u64 ldm_get_vnum (const u8 * block);
Large numbers in the LDM Database are often stored in a packed format. Each number is prefixed by a one byte width marker. All numbers in the database are stored in big-endian byte order. This function reads one of these numbers and returns the result
N.B. This function DOES NOT perform any range checking, though the most it will read is eight bytes.
n A number 0 Zero, or an error occurred