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

int main(int argc, char *argv[])
{
    assert(argc == 3);

    int fd_in = open(argv[1], O_RDONLY);
    assert(fd_in >= 0);

    struct stat st;
    fstat(fd_in, &st);

    // on mappe le fichier source en mémoire
    void *src = mmap(NULL, st.st_size, PROT_READ, MAP_PRIVATE, fd_in, 0);
    assert(src != MAP_FAILED);

    int fd_out = open(argv[2], O_RDWR | O_CREAT | O_TRUNC, 0644);
    assert(fd_out >= 0);

    // on fixe la taille du fichier de sortie
    ftruncate(fd_out, st.st_size);

    // on mappe le fichier destination en mémoire
    void *dst = mmap(NULL, st.st_size, PROT_WRITE, MAP_SHARED, fd_out, 0);
    assert(dst != MAP_FAILED);

    // copie mémoire → mémoire
    memcpy(dst, src, st.st_size);

    // nettoyage
    munmap(src, st.st_size);
    munmap(dst, st.st_size);
    close(fd_in);
    close(fd_out);

    return 0;
}