+ * tal_len - get the count of bytes in a tal_arr.
+ * @ptr: The tal allocated object array.
+ *
+ * Returns 0 if @ptr has no length property, but be aware that that is
+ * also a valid size!
+ */
+size_t tal_len(const tal_t *ptr);
+
+/**
+ * tal_first - get the first immediate tal object child.