semaphore.c

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#include "semaphore.h"

union semun {
	int 		val ;	/* for SETVAL */
	struct semid_ds *buf ; /* for IPC_STAT and IPC_SET */
	ushort	*array ; /* for GETALL and SETALL */
}; 

/* create semaphore */
int 
sem_create(key_t key)
{  
	union semun sem ;
	int semid; 
	 
	sem.val = 1; 
	/*
		int semget(key_t key, int nsems, int flag);
	*/ 
	semid = semget(key, 0, 0);  
	if (semid == -1)
	{  		
		semid = semget(key, 1, IPC_CREAT|0666);  
		if (semid == -1)
		{
			printf("sys alm: create semaphore failed\n");
			return semid;
		}
		else
			printf("sys not: create semaphore success\n");

		/*
		int semctl(int semid, int semnum, int cmd, union semunarg) ;
		*/
		/* init semaphore */
		semctl(semid, 0, SETVAL, sem);  
		return semid;  
	}  
	else
		printf("sys not: get semaphore success\n");
	
	return semid;
} 

/* delete semaphore */ 
void sem_delete(int semid)
{  
	/*
		int semctl(int semid, int semnum, int cmd, union semunagr);
	*/
	/* delete semaphore */	
	semctl(semid, 0, IPC_RMID, 0);  
	printf("sys not: delte semaphore success\n");
} 

/* p operation */
int p(int semid)
{  
	struct sembuf sops={0, -1, SEM_UNDO};
	
	/*
		int semop(int semid, struct sembuf semoparray[], size_t nops);
		semoparray is a point.		
	*/
	return(semop(semid, &sops, 1));  
}  

/* v operation */
int v(int semid)
{  
	struct sembuf sops={0, +1, SEM_UNDO};
	/* 
		int semop(int semid, struct sembuf semoparray[], int nops);
	*/
	return(semop(semid, &sops, 1));  
}