diff options
| author | Alex Crawford <alex.crawford@coreos.com> | 2015-08-03 23:11:53 -0700 |
|---|---|---|
| committer | Alex Crawford <alex.crawford@coreos.com> | 2015-08-04 03:23:43 -0700 |
| commit | dbe465c93ea8a87da95919d3f0ee802865802cfa (patch) | |
| tree | 1cc0d50e2a026e988a85672d531383f97776af7c /src/basic/list.h | |
| parent | 58a2e9acd8216f55b004e5432f76a851f7b233c0 (diff) | |
basic: add LIST_INSERT_BEFORE
Similar in function to LIST_INSERT_AFTER, this will insert a new element
into the list before the specified position. If the specified position
is NULL, the element is added as the tail of the list.
Diffstat (limited to 'src/basic/list.h')
| -rw-r--r-- | src/basic/list.h | 26 |
1 files changed, 26 insertions, 0 deletions
diff --git a/src/basic/list.h b/src/basic/list.h index 2939216adb..760abcdab3 100644 --- a/src/basic/list.h +++ b/src/basic/list.h @@ -123,6 +123,32 @@ } \ } while(false) +/* Insert an item before another one (a = where, b = what) */ +#define LIST_INSERT_BEFORE(name,head,a,b) \ + do { \ + typeof(*(head)) **_head = &(head), *_a = (a), *_b = (b); \ + assert(_b); \ + if (!_a) { \ + if (!*_head) { \ + _b->name##_next = NULL; \ + _b->name##_prev = NULL; \ + *_head = _b; \ + } else { \ + typeof(*(head)) *_tail = (head); \ + while (_tail->name##_next) \ + _tail = _tail->name##_next; \ + _b->name##_next = NULL; \ + _b->name##_prev = _tail; \ + _tail->name##_next = _b; \ + } \ + } else { \ + if ((_b->name##_prev = _a->name##_prev)) \ + _b->name##_prev->name##_next = _b; \ + _b->name##_next = _a; \ + _a->name##_prev = _b; \ + } \ + } while(false) + #define LIST_JUST_US(name,item) \ (!(item)->name##_prev && !(item)->name##_next) \ |