converting from bytea to integers

I'd like to convert some bytea data to an array of four byte integers
(and vice versa). I'm probably missing something obvious, but I don't
see an efficient way to generate a 4 byte integer from a bytea string
(could be big endian or little endian). Converting back to bytea
seems easy enough using to_hex.

Thanks for any suggestions,

John DeSoi, Ph.D.