code: protected void findContentFiles() throws CmsImportExportException, IOException, SAXException {
  
          Digester digester = new Digester();
          digester.setUseContextClassLoader(true);
          digester.setValidating(false);
          digester.setEntityResolver(new CmsXmlEntityResolver(null));
          digester.setRuleNamespaceURI(null);
          digester.setErrorHandler(new CmsXmlErrorHandler(CmsImportExportManager.EXPORT_MANIFEST));
  
          digester.addCallMethod("export/files/file", "addContentFile", 2);
          digester.addCallParam("export/files/file/source", 0);
          digester.addCallParam("export/files/file/uuidresource", 1);
          m_contentFiles.clear();
          digester.push(this);
          InputStream stream = null;
          try {
              stream = m_helper.getFileStream(CmsImportExportManager.EXPORT_MANIFEST);
              digester.parse(stream);
          } finally {
              if (stream != null) {
                  stream.close();
              }
          }
      }
docs: This method goes through the manifest, records all files from the manifest for which the content also
  exists in the zip file, and stores their resource ids in m_contentFiles.<p>
  
  @throws CmsImportExportException
  @throws IOException
  @throws SAXException