From: Alex Crawford <alex.crawford@coreos.com>
Date: Tue, 4 Aug 2015 06:11:53 +0000 (-0700)
Subject: basic: add LIST_INSERT_BEFORE
X-Git-Tag: v225~106^2~4
X-Git-Url: http://git.ipfire.org/gitweb.cgi?a=commitdiff_plain;h=dbe465c93ea8a87da95919d3f0ee802865802cfa;p=thirdparty%2Fsystemd.git

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.
---

diff --git a/src/basic/list.h b/src/basic/list.h
index 2939216adb6..760abcdab3b 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)                  \
 
diff --git a/src/test/test-list.c b/src/test/test-list.c
index f6da1a70533..160064d06a9 100644
--- a/src/test/test-list.c
+++ b/src/test/test-list.c
@@ -99,6 +99,50 @@ int main(int argc, const char *argv[]) {
         assert_se(items[1].item_prev == &items[3]);
         assert_se(items[3].item_prev == NULL);
 
+        LIST_REMOVE(item, head, &items[1]);
+        assert_se(LIST_JUST_US(item, &items[1]));
+
+        assert_se(items[0].item_next == NULL);
+        assert_se(items[2].item_next == &items[0]);
+        assert_se(items[3].item_next == &items[2]);
+
+        assert_se(items[0].item_prev == &items[2]);
+        assert_se(items[2].item_prev == &items[3]);
+        assert_se(items[3].item_prev == NULL);
+
+        LIST_INSERT_BEFORE(item, head, &items[2], &items[1]);
+        assert_se(items[0].item_next == NULL);
+        assert_se(items[2].item_next == &items[0]);
+        assert_se(items[1].item_next == &items[2]);
+        assert_se(items[3].item_next == &items[1]);
+
+        assert_se(items[0].item_prev == &items[2]);
+        assert_se(items[2].item_prev == &items[1]);
+        assert_se(items[1].item_prev == &items[3]);
+        assert_se(items[3].item_prev == NULL);
+
+        LIST_REMOVE(item, head, &items[0]);
+        assert_se(LIST_JUST_US(item, &items[0]));
+
+        assert_se(items[2].item_next == NULL);
+        assert_se(items[1].item_next == &items[2]);
+        assert_se(items[3].item_next == &items[1]);
+
+        assert_se(items[2].item_prev == &items[1]);
+        assert_se(items[1].item_prev == &items[3]);
+        assert_se(items[3].item_prev == NULL);
+
+        LIST_INSERT_BEFORE(item, head, NULL, &items[0]);
+        assert_se(items[0].item_next == NULL);
+        assert_se(items[2].item_next == &items[0]);
+        assert_se(items[1].item_next == &items[2]);
+        assert_se(items[3].item_next == &items[1]);
+
+        assert_se(items[0].item_prev == &items[2]);
+        assert_se(items[2].item_prev == &items[1]);
+        assert_se(items[1].item_prev == &items[3]);
+        assert_se(items[3].item_prev == NULL);
+
         LIST_REMOVE(item, head, &items[0]);
         assert_se(LIST_JUST_US(item, &items[0]));