消息队列创建以及使用示例

消息队列是消息的链接表，存放在内核中并由消息队列标示符标识。

1. 创建或打开一个队列

int msgget(key_t key, int flag);

key: 键 由ftok()生成

key_t ftok(const char* path, int id);

flag: IPC_CREAT 或 IPC_EXCL

2. 发送消息

int msgsnd(int msgid, const void* ptr, size_t nbyte, int flag);

msgid: 消息队列标识

ptr: 发送的消息，一般格式为：

struct _msg{

long mtype;

char _msg[512];

. . .

};

nbyte:消息大小，一般为sizeof(struct _msg)-sizeof(long)

flag: 0 默认阻塞方式

IPC_NOWAIT 非阻塞

3. 接收消息

int msgrcv(int msgid, void* ptr, size_t nbyte, long mtype, int flag);

msgQueue.h

#ifndef _MSGQUEUE_H_
#define _MSGQUEUE_H_

#include
#include
#include
#include
#include

using namespace std;

#define KEYPATH "/tmp/count"
#define KEYPROJ 'a'
#define NAMESIZE 16
#define MTYPE 2

typedef struct {
long mtype;
char name[NAMESIZE];
int iChiScore;
int iEngScore;
int iMathScore;
} S_SCORE_ST;
#endif

send.c

#include "msgQueue.h"

int main()
{
int iRet = 0;
key_t key;
int msgid;
S_SCORE_ST score_st;
do {
key = ftok(KEYPATH, KEYPROJ);
if (key < 0) {
iRet = -1;
cout << "ftok() error : " << key << endl;
break;
}

msgid = msgget(key, IPC_CREAT);
if (msgid < 0) {
iRet = -1;
cout << "msgget() error : " << msgid << endl;
break;
}

strcpy(score_st.name, "leex");
score_st.iChiScore = 100;
score_st.iEngScore = 100;
score_st.iMathScore = 100;
score_st.mtype = MTYPE;

iRet = msgsnd(msgid, &score_st, sizeof(score_st)-sizeof(long), 0);
if (iRet < 0) {
cout << "msgsnd() error : " << iRet << endl;
break;
}

} while(false);

return iRet;
}

recv.c

#include "msgQueue.h"

int main()
{
int iRet = 0;
key_t key;
int msgid;
S_SCORE_ST score_st;
do {
key = ftok(KEYPATH, KEYPROJ);
if (key < 0) {
iRet = -1;
cout << "ftok() error : " << key << endl;
break;
}

msgid = msgget(key, IPC_CREAT);
if (msgid < 0) {
iRet = -1;
cout << "msgget() error : " << msgid << endl;
break;
}

while (1) {
iRet = msgrcv(msgid, &score_st, sizeof(score_st)-sizeof(long), MTYPE, 0);
if (iRet < 0) {
cout << "msgrcv() error : " << iRet << endl;
break;
}
cout << "name:\t" << score_st.name << endl;
cout << "chinese score:\t" << score_st.iChiScore << endl;
cout << "english score:\t" << score_st.iEngScore << endl;
cout << "math score:\t" << score_st.iMathScore << endl;
}
} while(false);
return iRet;
}