    # File lib/rack/sendfile.rb, line 112
        def call(env)
          status, headers, body = @app.call(env)
          if body.respond_to?(:to_path)
            case type = variation(env)
            when 'X-Accel-Redirect'
              path = F.expand_path(body.to_path)
              if url = map_accel_path(env, path)
                headers[CONTENT_LENGTH] = '0'
                headers[type] = url
                obody = body
                body = Rack::BodyProxy.new([]) do
                  obody.close if obody.respond_to?(:close)
                end
              else
                env['rack.errors'].puts "X-Accel-Mapping header missing"
              end
            when 'X-Sendfile', 'X-Lighttpd-Send-File'
              path = F.expand_path(body.to_path)
              headers[CONTENT_LENGTH] = '0'
              headers[type] = path
              obody = body
              body = Rack::BodyProxy.new([]) do
                obody.close if obody.respond_to?(:close)
              end
            when '', nil
            else
              env['rack.errors'].puts "Unknown x-sendfile variation: '#{type}'.\n"
            end
          end
          [status, headers, body]
        end