code: @Override
      public RdfStream getFixity(final IdentifierConverter<Resource, FedoraResource> idTranslator, final URI digestUri,
              final long size) {
  
          try {
  
              LOGGER.debug("Checking resource: " + getPath());
  
              final String algorithm = ContentDigest.getAlgorithm(digestUri);
  
              final long contentSize = size < 0 ? getContentSize() : size;
  
              Collection<FixityResult> fixityResults = null;
              if (isProxy()) {
                  fixityResults = CacheEntryFactory.forProperty(getProperty(PROXY_FOR)).checkFixity(algorithm);
              } else if (isRedirect()) {
                  fixityResults =
                      CacheEntryFactory.forProperty(getProperty(REDIRECTS_TO)).checkFixity(algorithm);
              } else {
                  LOGGER.warn("URL Binary -- not proxy or redirect, so what is it?");
                  throw new RepositoryException("Binary resource marked as external is not proxy or redirect.");
              }
              return new FixityRdfContext(this, idTranslator, fixityResults, digestUri, contentSize);
          } catch (final RepositoryException e) {
              throw new RepositoryRuntimeException(e);
          }
      }
docs: /*
  (non-Javadoc)
  @see
  org.fcrepo.kernel.modeshape.FedoraBinaryImpl#getFixity(org.fcrepo.kernel.api.identifiers.IdentifierConverter,
  java.net.URI, long)