Add fr_dlist_entry_move

diff --git a/src/lib/util/dlist.h b/src/lib/util/dlist.h
index 994b760c1dfc4c46c94bdd4dd4e3fabd8ed185fd..08b63f9c09f22d81e3d2a95b86b7f5d787d05879 100644 (file)
--- a/src/lib/util/dlist.h
+++ b/src/lib/util/dlist.h
@@ -108,7 +108,7 @@ static inline CC_HINT(nonnull) bool fr_dlist_entry_in_list(fr_dlist_t const *ent
        return true;
 }
 
-/** Link in an entry after the current entry
+/** Link in a single entry after the current entry
  *
  * @param[in] entry    to link in entry after.
  * @param[in] to_link  entry to link in after.
@@ -121,7 +121,7 @@ static inline CC_HINT(nonnull) void fr_dlist_entry_link_after(fr_dlist_t *entry,
        entry->next = to_link;
 }
 
-/** Link in an entry before the current entry
+/** Link in a single entry before the current entry
  *
  * @param[in] entry    to link in entry before.
  * @param[in] to_link  entry to link in before.
@@ -134,6 +134,25 @@ static inline CC_HINT(nonnull) void fr_dlist_entry_link_before(fr_dlist_t *entry
        entry->prev = to_link;
 }
 
+/** Link in a sublist before the current entry
+ *
+ * @note This is not suitable for moving elements from a fr_dlist_head_t as
+ *      we need to snip out the head element. This is only suitable if the
+ *      two entries are not part of lists with head elements.
+ *
+ * @param[in] dst      to link src in before.
+ * @param[in] src      to link in before dst.
+ */
+static inline CC_HINT(nonnull) void fr_dlist_entry_move(fr_dlist_t *dst, fr_dlist_t *src)
+{
+       fr_dlist_t *src_end = src->prev;
+
+       dst->prev->next = src;
+       src->prev->next = dst;
+       src->prev = dst->prev;
+       dst->prev = src_end;
+}
+
 /** Replace one entry with another
  *
  * @param[in] entry            to replace.
@@ -651,6 +670,11 @@ static inline CC_HINT(nonnull) void fr_dlist_move(fr_dlist_head_t *list_dst, fr_
 
        if (fr_dlist_empty(list_src)) return;
 
+       /*
+        *      This is different to fr_dlist_entry_move
+        *      because we need need to snip out the
+        *      list head entry from the src.
+        */
        src->prev->next = dst;
        src->next->prev = dst->prev;