sharemem.h

此源码是著名的教材BeginningLinux Programming中文名字叫Linux程序设计书中的源代码

#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <sys/types.h>
#include <sys/ipc.h>
#include <sys/sem.h>
#include <sys/shm.h>
#include <errno.h>

#define SHM_SIZE 1024

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

/*创建信号量函数*/
int createsem (const char * pathname,  int proj_id,  int members,  int init_val)
{
	key_t		msgkey;
	int		index,  sid;
	union semun	semopts;
			
	if ((msgkey = ftok(pathname, proj_id)) == -1)
	{
		perror ("ftok error!\n");
		return -1;
	}

	if ((sid = semget (msgkey, members, IPC_CREAT | 0666)) == -1)
	{
		perror ("semget call failed.\n");
		return -1;
	}

	/*初始化操作*/
	semopts.val = init_val;
	for (index = 0; index < members; index++)
	{
		semctl (sid, index, SETVAL, semopts);
	}
	return (sid);
}

/*打开信号量函数*/
int opensem(const char * pathname, int proj_id)
{
	key_t	msgkey;
	int	sid;         
                                                                                                 
 	if ((msgkey = ftok(pathname, proj_id)) == -1)
	{
		perror ("ftok error!\n");
		return -1;
	}

	if ((sid = semget(msgkey, 0, IPC_CREAT | 0666)) == -1)
	{
		perror("semget call failed.\n");
		return -1;
	}

	return (sid);

}

/*P操作函数*/
int sem_p(int semid, int index)
{
	struct sembuf buf = {0,-1,IPC_NOWAIT};

	if (index < 0)
	{
		perror("index of array cannot equals a minus value!");
		return -1;
	}

	buf.sem_num = index;
	if (semop (semid ,& buf,1) == -1)
	{
		perror ("a wrong operation to semaphore occurred!");
		return -1;
	}
	return 0;
} 

/*v操作函数*/
int sem_v (int semid, int index)
{
	struct sembuf buf = {0, +1, IPC_NOWAIT};

	if (index < 0)
	{
		perror("index of array cannot equals a minus value!");
		return -1;
	}

	buf.sem_num = index;
	if (semop (semid,& buf,1) == -1)
	{
		perror ("a wrong operation to semaphore occurred!");
		return -1;
	}

	return 0;
} 

/*删除信号集函数*/
int sem_delete (int semid)
{
	return (semctl(semid, 0, IPC_RMID));
}

/*等待信号为1*/
int wait_sem( int semid, int index)
{
	
	while (semctl (semid, index, GETVAL, 0) == 0)
	{
		sleep (1);
	}

	return 1 ;
}


/*创建共享内存函数*/
int createshm( char * pathname, int proj_id, size_t size)
{
	key_t	shmkey;
	int		sid;
			
	/*获取键值*/
	if ((shmkey = ftok(pathname, proj_id)) == -1)
	{
		perror("ftok error!\n");
		return -1;
	}

	if ((sid = shmget(shmkey, size, IPC_CREAT | 0666)) == -1)
	{
				
		perror ("shmget call failed.\n");
		return -1;
	}
	return (sid);
}