slist: add sys_slist_get() to fetch and remove the head

More straightforward than doing sys_slist_peek_head() followed by
sys_slist_remove().

Also add a version that does not check if the list is non-empty to be
used when the list is known bo be non-empty.

Change-Id: I8fd10e20e2c84c7d8972c9207f3d4917884808cb
Signed-off-by: Benjamin Walsh <[email protected]>

include/misc/slist.h

@@ -198,6 +198,39 @@ static inline void sys_slist_insert(sys_slist_t *list,
 	}
 }
 
+/**
+ * @brief Fetch and remove the first node of the given list
+ *
+ * List must be known to be non-empty.
+ *
+ * @param list A pointer on the list to affect
+ *
+ * @return A pointer to the first node of the list
+ */
+static inline sys_snode_t *sys_slist_get_not_empty(sys_slist_t *list)
+{
+	sys_snode_t *node = list->head;
+
+	list->head = node->next;
+	if (list->tail == node) {
+		list->tail = list->head;
+	}
+
+	return node;
+}
+
+/**
+ * @brief Fetch and remove the first node of the given list
+ *
+ * @param list A pointer on the list to affect
+ *
+ * @return A pointer to the first node of the list (or NULL if empty)
+ */
+static inline sys_snode_t *sys_slist_get(sys_slist_t *list)
+{
+	return sys_slist_is_empty(list) ? NULL : sys_slist_get_not_empty(list);
+}
+
 /**
  * @brief Remove a node
  *