# File lib/rmail/parser/multipart.rb, line 68
      def read_chunk_low(chunk_size)

        if @pushback
          return standard_read_chunk(chunk_size)
        end

        input_gave_nil = false
        loop {
          return nil if @eof || @delimiter

          unless @chunks.empty?
            chunk, @delimiter, @delimiter_is_last = @chunks.shift
            return chunk
          end

          chunk = standard_read_chunk(chunk_size)

          if chunk.nil?
            input_gave_nil = true
          end
          if @caryover
            if chunk
              @caryover << chunk
            end
            chunk = @caryover
            @caryover = nil
          end

          if chunk.nil?
            @eof = true
            return nil
          elsif @in_epilogue
            return chunk
          end

          start = 0
          found_last_delimiter = false

          while !found_last_delimiter and
              (start < chunk.length) and
              (found = chunk.index(@delimiter_re, start))

            if $~[2] == '' and !input_gave_nil
              break
            end

            delimiter = $~[0]

            # check if delimiter had the trailing --
            if $~.begin(1)
              found_last_delimiter = true
            end

            temp = if found == start
                     nil
                   else
                     chunk[start, found - start]
                   end

            @chunks << [ temp, delimiter, found_last_delimiter ]

            start = $~.end(0)
          end

          chunk = chunk[start..-1] if start > 0

          # If something that looks like a delimiter exists at the end
          # of this chunk, refrain from returning it.
          unless found_last_delimiter or input_gave_nil
            start = chunk.rindex(/\n/) || 0
            if chunk.index(@might_be_delimiter_re, start)
              @caryover = chunk[start..-1]
              chunk[start..-1] = ''
              chunk = nil if chunk.length == 0
            end
          end

          unless chunk.nil?
            @chunks << [ chunk, nil, false ]
          end
          chunk, @delimiter, @delimiter_is_last = @chunks.shift

          if chunk
            return chunk
          end
        }
      end