code: private int matchXmlNamespaceAttribute(String s) {
          /*
           * The regex we're simulating is: "xmlns\\s*=\\s*\".+?\".*"
           */
          StringPrefixSlicer stringSlicer = new StringPrefixSlicer(s);
          if (stringSlicer.removePrefix("xmlns") == false) return -1;
  
          stringSlicer.removeRepeatingPrefix(" ");
          if (stringSlicer.removePrefix("=") == false) return -1;
          stringSlicer.removeRepeatingPrefix(" ");
  
          if (stringSlicer.removePrefix("\"") == false) return -1;
          if (stringSlicer.removePrefixEndingWith("\"") == false) return -1;
  
          return s.length() - stringSlicer.getString().length();
      }
docs: Checks if the string starts with a complete XML namespace attribute, and
  if so, returns the number of characters that match.
  
  @param s
  The string to check for an XML namespace definition.
  
  @return -1 if no XML namespace definition was found, otherwise the length
  of the identified XML namespace definition.