docs: private int copyPartial(final byte[] buffer, final byte[] response,
          final int num, final int read) {
          final int result;
          if (num > 0) {
              System.arraycopy(
                  response, read, response, 0, this.count - read
              );
              System.arraycopy(buffer, 0, response, this.count - read, read);
              result = this.count;
          } else {
              System.arraycopy(buffer, 0, response, 0, read);
              result = read;
          }
          return result;
      }