Re: Handlers

["Vesa Jääskeläinen" <chaac@nic.fi>]

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Marco Gerards wrote:
> If I knew a better way, I would have used it.  I think the
> alternatives will all end up in either code duplication or a loss of
> type safety that now is at least present through warnings.  But please
> understand that you only have to use the macros, not change them :-)
> 
> Suggestions are welcome.

Hi,

Well... How about something like this?

It only requires one cast and no macros at all.

Thanks,
Vesa Jääskeläinen

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#include <stdio.h>
#include <stdlib.h>
#include <string.h>

typedef struct grub_list 
{
	struct grub_list *next;
} grub_list_t;

typedef struct
{
	/* Has to be first */
	grub_list_t entry;

	/* Just some data */
	char name[32];
} grub_fs_t;

void grub_list_add(grub_list_t **list, grub_list_t *item)
{
	item->next = *list;
	*list = item;
}

void grub_list_remove(grub_list_t **list, grub_list_t *item)
{
	grub_list_t *prev = 0;
	grub_list_t *tmp = *list;
	
	while (tmp)
	{
		if (tmp == item)
		{
			if (! prev)
			{
				*list = tmp->next;
				tmp->next = 0;
				return;
			}
			else
			{
				prev->next = tmp->next;
				tmp->next = 0;
				return;
			}
		}
		
		prev = tmp;
		tmp = tmp->next;
	}
}

int grub_list_iterate(grub_list_t *list, int (*hook) (const grub_list_t *item))
{
	while (list)
	{
		if (hook(list))
			return 1;

		list = list->next;
	}

	return 0;
}

int grub_fs_print (const grub_list_t *list_item)
{
	grub_fs_t *item = (grub_fs_t *)list_item;

	printf("'%s'\n", item->name);

	return 0;
}

int main()
{
	grub_fs_t item1;
	grub_fs_t item2;
	grub_fs_t item3;

	grub_list_t *fs_list = 0;

	memset(&item1, 0, sizeof(item1));
	memset(&item2, 0, sizeof(item2));
	memset(&item3, 0, sizeof(item3));

	strcpy(item1.name, "item 1");
	strcpy(item2.name, "item 2");
	strcpy(item3.name, "item 3");

	grub_list_add(&fs_list, &item1.entry);
	grub_list_add(&fs_list, &item2.entry);
	grub_list_add(&fs_list, &item3.entry);

	printf("---\n");
	grub_list_iterate(fs_list, grub_fs_print);
	
	printf("---\n");
	grub_list_remove(&fs_list, &item2.entry);
	grub_list_iterate(fs_list, grub_fs_print);

	printf("---\n");
	grub_list_remove(&fs_list, &item2.entry);
	grub_list_iterate(fs_list, grub_fs_print);

	printf("---\n");
	grub_list_remove(&fs_list, &item1.entry);
	grub_list_iterate(fs_list, grub_fs_print);

	printf("---\n");
	grub_list_remove(&fs_list, &item3.entry);
	grub_list_iterate(fs_list, grub_fs_print);

	printf("---\n");
	grub_list_remove(&fs_list, &item3.entry);
	grub_list_iterate(fs_list, grub_fs_print);
	printf("---\n");

	return 0;
}