sem.c

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/*
 * =====================================================================================
 *
 *       Filename:  sem.c
 *
 *    Description:  
 *
 *        Version:  1.0
 *        Created:  2008年11月24日 21时14分05秒
 *       Revision:  none
 *       Compiler:  gcc
 *
 *         Author:  杨小合
 *        Company:  北华航天学院
 *
 * =====================================================================================
 */
#include"sem.h"

int set_semvalue(int sem_id,int value)
{
	union semun sem_union;
	sem_union.val=value;
	if(semctl(sem_id,0,SETVAL,sem_union)==-1)
		return 0;
	return 1;
}

int semaphore_p(int sem_id)
{
	struct sembuf sem_p;

	sem_p.sem_num=0;
	sem_p.sem_op=-1;
	sem_p.sem_flg=SEM_UNDO;
	if(semop(sem_id,&sem_p,1)==-1)
	{
		fprintf(stderr,"semaphore_p failed\n");
		return 0;
	}
	return 1;
}

int semaphore_v(int sem_id)
{
	struct sembuf sem_v;
	sem_v.sem_num=0;
	sem_v.sem_op=1;
	sem_v.sem_flg=SEM_UNDO;
	if(semop(sem_id,&sem_v,1)==-1)
	{
		fprintf(stderr,"semaphore_v failed\n");
		return 0;
	}
	return 1;
}

void del_semvalue(int sem_id)
{
	union semun sem_union;
	if(semctl(sem_id,0,IPC_RMID,sem_union)==-1)
	{
		fprintf(stderr,"Failed to delete semaphore\n");
	}
}