linux进程间通信（posix消息队列）实例

/*
*
*       Filename:  producer.c
*
*    Description:  生产者进程
*
*        Version:  1.0
*        Created:  09/30/2011 04:52:23 PM
*       Revision:  none
*       Compiler:  gcc(g++)
*
*         Author:  |Zhenghe Zhang|, |zhenghe.zhang@gmail.com|
*        Company:  |Shenzhen XXX Technology Co., Ltd.|
*
*/

#include <stdio.h>
#include <mqueue.h>
#include <sys/stat.h>
#include <stdlib.h>
#include <unistd.h>
#include <time.h>
#include <string.h>

#define MAXSIZE     10   //定义buf大小
#define BUFFER      8192 //定义Msg大小

struct MsgType{
int len;
char buf[MAXSIZE];
char x;
short y;
};

int main()
{
/*消息队列*/
mqd_t msgq_id;
struct MsgType msg;

unsigned int prio = 1;
unsigned int send_size = BUFFER;

struct mq_attr msgq_attr;
const char *file = "/posix";

/*mq_open() for creating a new queue (using default attributes) */
/*mq_open() 创建一个新的 POSIX 消息队列或打开一个存在的队列*/
msgq_id = mq_open(file, O_RDWR | O_CREAT, S_IRWXU | S_IRWXG, NULL);
if(msgq_id == (mqd_t)-1)
{
perror("mq_open");
exit(1);
}

/* getting the attributes from the queue        --  mq_getattr() */
if(mq_getattr(msgq_id, &msgq_attr) == -1)
{
perror("mq_getattr");
exit(1);
}

printf("Queue \"%s\":\n\t- stores at most %ld messages\n\t- \
large at most %ld bytes each\n\t- currently holds %ld messages\n",
file, msgq_attr.mq_maxmsg, msgq_attr.mq_msgsize, msgq_attr.mq_curmsgs);

/*setting the attributes of the queue        --  mq_setattr() */
/*mq_setattr() 设置消息队列的属性，设置时使用由 newattr 指针指向的 mq_attr 结构的信息。*/
/*属性中只有标志 mq_flasgs 里的 O_NONBLOCK 标志可以更改，其它在 newattr 内的域都被忽略 */
if(mq_setattr(msgq_id, &msgq_attr, NULL) == -1)
{
perror("mq_setattr");
exit(1);
}

int i = 0;
while(i < 10)
{
msg.len = i;
memset(msg.buf, 0, MAXSIZE);
sprintf(msg.buf, "0x%x", i);
msg.x = (char)(i + 'a');
msg.y = (short)(i + 100);

printf("msg.len = %d, msg.buf = %s, msg.x = %c, msg.y = %d\n", msg.len, msg.buf, msg.x, msg.y);

/*sending the message      --  mq_send() */
/*mq_send() 把 msg_ptr 指向的消息加入由 mqdes 引用的消息队列里。*/
/*参数 msg_len 指定消息 msg_ptr 的长度：这个长度必须小于或等于队列 mq_msgsize 属性的值。零长度的消息是允许。*/
if(mq_send(msgq_id, (char*)&msg, sizeof(struct MsgType), prio) == -1)
{
perror("mq_send");
exit(1);
}

i++;
sleep(1);
}

sleep(30); //等待消费者进程退出

/*closing the queue        -- mq_close() */
/*mq_close() 关闭消息队列描述符 mqdes。如果调用进程在消息队列 mqdes 绑定了通知请求，*/
/*那么这个请求被删除，此后其它进程就可以绑定通知请求到此消息队列。*/
if(mq_close(msgq_id) == -1)
{
perror("mq_close");
exit(1);
}

/*mq_unlink() 删除名为 name 的消息队列。消息队列名将被直接删除。*/
/*消息队列本身在所有引用这个队列的描述符被关闭时销毁。*/
if(mq_unlink(file) == -1)
{
perror("mq_unlink");
exit(1);
}

return 0;
}

/*
*
*       Filename:  consumer.c
*
*    Description:  消费者进程
*
*        Version:  1.0
*        Created:  09/30/2011 04:52:23 PM
*       Revision:  none
*       Compiler:  gcc(g++)
*
*         Author:  |Zhenghe Zhang|, |zhenghe.zhang@gmail.com|
*        Company:  |Shenzhen XXX Technology Co., Ltd.|
*
*/

#include <stdio.h>
#include <mqueue.h>
#include <sys/stat.h>
#include <stdlib.h>
#include <unistd.h>
#include <time.h>
#include <string.h>

#define MAXSIZE     10   //定义buf大小
#define BUFFER      8192 //定义Msg大小

struct MsgType{
int len;
char buf[MAXSIZE];
char x;
short y;
};

int main()
{
/*消息队列*/
mqd_t msgq_id;
struct MsgType msg;

unsigned int sender;
struct mq_attr msgq_attr;

unsigned int recv_size = BUFFER;
const char *file = "/posix";

/* mq_open() for opening an existing queue */
msgq_id = mq_open(file, O_RDWR);
if(msgq_id == (mqd_t)-1)
{
perror("mq_open");
exit(1);
}

/* getting the attributes from the queue        --  mq_getattr() */
if(mq_getattr(msgq_id, &msgq_attr) == -1)
{
perror("mq_getattr");
exit(1);
}

printf("Queue \"%s\":\n\t- stores at most %ld messages\n\t- \
large at most %ld bytes each\n\t- currently holds %ld messages\n",
file, msgq_attr.mq_maxmsg, msgq_attr.mq_msgsize, msgq_attr.mq_curmsgs);

if(recv_size < msgq_attr.mq_msgsize)
recv_size = msgq_attr.mq_msgsize;

int i = 0;
while(i < 10) //运行一个consumenr，为 10 ，同时运行两个consumer进程，为 5
{
msg.len = -1;
memset(msg.buf, 0, MAXSIZE);
msg.x = ' ';
msg.y = -1;

/* getting a message */

/*mq_receive() 从由描述符 mqdes 引用的队列时删除优先级最高的最老的消息，并把放置到 msg_ptr 的缓存区内。*/
/*参数 msg_len 指定缓冲区 msg_ptr 的大小：它必须大于队列的 mq_msgsize 属性(参数 mq_getattr)。*/
/*如果 prio 不是 NULL，那么它指向的内存用于返回收到消息相关的优先级。*/
if (mq_receive(msgq_id, (char*)&msg, recv_size, &sender) == -1)
{
perror("mq_receive");
exit(1);
}

printf("msg.len = %d, msg.buf = %s, msg.x = %c, msg.y = %d\n", msg.len, msg.buf, msg.x, msg.y);

i++;
sleep(2);
}

if(mq_close(msgq_id) == -1)
{
perror("mq_close");
exit(1);
}

return 0;
}