/*      escape_string(string)        */
static VALUE escape_string(VALUE klass, VALUE str)
{
    VALUE ret;
    Check_Type(str, T_STRING);
    ret = rb_str_new(0, (RSTRING(str)->len)*2+1);
    RSTRING(ret)->len = mysql_escape_string(RSTRING(ret)->ptr, RSTRING(str)->ptr, RSTRING(str)->len);
    return ret;
}