anchor.diff:          // If the Range header was received, handle it.
           String range = request.headers.value("range");
           if (range != null) {
  -          // We only support one range, where the standard support several.
  -          Match matches = new RegExp(r"^bytes=(\d*)\-(\d*)$").firstMatch(range);
  -          // If the range header have the right format, handle it.
  -          if (matches != null) {
  -            // Serve sub-range.
  -            int start;
  -            int end;
  -            if (matches[1].isEmpty) {
  -              start = matches[2].isEmpty ? length : length - int.parse(matches[2]);
  -              end = length;
  -            } else {
  -              start = int.parse(matches[1]);
  -              end = matches[2].isEmpty ? length : int.parse(matches[2]) + 1;
  -            }
  -
  -            // Override Content-Length with the actual bytes sent.
  -            response.headers.set(HttpHeaders.CONTENT_LENGTH, end - start);
  -
  -            // Set 'Partial Content' status code.
  -            response.statusCode = HttpStatus.PARTIAL_CONTENT;
  -            response.headers.set(HttpHeaders.CONTENT_RANGE,
  -                                 "bytes $start-${end - 1}/$length");
  -
  -            // Pipe the 'range' of the file.
  -            file.openRead(start, end).pipe(response)
  -                .catchError(_errorHandler);
  -            return;
  -          }
  +          _sendRange(file, response, range, length);
  +          return;
           }
   
           /*
  
positive.code: 
          String ext = extension(file.path);
          if (_extToContentType.containsKey(ext.toLowerCase())) {
            response.headers.contentType =
                ContentType.parse(_extToContentType[ext.toLowerCase()]);
          }
  
          if (request.method == 'HEAD') {
  
negative.code:   void addMIMETypes(Map<String, String> types){
      _extToContentType.addAll(types);
    }
    
    /**
     * Serve the file [file] to the [request]. The content of the file will be
     * streamed to the response. If a supported [:Range:] header is received, only
  