Descriptor verifies that the embedded Data field matches the Size and Digest fields of the given v1.Descriptor, returning an error if the Data field is missing or if it contains incorrect data.

ReadCloser wraps the given io.ReadCloser to verify that its contents match the provided v1.Hash before io.EOF is returned.

SizeUnknown is a sentinel value to indicate that the expected size is not known.

Error provides information about the failed hash verification.