#define rb_str_set_len(str, length) (RSTRING_LEN(str) = (length))

static VALUE escape_string(VALUE klass, VALUE str)
{
    VALUE ret;
    Check_Type(str, T_STRING);
    ret = rb_str_new(0, (RSTRING_LEN(str))*2+1);
    rb_str_set_len(ret, mysql_escape_string(RSTRING_PTR(ret), RSTRING_PTR(str), RSTRING_LEN(str)));
    return ret;
}