* (too short? error)
*
* hbytes range VALUE START SIZE => substring (or error)
+ * hbytes overwrite VAR START VALUE
+ * hbytes trimleft VALUE removes any leading 0 octets
+ * hbytes repeat VALUE COUNT => COUNT copies of VALUE
*
* hbytes h2ulong HEX => ulong (HEX len must be 4)
* hbytes ulong2h UL => hex