[Freeciv-Dev] Re: [PATCH] Small improvement at genlist and maphand

[Raimar Falke <hawk@xxxxxxxxxxxxxxxxxxxxxxx>]

On Mon, Aug 20, 2001 at 11:15:02PM +0300, Markus Linnala wrote:
> Raimar Falke <hawk@xxxxxxxxxxxxxxxxxxxxxxx> writes:
> 
> > It is. I would like a discussion what is preferred: id or pointer. If
> > one type is selected we can start our crusade.

I like ids more but a lot of the methods in the call chains need
certain attributes of an object (unit, citiy,...). These attributes
are only accessible with a pointer or accessor methods (which I
consider silly in freeciv). So to me the rule should be to transfer
pointers as arguements and let only handle the lower network layers
with ids.

I see one disadvantage of pointers: the validity isn't automatically
checked. If a method has an id and want to access some attributes it
has to use a find_object_by_id method. Such a method will test if the
given id is still valid. A pointer will always be valid. So a new
field in every struct is needed to indicate invalid structs. Such a
flag will be set if a remove_unit packet is received for example.

> With get_player, I think we need both and both inlined.
> get_player is there to make things more understandable. Maybe we
> should make some extra checks.
> 
> ------------------------------------------------------------------------
> struct player *get_player(int player_id)
> {
>     assert(player_id >= 0 && player_id < game.max_players);
>     return &game.players[player_id];
> }
> int get_player_by_id(struct player *pplayer)
> {
>     assert(pplayer->player_no >= 0 && pplayer->player_no < game.max_players);
>     return pplayer->player_no;
> }
> ------------------------------------------------------------------------
> 
> Or something like that. Well, not so good example. But as simple
> functions as these are, you might get smaller code size and game
> is definitely faster when you get rid of actual function call.

IMHO the access to a id/player_no field shouldn't be made more
complex. However I would like methods like "is_valid_punit" and
"ensure_valid_punit".

        Raimar

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