make_partial_content

# File lib/webrick/httpservlet/filehandler.rb, line 72
      def make_partial_content(req, res, filename, filesize)
        mtype = HTTPUtils::mime_type(filename, @config[:MimeTypes])
        unless ranges = HTTPUtils::parse_range_header(req['range'])
          raise HTTPStatus::BadRequest,
            "Unrecognized range-spec: \"#{req['range']}\""
        end
        open(filename, "rb"){|io|
          if ranges.size > 1
            time = Time.now
            boundary = "#{time.sec}_#{time.usec}_#{Process::pid}"
            body = ''
            ranges.each{|range|
              first, last = prepare_range(range, filesize)
              next if first < 0
              io.pos = first
              content = io.read(last-first+1)
              body << "--" << boundary << CRLF
              body << "Content-Type: #{mtype}" << CRLF
              body << "Content-Range: bytes #{first}-#{last}/#{filesize}" << CRLF
              body << CRLF
              body << content
              body << CRLF
            }
            raise HTTPStatus::RequestRangeNotSatisfiable if body.empty?
            body << "--" << boundary << "--" << CRLF
            res["content-type"] = "multipart/byteranges; boundary=#{boundary}"
            res.body = body
          elsif range = ranges[0]
            first, last = prepare_range(range, filesize)
            raise HTTPStatus::RequestRangeNotSatisfiable if first < 0
            if last == filesize - 1
              content = io.dup
              content.pos = first
            else
              io.pos = first
              content = io.read(last-first+1)
            end
            res['content-type'] = mtype
            res['content-range'] = "bytes #{first}-#{last}/#{filesize}"
            res['content-length'] = last - first + 1
            res.body = content
          else
            raise HTTPStatus::BadRequest
          end
        }
      end