/* Check the magic number */
    if (read(zs->zs_fh, header, sizeof(header)) != sizeof(header) ||
        memcmp(header, z_magic, sizeof(z_magic)) != 0) {
        errno = EFTYPE;
        return (-1);
    }

    /* Check the magic number */
    Inline_Stack_Reset;
    Inline_Stack_Push(zs->zs_fh); /* a SV* of a IO handle passed in earlier */
    Inline_Stack_Push(header);
    Inline_Stack_Push(sizeof(header));
    perl_call_pv("CORE::read",G_SCALAR);
    read_rval = (ssize_t)POPi;
    Inline_Stack_Done;

    if (read_rval != sizeof(header) ||
        memcmp(header, z_magic, sizeof(z_magic)) != 0) {
        errno = EFTYPE;
        return (-1);
    }