code: public String getSitePath(String rootPath) {
  
          String result = null;
          if (CmsStringUtil.isNotEmpty(rootPath)) {
              if (rootPath.startsWith(m_siteRoot)) {
                  result = rootPath.substring(m_siteRoot.length());
              }
          }
          return result;
      }
docs: Returns the site path for the given root path in case the root path
  actually starts with this site root, or <code>null</code> in case
  the root path does not.<p>
  
  @param rootPath the root path to get the site path for
  
  @return the site path for the given root path in case the root path
  actually starts with this site root, or <code>null</code> in case
  the root path does not