docs: protected void flushCacheWithAppend(byte[] bufferToAppend, int off, int len) throws IOException {
          byte[] chunkHeader = (Integer.toHexString(cachePosition + len) + "\r\n").getBytes(StandardCharsets.US_ASCII);
          stream.write(chunkHeader, 0, chunkHeader.length);
          stream.write(cache, 0, cachePosition);
          stream.write(bufferToAppend, off, len);
          stream.write(ENDCHUNK, 0, ENDCHUNK.length);
          cachePosition = 0;
      }