NewSet creates an empty set of digests which may have digests added.

ShortCodeTable returns a map of Digest to unique short codes.

ErrDigestAmbiguous is used when multiple digests are found in a set.

ErrDigestNotFound is used when a matching digest could not be found in a set.

Set is used to hold a unique set of digests which may be easily referenced by a string representation of the digest as well as short representation.