/*
 * CS560: Operating Systems
 * Jim Plank 
 * dphil_5.c -- Dining philosophers solution #5 -- the book's solution
 * 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
#define BLOCKED 5

typedef struct {
  cbthread_gsem *sems;
  int *sticks_free;
  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->sticks_free[s1] || !m->sticks_free[s2])) {
    m->my_pstates[p->id] = BLOCKED;
    cbthread_gsem_P(m->sems[p->id], i_am_hungry, p);
  }
  
  if (m->my_pstates[p->id] == BEGIN) {
    m->sticks_free[s1] = 0;
    m->sticks_free[s2] = 0;
    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_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;
  int before, after;

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

  if (m->my_pstates[p->id] == GOT_STICK_2) {  /* Put down first stick */
    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) {  /* Check the philosopher that shares s1 */
    m->sticks_free[s1] = 1;
    before = (p->id + p->s->nphil - 1) % p->s->nphil;
    if (m->my_pstates[before] == BLOCKED) {
      cbthread_gsem_V(m->sems[before]);
      m->my_pstates[before] = BEGIN;
    }
    m->my_pstates[p->id] = BEGIN;       /* Put down s2 */
    put_down_stick(p, s2, i_am_sated);

  } else {
    m->sticks_free[s2] = 1;
    after = (p->id + 1) % p->s->nphil; /* Check the philosopher that shares s2 */
    if (m->my_pstates[after] == BLOCKED) {
      cbthread_gsem_V(m->sems[after]);
      m->my_pstates[after] = BEGIN;
    }
    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->sticks_free = talloc(int, s->nphil);
  m->sems = talloc(cbthread_gsem, s->nphil);
  for (i = 0; i < s->nphil; i++) {
    m->sems[i] = cbthread_make_gsem(0);
    m->my_pstates[i] = BEGIN;
    m->sticks_free[i] = 1;
  }
  s->v = (void *) m;
  return;
}