#include <stdio.h>
#include <pthread.h>
#include <semaphore.h>

#define READERS 15
#define WRITERS 10

int bufferw = 0, bufferr = 0, counterw = WRITERS, counterr = READERS;
int i;

pthread_mutex_t mutex;
pthread_cond_t condw, condr;
pthread_t r[READERS], w[WRITERS];

void *writer(void *ptr) {

	pthread_mutex_lock(&mutex);

	{
	  bufferw++;
	  while(!(counterr == 0) && (bufferw == 0)) pthread_cond_wait(&condw, &mutex);
	  counterw++;

	  pthread_mutex_unlock(&mutex);

	  printf("ReaderQ: %d, WriterQ: %d [in: R: %d W: %d] \n", counterr, counterw,
	  bufferr, bufferw);

	  pthread_mutex_lock(&mutex);

  	  bufferw--;
	  counterw--;
	}

	if(counterw > 0) pthread_cond_signal(&condw);
	else pthread_cond_broadcast(&condr);

	pthread_mutex_unlock(&mutex);

        pthread_exit(0);
}

void *reader(void *ptr) {

	pthread_mutex_lock(&mutex);

	{

	  while(!(counterw == 0)) pthread_cond_wait(&condr, &mutex);
	  ++counterr;
	  pthread_mutex_unlock(&mutex);

	  printf("ReaderQ: %d, WriterQ: %d [in: R: %d W: %d] \n", counterr, counterw,
	  bufferr, bufferw);

	  pthread_mutex_lock(&mutex);

	}

	if (--counterr == 0) pthread_cond_signal(&condw);
     	pthread_mutex_unlock(&mutex);

        pthread_exit(0);
}


int main(int argc, char* argv[]) {

	pthread_mutex_init(&mutex, 0);

	pthread_cond_init(&condw, 0);
	pthread_cond_init(&condr, 0);

	for(i=0; i<WRITERS; i++) pthread_create(&w[i], NULL, writer, NULL);
	for(i=0; i<READERS; i++) pthread_create(&r[i], NULL, reader, NULL);

	for(i=0; i<WRITERS; i++) pthread_join(w[i], NULL);
	for(i=0; i<READERS; i++) pthread_join(r[i], NULL);

	pthread_cond_destroy(&condw);
	pthread_cond_destroy(&condr);
	pthread_mutex_destroy(&mutex);

 return 0;
}