docs: private Map /* String, String */ parseHeaders(String headerPart) {
          final int len = headerPart.length();
          Map<String, String> headers = new HashMap<String, String>();
          int start = 0;
          for (; ;) {
              int end = parseEndOfLine(headerPart, start);
              if (start == end) {
                  break;
              }
              String header = headerPart.substring(start, end);
              start = end + 2;
              while (start < len) {
                  int nonWs = start;
                  while (nonWs < len) {
                      char c = headerPart.charAt(nonWs);
                      if (c != ' ' && c != '\t') {
                          break;
                      }
                      ++nonWs;
                  }
                  if (nonWs == start) {
                      break;
                  }
                  // Continuation line found
                  end = parseEndOfLine(headerPart, nonWs);
                  header += " " + headerPart.substring(nonWs, end);
                  start = end + 2;
              }
              parseHeaderLine(headers, header);
          }
          return headers;
      }