/*
 * CS560: Operating Systems
 * Jim Plank 
 * dphil_3.c -- Dining philosophers solution #3 -- grab the sticks with semaphores
 * January, 2009
 */

#include <stdio.h>
#include <stdlib.h>
#include "cbthread.h"
#include "dphil.h"

#define talloc(ty, sz) (ty *) malloc ((sz) * sizeof(ty))

#define BEGIN 0
#define GOT_STICK_1 1
#define GOT_STICK_2 2
#define GOT_SEM_1 3
#define GOT_SEM_2 4

typedef struct {
  cbthread_gsem *sems;
  int *my_pstates;
} MyPhil;

void i_am_hungry(Philosopher *p)
{
  MyPhil *m;
  int s1, s2;

  m = (MyPhil *) p->s->v;
  s1 = p->id;
  s2 = (p->id+1)%p->s->nphil;

  if (m->my_pstates[p->id] == BEGIN) {
    m->my_pstates[p->id] = GOT_SEM_1;
    cbthread_gsem_P(m->sems[s1], i_am_hungry, p);

  } else if (m->my_pstates[p->id] == GOT_SEM_1) {
    m->my_pstates[p->id] = GOT_STICK_1;
    pick_up_stick(p, s1, i_am_hungry);

  } else if (m->my_pstates[p->id] == GOT_STICK_1) {
    m->my_pstates[p->id] = GOT_SEM_2;
    cbthread_gsem_P(m->sems[s2], i_am_hungry, p);

  } else if (m->my_pstates[p->id] == GOT_SEM_2) {
    m->my_pstates[p->id] = GOT_STICK_2;
    pick_up_stick(p, s2, i_am_hungry);

  } else {
    p->state = GOTSTICKS;
    philosopher(p);
    cbthread_exit();
  }
}

void i_am_sated(Philosopher *p)
{
  MyPhil *m;
  int s1, s2;

  m = (MyPhil *) p->s->v;
  s1 = p->id;
  s2 = (p->id+1)%p->s->nphil;

  if (m->my_pstates[p->id] == GOT_STICK_2) {
    m->my_pstates[p->id] = GOT_STICK_1;
    put_down_stick(p, s1, i_am_sated);
  } else if (m->my_pstates[p->id] == GOT_STICK_1) {
    cbthread_gsem_V(m->sems[s1]);
    m->my_pstates[p->id] = BEGIN;
    put_down_stick(p, s2, i_am_sated);
  } else {
    cbthread_gsem_V(m->sems[s2]);
    p->state = STARTING;
    philosopher(p);
    cbthread_exit();
  }
}

void initialize_simulation(Simulation *s)
{
  MyPhil *m;
  int i;

  m = talloc(MyPhil, 1);
  m->my_pstates = talloc(int, s->nphil);
  m->sems = talloc(cbthread_gsem, s->nphil);
  for (i = 0; i < s->nphil; i++) {
    m->sems[i] = cbthread_make_gsem(1);
    m->my_pstates[i] = BEGIN;
  }
  s->v = (void *) m;
  return;
}