System V共享内存使用实例

野性酷女 2022-04-16 06:49 106阅读 0赞

#include <stdlib.h>
    #include <stdio.h>
    #include <sys/shm.h>
    #include <sys/errno.h>
    #include <pthread.h>
    #include <string.h>
    #include <malloc.h>
    #include <signal.h>
    
    #define BUFFER_SIZE 1000
    
    typedef struct SHMSTRU
    {
    	pthread_mutex_t lock;
    	char buffer[BUFFER_SIZE];
    }ShmStru;
    
    typedef enum
    {
    	false,
    	true
    }bool;
    
    void signalCancel(int);
    
    bool isExit = false;
    
    int main(void)
    {
    	int key = 1000;
    	int shmid = 0;	
    	ShmStru *pShmStru = NULL;
    	int exist = 0;
    	int cPid = 0;
    	int ret = 0;
    
    	struct shmid_ds shmDs;
    
    	signal(SIGINT, signalCancel);
    
    	shmid = shmget(key, sizeof(ShmStru), IPC_EXCL | IPC_CREAT);
    	if (-1 == shmid)
    	{
    		if (EEXIST == errno)
    		{
    			printf("INFO: The shared memory is exist!\n");
    			shmid = shmget(key, 0, 0);
    			exist = 1;
    		}
    		else
    		{
    			printf("ERROR: Create shared memory failed, ErrorCode: %d!\n", errno);
    			return -1;
    		}
    	}
    
    	memset(&shmDs,0x00, sizeof(struct shmid_ds));
    	
    	//Get the info of the shared memory
    	if (exist)
    	{
    		ret = shmctl(shmid, IPC_STAT, &shmDs);
    		if (-1 != ret)
    		{
    			printf("INFO: The current attache processes num: %d!\n", (int)shmDs.shm_nattch);
    		}
    	}	
    
    	pShmStru = (ShmStru *)shmat(shmid, 0, 0);
    	if ((void *)-1 == pShmStru)
    	{
    		perror("");
    		return -1;
    	}	
    
    	if (!exist)
    	{
    		strcpy(pShmStru->buffer, "The initial information!");
    		pthread_mutex_init(&pShmStru->lock, 0);
    	}
    
    	cPid = fork();
    	if (0 == cPid)
    	{
    		while (!isExit)
    		{
    			pthread_mutex_lock(&pShmStru->lock);
    			printf("Child: The info in shared memory is %s!\n", pShmStru->buffer);
    			strcpy(pShmStru->buffer, "The information set by the child!");	
    			pthread_mutex_unlock(&pShmStru->lock);
    			usleep(1000000);
    		}
    		shmdt(pShmStru);
    	}
    	else
    	{
    		while (!isExit)
    		{
    			pthread_mutex_lock(&pShmStru->lock);
    			printf("Parent: The info in shared memory is %s!\n", pShmStru->buffer);
    			strcpy(pShmStru->buffer, "The information set by the parent!");
    			pthread_mutex_unlock(&pShmStru->lock);
    			usleep(1000000);
    		}
    		shmdt(pShmStru);
    		shmctl(shmid, IPC_RMID, 0);
    	}
    	
    	return 1;
    }
    
    void signalCancel(int i)
    {
    	printf("INFO: Catch the cancel signal!\n");
    	isExit = true;
    }