rdwr_lock.c

#include "rdwr_lock.h"

int pthread_rdwr_init_np(pthread_rdwr_t *rdwrp, pthread_rdwrattr_t  *attrp )	
{	

          rdwrp->readers_reading = 0;	
          rdwrp->writer_writing = 0;	
          pthread_mutex_init(&(rdwrp->mutex), NULL);	
          pthread_cond_init(&(rdwrp->lock_free), NULL);	
          //printf("RDWR lock initialized...\n\n");
          return 0;	
}

int pthread_rdwr_rlock_np(pthread_rdwr_t *rdwrp)	
{	

          pthread_mutex_lock(&(rdwrp->mutex));	
          while(rdwrp->writer_writing) {	
                  pthread_cond_wait(&(rdwrp->lock_free), &(rdwrp->mutex));	
          }	
          rdwrp->readers_reading++;	
          pthread_mutex_unlock(&(rdwrp->mutex));	
          //printf("Read Lock Taken...\n\n");
          return 0;	
}

int pthread_rdwr_wlock_np(pthread_rdwr_t *rdwrp)	
{	
          pthread_mutex_lock(&(rdwrp->mutex));	
          while (rdwrp->writer_writing || rdwrp->readers_reading) {	
                   pthread_cond_wait(&(rdwrp->lock_free), &(rdwrp->mutex));	
          }	
          rdwrp->writer_writing++;	
          pthread_mutex_unlock(&(rdwrp->mutex));
           //printf("Write Lock Taken...\n\n");	
           //printf("Toodles!\n");
         return 0;	
}

int pthread_rdwr_runlock_np(pthread_rdwr_t *rdwrp) {	
          pthread_mutex_lock(&(rdwrp->mutex));	
          if (rdwrp->readers_reading == 0) {	
                    pthread_mutex_unlock(&(rdwrp->mutex));	
                    return -1;	
          } else {	
                    rdwrp->readers_reading--;	
                    if (rdwrp->readers_reading == 0)	
                              pthread_cond_signal(&(rdwrp->lock_free));	
                    pthread_mutex_unlock(&(rdwrp->mutex));	
                     //printf("Read Lock Released...\n\n");
                    return 0;	
          }	
}

int pthread_rdwr_wunlock_np(pthread_rdwr_t *rdwrp) {	
          pthread_mutex_lock(&(rdwrp->mutex));	
          if (rdwrp->writer_writing == 0) {	
                    pthread_mutex_unlock(&(rdwrp->mutex));
                    //printf("Write Lock Released with -1...\n\n");	
                    return -1;	
          } else {	
                    rdwrp->writer_writing = 0;	
                    pthread_cond_broadcast(&(rdwrp->lock_free));	
                    pthread_mutex_unlock(&(rdwrp->mutex));	
                    //printf("Write Lock Released...\n\n");
                    return 0;	
          }	
}