linux下生产者与消费者C实现

最近做毕设涉及到了生产者与消费者模型，这个东东只在操作系统课程上有点印象，于是花了点时间看了下《unix环境高级编程 》的线程部分，在此记录一下。

1.多线程的概念就不多说了，pthread.h头文件中包含的几个基本概念及函数：

• pthread_t————线程ID数据类型，线程ID只在它所属的进程环境中有效;

• int pthread_create(pthread_t *tidp, const pthread_attr_t *attr, func(void), arg)————创建新的线程，若成功返回0设置tidp指向的单元为新线程的线程IDattr用来设置线程属性，一般默认为NULLfunc为新线程调用的入口函数，该函数只能有一个无类型指针参数arg，若要向函数传递多个参数，需要将所有参数放到一个结构中，再把结构地址传递给arg

• pthread_t pthread_self(void)————获取自身线程ID

• void pthread_exit(void *rval_ptr)———终止本线程，用rval_ptr指向的值作为退出码

• int pthread_join(pthread_t thread, void **rval_ptr)————调用该函数的线程将阻塞，直到thread线程调用pthread_exit、从启动例程返回或被取消，rval_ptr将包含返回码

• int pthread_cancel(pthread_t tid)————该函数用来请求取消统一进程中的其他线程

 

2.线程同步————互斥量、读写锁，条件变量

    ​读写锁即共享——独占锁，适合于读的次数远大于写的情况，比较好理解，就不多说了。

　 条件变量由互斥量保护，线程在改变条件状态之前必须先锁定互斥量。

    ​生产者与消费者模型用到了互斥量和条件变量，对队列进行读写，下面直接上代码:

• 队列操作(数据结构的内容)，采用链式结构：

#include <stdio.h>
#include <stdlib.h>
#include <stdbool.h>
#include <string.h>
#include <time.h>
#include <unistd.h>
#include <pthread.h>

#define MAXLENGTH 10    //the maxlength of queue

typedef char * datatype;
typedef struct node {    //define node
    datatype name;
    struct node *next;
} node;
typedef struct queue {    //define queue
    node *front, *rear;
    int len;
} queue;

void queue_init(queue *q)
{
    q->front = q->rear = NULL;
    q->len = 0;
}

void  queue_put(queue *q, datatype new_name)　　//入队
{
    node *mynode = (node *)malloc(sizeof(node));
    mynode->name = new_name;
    mynode->next = NULL;
    if (q->rear)
        q->rear->next = mynode;
    q->rear = mynode;
    if (q->front == NULL)
        q->front = mynode;
    q->len++;
}

datatype queue_get(queue *q)　　　//出队
{
    node *mynode;
    datatype myname;
    if (q->front != NULL)
        mynode = q->front;
    myname = mynode->name;
    q->front = q->front->next;
    q->len--;
    free(mynode);
    return myname;
}

void queue_print(queue *q)　　//print queue
{
    node *tmp = q->front;
    while(tmp != NULL)
    {
        printf("%s ", tmp->name);
        tmp = tmp->next;
    }
    printf("
");
}

• 生产者与消费者函数：

/*define mutex and condtion var*/
pthread_cond_t q_not_full = PTHREAD_COND_INITIALIZER;
pthread_cond_t q_not_empty = PTHREAD_COND_INITIALIZER;
pthread_mutex_t qlock = PTHREAD_MUTEX_INITIALIZER;

/*
 * producer function
 */
void producer(void *q)
{
//    printf("start porducer:
");
    queue *qt = q;    //传入的队列
    while(1)
    {
        pthread_mutex_lock(&qlock);
//        printf("producer has locked the qlock
");
        while(qt->len >= MAXLENGTH)    //queue is full
        {
//            printf("producer is going to waiting
");
            pthread_cond_wait(&q_not_full, &qlock);
        }
        queue_put(qt, "* ");
//        printf("after producer: queue's length is %d
", qt->len);
        pthread_mutex_unlock(&qlock);
        pthread_cond_signal(&q_not_empty);

//        printf("producer has unlocked the qlock
");
//        sleep(1);
    }
}

/*
 * consumer function
 */
void consumer(void *q)
{
//    printf("start consumer:
");
    queue *qt = q;
    while(1)
    {
        pthread_mutex_lock(&qlock);
//        printf("consumer has locked the qlock
");
        while(qt->len <= 0)    //queue is empty
        {
//            printf("consumer is going to waiting
");
            pthread_cond_wait(&q_not_empty, &qlock);
        }
        datatype back_name = queue_get(qt);
//        printf("after consumer, queue's length is %d
", qt->len);
        pthread_mutex_unlock(&qlock);
        pthread_cond_signal(&q_not_full);
//        now process the back_name
//        printf("cousumer has unlocked the qlock
");
//        sleep(1);
    }
}

• 主函数(测试):

//gcc编译时加上-lpthread
int main() {
    pthread_t tid1, tid2;
    queue *q=(queue *)malloc(sizeof(queue));
    queue_init(q);
//    queue_put(q, "one");
//    queue_put(q, "two");
//    queue_put(q, "three");
//    queue_get(q);
//    printf("len = %d
", q->len);
//    queue_print(q);

    long stime = clock();
    long etime = clock();

    pthread_create(&tid1, NULL, (void *)producer, (void *)q);
    pthread_create(&tid2, NULL, (void *)consumer, (void *)q);

    while((float)(etime-stime)/CLOCKS_PER_SEC < 0.00001)
    {
        etime = clock();
    }
    return 0;
}

 参考：《unix环境高级编程》