/* We have the users call sleep() when the queue is full, 
   and we have the printers call sleep() when the queue is empty.
   That's one way to make it work, but it's not a good way. */
   
#include <stdio.h>
#include <unistd.h>
#include <stdlib.h>
#include <pthread.h>
#include "printqsim.h"

typedef struct {
  Job **b;
  int head;
  int tail;
  int njobs;
  pthread_mutex_t *lock;
} Buffer;
  
void initialize_v(Spq *s)
{
  Buffer *b;

  b = (Buffer *) malloc(sizeof(Buffer));
  b->b = (Job **) malloc(sizeof(Job *)*s->bufsize);
  b->head = 0;
  b->tail = 0;
  b->njobs = 0;
  b->lock = (pthread_mutex_t *) malloc(sizeof(pthread_mutex_t));
  pthread_mutex_init(b->lock, NULL);
  s->v = (void *) b;
}

void submit_job(Spq *s, Job *j)
{
  Buffer *b;

  b = (Buffer *) s->v;

  while(1) {
    pthread_mutex_lock(b->lock);
    if (b->njobs < s->bufsize) {
      b->b[b->head] = j;
      b->head = (b->head + 1) % s->bufsize;
      b->njobs++;
      pthread_mutex_unlock(b->lock);
      return;
    } else {         // Here's the new code -- when the queue is full, unlock the mutex and sleep.
      pthread_mutex_unlock(b->lock);
      printf("%4ld: user %2d sleeping because the queue is full\n", time(0)-s->starttime, s->id);
      fflush(stdout);
      sleep(1);
    }
  }
}

Job *get_print_job(Spq *s)
{
  Buffer *b;
  Job *j;

  b = (Buffer *) s->v;

  while(1) {
    pthread_mutex_lock(b->lock);
    if (b->njobs > 0) {
      j = b->b[b->tail];
      b->tail = (b->tail + 1) % s->bufsize;
      b->njobs--;
      pthread_mutex_unlock(b->lock);
      return j;
    } else {
      pthread_mutex_unlock(b->lock);
      printf("%4ld: prnt %2d sleeping because the queue is empty\n",
             time(0)-s->starttime, s->id);
      fflush(stdout);
      sleep(1);
    }
  }
  
  
}