#include <stdio.h>
#include <errno.h>
#include <unistd.h>

#include <net/if.h>
#include <sys/ipc.h>
#include <sys/sem.h>


#define TESTSEMID	100
#define	SEMSIZE		1

#if defined(__GNU_LIBRARY__) && !defined(_SEM_SEMUN_UNDEFINED)
/* union semun is defined by including <sys/sem.h> */
#else
/* according to X/OPEN we have to define it ourselves */
union semun {
        int16_t val;                    /* value for SETVAL */
        struct semid_ds *buf;       /* buffer for IPC_STAT, IPC_SET */
        unsigned short int *array;  /* array for GETALL, SETALL */
        struct seminfo *__buf;      /* buffer for IPC_INFO */
};
#endif


int	test_semid;

void 
to_show(){

	union 	semun arg;
	unsigned short int allval[SEMSIZE];
	int i;
	
	arg.array = allval;

	if (semctl(test_semid, 0 , GETALL, arg) < 0) {
            printf("semctl failed for[%s].\n", strerror(errno));
            return ;
	}

	for( i=0; i < SEMSIZE; i++)
		printf("\t semval[%d] = %d \n", i , allval[i]);
	return; 
}

int
create_test_semaphore(void)
{
		int     key, i;
        char    fn[100];
		union 	semun arg;
		unsigned short int allval[SEMSIZE];

        sprintf(fn, ".");
        if ((key = ftok(fn, TESTSEMID)) < 0) {
                printf("ftok failed for[%s].\n", strerror(errno));
                return -1;
        }

        if ((test_semid = semget(key, SEMSIZE, IPC_CREAT | IPC_EXCL | 0666)) < 0) {
			if (errno == EEXIST) {
				printf("Test semaphore has existed.\n");
				printf("Get test semaphore...\n");
				if ((test_semid = semget(key, 0, 0666)) < 0) {
					printf("semget failed for[%s].\n", strerror(errno));
					return -1;
				} else {
					to_show();
					printf("Get test semaphore successfully.\n");
					return 0;
				}
			}
			printf("semget failed[%s].\n", strerror(errno));
			return -1;
        }
	
	for (i = 0; i< SEMSIZE; i++)
		allval[i] = 8;
	arg.array = allval;

	if (semctl(test_semid, SEMSIZE, SETALL, arg) < 0) {
            printf("semctl failed for[%s].\n", strerror(errno));
            return -1;
	}
	
	return 0;
}

int
mutex_op_semaphore(int op)
{
	int	i;
	struct sembuf oparray[SEMSIZE];
	
	for (i = 0; i < SEMSIZE; i++) {
		oparray[i].sem_num = i;
		oparray[i].sem_op = op;
		oparray[i].sem_flg = SEM_UNDO;
	}

	if (semop(test_semid, oparray, SEMSIZE) < 0) {
		printf("semop failed for[%s].\n", strerror(errno));
		return -1;
	} else
		return 0;
}

int
main(void)
{
	int	ret;

//	printf("Create test semaphore...\n");
	if (create_test_semaphore() < 0) {
		printf("Create test semaphore failed.\n");
		return -1;
	} //else
		//printf("Create test semaphore successfully.\n");

	printf("before Get semaphore exclusively...\n");
	to_show();
	if (mutex_op_semaphore(-1) < 0) {
		printf("Get test semaphore failed.\n");
		return -1;
	} else
		printf("after Get semaphore ...\n");

	to_show();

	sleep(5);	

	printf("before release semaphore exclusively...\n");
	to_show();

	if (mutex_op_semaphore(1) < 0) {
		printf("Release test semaphore failed.\n");
		return -1;
	} else 
		printf("before release semaphore exclusively...\n");
	to_show();
	return 0;
}