#include <pthread.h>
#include <stdio.h>
#include <stdlib.h>

#define FALSE	0 
#define TRUE	1 
#define N	2		/* number of processes */

int Tc[]={5000000,100000000};	/* time for each proc. in critical region */
int Tn[]={1000000,10000000};	/* time for each proc. in noncritical region */

int turn;			/* whose turn is it? */ 
int interested[N];		/* all values initially 0 (FALSE) */ 

void enter_region(int process)	/* process is 0 or 1 */ 
{
  int other;			/* number of the other process */
  
  other = 1 - process;		/* number of the other process */ 
  interested[process] = TRUE;	/* show that you are interested */
  turn = process;		/* set flag */ 
  while (turn == process && interested[other] == TRUE) ;  /* null statement */ 
} 

void leave_region(int process)	/* process: who is leaving */ 
{
  interested[process] = FALSE;	/* indicate departure from critical region */ 
}

void compute(int T)		/* compute for some time */ 
{
  int i;
  for(i=0;i<T;i++);
}

void critical_region(int process)	/* print PID and compute a while */
{
  int i;
  for(i=0;i<10;i++) {
    /* printf("%d",process); */
    fprintf(stdout,"%d",process); fflush(stdout);
    compute(Tc[process]);
  } 
}

void noncritical_region(int process)	/* print PID and compute a while */
{
  int i;
  for(i=0;i<10;i++) {
    /* printf("%c",(int)'a'+process); */
    fprintf(stdout,"%c",(int)'a'+process); fflush(stdout);
    compute(Tn[process]);
  } 
}

void *one_thread(void *tid)
{
  int i,j,process;

  process = (int)tid;
  while(TRUE) {
    enter_region(process);
    critical_region(process);
    leave_region(process);
    noncritical_region(process);
  }
  pthread_exit(NULL);
}

int main(int argc, char *argv[])
{
  pthread_t threads[N];
  int status, i;

  /* We use threads instead of processes in this example */
  for(i=0;i<N;i++) {
    printf("Main: creating thread %d\n",i);
    status = pthread_create(&threads[i],NULL,one_thread,(void *)i);
    if(status != 0) {
      printf("pthread_create returned error code %d\n",status);
      exit(-1);
    }
  }
  sleep(60);			/* Let threads run for a while */
}