两生产者一消费者问题c代码

下面是经典的两生产者一消费者问题的C语言代码实现：

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

#define BUFFER_SIZE 10
#define PRODUCER_NUM 2
#define CONSUMER_NUM 1
#define ITEM_NUM 20

int buffer[BUFFER_SIZE];
int count = 0;
int in = 0, out = 0;

pthread_mutex_t lock = PTHREAD_MUTEX_INITIALIZER;
pthread_cond_t not_full = PTHREAD_COND_INITIALIZER;
pthread_cond_t not_empty = PTHREAD_COND_INITIALIZER;

void *producer(void *arg)
{
    int id = *(int *)arg;
    int item;
    for (int i = 0; i < ITEM_NUM; i++) {
        item = rand() % 1000;
        pthread_mutex_lock(&lock);
        while (count == BUFFER_SIZE) {
            printf("Producer %d is waiting because buffer is full.\n", id);
            pthread_cond_wait(&not_full, &lock);
        }
        buffer[in] = item;
        printf("Producer %d produces item %d at position %d.\n", id, item, in);
        in = (in + 1) % BUFFER_SIZE;
        count++;
        pthread_cond_signal(&not_empty);
        pthread_mutex_unlock(&lock);
    }
    pthread_exit(NULL);
}

void *consumer(void *arg)
{
    int id = *(int *)arg;
    int item;
    for (int i = 0; i < ITEM_NUM; i++) {
        pthread_mutex_lock(&lock);
        while (count == 0) {
            printf("Consumer %d is waiting because buffer is empty.\n", id);
            pthread_cond_wait(&not_empty, &lock);
        }
        item = buffer[out];
        printf("Consumer %d consumes item %d at position %d.\n", id, item, out);
        out = (out + 1) % BUFFER_SIZE;
        count--;
        pthread_cond_signal(&not_full);
        pthread_mutex_unlock(&lock);
    }
    pthread_exit(NULL);
}

int main()
{
    pthread_t producers[PRODUCER_NUM], consumer_threads[CONSUMER_NUM];
    int producer_ids[PRODUCER_NUM], consumer_ids[CONSUMER_NUM];

    for (int i = 0; i < PRODUCER_NUM; i++) {
        producer_ids[i] = i;
        pthread_create(&producers[i], NULL, producer, &producer_ids[i]);
    }
    for (int i = 0; i < CONSUMER_NUM; i++) {
        consumer_ids[i] = i;
        pthread_create(&consumer_threads[i], NULL, consumer, &consumer_ids[i]);
    }

    for (int i = 0; i < PRODUCER_NUM; i++) {
        pthread_join(producers[i], NULL);
    }
    for (int i = 0; i < CONSUMER_NUM; i++) {
        pthread_join(consumer_threads[i], NULL);
    }

    return 0;
}

在程序中，我们定义了一个大小为10的缓冲区`buffer`，并使用一个计数器`count`来记录缓冲区中剩余的数据项数目。两个指针`in`和`out`分别用于指示下一个可写入数据的位置和下一个可读取数据的位置。

我们使用两个条件变量`not_full`和`not_empty`分别表示缓冲区不满和不空。当缓冲区已满时，生产者会进入等待状态，等待消费者信号通知可以继续生产。当缓冲区为空时，消费者会进入等待状态，等待生产者信号通知可以继续消费。

在主函数中，我们创建了两个生产者线程和一个消费者线程，并使用`pthread_create`函数启动线程。在所有线程结束之后，我们使用`pthread_join`函数等待线程结束并释放资源。

以上就是两生产者一消费者问题的C语言代码实现。