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basic: add LIST_INSERT_BEFORE

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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.
This commit is contained in:
Alex Crawford
2015-08-04 03:23:43 -07:00
parent 58a2e9acd8
commit dbe465c93e
2 changed files with 70 additions and 0 deletions
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src/basic/list.h
+26
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@@ -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) \