util: update three other copies of our dlinklist.h macros

ldb and tevent have their own copies of these macros. This brings them
in sync with the master copy of dlinklist.h

1 files changed, 115 insertions, 48 deletions

diff --git a/lib/tevent/tevent_util.h b/lib/tevent/tevent_util.h
index 829cbc2f6e..46a4506dac 100644
--- a/lib/tevent/tevent_util.h
+++ b/lib/tevent/tevent_util.h
@@ -1,7 +1,7 @@
 /*
    Unix SMB/CIFS implementation.
 
-   Copyright (C) Andrew Tridgell 1998-2005
+   Copyright (C) Andrew Tridgell 1998-2010
    Copyright (C) Jelmer Vernooij 2005
 
    This program is free software; you can redistribute it and/or modify
@@ -24,55 +24,94 @@
 #ifndef _DLINKLIST_H
 #define _DLINKLIST_H
 
+/*
+  February 2010 - changed list format to have a prev pointer from the
+  list head. This makes DLIST_ADD_END() O(1) even though we only have
+  one list pointer.
+
+  The scheme is as follows:
+
+     1) with no entries in the list:
+          list_head == NULL
+
+     2) with 1 entry in the list:
+          list_head->next == NULL
+          list_head->prev == list_head
+
+     3) with 2 entries in the list:
+          list_head->next == element2
+          list_head->prev == element2
+	  element2->prev == list_head
+	  element2->next == NULL
+
+     4) with N entries in the list:
+          list_head->next == element2
+          list_head->prev == elementN
+	  elementN->prev == element{N-1}
+	  elementN->next == NULL
+
+  This allows us to find the tail of the list by using
+  list_head->prev, which means we can add to the end of the list in
+  O(1) time
 
-/* hook into the front of the list */
+
+  Note that the 'type' arguments below are no longer needed, but
+  are kept for now to prevent an incompatible argument change
+ */
+
+
+/*
+   add an element at the front of a list
+*/
 #define DLIST_ADD(list, p) \
 do { \
         if (!(list)) { \
-		(list) = (p); \
-		(p)->next = (p)->prev = NULL; \
+		(p)->prev = (list) = (p);  \
+		(p)->next = NULL; \
 	} else { \
+		(p)->prev = (list)->prev; \
 		(list)->prev = (p); \
 		(p)->next = (list); \
-		(p)->prev = NULL; \
 		(list) = (p); \
-	}\
+	} \
 } while (0)
 
-/* remove an element from a list - element doesn't have to be in list. */
+/*
+   remove an element from a list
+   Note that the element doesn't have to be in the list. If it
+   isn't then this is a no-op
+*/
 #define DLIST_REMOVE(list, p) \
 do { \
 	if ((p) == (list)) { \
+		if ((p)->next) (p)->next->prev = (p)->prev; \
 		(list) = (p)->next; \
-		if (list) (list)->prev = NULL; \
+	} else if ((list) && (p) == (list)->prev) {	\
+		(p)->prev->next = NULL; \
+		(list)->prev = (p)->prev; \
 	} else { \
 		if ((p)->prev) (p)->prev->next = (p)->next; \
 		if ((p)->next) (p)->next->prev = (p)->prev; \
 	} \
-	if ((p) != (list)) (p)->next = (p)->prev = NULL; \
+	if ((p) != (list)) (p)->next = (p)->prev = NULL;	\
 } while (0)
 
-/* promote an element to the top of the list */
-#define DLIST_PROMOTE(list, p) \
+/*
+   find the head of the list given any element in it.
+   Note that this costs O(N), so you should avoid this macro
+   if at all possible!
+*/
+#define DLIST_HEAD(p, result_head) \
 do { \
-          DLIST_REMOVE(list, p); \
-          DLIST_ADD(list, p); \
-} while (0)
+       (result_head) = (p); \
+       while (DLIST_PREV(result_head)) (result_head) = (result_head)->prev; \
+} while(0)
 
-/* hook into the end of the list - needs a tmp pointer */
-#define DLIST_ADD_END(list, p, type) \
-do { \
-		if (!(list)) { \
-			(list) = (p); \
-			(p)->next = (p)->prev = NULL; \
-		} else { \
-			type tmp; \
-			for (tmp = (list); tmp->next; tmp = tmp->next) ; \
-			tmp->next = (p); \
-			(p)->next = NULL; \
-			(p)->prev = tmp; \
-		} \
-} while (0)
+/* return the last element in the list */
+#define DLIST_TAIL(list) ((list)?(list)->prev:NULL)
+
+/* return the previous element in the list. */
+#define DLIST_PREV(p) (((p)->prev && (p)->prev->next != NULL)?(p)->prev:NULL)
 
 /* insert 'p' after the given element 'el' in a list. If el is NULL then
    this is the same as a DLIST_ADD() */
@@ -81,34 +120,62 @@ do { \
         if (!(list) || !(el)) { \
 		DLIST_ADD(list, p); \
 	} else { \
-		p->prev = el; \
-		p->next = el->next; \
-		el->next = p; \
-		if (p->next) p->next->prev = p; \
+		(p)->prev = (el);   \
+		(p)->next = (el)->next;		\
+		(el)->next = (p);		\
+		if ((p)->next) (p)->next->prev = (p);	\
+		if ((list)->prev == (el)) (list)->prev = (p); \
 	}\
 } while (0)
 
-/* demote an element to the end of the list, needs a tmp pointer */
-#define DLIST_DEMOTE(list, p, tmp) \
+
+/*
+   add to the end of a list.
+   Note that 'type' is ignored
+*/
+#define DLIST_ADD_END(list, p, type)			\
+do { \
+	if (!(list)) { \
+		DLIST_ADD(list, p); \
+	} else { \
+		DLIST_ADD_AFTER(list, p, (list)->prev); \
+	} \
+} while (0)
+
+/* promote an element to the from of a list */
+#define DLIST_PROMOTE(list, p) \
+do { \
+          DLIST_REMOVE(list, p); \
+          DLIST_ADD(list, p); \
+} while (0)
+
+/*
+   demote an element to the end of a list.
+   Note that 'type' is ignored
+*/
+#define DLIST_DEMOTE(list, p, type)			\
 do { \
-		DLIST_REMOVE(list, p); \
-		DLIST_ADD_END(list, p, tmp); \
+	DLIST_REMOVE(list, p); \
+	DLIST_ADD_END(list, p, NULL);		\
 } while (0)
 
-/* concatenate two lists - putting all elements of the 2nd list at the
-   end of the first list */
-#define DLIST_CONCATENATE(list1, list2, type) \
+/*
+   concatenate two lists - putting all elements of the 2nd list at the
+   end of the first list.
+   Note that 'type' is ignored
+*/
+#define DLIST_CONCATENATE(list1, list2, type)	\
 do { \
-		if (!(list1)) { \
-			(list1) = (list2); \
-		} else { \
-			type tmp; \
-			for (tmp = (list1); tmp->next; tmp = tmp->next) ; \
-			tmp->next = (list2); \
-			if (list2) { \
-				(list2)->prev = tmp;	\
-			} \
+	if (!(list1)) { \
+		(list1) = (list2); \
+	} else { \
+		(list1)->prev->next = (list2); \
+		if (list2) { \
+			void *_tmplist = (void *)(list1)->prev; \
+			(list1)->prev = (list2)->prev; \
+			(list2)->prev = _tmplist; \
 		} \
+	} \
 } while (0)
 
 #endif /* _DLINKLIST_H */