# File lib/mail/parsers/rfc2822_obsolete.rb, line 164
    def _nt_obs_char
      start_index = index
      if node_cache[:obs_char].has_key?(index)
        cached = node_cache[:obs_char][index]
        if cached
          cached = SyntaxNode.new(input, index...(index + 1)) if cached == true
          @index = cached.interval.end
        end
        return cached
      end

      i0 = index
      if has_terminal?('\G[\\x00-\\x09]', true, index)
        r1 = true
        @index += 1
      else
        r1 = nil
      end
      if r1
        r0 = r1
      else
        if has_terminal?('\G[\\x0B-\\x0C]', true, index)
          r2 = true
          @index += 1
        else
          r2 = nil
        end
        if r2
          r0 = r2
        else
          if has_terminal?('\G[\\x0E-\\x7F]', true, index)
            r3 = true
            @index += 1
          else
            r3 = nil
          end
          if r3
            r0 = r3
          else
            @index = i0
            r0 = nil
          end
        end
      end

      node_cache[:obs_char][start_index] = r0

      r0
    end