anillo.c

anillo.c

// lista circular - procesos y pipes

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <sys/types.h>

#define MAX_P 2
#define MAX_BUFFER 100

void main (int argc, char ** argv)
{
	pid_t pid, pid_in, pid_out;
	int index;
	int fd [MAX_P][2];
	int *fd_in, *fd_out;

	char *msg;
	int msg_len;
	char buffer[100];

	pid_in = getpid ();

	for (index = 0; index < MAX_P; index++)
		pipe (fd[index]);

	for (index = 1; index < MAX_P; index++)
	{
		pid = fork ();
		if (pid != 0)
		{
			close (fd [index-1][0]);
			fd_out = &fd [index-1][1];
		}
		else
		{
			close (fd [index-1][1]);
			fd_in = &fd [index-1][0];
		}


		if (pid != 0) break;
	}
	pid = getpid ();
	if (index == MAX_P) pid_out = getpid ();
	//printf("%d\n", getpid ());

	//conectamos el ultimo pipe
	if (pid == pid_in) 
	{
		close (fd [MAX_P-1][1]);
		fd_in = &fd [MAX_P-1][0];
	}
	if (pid == pid_out)
	{
		close (fd [MAX_P-1][0]);
		fd_out = &fd [MAX_P-1][1];
	}

	if (pid == pid_in)
	{   
		msg = "raiz ";
		write (*fd_out, msg, strlen (msg)+1);

		read (*fd_in, buffer, sizeof (buffer));
		printf("raiz imprime: %s\n", buffer);

	}
	else if (pid == pid_out)
	{
		read (*fd_in, buffer, sizeof (buffer));
		strcat (buffer, "hoja");
		write (*fd_out, buffer, strlen(buffer)+1);
	}
	else
	{
		read (*fd_in, buffer, sizeof (buffer));
		strcat (buffer, "nodo ");
		write (*fd_out, buffer, strlen (buffer)+1);		
	}
}