#include <stdio.h>
#include <fcntl.h>
#include <unistd.h>
#include <sys/mman.h>
#include <string.h>

#define FILE_PATH "example.txt"
#define FILE_SIZE 4096  // File size for mmap

void use_write(int fd) {
    const char *write_data = "Hello from write()\n syscall!\n";
    char read_buf[100] = {0};
    write(fd, write_data, strlen(write_data));
}

void use_mmap(int fd) {
    // Extend file size for mmap
    ftruncate(fd, FILE_SIZE);

    // Memory-map the file
    char *map = mmap(NULL, FILE_SIZE, PROT_READ | PROT_WRITE, MAP_SHARED, fd, 0);
    if (map == MAP_FAILED) {
        perror("mmap failed");
        return;
    }

    // Write data using mmap
    const char *mmap_data = "Hello from mmap!\n";
    strcpy(map, mmap_data);
}

int main() {
    int fd = open(FILE_PATH, O_RDWR | O_CREAT, 0644);
    if (fd < 0) {
        perror("open failed");
        return 1;
    }

    printf("Using syscall write\n");
    use_write(fd);

    printf("Using mmap\n");
    use_mmap(fd);

    close(fd);
    return 0;
}