code: public String removeSiteRoot(String resourcename) {
  
          if (m_siteRoot == null) {
              // site root has not been set
              return resourcename;
          }
  
          String siteRoot = CmsRequestContext.getAdjustedSiteRoot(m_siteRoot, resourcename);
          if ((siteRoot.equals(m_siteRoot)) && resourcename.startsWith(siteRoot)) {
              resourcename = resourcename.substring(siteRoot.length());
          }
          return resourcename;
      }
docs: Removes the report site root prefix from the absolute path in the resource name,
  that is adjusts the resource name for the report site root.<p>
  
  If the site root for this report has not been set,
  or the resource name does not start with the report site root,
  the name it is left untouched.<p>
  
  @param resourcename the resource name (full path)
  
  @return the resource name adjusted for the report site root
  
  @see CmsRequestContext#removeSiteRoot(String)