shm_s.cpp

在Linux测试共享共享内存消息

#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <string.h>
#include <time.h>
#include <sys/shm.h>
#include <sys/sem.h>
#include <sys/ipc.h>

#define SEGSIZE 1024
#define READTIME 1

union semun {
	int val;
	struct semid_ds *buf;
	unsigned short *array;
} arg;

//生成信号量
int sem_creat(key_t key)
{
	union semun sem;
	int semid;
	sem.val = 0;
	semid = semget(key,1,IPC_CREAT|0666);
	if (-1 == semid){
		printf("create semaphore error\n");
		exit(-1);
	}
	semctl(semid,0,SETVAL,sem);
	return semid;
}

//删除信号量
void del_sem(int semid)
{
	union semun sem;
	sem.val = 0;
	semctl(semid,0,IPC_RMID,sem);
}

//p
int p(int semid)
{
	int ret;

	struct sembuf sops={0,+1,IPC_NOWAIT};
	printf("shm_s-p():before semop(),time=%ld ...\n",time(NULL));
	ret=semop(semid,&sops,1);
	printf("shm_s-p():after semop(),ret=%d,time=%ld ...\n",ret,time(NULL));

	return ret;
}

//v
int v(int semid)
{
	int ret;

	struct sembuf sops={0,-1,IPC_NOWAIT};
	printf("shm_s-v():before semop(),time=%ld ...\n",time(NULL));
	ret=semop(semid,&sops,1);
	printf("shm_s-v():after semop(),ret=%d,time=%ld ...\n",ret,time(NULL));

	return ret;
}

int main()
{
	key_t key;
	int shmid,semid;
	char *shm;
	char msg[7] = "-data-";
	char i;
	struct shmid_ds buf;

	printf("======= Run Server Program ===========\n");

	key = ftok("./",0);
	shmid = shmget(key,SEGSIZE,IPC_CREAT|0604);
	if (-1 == shmid){
		printf(" create shared memory error\n");
		return -1;
	}

	shm = (char *)shmat(shmid,0,0);
	if (-1 == (int)shm){
		printf(" attach shared memory error\n");
		return -1;
	}

	semid = sem_creat(key);
	for (i = 0;i <= 3;i++){
		sleep(1);
		p(semid);
		sleep(READTIME);
		msg[5] = '0' + i;
		memcpy(shm,msg,sizeof(msg));
		sleep(58);
		v(semid);
	}

	shmdt(shm);
	shmctl(shmid,IPC_RMID,&buf);
	del_sem(semid);
	return 0;
}

//编译服务端程序：
	//gcc -o shm_s shm_s.c -g