util: added TLIST_*() macros

The TLIST_*() macros are like the DLIST_*() macros, but take both a
head and tail pointer for the list. This means that adding an element
to the end of the list is efficient (it doesn't need to walk the
list).

We should move all uses of the DLIST_*() macros which use
DLIST_ADD_END() to use the TLIST_*() macros instead.

diff --git a/lib/util/dlinklist.h b/lib/util/dlinklist.h
index f018d873f6b7b6523210eb79406845bd81ba4020..44747d684aad3c5939ce5a7dedff2085336a043c 100644 (file)
--- a/lib/util/dlinklist.h
+++ b/lib/util/dlinklist.h
@@ -110,4 +110,50 @@ do { \
                } \
 } while (0)
 
+/*
+   The TLIST_*() macros are meant for when you have two list pointers,
+   one pointing at the head of the list and one pointing at the tail
+   of the list. This makes the common case of adding to the end of the
+   list and removing from the front of the list efficient
+
+   TLIST stands for "tailed list"
+
+   Note: When initialising the structure containing your lists, make
+   sure that you set both head and tail to NULL
+
+   Also, do not mix the TLIST_*() macros with the DLIST_* macros!
+*/
+
+/* TLIST_ADD_FRONT adds elements to the front of the list. */
+#define TLIST_ADD_FRONT(listhead, listtail, p) \
+do { \
+       DLIST_ADD(listhead, p); \
+       if (NULL == (listtail)) { \
+               (listtail) = (p); \
+       } \
+} while (0)
+
+/* TLIST_ADD_END adds elements to the end of the list. */
+#define TLIST_ADD_END(listhead, listtail, p) \
+do { \
+       if ((listtail) == NULL) { \
+               DLIST_ADD(listhead, p); \
+               (listtail) = (listhead); \
+       } else { \
+               (listtail)->next = (p); \
+               (p)->prev = (listtail); \
+               (p)->next = NULL; \
+               (listtail) = (p); \
+       } \
+} while (0)
+
+/* TLIST_REMOVE removes an element from the list */
+#define TLIST_REMOVE(listhead, listtail, p) \
+do { \
+       if ((p) == (listtail)) { \
+               (listtail) = (p)->prev; \
+       } \
+       DLIST_REMOVE(listhead, p); \
+} while (0)
+
 #endif /* _DLINKLIST_H */