# File lib/rack/sendfile.rb, line 106
106:     def call(env)
107:       status, headers, body = @app.call(env)
108:       if body.respond_to?(:to_path)
109:         case type = variation(env)
110:         when 'X-Accel-Redirect'
111:           path = F.expand_path(body.to_path)
112:           if url = map_accel_path(env, path)
113:             headers[type] = url
114:             body = []
115:           else
116:             env['rack.errors'] << "X-Accel-Mapping header missing"
117:           end
118:         when 'X-Sendfile', 'X-Lighttpd-Send-File'
119:           path = F.expand_path(body.to_path)
120:           headers[type] = path
121:           body = []
122:         when '', nil
123:         else
124:           env['rack.errors'] << "Unknown x-sendfile variation: '#{variation}'.\n"
125:         end
126:       end
127:       [status, headers, body]
128:     end