I have a 2-yr-old dog who growls at me if I try to approach him while he is laying down, resting, or sleeping. Is his growling acceptable?

Great web site! I have a 2 year old male shar pei who growls at me if I try to approach him while he is laying down/resting/sleeping. If I proceed to approach him when he growls, he will then bark viciously and snap at me. A few seconds after he does that, he seems out of sorts and remorseful, and comes right over to me to give me a kiss/lick. Although it is frightening when he snaps, is this acceptable? After all, I WAS interrupting his sleep and I myself wouldn't be a happy camper if someone woke me up when I was resting. Or, is it unacceptable for a dog to snap at its owner at ANY given time?