/*
 * CS170: Operating Systes
 * 	adapted from CS460: Operating Systems
 * 	Jim Plank
 * dphil_4.c -- Dining philosophers solution 
 * an asymmetrical solution.
 */


#include <stdio.h>
#include <pthread.h>
#include "dphil.h"



typedef struct sticks {
  pthread_mutex_t *lock[MAXTHREADS];
  int phil_count;
} Sticks;


void pickup(Phil_struct *ps)
{
  Sticks *pp;
  int phil_count;

  pp = (Sticks *) ps->v;
  phil_count = pp->phil_count;
  
  if (ps->id % 2 == 1) {
    pthread_mutex_lock(pp->lock[ps->id]);       /* lock up left stick */
    pthread_mutex_lock(pp->lock[(ps->id+1)%phil_count]); /* lock right stick */ 
  } else {
    pthread_mutex_lock(pp->lock[(ps->id+1)%phil_count]); /* lock right stick */ 
    pthread_mutex_lock(pp->lock[ps->id]);       /* lock up left stick */
  }
}

void putdown(Phil_struct *ps)
{
  Sticks *pp;
  int i;
  int phil_count;

  pp = (Sticks *) ps->v;
  phil_count = pp->phil_count;

  if (ps->id % 2 == 1) {
    pthread_mutex_unlock(pp->lock[(ps->id+1)%phil_count]); /* unlock right stick */ 
    pthread_mutex_unlock(pp->lock[ps->id]);  /* unlock left stick */
  } else {
    pthread_mutex_unlock(pp->lock[ps->id]);  /* unlock left stick */
    pthread_mutex_unlock(pp->lock[(ps->id+1)%phil_count]); /* unlock right stick */ 
  }
}

void *initialize_state(int phil_count)
{
  Sticks *pp;
  int i;

  pp = (Sticks *) malloc(sizeof(Sticks));
  pp->phil_count = phil_count;
  for (i = 0; i < phil_count; i++) {
    pp->lock[i] = (pthread_mutex_t *) malloc(sizeof(pthread_mutex_t));
  }
  for (i = 0; i < phil_count; i++) {
    pthread_mutex_init(pp->lock[i], NULL);
  }

  return (void *) pp;
}