util: Add list_is_singular() helper function

Returns whether the list has exactly one element.

Reviewed-by: Matt Turner <mattst88@gmail.com>

diff --git a/src/util/list.h b/src/util/list.h
index b98ce59..066f9b8 100644 (file)
--- a/src/util/list.h
+++ b/src/util/list.h
@@ -99,6 +99,14 @@ static inline bool list_empty(struct list_head *list)
    return list->next == list;
 }
 
+/**
+ * Returns whether the list has exactly one element.
+ */
+static inline bool list_is_singular(const struct list_head *list)
+{
+   return list->next != NULL && list->next->next == list;
+}
+
 static inline unsigned list_length(struct list_head *list)
 {
    struct list_head *node;