(), pDel->data);
        delete pDel;
        sem_post(&semProducer); // semProducer++
    }

    return nullptr;
}