Re: [gtk-list] g_[s]list_qsort suggestion

[Tim Janik <timj gtk org>]

On Fri, 5 Jun 1998 dramboz@imaginet.fr wrote:

> 
> Hello,
> 
>   What about adding a function to quickly sort GLists 
> and GSLists ? 
> 
>   Here's a simple implementation using qsort :
> 
> 
> 
> typedef gint (*GQSortFunc) ( const gpointer value1,
> 			     const gpointer value2); 

hm, as has been pointed out a few times already,
const gpointer doesn't work, we would ned tzo have some
typedef const void * gconstpointer;

> GList*
> g_list_qsort( GList *list, GQSortFunc func) {
>     GList *item;
>     gpointer *base, *tmp;
>     guint size;
> 
>     g_return_val_if_fail( list != NULL, list);
>     g_return_val_if_fail( func != NULL, list);
> 
>     size = g_list_length( list);
> 
>     base = tmp = g_malloc( size*sizeof( gpointer));
>     g_return_val_if_fail( base != NULL, list);
> 
>     item = list;
>     while ( item) {
> 	*tmp++ = item->data;
> 	item = item->next;
>     }
>     
>     qsort( base, size, sizeof( gpointer), func);
>     
>     tmp = base;
>     item = list;
>     while ( item) {
> 	item->data = *tmp++;
> 	item = item->next;
>     }

though just changing the ->data portion of all the GList structures is
an efficient solution, this is not always what's needed. we loose the
ability to hold GList pointers across g_list_qsort() invokations with this.

GList *sort_me;

[...]

GList *first_item;

first_item = sort_me;

sort_me = g_list_qsort (sort_me, SomeSortFunc);

[now, `first_item' still points to the first GList structure, but not to the same
 ->data anymore.]

>     
>     g_free( base);
>     
>     return list;
> }

could we try to get around this limitation?


---
ciaoTJ