식사하는 철학자 코드인데요

#define N        5               /* number of philosophers */
#define LEFT     (i + N - 1) % N /* number of i's left neighbor */
#define RIGHT    (i + 1) % N     /* number of i's right neighbor */
#define THINKING 0               /* philosopher is thinking */
#define HUNGRY   1               /* philosopher is trying to get forks */
#define EATING   2               /* philosopher is eating */
 
typedef int semaphore;           /* semaphores are a special kind of int */
int state[N];                    /* array to keep track of everyone's state */
semaphore mutex = 1 ;            /* mutual exclusion for critical regions */
semaphore s[N];                  /* one semaphore per philosopher */
 
void philosopher(int i)          /* i: philosopher number, from 0 to N-1 */
{
    while (TRUE) {               /* repeat forever */
        think( );                /* philosopher is thinking */
        take_forks(i);           /* acquire two forks or block */
        eat();                   /* yum-yum, spaghetti */
        put_forks(i);            /* put both forks back on table */
    }
}
 
void take_forks(int i)           /* i: philosopher number, from 0 to N-1 */
{
    down(&mutex);                /* enter critical region */
    state[i] = HUNGRY;           /* record fact that philosopher i is hungry */
    test(i);                     /* try to acquire 2 forks */
    up(&mutex);                  /* exit critical region */
    down(&s[i]);                 /* block if forks were not acquired */
}
 
void put_forks(i)                /* i: philosopher number, from 0 to N-1 */
{
    down(&mutex);                /* enter critical region */
    state[i] = THINKING;         /* philosopher has finished eating */
    test(LEFT);                  /* see if left neighbor can now eat */
    test(RIGHT);                 /* see if right neighbor can now eat */
    up(&mutex);                  /* exit critical region */
}
 
void test(i)                     /* i: philosopher number, from 0 to N-1 */
{
    if(state[i] == HUNGRY && state[LEFT] != EATING && state[RIGHT] != EATING) {
        state[i] = EATING;
        up(&s[i]);
    }
}