lzw static method

Uint8List lzw(Uint8List input, { int earlyChange = 1, })

Implementation

static Uint8List lzw(Uint8List input, {int earlyChange = 1}) {
  final List<int> out = <int>[];
  final List<List<int>> table = <List<int>>[];
  void reset() {
    table.clear();
    for (int i = 0; i < 256; i++) {
      table.add(<int>[i]);
    }
    table.add(<int>[]);
    table.add(<int>[]);
  }

  reset();
  int codeWidth = 9;
  int buffer = 0;
  int bits = 0;
  List<int>? previous;
  for (final int byte in input) {
    buffer = (buffer << 8) | byte;
    bits += 8;
    while (bits >= codeWidth) {
      final int code = (buffer >> (bits - codeWidth)) & ((1 << codeWidth) - 1);
      bits -= codeWidth;
      if (code == 256) {
        reset();
        codeWidth = 9;
        previous = null;
        continue;
      }
      if (code == 257) return Uint8List.fromList(out);
      List<int> entry;
      if (code < table.length && table[code].isNotEmpty) {
        entry = table[code];
      } else if (previous != null) {
        entry = <int>[...previous, previous.first];
      } else {
        return Uint8List.fromList(out);
      }
      out.addAll(entry);
      if (previous != null) table.add(<int>[...previous, entry.first]);
      previous = entry;
      if (table.length + earlyChange >= (1 << codeWidth) && codeWidth < 12) codeWidth++;
    }
  }
  return Uint8List.fromList(out);
}