Linux消息队列实践(2)

#include <sys/types.h>
#include <sys/ipc.h>
#include <sys/msg.h>
　　int msgget(key_t key, int msgflg);
　　int msgctl(int msqid, int cmd, struct msqid_ds *buf);
　　int msgsnd(int msqid, const void *msgp, size_t msgsz, int msgflg);
　　ssize_t msgrcv(int msqid, void *msgp, size_t msgsz, long msgtyp, int msgflg);

int msgctl(int msqid, int cmd, struct msqid_ds *buf);

struct msqid_ds
{
struct ipc_perm msg_perm; /* Ownership and permissions */
time_t msg_stime; /* Time of last msgsnd(2) */
time_t msg_rtime; /* Time of last msgrcv(2) */
time_t msg_ctime; /* Time of last change */
unsigned long __msg_cbytes; /* Current number of bytes in
queue (nonstandard) */
msgqnum_t msg_qnum; /* Current number of messages
in queue */
msglen_t msg_qbytes; /* Maximum number of bytes
allowed in queue */
pid_t msg_lspid; /* PID of last msgsnd(2) */
pid_t msg_lrpid; /* PID of last msgrcv(2) */
};

struct ipc_perm
{
key_t __key; /* Key supplied to msgget(2) */
uid_t uid; /* Effective UID of owner */
gid_t gid; /* Effective GID of owner */
uid_t cuid; /* Effective UID of creator */
gid_t cgid; /* Effective GID of creator */
unsigned short mode; /* Permissions */
unsigned short __seq; /* Sequence number */
};

//实践:IPC_STAT
int main()
{
int msgid = msgget(0x1234, 0666);
if (msgid == ⑴)
{
err_exit("msgget error");
}

struct msqid_ds buf;
if (msgctl(msgid,IPC_STAT,&buf) == ⑴)
{
err_exit("msgctl error");
}

printf("buf.msg_perm.mode = %o
",buf.msg_perm.mode); //%o以8进制打印
cout << "buf.__msg_cbytes = " << buf.__msg_cbytes << endl;
cout << "buf.msg_qbytes = " << buf.msg_qbytes << endl;
cout << "buf.msg_lspid = " << buf.msg_lspid << endl;
}

//实践:IPC_SET,1般需要先获得,然后再设置
int main()
{
int msgid = msgget(0x1234, 0666);
if (msgid == ⑴)
{
err_exit("msgget error");
}

//获得消息队列的属性
struct msqid_ds buf;
if (msgctl(msgid,IPC_STAT,&buf) == ⑴)
{
err_exit("msgctl get error");
}

//设置消息队列的属性
buf.msg_perm.mode = 0644;
if (msgctl(msgid,IPC_SET,&buf) == ⑴)
{
err_exit("msgctl set error");
}

//获得并打印
if (msgctl(msgid,IPC_STAT,&buf) == ⑴)
{
err_exit("msgctl get error");
}

printf("buf.msg_perm.mode = %o
",buf.msg_perm.mode); //%o以8进制打印
}

//实践:IPC_RMID,删除消息队列
/**说明:可以通过在多个窗口上运行几个该程序,测试出:
　　消息队列并没有应用”援用计数”的功能!
*/
int main()
{
int msgid = msgget(0x1234, 0666);
if (msgid == ⑴)
{
err_exit("msgget error");
}

int choice = 0;
cout << "Please input Your choice: 0-delete, other-continue: ";
cin >> choice;
if (!choice)
{
//delete msg
if (msgctl(msgid,IPC_RMID,NULL) == ⑴)
{
err_exit("msgctl IPC_RMID error");
}
else
{
cout << "msgid = " << msgid << ", IPC_RMID OK!" << endl;
}
}
}

int msgsnd(int msqid, const void *msgp, size_t msgsz, int msgflg);

struct msgbuf
{
long mtype; /* message type, must be > 0 */
char mtext[1]; /* message data */
};

//实践
/**发送结构*/
struct msgBuf
{
long mtype; /* message type, must be > 0 */
char mtext[1024]; /* message data */
};

int main()
{
int msgid = msgget(0x1234,0666|IPC_CREAT);
if (msgid == ⑴)
{
err_exit("msgget error");
}

//初始化消息结构
struct msgBuf myBuffer;
myBuffer.mtype = 1;
strcpy(myBuffer.mtext,"Hello XiaoFang!");

//向消息队列发送消息
if (msgsnd(msgid,&myBuffer,strlen(myBuffer.mtext),IPC_NOWAIT) == ⑴)
{
err_exit("msgsnd error");
}

return 0;
}

ssize_t msgrcv(int msqid, void *msgp, size_t msgsz, long msgtyp, int msgflg);

//实践:消息发送
int main()
{
int msgid = msgget(0x1234,0666|IPC_CREAT);
if (msgid == ⑴)
{
err_exit("msgget error");
}

struct msgBuf myBuffer;
for (int i = 0; i < 128; ++i)
{
myBuffer.mtype = i+1;
sprintf(myBuffer.mtext,"Hello, My number is %d",i+1);
if (msgsnd(msgid,&myBuffer,strlen(myBuffer.mtext),IPC_NOWAIT) == ⑴)
{
err_exit("msgsnd error");
}
}

return 0;
}

//实践:消息接收:从队首不断的取数据
int main()
{
int msgid = msgget(0x1234,0666);
if (msgid == ⑴)
{
err_exit("msgget error");
}

//从队首不断的取数据,连续取10个
struct msgBuf myBuffer;
for (int i = 0; i < 10; ++i)
{
int recvBytes = 0;
if ((recvBytes = msgrcv(msgid,&myBuffer,sizeof(myBuffer.mtext),0,IPC_NOWAIT)) == ⑴)
{
err_exit("msgrcv error");
}
else
{
cout << "receive recvBytes = " << recvBytes << endl;
cout << "myBuffer.mtype = " << myBuffer.mtype << endl;
cout << " " << myBuffer.mtext << endl;
}
}
cout << "strlen(myBuffer.mtext) = " << strlen(myBuffer.mtext) << endl;

return 0;
}