HuffmanTable constructor

HuffmanTable(List<int> lengths)

Implementation

HuffmanTable(List<int> lengths) {
  final listSize = lengths.length;

  for (var i = 0; i < listSize; ++i) {
    if (lengths[i] > maxCodeLength) {
      maxCodeLength = lengths[i];
    }
    if (lengths[i] < minCodeLength) {
      minCodeLength = lengths[i];
    }
  }

  final size = 1 << maxCodeLength;
  table = Uint32List(size);

  for (var bitLength = 1, code = 0, skip = 2; bitLength <= maxCodeLength;) {
    for (var i = 0; i < listSize; ++i) {
      if (lengths[i] == bitLength) {
        var reversed = 0;
        var rtemp = code;
        for (var j = 0; j < bitLength; ++j) {
          reversed = (reversed << 1) | (rtemp & 1);
          rtemp >>= 1;
        }

        for (var j = reversed; j < size; j += skip) {
          table[j] = (bitLength << 16) | i;
        }

        ++code;
      }
    }

    ++bitLength;
    code <<= 1;
    skip <<= 1;
  }
}