exoticPruned function

Implementation

ExoticPruned exoticPruned(BitString bits, List<Cell> refs) {
  var reader = BitReader(bits);
  var type = reader.loadUint(8);

  if (type != 1) {
    throw 'Pruned Branch cell must have type 1, got $type';
  }
  if (refs.isNotEmpty) {
    throw 'Pruned Branch cell can not have refs, got ${refs.length}';
  }

  LevelMask mask;
  if (bits.length == 280) {
    // Special case for config proof - this test proof is generated in the moment of voting for a slashing.
    // It seems that tools generate it incorrectly and therefore doesn't have mask in it, so we need to hardcode it equal to 1

    mask = LevelMask(1);
  } else {
    mask = LevelMask(reader.loadUint(8));
    if (mask.level < 1 || mask.level > 3) {
      throw 'Pruned Branch cell level must be >= 1 and <= 3, got ${mask.level}/${mask.value}';
    }
    //                                                       256 Hash + 16 Depth
    final size = 8 + 8 + (mask.apply(mask.level - 1).hashCount * (256 + 16));
    if (bits.length != size) {
      throw 'Pruned Branch cell must have exactly $size bits, got ${bits.length}';
    }
  }

  var pruned = <PrunedCell>[];
  var hashes = <Uint8List>[];
  var depths = <int>[];

  for (var i = 0; i < mask.level; i += 1) {
    hashes.add(reader.loadList(32));
  }
  for (var i = 0; i < mask.level; i += 1) {
    depths.add(reader.loadUint(16));
  }
  for (var i = 0; i < mask.level; i += 1) {
    pruned.add(PrunedCell(
      depth: depths[i],
      hash: hashes[i],
    ));
  }

  return ExoticPruned(
    mask: mask.value,
    pruned: pruned,
  );
}