# File lib/mail/parsers/rfc2822.rb, line 304
    def _nt_CFWS
      start_index = index
      if node_cache[:CFWS].has_key?(index)
        cached = node_cache[:CFWS][index]
        if cached
          cached = SyntaxNode.new(input, index...(index + 1)) if cached == true
          @index = cached.interval.end
        end
        return cached
      end

      i0, s0 = index, []
      s1, i1 = [], index
      loop do
        i2, s2 = index, []
        s3, i3 = [], index
        loop do
          r4 = _nt_FWS
          if r4
            s3 << r4
          else
            break
          end
        end
        r3 = instantiate_node(SyntaxNode,input, i3...index, s3)
        s2 << r3
        if r3
          r5 = _nt_comment
          s2 << r5
        end
        if s2.last
          r2 = instantiate_node(SyntaxNode,input, i2...index, s2)
          r2.extend(CFWS0)
        else
          @index = i2
          r2 = nil
        end
        if r2
          s1 << r2
        else
          break
        end
      end
      r1 = instantiate_node(SyntaxNode,input, i1...index, s1)
      s0 << r1
      if r1
        r7 = _nt_FWS
        if r7
          r6 = r7
        else
          r6 = instantiate_node(SyntaxNode,input, index...index)
        end
        s0 << r6
      end
      if s0.last
        r0 = instantiate_node(SyntaxNode,input, i0...index, s0)
        r0.extend(CFWS1)
      else
        @index = i0
        r0 = nil
      end

      node_cache[:CFWS][start_index] = r0

      r0
    end