#include <stdio.h>

#include <stdlib.h>

#include <unistd.h>

#include <fcntl.h>

#include <string.h>

// this process says hi to another process

// and the other process says hi back



int main() {

    int w_fd = open("./fifo_a2b", O_WRONLY);

    int r_fd = open("./fifo_b2a", O_RDONLY);

    printf("I am process with PID %d\n", getpid());



    char *msg = malloc(sizeof(char) * 100);

    memset(msg, 0, sizeof(char) * 100);

    sprintf(msg, "Hello, my name is %d", getpid());

    int size = strlen(msg);

    if(-1 == write(w_fd, &size, sizeof(int))) {

        perror("Error sending message length");

    }



    if(-1 == write(w_fd, msg, size * sizeof(char))) {

        perror("Error saying hi");

    }

    free(msg);

    size = 0;

    if(-1 == read(r_fd, &size, sizeof(int))) {

        perror("Error reading message length");

    }



    if(size > 0) {

        msg = malloc(sizeof(char) * (size + 1));

        if(-1 == read(r_fd, msg, sizeof(char) * size)) {

            perror("Error reading message");

        }

        msg[size] = 0;

        printf("Received message: %s\n", msg);

        free(msg);

    }

    close(r_fd);

    close(w_fd);



    return 0;

}