#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <sys/wait.h>

void writer_process(int fd_write, FILE *file) {
    unsigned char c;
    // Close the unused read end of the pipe
    close(fd_write - 1); // fd[0] is read end, fd[1] is write end, so fd_write - 1 points to read end

    // Write the file data byte by byte to the pipe
    while (fread(&c, 1, 1, file) > 0) {
        write(fd_write, &c, 1);
    }
    
    // Close the write end of the pipe after finishing
    close(fd_write);
    exit(0); // Exit after writing
}

void reader_process(int fd_read) {
    unsigned char read_char;
    int i = 1;

    // Close the unused write end of the pipe
    close(fd_read + 1); // fd[1] is write end, so fd_read + 1 points to write end

    // Read from the pipe and print in hexadecimal format
    while (read(fd_read, &read_char, 1) > 0) {
        printf(" %02x", read_char);
        if (++i > 16) { // Print 16 bytes per line
            printf("\n");
            i = 1;
        }
    }
    printf("\n");

    // Close the read end of the pipe after finishing
    close(fd_read);
    exit(0); // Exit after reading and printing
}

int main(int argc, char *argv[]) {
    if (argc < 2) {
        fprintf(stderr, "Usage: %s <filename>\n", argv[0]);
        exit(1);
    }

    // Open the file in binary mode
    FILE *file = fopen(argv[1], "rb");
    if (file == NULL) {
        fprintf(stderr, "Can't open file %s\n", argv[1]);
        exit(1);
    }

    int fd[2];
    if (pipe(fd) != 0) {
        fprintf(stderr, "Error while creating pipe!\n");
        exit(1);
    }

    // Fork writer process
    pid_t writer_pid = fork();
    if (writer_pid < 0) {
        fprintf(stderr, "Failed to create writer process.\n");
        exit(1);
    } else if (writer_pid == 0) {
        // Writer process logic
        writer_process(fd[1], file);
    }

    // Close file in the parent after creating the writer
    fclose(file);

    // Fork reader process
    pid_t reader_pid = fork();
    if (reader_pid < 0) {
        fprintf(stderr, "Failed to create reader process.\n");
        exit(1);
    } else if (reader_pid == 0) {
        // Reader process logic
        reader_process(fd[0]);
    }

    // In the father process: close both ends of the pipe
    close(fd[0]);
    close(fd[1]);

    // Wait for both children to finish
    waitpid(writer_pid, NULL, 0);
    waitpid(reader_pid, NULL, 0);

    return 0;
}