persistable sclass HuffmanByteArray is BitIO {
  settable byte[] data;
  gettable int[] histogram;
  gettable HuffmanTreeMaker tm;
  gettable new HuffmanTree tree;
  
  // options
  settable bool startWithMagicCode;
  settable S magicCode = "HUF1";
  
  *(byte[] *data) {}

  public void readWrite(BitHead head) {
    if (head.writeMode() && histogram == null) {
      histogram = byteHistogramArray(data);
      tm = new HuffmanTreeMaker;
      tm.importByteHistogram(histogram);
      tree = tm!;
    }

    // Part 1 (magic code)
    if (startWithMagicCode)
      head.exchangeASCII(magicCode);
  
    // Part 2 (Huffman character tree)
    tree.readWrite(head);

    // Part 3a (size)

    new VariableSizeUIntForBitHead().chunkSize(3).readWrite(head, -> data.length, size -> data = new byte[size]);
    //print("length " + data.length);
    
    // Part 3 (text)
    if (head.writeMode()) {
      fOr (b : data)
        tree.writeCharacter(b, head);
    }
    
    if (head.readMode()) {
      for i over data: {
        if (head.isEOF()) break;
        data[i] = toUByte(tree.readSymbol(head));
      }
    }
  }
  
  byte[] get() { ret data; }
  
  // update selfType
  public selfType fromByteArray(byte[] data) { BitIO.super.fromByteArray(data); this; }
  public selfType load(byte[] data) { BitIO.super.load(data); this; }
}

Began life as a copy of #1035674