昨天把socket学习了一下:
今天开始学习queue.
以下是queue.c代码
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#include <stdio.h>
#include <stdlib.h>
#include <ctype.h>
#include <sys/types.h>
#include <sys/ipc.h>
#include <sys/msg.h>
#include <errno.h>
#define MSG_MAX 4056 // <= 4056 max size of message (bytes)
/* message buffer for msgsnd and msgrcv calls */ //定义的信息
struct sMsgBuf {
long mtype; // type of message
long ModuleID;//module ID
char mtext[MSG_MAX]; //message text */
};
//创建queue
int open_queue( key_t keyval )
{
int qid;
if((qid = msgget( keyval, IPC_CREAT | 0660 )) == -1)
{
return(-1);
}
return(qid);
}
//send queue message
//qid = queue id
//qbuf = send message buffer
int send_message( int qid, struct sMsgBuf *qbuf )
{
int result, length;
/* The length is essentially the size of the structure minus sizeof(mtype) */
length = sizeof(struct sMsgBuf) - sizeof(long);
if((result = msgsnd( qid, qbuf, length, 0)) == -1)
{
return(-1);
}
return(result);
}
//read queue message
//qid = queue id
//type = message type
//qbuf = read message buffer
//return int = err code
int read_message( int qid, long type, struct sMsgBuf *qbuf )
{
int result, length;
/* The length is essentially the size of the structure minus sizeof(mtype) */
length = sizeof(struct sMsgBuf) - sizeof(long);
if((result = msgrcv( qid, qbuf, length, type, 0)) == -1)
{
return(-1);
}
return(result);
}
//查看队列是否有消息
int peek_message( int qid, long type )
{
int result, length;
//忽略了缓冲区的地址和长度。这样，系统调用将会失败。尽管如此，
//可以检查返回的E 2 B I G值，它说明符合条件的消息确实存在。
if((result = msgrcv( qid, NULL, 0, type, IPC_NOWAIT)) == -1)
{
if(errno == E2BIG)
return 1;
}
return 0;
}
//sample queue
int CreateQue()
{
int qid;
key_t msgkey;
struct sMsgBuf msgbuf;
/* Generate our IPC key value */
msgkey = ftok(".", 'm');
/* Open/create the queue */
if(( qid = open_queue( msgkey)) == -1) {
perror("open_queue");
exit(1);
}
msgbuf.mtype = 1;
msgbuf.ModuleID=100;
strcpy(msgbuf.mtext,"love");
if((send_message( qid, &msgbuf )) == -1) {
perror("send_message");
exit(1);
}
}
int get_queue_ds( int qid, struct msqid_ds *qbuf )
{
if( msgctl( qid, IPC_STAT, qbuf) == -1)
{
return(-1);
}
return(0);
}
int change_queue_mode( int qid, char *mode )
{
struct msqid_ds tmpbuf;
/* Retrieve a current copy of the internal data structure */
get_queue_ds( qid, &tmpbuf);
/* Change the permissions using an old trick */
sscanf(mode, "%ho", &tmpbuf.msg_perm.mode);
/* Update the internal data structure */
if( msgctl( qid, IPC_SET, &tmpbuf) == -1)
{
return(-1);
}
return(0);
}
int Remove_queue(int qid )
{
if( msgctl( qid, IPC_RMID, 0) == -1)
{
return(-1);
}
return(0);
//(void)msgctl(qid,IPC_RMID,0);
}
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