static int
read_file(const char *filename, char **r_buf, long *r_size)
{
    assert(r_buf != NULL);

    // attempt to open the file
    FILE *fp = fopen(filename, "r");
    if (!fp)
        spark_err_raisef(SPK_EIO, "unable to open file %s", filename);

    // determine its size
    fseek(fp, 0, SEEK_END);
    long size = ftell(fp);

    // allocate a buffer and read into
    char *data = malloc(size);
    if (!data)
        spark_err_raise(SPK_ENOMEM);
    fseek(fp, 0, SEEK_SET);
    fread(data, 1, size, fp);
    if (ferror(fp))
        spark_err_raisef(SPK_EIO, "unable to read file %s", filename);

    // return the size of file read and its contents
    if (r_size)
        *r_size = size;
    *r_buf = data;

    return 0;
}

int
main(int argc, char **argv)
{
    int err = 0;

    char *f1 = NULL;
    if ((err = read_file("ok.txt", &f1, NULL)))
        goto handle_error;

    char *f2 = NULL;
    if ((err = read_file("bad.txt", &f2, NULL)))
        goto handle_error;

    char *f3 = NULL;
    if ((err = read_file("nonexisting.txt", &f3, NULL)))
        goto handle_error;

    return 0;

handle_error:
    fprintf(stderr, "%s\n", spark_err_msg());
    return err;
}