内存共享

#include <sys/types.h>
#include <sys/ipc.h>
#include <sys/sem.h>
#include <unistd.h>
#include <sys/shm.h>
#include <sys/wait.h>

#include <stdio.h>
#include <stdlib.h>
#include <string.h>

int CreateProcessSem(key_t k);
int InitProcessSem(int id,int n);
int DestroyProcessSem(int id);
int ProcessSemP(int id,int n);
int ProcessSemV(int id,int n);

int main(int argc,char* argv[])
{
char *pShm=NULL;
int ShmID=0;
int SemID=0;
pid_t pid;

ShmID=shmget(1234,64,0666|IPC_CREAT);//得到一个共享内存标识符
if(ShmID<0)
{
	printf("open share memory failed\n");
	
	return 1;
}
SemID=CreateProcessSem(5678);
if(SemID<0)
{
	printf("Open semaphore set failed\n");
	return 2;
}


InitProcessSem(SemID,0);

pid = fork();
if(pid<0)
{
	printf("fork erro");
	return 3;
}
else if(pid==0)
{
	pShm=shmat(ShmID,NULL,0);//0 读写模式
	if(-1==(long)pShm)
	{
		printf("attach share failed");
		return 3;
	}
	while(1)
	{
		ProcessSemP(SemID,1);
		printf("%d character in share memory\n",(int)strlen(pShm));
		if(strncmp("exit",pShm,4)==0)
		{
			break;
		}
		
	}
	shmdt(pShm);
	return 0;
	
}
else
{
	pShm=shmat(ShmID,NULL,0);
	if(-1==(long)pShm)
	{
		printf("attach share memory failed\n");
		return 3;
	}
	while(1)
	{
	  printf("please input:\n");
	  fgets(pShm,64,stdin);
	  ProcessSemV(SemID,1);
	  if(strncmp("exit",pShm,4)==0)
	  {
	  	break;
	  }
	  
	  
	  }
	shmdt(pShm);// 断开链接
	wait(NULL);	
	
	
}
DestroyProcessSem(SemID);
shmctl(ShmID,IPC_RMID,NULL);//删除内存
return 0;

}

int CreateProcessSem(key_t key)
{
int id=0;
id=semget(key,1,0666 | IPC_CREAT);//是获取与某个键关联的信号量集标识
//创建的信号量集中的信号量的个数
if(id<0)
{
printf(“semget failed\n”);

}
return id;

}
int InitProcessSem(int id,int n)
{
int ret=0;

if(n<0)
{
	printf("the init value is ivable\n");
	return -1;
}
ret=semctl(id,0,SETVAL,n);//系统调用semctl()的第一个参数是信号量集IPC标识符。第二个参数是操作信号在信号集中的编号
//GETVAL返回信号量集中的一个单个的信号量的值。
if(ret<0)
{	
	printf(" semcrl  failed\n");
	return -2;
}
return 0;

}

int DestroyProcessSem(int id)
{
int ret=0;
ret=semctl(id,0,IPC_RMID,0);
if(ret<0)
{
printf(“semtrl delete sem set failed”);
return -1;
}
return 0;
}
int ProcessSemP(int id,int n)
{
struct sembuf sb={0};
if(n<0)
{
printf(“value error”);
return -1;
}
sb.sem_num=0;
sb.sem_op=-n;
sb.sem_flg=SEM_UNDO;//程序结束时(不论正常或不正常)，保证信号值会被重设为semop()调用前的值。
return semop(id,&sb,1);
}
int ProcessSemV(int id,int n)
{
struct sembuf sb={0};
if(n<0)
{
printf(“value error”);
return -1;
}
sb.sem_num=0;
sb.sem_op=n;
sb.sem_flg=SEM_UNDO;
return semop(id,&sb,1);//信号操作结构的数量
}

#include <semaphore.h>

#include <stdio.h>
#include <stdlib.h>
#include <string.h>

#include <pthread.h>

void *printThread(void *pv);

struct StringBuf
{
char buf[64];
sem_t sem;
};
int main(int argc,char *argv[])
{
pthread_t tid;
int ret = 0;

struct StringBuf st = {""};
sem_init(&st.sem,0,0);

ret = pthread_create(&tid,NULL,printThread,&st);
if(ret != 0)
{
	printf("pthread create failed\n");
	sem_destroy(&st.sem);
	return 1;
}

while(1)
{
	fgets(st.buf,64,stdin);
	sem_post(&st.sem);
	if(strncmp(st.buf,"exit",4) == 0)
	{
		break;	
	}
}

pthread_join(tid,NULL);

sem_destroy(&st.sem);
return 0;

}

void *printThread(void *pv)
{
struct StringBuf *pst = (struct StringBuf *)pv;

while(1)
{
	sem_wait(&pst->sem);
	if(strncmp(pst->buf,"exit",4) == 0)
	{
		break;
	}
	printf("In thread,buf is %s\n",pst->buf);
	memset(pst->buf,0,64);
}

return (void *)0;

}