rwlock.c

实现了面向多线程应用程序的读写锁

#include	<errno.h>
#include	"pthread_rwlock.h"


/*
int	pthread_rwlock_init(pthread_rwlock_t *rw, int *attr)
{
	int	result;
	
	if(attr != 0);
		return(EINVAL);
		
	if( (result = pthread_mutex_init(&rw->rw_mutex,NULL)) != 0)
		goto err1;
	
	if( (result = pthread_cond_init(&rw->rw_condreaders,NULL)) != 0)
		goto err2;
		
	if( (result = pthread_cond_init(&rw->rw_condwriter,NULL)) != 0)
		goto err3;
	
	rw->rw_nwaitreaders = 0;
	rw->rw_nwaitwriters = 0;
	rw->rw_magic = 1;
	
	return(0);
	
	err3:
		pthread_cond_destroy(&rw->rw_condreaders);
	err2:
		pthread_mutex_destroy(&rw->rw_mutex);
	err1:
		return(result);
		
}
*/


int pthread_rwlock_destroy(pthread_rwlock_t *rw)
{
	if(rw -> rw_magic != RW_MAGIC)
		return(EINVAL);
	if(rw->rw_refcount != 0 ||
		rw -> rw_nwaitreaders != 0 || rw -> rw_nwaitwriters !=0)
		return(EBUSY);
	
	pthread_mutex_destroy(&rw->rw_mutex);
	pthread_cond_destroy(&rw->rw_condreaders);
	pthread_cond_destroy(&rw->rw_condwriters);
	
	rw -> rw_magic = 0;
	
	return(0);
}

int	pthread_rwlock_rdlock(pthread_rwlock_t *rw)
{
	int	result;
	
	if(rw -> rw_magic != RW_MAGIC)
		return(EINVAL);
		
	if( (result = pthread_mutex_lock(&rw->rw_mutex)) != 0 )
		return(result);
	
	while(rw -> rw_refcount < 0 || rw -> rw_nwaitwriters >0)
	{
		rw -> rw_nwaitreaders++;
		result = pthread_cond_wait( &rw -> rw_condreaders, &rw -> rw_mutex);
		rw -> rw_nwaitreaders--;
		if(result != 0)
			break;
	}
	
	if(result == 0)
		rw -> rw_refcount++;
		
	pthread_mutex_unlock( &rw -> rw_mutex);
	
	return(result);	
}

int pthread_rwlock_tryrdlock(pthread_rwlock_t *rw)
{
	int	result;
	
	if(rw -> rw_magic != RW_MAGIC)
		return(EINVAL);
		
	if( (result = pthread_mutex_lock(&rw->rw_mutex)) != 0 )
		return(result);
	
	if(rw -> rw_refcount < 0 || rw -> rw_nwaitwriters >0)
		result = EBUSY;
	else
		rw -> rw_refcount++;
	
	pthread_mutex_unlock(&rw->rw_mutex);
	
	return(result);
} 

int pthread_rwlock_trywrlock(pthread_rwlock_t *rw)
{
	int	result;
	
	if(rw -> rw_magic != RW_MAGIC)
		return(EINVAL);
		
	if( (result = pthread_mutex_lock(&rw->rw_mutex)) != 0 )
		return(result);
	
	if(rw -> rw_refcount != 0)
		result = EBUSY;
	else
		rw -> rw_refcount = -1;
	
	pthread_mutex_unlock(&rw->rw_mutex);
	
	return(result);
}

int	pthread_rwlock_wrlock(pthread_rwlock_t *rw)
{
	int	result;
	
	if(rw -> rw_magic != RW_MAGIC)
		return(EINVAL);
		
	if( (result = pthread_mutex_lock(&rw->rw_mutex)) != 0 )
		return(result);
	
	while(rw -> rw_refcount != 0)
	{
		rw -> rw_nwaitwriters++;
		result = pthread_cond_wait( &rw -> rw_condwriters, &rw -> rw_mutex);
		rw -> rw_nwaitwriters--;
		if(result != 0)
			break;
	}
	
	if(result == 0)
		rw -> rw_refcount = -1;
		
	pthread_mutex_unlock( &rw -> rw_mutex);
	
	return(result);	
	
}

int	pthread_rwlock_unlock(pthread_rwlock_t *rw)
{
	int	result;
	
	if(rw -> rw_magic != RW_MAGIC)
		return(EINVAL);
		
	if( (result = pthread_mutex_lock(&rw->rw_mutex)) != 0 )
		return(result);
	
	if(rw -> rw_refcount > 0)
		rw -> rw_refcount--;
	else if (rw -> rw_refcount == -1)
		rw -> rw_refcount = 0;
	else
		printf("unlock error!\n");
	
	if(rw -> rw_nwaitwriters > 0)
		{
			if(rw -> rw_refcount ==0)
				result = pthread_cond_signal(&rw -> rw_condwriters);
		}
		else if (rw -> rw_nwaitreaders > 0)
			result = pthread_cond_broadcast(&rw -> rw_condreaders);
	
	pthread_mutex_unlock( &rw -> rw_mutex);
	
	return(result);	
}
pthread_rwlock_t rw = PTHREAD_RWLOCK_INITIALIZER;
int i = 10;
void reader1()
{
	while(1)
	{
		pthread_rwlock_rdlock(&rw);
		printf("11 is %d\n",i);
		sleep(10);
		pthread_rwlock_unlock(&rw);
     	
	}
		
}

void reader2()
{
	while(1)
	{
		sleep(2);
		pthread_rwlock_rdlock(&rw);
		printf("12 is %d\n",i);
		pthread_rwlock_unlock(&rw);
		usleep(1);
	}
}

void writer()
{
	sleep(2);
	pthread_rwlock_wrlock(&rw);
	i = 30;
	printf("13 is %d\n",i);
	sleep(10);
	pthread_rwlock_unlock(&rw);
	
}


int main()
{
	pthread_t id[3];
	int i,ret1,ret2,ret3;
	
	
	ret1 = pthread_create(&id[0],NULL,(void *) reader1,NULL);
	ret2 = pthread_create(&id[1],NULL,(void *) reader2,NULL);
//	ret3 = pthread_create(&id[2],NULL,(void *) writer,NULL);
	
	pthread_join(id[0],NULL);
	pthread_join(id[1],NULL);
	pthread_join(id[2],NULL);
	
}