list: list_del_from()

Deletion from a specific list.

diff --git a/ccan/list/list.h b/ccan/list/list.h
index 5b4f81c965725d473f7cfc6df52812c21fc7cfc4..02835a6b51e092c4b95fbc21a88bb71bbb46910a 100644 (file)
--- a/ccan/list/list.h
+++ b/ccan/list/list.h
@@ -1,6 +1,7 @@
 #ifndef CCAN_LIST_H
 #define CCAN_LIST_H
 #include <stdbool.h>
+#include <assert.h>
 #include <ccan/container_of/container_of.h>
 
 /**
@@ -164,9 +165,30 @@ static inline void list_add_tail(struct list_head *h, struct list_node *n)
 }
 
 /**
- * list_del - delete an entry from a linked list.
+ * list_empty - is a list empty?
+ * @h: the list_head
+ *
+ * If the list is empty, returns true.
+ *
+ * Example:
+ *     assert(list_empty(&parent->children) == (parent->num_children == 0));
+ */
+static inline bool list_empty(const struct list_head *h)
+{
+       (void)list_debug(h);
+       return h->n.next == &h->n;
+}
+
+/**
+ * list_del - delete an entry from an (unknown) linked list.
  * @n: the list_node to delete from the list.
  *
+ * Note that this leaves @n in an undefined state; it can be added to
+ * another list, but not deleted again.
+ *
+ * See also:
+ *     list_del_from()
+ *
  * Example:
  *     list_del(&child->list);
  *     parent->num_children--;
@@ -183,18 +205,33 @@ static inline void list_del(struct list_node *n)
 }
 
 /**
- * list_empty - is a list empty?
- * @h: the list_head
+ * list_del_from - delete an entry from a known linked list.
+ * @h: the list_head the node is in.
+ * @n: the list_node to delete from the list.
  *
- * If the list is empty, returns true.
+ * This explicitly indicates which list a node is expected to be in,
+ * which is better documentation and can catch more bugs.
+ *
+ * See also: list_del()
  *
  * Example:
- *     assert(list_empty(&parent->children) == (parent->num_children == 0));
+ *     list_del_from(&parent->children, &child->list);
+ *     parent->num_children--;
  */
-static inline bool list_empty(const struct list_head *h)
+static inline void list_del_from(struct list_head *h, struct list_node *n)
 {
-       (void)list_debug(h);
-       return h->n.next == &h->n;
+#ifdef CCAN_LIST_DEBUG
+       {
+               /* Thorough check: make sure it was in list! */
+               struct list_node *i;
+               for (i = h->n.next; i != n; i = i->next)
+                       assert(i != &h->n);
+       }
+#endif /* CCAN_LIST_DEBUG */
+
+       /* Quick test that catches a surprising number of bugs. */
+       assert(!list_empty(h));
+       list_del(n);
 }
 
 /**

diff --git a/ccan/list/test/run-with-debug.c b/ccan/list/test/run-with-debug.c
index d34c660e6582b96b3eedd9443684c22dd012ef0b..f76bccc12773ee2e6a55e6ae0c13ee790361f0db 100644 (file)
--- a/ccan/list/test/run-with-debug.c
+++ b/ccan/list/test/run-with-debug.c
@@ -102,21 +102,23 @@ int main(int argc, char *argv[])
        }
        ok1(i == 3);
 
-       /* Test list_for_each_safe and list_del. */
+       /* Test list_for_each_safe, list_del and list_del_from. */
        i = 0;
        list_for_each_safe(&parent.children, c, n, list) {
                switch (i++) {
                case 0:
-                       ok1(c == &c1);
+                       ok1(c == &c1);  
+                       list_del(&c->list);
                        break;
                case 1:
                        ok1(c == &c2);
+                       list_del_from(&parent.children, &c->list);
                        break;
                case 2:
                        ok1(c == &c3);
+                       list_del_from(&parent.children, &c->list);
                        break;
                }
-               list_del(&c->list);
                ok1(list_check(&parent.children, NULL));
                if (i > 2)
                        break;

diff --git a/ccan/list/test/run.c b/ccan/list/test/run.c
index 7c71e396ca36e8823435bf8b81d5e96d4e9b91dc..13a1da4198134d88cbeb56020c1ee9acd7cce24a 100644 (file)
--- a/ccan/list/test/run.c
+++ b/ccan/list/test/run.c
@@ -101,21 +101,23 @@ int main(int argc, char *argv[])
        }
        ok1(i == 3);
 
-       /* Test list_for_each_safe and list_del. */
+       /* Test list_for_each_safe, list_del and list_del_from. */
        i = 0;
        list_for_each_safe(&parent.children, c, n, list) {
                switch (i++) {
                case 0:
-                       ok1(c == &c1);
+                       ok1(c == &c1);  
+                       list_del(&c->list);
                        break;
                case 1:
                        ok1(c == &c2);
+                       list_del_from(&parent.children, &c->list);
                        break;
                case 2:
                        ok1(c == &c3);
+                       list_del_from(&parent.children, &c->list);
                        break;
                }
-               list_del(&c->list);
                ok1(list_check(&parent.children, NULL));
                if (i > 2)
                        break;