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

int fd0, fd1;

void envoyer(char *msg)
{
  int n = strlen(msg) + 1;
  write(STDOUT_FILENO, &n, sizeof(int));
  write(STDOUT_FILENO, msg, n);
}

void fils0(void)
{
  envoyer("coucou !"); envoyer("ça va ?");
}

void fils1(void)
{
  envoyer("salut !");
}

int recevoir(int fd, char *buf)
{
  int n;

  if(read(fd, &n, sizeof(int)) != sizeof(int))
    return -1;

  read(fd, buf, n);
  return 0;
}

void *tache(void *arg)
{
  int num = (int)(arg);
  char buf[1024];
  int fd, n;

  fd = num ? fd1 : fd0;
  do {
    n = recevoir(fd, buf);
    if(n != 0)
      break;
    printf("Fils %d: %s\n", num, buf);
  } while(1);

  return NULL;
}

void entrelacer(void)
{
  int n;
  pthread_t p1, p2;

  pthread_create(&p1, NULL, tache, (void *)0);
  pthread_create(&p2, NULL, tache, (void *)1);

  pthread_join(p1, NULL);
  pthread_join(p2, NULL);
}

int main(int argc, char *argv[])
{
  pid_t pid;
  int tube[2];

  pipe(tube);

  pid = fork();

  if(pid == 0) { /* fils 0 */
    dup2(tube[1], 1);
    close(tube[0]);
    close(tube[1]);

    fils0();

    exit(0);
  }

  fd0 = tube[0];
  close(tube[1]);
  
  pipe(tube);

  pid = fork();

  if(pid == 0) { /* fils 1 */
    close(fd0);
    dup2(tube[1], 1);
    close(tube[0]);
    close(tube[1]);

    fils1();

    exit(0);
  }

  fd1 = tube[0];
  close(tube[1]);

  entrelacer();

  return 0;
}