diff options
| author | David Lamparter <equinox@opensourcerouting.org> | 2021-09-29 22:15:11 +0200 |
|---|---|---|
| committer | David Lamparter <equinox@opensourcerouting.org> | 2021-10-19 14:55:39 +0200 |
| commit | d259ca0989c793767c912622437c3c5b2c6d84b2 (patch) | |
| tree | 6dac6cc1a48f47edde0c52a248dff2c1c09256e7 /lib/typesafe.h | |
| parent | f45897e45c57db80b21e31d44723733a17bfac54 (diff) | |
lib: use sentinel for single-linked lists
Using a non-NULL sentinel allows distinguishing between "end of list"
and "item not on any list". It's a compare either way, just the value
is different.
Signed-off-by: David Lamparter <equinox@opensourcerouting.org>
Diffstat (limited to 'lib/typesafe.h')
| -rw-r--r-- | lib/typesafe.h | 27 |
1 files changed, 19 insertions, 8 deletions
diff --git a/lib/typesafe.h b/lib/typesafe.h index ecf7d10eb1..b03934b964 100644 --- a/lib/typesafe.h +++ b/lib/typesafe.h @@ -132,6 +132,10 @@ struct slist_head { size_t count; }; +/* this replaces NULL as the value for ->next on the last item. */ +extern struct slist_item typesafe_slist_sentinel; +#define _SLIST_LAST &typesafe_slist_sentinel + static inline void typesafe_list_add(struct slist_head *head, struct slist_item **pos, struct slist_item *item) { @@ -165,6 +169,7 @@ MACRO_REQUIRE_SEMICOLON() /* end */ macro_inline void prefix ## _init(struct prefix##_head *h) \ { \ memset(h, 0, sizeof(*h)); \ + h->sh.first = _SLIST_LAST; \ h->sh.last_next = &h->sh.first; \ } \ macro_inline void prefix ## _fini(struct prefix##_head *h) \ @@ -190,13 +195,13 @@ macro_inline void prefix ## _add_after(struct prefix##_head *h, \ macro_inline type *prefix ## _del(struct prefix##_head *h, type *item) \ { \ struct slist_item **iter = &h->sh.first; \ - while (*iter && *iter != &item->field.si) \ + while (*iter != _SLIST_LAST && *iter != &item->field.si) \ iter = &(*iter)->next; \ - if (!*iter) \ + if (*iter == _SLIST_LAST) \ return NULL; \ h->sh.count--; \ *iter = item->field.si.next; \ - if (!item->field.si.next) \ + if (item->field.si.next == _SLIST_LAST) \ h->sh.last_next = iter; \ item->field.si.next = NULL; \ return item; \ @@ -204,11 +209,11 @@ macro_inline type *prefix ## _del(struct prefix##_head *h, type *item) \ macro_inline type *prefix ## _pop(struct prefix##_head *h) \ { \ struct slist_item *sitem = h->sh.first; \ - if (!sitem) \ + if (sitem == _SLIST_LAST) \ return NULL; \ h->sh.count--; \ h->sh.first = sitem->next; \ - if (h->sh.first == NULL) \ + if (h->sh.first == _SLIST_LAST) \ h->sh.last_next = &h->sh.first; \ sitem->next = NULL; \ return container_of(sitem, type, field.si); \ @@ -226,13 +231,17 @@ macro_inline void prefix ## _swap_all(struct prefix##_head *a, \ } \ macro_pure const type *prefix ## _const_first(const struct prefix##_head *h) \ { \ - return container_of_null(h->sh.first, type, field.si); \ + if (h->sh.first != _SLIST_LAST) \ + return container_of(h->sh.first, type, field.si); \ + return NULL; \ } \ macro_pure const type *prefix ## _const_next(const struct prefix##_head *h, \ const type *item) \ { \ const struct slist_item *sitem = &item->field.si; \ - return container_of_null(sitem->next, type, field.si); \ + if (sitem->next != _SLIST_LAST) \ + return container_of(sitem->next, type, field.si); \ + return NULL; \ } \ TYPESAFE_FIRST_NEXT(prefix, type) \ macro_pure type *prefix ## _next_safe(struct prefix##_head *h, type *item) \ @@ -241,7 +250,9 @@ macro_pure type *prefix ## _next_safe(struct prefix##_head *h, type *item) \ if (!item) \ return NULL; \ sitem = &item->field.si; \ - return container_of_null(sitem->next, type, field.si); \ + if (sitem->next != _SLIST_LAST) \ + return container_of(sitem->next, type, field.si); \ + return NULL; \ } \ macro_pure size_t prefix ## _count(const struct prefix##_head *h) \ { \ |