Major Description
The Java API docs for InputStream.skip and Reader.skip seem to indicate that returning a negative value is breaking the contract.
The contract for Reader.skip is the more clear one, while I have taken the assumption that all Derby InputStreams will return 0 only when EOF has been reached or 0 is passed in as the amount of bytes to skip.
Bad checking in a skip method also caused Derby to enter an infinite loop in a skip method.
It should also be noted that skipping bytes/characters should be done in a loop, as skip is free to skip a smaller amount of bytes than requested. This is true even if EOF is not reached.