消息队列函数

Posted 2020-09-22 一生不过烟花

1.消息队列结构体的定义

typedef struct{
        uid_t   uid;   /* owner`s user id */
        gid_t   gid;    /* owner`s group id */
        udi_t   cuid;   /* creator`s user id */
        gid_t   cgid;   /* creator`s group id */
        mode_t  mode;   /* read-write permissions 0400 MSG_R 0200 MSG_W*/
        ulong_t seq;    /* slot usage sequence number*/
}ipc_perm;

typedef stuct{
        struct ipc_perm msg_perm;      /* read_write perms */
        struct msg      *msg_first;     /* ptr to first message on queue */
        struct msg      *msg_last;      /* ptr to last message on queue */
        msglen_t         msg_cbytes;     /* used bytes current on queue */
        msgqnum_t       msg_qnum;       /* current num of message on queue */
        msglen_t        msg_qbytes;     /* max # of bytes allowed on queue */
        pid_t                msg_lspid;      /* pid of last msgsnd() */
        pid_t                msg_lrpid;      /* pid of last msgrcv() */
        time_t              msg_stime;      /* time of last msgsnd() */
        time_t              msg_rtime;      /* time of last msgrcv() */
        time_t              msg_ctime;      /* time of last msgctl() */
}msqid_ds;

typedef struct
{
        long mtype;
        char mbuf[MSGLEN];
}Message;

2.创建消息队列：

      /***************************************************
Function:
        int msgget(ket_t key,int oflag);
Explain:
        create or view a message queue
Return  :
        a int indetify
Include:
        sys/msg.h
introduction:
        oflag: 0400 msg_r  
               0200 msg_w
               0600 msg_wr
        ipc_creat: NO exist and then creat a queue
                   exist : reference a queue
        ipc_creat|ipc_excl: NO exist and then creat a queue
                            exist : return error
****************************************************/
#include<stdio.h>
#include<sys/msg.h>
#include<stdlib.h>

int MsgGet(int key)
{
        int ret;
        ret=msgget(key,0600|IPC_CREAT);
//      ret=msgget(key,0600|IPC_CREAT|IPC_EXCL);
        if(ret<0)
                perror("creat msgid error");
        printf("msgid=%d/n",ret);
        system("ipcs -q -i ret");
        return ret;
}
int main(int argc,char *agrv[])
{
        int key;
        printf("pleasse input msgkey:");
        scanf("%d",&key);
        MsgGet(key);
        return 0;
}

3.向消息队列中发送消息msgsnd

/***********************************************************************************
Function:
        int msgsnd(int msqid,const void *ptr,size_t length,int flag)
Explain:
        send a message to a queue
Return:
        len: send message len;
Include:
        sys/msg.h
Introduction:
        flag: 0 : if queue full  wait:1>具备存放新消息的空间
                                      2>由msqid标识的消息队列从系统中删除(返回EIDRM错误)
                                      3>调用线程被某个捕获的信号所中断(返回EINTR错误)
              IPC_NOWAIT:如果没有存放新消息的空间,函数马上返回
                                      1>指定的队列中有太多的字节
                                      2>在系统范围存在太多的消息
*****************************************************************************************/
#include "typemsg.h"
int MsgSnd(int msqid,char *buf,int len,int flag)
{
        int ret;
        ret=msgsnd(msqid,buf,len,flag);
        if(ret<0)
                perror("msgsnd error");
        system("ipcs -q");
        return ret;
}

int main()
{
        int msqid,len,stype;
        Message msgb;
        memset(&msgb,0,sizeof(Message));
        printf("msgsnd:please input msqid:");
        scanf("%d",&msqid);
        printf("please input msgtype:");
        scanf("%d",&stype);
        msgb.mtype=stype;
        strcpy(msgb.mbuf,"zhangweia");
        MsgSnd(msqid,(char *)&msgb,sizeof(Message),0);
        return 0;
}

4.从队列中获取消息 msgrcv

/*********************************************************************
Function:
        int msgrcv(int msqid,const void *ptr,size_t msglen,long type,int flag)
Explain:
        recv message order by type 
        msgrcv error: Argument list too long  --> msglen的长度小于消息体中消息的长度
Para  :
        ptr:  point to message struct 
        msglen: 由ptr指向的缓冲区中数据部分的大小,这个是该函数能够返回的最大数据量
        type: message type;

                           1> 0:返回队列中最早的消息
                           2> 大于0:返回消息队列中类型为type的第一个消息
                           3> 小于0:返回消息队列中类型小于或者等于type的绝对值的消息类型中最小的第一个消息
        flag: 0<wait> 没有消息或者消息类型不符合的时候,线程等待
                  响应: 1>有一个所请求类型的消息可以获取
                        2>msqid的消息队列被系统删除,返回一个EIDRM
                        3>调用线程被某个捕获的信号所中断
              IPC_NOWAIT:在没有数据的情况下,立即返回一个ENOMSG错误
              MSGNOERROR:当所接受的消息数据部分大于msglen长度时,获取截短的数据部分,否则返回E2BIG错误
Return:
        message len
*********************************************************************/
#include "typemsg.h"
int MsgRcv(int msqid,char *buf,int msglen,long type,int flag)
{
        int ret;
        ret=msgrcv(msqid,buf,msglen,type,flag);
        if(ret<0)
        perror("msgrcv error");
        system("ipcs -q");
        return ret;

}

int main()
{
        int msqid,len;
        long ttype;
        Message mbuf;
        printf("msgrcv:please input recv msqid:");
        scanf("%d",&msqid);
        MsgRcv(msqid,(char *)&mbuf,8900,0,IPC_NOWAIT);
        printf("recv message=%s/n",mbuf.mbuf);
        Put_String((unsigned char *)&mbuf,sizeof(Message));
        return 0;
}

6.消息队列的控制msgctl

/**********************************************************
Function:
        int msgctl(int msqid,int cmd,struct msqid_ds *buff)
Explain:
        cdm: IPC_RMID; delete msqid 
             IPC_SET:  
             IPC_STAT:  return msqid stat

*********************************************************/
#include "typemsg.h"
int MsgCtl(int msqid,int cmd,struct msqid_ds *buff)
{
        int ret;
        ret=msgctl(msqid,cmd,buff);
        if(ret<0)
        {
                perror("msgctl error");
                return -1;
        }
        return 0;
}

int main()
{
        int msqid,type;
        struct msqid_ds info;
        printf("please input msqid /nand type(1:icp_rmid;2:ipc_stat)");
        scanf("%d%d",&msqid,&type);
        if(type==1)
        {
                MsgCtl(msqid,IPC_RMID,NULL);
                printf("delete queue success:%d/n",msqid);
        }else if(type==2)
        {
                MsgCtl(msqid,IPC_STAT,&info);
                printf("get queue stat:%d/n",msqid);
        }
        return 0;

}