Question: How can i refresh grid data when new data added in exts?

Answer: 
Making it const and making it static do two different things.

* if it is const, each function call gets its own unchangeable instance of the struct
* if it is static there is one changeable instance of the struct shared across all function calls

It sounds as though what you want is a struct instance that is both static and const, which is a reasonable thing to do.

Performance wise, the static version should have a slight edge, as construction of the struct instance will only be done once.
...

```
// so, do you want odor-free, or fast ?
switch (str[0]){
case 'g': case 'G':
  return GB_UNIT;
case 'k': case 'K':
  return KB_UNIT;
case 'm': case 'M':
  return MB_UNIT;
}

```