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

pthread_cond_t pcond;
pthread_cond_t ccond;
pthread_mutex_t mutex;

struct Node{
    int num;
    struct Node* next;
};
struct Node* head = NULL;
int cnt = 0;

void* producer(void* arg);
void* consumer(void* arg);

int main(int argc, char const *argv[])
{
    pthread_cond_init(&pcond, NULL);
    pthread_cond_init(&ccond, NULL);
    pthread_mutex_init(&mutex, NULL);

    pthread_t t1[5], t2[5];

    for (size_t i = 0; i < 5; i++)
    {
        pthread_create(&t1[i], NULL, producer, NULL);
    }

    for (size_t i = 0; i < 5; i++)
    {
        pthread_create(&t2[i], NULL, consumer, NULL);
    }

    for (size_t i = 0; i < 5; i++)
    {
        pthread_join(t1[i], NULL);
        pthread_join(t2[i], NULL);
    }

    pthread_cond_destroy(&pcond);
    pthread_cond_destroy(&ccond);
    pthread_mutex_destroy(&mutex);

    return 0;
}

void* producer(void* arg){
    while(1){
        pthread_mutex_lock(&mutex);
        while(cnt > 20){
            pthread_cond_wait(&pcond, &mutex);
        }
        struct Node* newNode = (struct Node*)malloc(sizeof(struct Node));
        //newNode->num = rand() % 1000;
        newNode->num = cnt++;
        newNode->next = head;
        head = newNode;
        printf("生产者 - id: %lu  num: %d\n", pthread_self(), newNode->num);
        pthread_mutex_unlock(&mutex);
        pthread_cond_signal(&ccond);
        sleep(rand()%3);
    }

    return NULL;
}

void* consumer(void* arg){
    while(1){
        pthread_mutex_lock(&mutex);
        // 这里最好不要用if判断，可能出现并发处理问题，因为被唤醒的线程都会在pthread_cond_wait处等待唤醒，如果是if条件，在唤醒出继续往下执行时可能遇到head又为空的情况
        // 需要用while循环再判断一次head是否为空，如果为空，pthread_cond_wait将继续阻塞线程
        while(head == NULL){
            pthread_cond_wait(&ccond, &mutex);
        }
        struct Node* node = head;
        printf("\t\t消费者 -  id: %lu  num: %d\n", pthread_self(), node->num);
        head = head->next;
        free(node);
        cnt--;
        pthread_mutex_unlock(&mutex);
        pthread_cond_signal(&pcond);
        sleep(rand()%6);
    }
    
    return NULL;
}