code: 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;
      }
docs: Writes the cache and bufferToAppend to the underlying stream
  as one large chunk
  @param bufferToAppend
  @param off
  @param len
  @throws IOException
  
  @since 3.0