生产者消费者问题C语言代码

以下是一个简单的生产者消费者问题的C语言代码，使用信号量来同步生产者和消费者的操作：

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

#define BUFFER_SIZE 5 // 缓冲区大小
#define PRODUCER_NUM 3 // 生产者数量
#define CONSUMER_NUM 2 // 消费者数量
#define ITEM_NUM 10    // 每个生产者/消费者要生产/消费的物品数量

int buffer[BUFFER_SIZE];  // 缓冲区
int in = 0, out = 0;      // 缓冲区的输入和输出指针
sem_t empty, full, mutex; // 信号量

void *producer(void *arg) {
    int id = *((int *)arg);
    for (int i = 0; i < ITEM_NUM; i++) {
        // 生产一个物品
        int item = rand() % 1000;

        // 等待空缓冲区
        sem_wait(&empty);
        sem_wait(&mutex);

        // 将物品放入缓冲区
        buffer[in] = item;
        printf("Producer %d: produce item %d at buffer[%d]\n", id, item, in);
        in = (in + 1) % BUFFER_SIZE;

        sem_post(&mutex);
        sem_post(&full);
    }
    return NULL;
}

void *consumer(void *arg) {
    int id = *((int *)arg);
    for (int i = 0; i < ITEM_NUM; i++) {
        // 等待满缓冲区
        sem_wait(&full);
        sem_wait(&mutex);

        // 取出一个物品
        int item = buffer[out];
        printf("Consumer %d: consume item %d at buffer[%d]\n", id, item, out);
        out = (out + 1) % BUFFER_SIZE;

        sem_post(&mutex);
        sem_post(&empty);

        // 消耗物品
        sleep(1);
    }
    return NULL;
}

int main() {
    // 初始化信号量
    sem_init(&empty, 0, BUFFER_SIZE);
    sem_init(&full, 0, 0);
    sem_init(&mutex, 0, 1);

    // 创建生产者线程
    pthread_t producers[PRODUCER_NUM];
    int producer_ids[PRODUCER_NUM];
    for (int i = 0; i < PRODUCER_NUM; i++) {
        producer_ids[i] = i;
        pthread_create(&producers[i], NULL, producer, &producer_ids[i]);
    }

    // 创建消费者线程
    pthread_t consumers[CONSUMER_NUM];
    int consumer_ids[CONSUMER_NUM];
    for (int i = 0; i < CONSUMER_NUM; i++) {
        consumer_ids[i] = i;
        pthread_create(&consumers[i], NULL, consumer, &consumer_ids[i]);
    }

    // 等待线程结束
    for (int i = 0; i < PRODUCER_NUM; i++) {
        pthread_join(producers[i], NULL);
    }
    for (int i = 0; i < CONSUMER_NUM; i++) {
        pthread_join(consumers[i], NULL);
    }

    // 销毁信号量
    sem_destroy(&empty);
    sem_destroy(&full);
    sem_destroy(&mutex);

    return 0;
}

在这个代码中，生产者线程和消费者线程都会不断地生产和消费物品，直到达到指定数量。它们通过信号量来同步操作，当缓冲区为空时，消费者线程会等待信号量`full`，而生产者线程会等待信号量`empty`。当缓冲区达到满时，生产者线程会等待信号量`full`，而消费者线程会等待信号量`empty`。同时，它们还需要获取互斥量`mutex`来保证缓冲区的读写操作不会冲突。